| 1. |
- MacDonald, Amy M., et al.
(författare)
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Maternal and child biomonitoring strategies and levels of exposure in western Canada during the past seventeen years : The Alberta Biomonitoring Program
- 2022
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Ingår i: International journal of hygiene and environmental health. - : Elsevier BV. - 1438-4639 .- 1618-131X. ; 244
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Tidskriftsartikel (refereegranskat)abstract
- The Alberta Biomonitoring Program (ABP) was created in 2005 with the initial goal of establishing baseline levels of exposure to environmental chemicals in specific populations in the province of Alberta, Canada, and was later expanded to include multiple phases. The first two phases focused on evaluating exposure in pregnant women (Phase One, 2005) and children (Phase Two, 2004–2006) by analyzing residual serum specimens. Phase Three (2013–2016) employed active recruitment techniques to evaluate environmental exposures using a revised list of chemicals in paired serum pools from pregnant women and umbilical cord blood. These three phases of the program monitored a total of 226 chemicals in 285 pooled serum samples representing 31,529 individuals. Phase Four (2017–2020) of the ABP has taken a more targeted approach, focusing on the impact of the federal legalization of cannabis on the exposure of pregnant women in Alberta to cannabis, as well as tobacco and alcohol using residual prenatal screening serum specimens. Chemicals monitored in the first three phases include herbicides, neutral pesticides, metals, metalloids, and micronutrients, methylmercury, organochlorine pesticides, organophosphate pesticides, parabens, phthalate metabolites, perfluoroalkyl substances (PFAS), phenols, phytoestrogens, polybrominated compounds, polychlorinated biphenyls (PCBs), dioxins and furans, polycyclic aromatic hydrocarbons (PAHs), and tobacco biomarkers. Phase Four monitored six biomarkers of tobacco, alcohol, and cannabis. All serum samples were pooled. Mean concentrations and 95% confidence intervals (CIs) were calculated for the chemicals detected in ≥25% of the sample pools. cross the first three phases, the data from the ABP has provided baseline exposure levels for the chemicals in pregnant women, children, and newborns across the province. Comparison within and among the phases has highlighted differences in exposure levels with age, geography, seasonality, sample type, and time. The strategies employed throughout the program phases have been demonstrated to provide effective models for population biomonitoring.
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| 2. |
- Alavaisha, Edmond, 1988-
(författare)
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Agricultural expansion impacts on wetland ecosystem services from Kilombero Valley, Tanzania
- 2020
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Land use change has major impact on the world’s wetland ecosystems and biodiversity. The motivation behind this change has been to increase agricultural production, often resulting in negative effects on water quality and soil fertility. Tanzania has carried out a large expansion and intensification of agriculture under the Kilimo kwanza (First agriculture) initiative which has triggered the need for better knowledge on land use change effects and associated ecosystem functioning. This thesis considers small-scale irrigation schemes to understand the effects of agriculture expansion and farming practices on nutrients, water quality and ecosystem services (ES) in Kilombero Valley, Tanzania. The study approach is multidisciplinary involving interviews, remote sensing, geographical information system techniques, and in-field soil and water ecological sampling. The major land use change in the valley during the last three decades was transformation from forest, bushland and grassland into cultivated land. The rate of change was faster adjacent to irrigation schemes and most changes occurred downstream irrigation canals, close to the floodplain. Irrigation and fertilization contributed to soil carbon and nitrogen accumulation in crop fields, which both declined in concentration with depth into the soil. However, such management practices and agricultural land expansion had impacts on several ES – especially water quality in streams. Streams surrounded mainly by cultivated land, as well as downstream areas, had lower water quality compared to streams with less settlement, more natural vegetation and upstream areas. Furthermore, when evaluated, macroinvertebrates indices were found to be a good indicator of water quality and a complement to chemical and physical water analysis. Irrigation farming produced more food compared to rainfed farming, and also other ES such as flood regulation, erosion control and several cultural services, depending on the river discharge. The thesis shows the importance to use irrigation/fertilization management to enhance soil fertility and preserve soil structure, but also the need for proper irrigation management to prevent flooding and erosion, conserve natural vegetation, and protect water quality. To enhance nature conservation, preserve biodiversity and secure future supply of ES in the valley, investment in irrigation infrastructures should be done at small-scale to mitigate the large-scale exploitation of Kilombero wetland.
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| 3. |
- Alavaisha, Edmond, et al.
(författare)
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Assessment of Water Quality Across Irrigation Schemes : A Case Study of Wetland Agriculture Impacts in Kilombero Valley, Tanzania
- 2019
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Ingår i: Water. - : MDPI AG. - 2073-4441. ; 11:4
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Tidskriftsartikel (refereegranskat)abstract
- Coupled change in land and water use due to increased farming intensity is a main factor affecting water quality and quantity, ecological functions and biodiversity globally. Prolonging growing seasons and increasing productivity in wetlands through irrigation have been targeted for increasing food security, particularly in developing countries. Nevertheless, irrigation and drainage have often been associated with degradation of water quality through increased agrochemical and fertiliser runoff and leaching at local scales. In this study, we investigated water quality in streams used for irrigation in a wetland area in Kilombero Valley, Tanzania. We measured physical-chemical water parameters and collected macroinvertebrates with different sensitivity to water quality across several small irrigation schemes covering various conditions. Turbidity, temperature, nitrate-N, and ammonium-N were significantly higher at sampling sites downstream of irrigation compared to upstream. Macroinvertebrate diversity, richness and average score per taxa (ASPT) were higher in general in sampling sites upstream of irrigation, with more sensitive macroinvertebrates decreasing in abundance downstream. There was a positive correlation between physical-chemical parameters and macroinvertebrate indices across the sites. We demonstrate that macroinvertebrate indices can be used as a quick assessment of water quality in response to irrigation schemes in small-scale farming systems of Tanzania. This in turn can allow us to track changes affecting wetland ecosystem function and biodiversity at higher trophic levels and across larger scales, thereby providing useful early warnings to help avoid widespread degradation under widespread agricultural intensification.
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| 4. |
- Bishop, Kevin, 1960-, et al.
(författare)
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The Relationship Between Land Use and Water
- 2012
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Ingår i: EOS. - 0096-3941 .- 2324-9250. ; 93, s. 259-
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Tidskriftsartikel (övrigt vetenskapligt/konstnärligt)abstract
- The question posed in the title of this workshop formed its focus as an international group of more than 50 researchers and managers gathered to discuss our current level of understanding of land-water interactions and the potential impacts this has for resource management. Special emphasis was placed on the Ethiopian highlands, which deliver more than 85% of the flow in the Nile in Egypt. The 2-day workshop, held at the Swedish University of Agricultural Sciences in Uppsala, was cosponsored by the Swedish Ministry for Foreign Affairs as part of its special allocation for global food security and by the International Union of Forest Research Organizations' Unit 3.05, Forest Operations Ecology.
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| 5. |
- Bogaart, Patrick W., et al.
(författare)
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Streamflow recession patterns can help unravel the role of climate and humans in landscape co-evolution
- 2016
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Ingår i: Hydrology and Earth System Sciences. - : Copernicus GmbH. - 1027-5606 .- 1607-7938. ; 20:4, s. 1413-1432
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Tidskriftsartikel (refereegranskat)abstract
- Traditionally, long-term predictions of river discharges and their extremes include constant relationships between landscape properties and model parameters. However, due to the co-evolution of many landscape properties more sophisticated methods are necessary to quantify future landscape-hydrological model relationships. As a first step towards such an approach we use the Brutsaert and Nieber (1977) analysis method to characterize streamflow recession behaviour of approximate to 200 Swedish catchments within the context of global change and landscape co-evolution. Results suggest that the Brutsaert-Nieber parameters are strongly linked to the climate, soil, land use, and their interdependencies. Many catchments show a trend towards more non-linear behaviour, meaning not only faster initial recession but also slower recession towards base flow. This trend has been found to be independent from climate change. Instead, we suggest that land cover change, both natural (restoration of natural soil profiles in forested areas) and anthropogenic (reforestation and optimized water management), is probably responsible. Both change types are characterised by system adaptation and change, towards more optimal ecohydrological conditions, suggesting landscape co-evolution is at play. Given the observed magnitudes of recession changes during the past 50 years, predictions of future river discharge critically need to include the effects of landscape co-evolution. The interconnections between the controls of land cover and climate on river recession behaviour, as we have quantified in this paper, provide first-order handles to do so.
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| 6. |
- Bring, Arvid, et al.
(författare)
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Role-play simulations as an aid to achieve complex learning outcomes in hydrological science
- 2019
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Ingår i: Hydrology and Earth System Sciences. - : Copernicus GmbH. - 1027-5606 .- 1607-7938. ; 23:5, s. 2369-2378
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Tidskriftsartikel (refereegranskat)abstract
- Students in hydrology are expected to become proficient in a set of quantitative skills while also acquiring the ability to apply their problem-solving abilities in real-life situations. To achieve both these types of learning outcomes, there is broad evidence that activity-based learning is beneficial. In this paper, we argue that role-play simulations in particular are useful for achieving complex learning outcomes, i.e., making students able to coordinate and integrate various analytical skills in complicated settings. We evaluated the effects of an integrated water resources management (IWRM) negotiation simulation next to more traditional teaching methods intended to foster quantitative understanding. Results showed that despite similar student-reported achievement of both complex and quantitative intended learning outcomes, the students favored the negotiation simulation over the traditional method. This implies that role-play simulations can motivate and actively engage a classroom, thereby creating a space for potential deeper learning and longer retention of knowledge. While our findings support the utility of simulations to teach complex learning outcomes and indicate no shortcoming in achieving such outcomes next to traditional methods aimed at quantitative learning outcomes, simulations are still not widely used to foster activity-based learning in the classroom. We thus conclude by presenting three particularly challenging areas of role-play simulations as learning tools that serve as potential barriers to their implementation and suggest ways to overcome such roadblocks.
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| 7. |
- Dahlke, Helen E., et al.
(författare)
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Contrasting trends in floods for two sub-arctic catchments in northern Sweden - does glacier presence matter?
- 2012
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Ingår i: Hydrology and Earth System Sciences. - : Copernicus GmbH. - 1027-5606 .- 1607-7938. ; 16:7, s. 2123-2141
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Tidskriftsartikel (refereegranskat)abstract
- Our understanding is limited to how transient changes in glacier response to climate warming will influence the catchment hydrology in the Arctic and Sub-Arctic. This understanding is particularly incomplete for flooding extremes because understanding the frequency of such unusual events requires long records of observation not often available for the Arctic and Sub-Arctic. This study presents a statistical analysis of trends in the magnitude and timing of flood extremes and the mean summer discharge in two sub-arctic catchments, Tarfala and Abisko, in northern Sweden. The catchments have different glacier covers (30% and 1%, respectively). Statistically significant trends (at the 5% level) were identified for both catchments on an annual and on a seasonal scale (3-months averages) using the Mann-Kendall trend test. Stationarity of flood records was tested by analyzing trends in the flood quantiles, using generalized least squares regression. Hydrologic trends were related to observed changes in the precipitation and air temperature, and were correlated with 3-months averaged climate pattern indices (e.g. North Atlantic oscillation). Both catchments showed a statistically significant increase in the annual mean air temperature over the comparison time period of 1985-2009 (Tarfala and Abisko p < 0.01), but did not show significant trends in the total precipitation (Tarfala p = 0.91, Abisko p = 0.44). Despite the similar climate evolution over the studied period in the two catchments, data showed contrasting trends in the magnitude and timing of flood peaks and the mean summer discharge. Hydrologic trends indicated an amplification of the streamflow and flood response in the highly glacierized catchment and a dampening of the response in the non-glacierized catchment. The glacierized mountain catchment showed a statistically significant increasing trend in the flood magnitudes (p = 0.04) that is clearly correlated to the occurrence of extreme precipitation events. It also showed a significant increase in mean summer discharge (p = 0.0002), which is significantly correlated to the decrease in glacier mass balance and the increase in air temperature (p = 0.08). Conversely, the non-glacierized catchment showed a significant decrease in the mean summer discharge (p = 0.01), the flood magnitudes (p = 0.07) and an insignificant trend towards earlier flood occurrences (p = 0.53). These trends are explained by a reduction of the winter snow pack due to higher temperatures in the winter and spring and an increasing soil water storage capacity or catchment storage due to progressively thawing permafrost.
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| 8. |
- Dahlke, Helen E., et al.
(författare)
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Dissecting the variable source area concept - Subsurface flow pathways and water mixing processes in a hillslope
- 2012
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Ingår i: Journal of Hydrology. - : Elsevier BV. - 0022-1694 .- 1879-2707. ; 420, s. 125-141
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Tidskriftsartikel (refereegranskat)abstract
- This study uses an instrumented (trenched) 0.5 ha hillslope in the southern tier of New York State, USA, to provide new data and insights on how variable source areas and associated flow pathways form and combine to connect rainfall with downstream water flows across a hillslope. Measurements of water fluxes in the trench, upslope water table dynamics, surface and bedrock topography, and isotopic and geochemical tracers have been combined for a four-dimensional (space-time) characterization of subsurface storm flow responses. During events with dry antecedent conditions infiltrating rainwater was found to percolate through a prevailing fragipan layer to deeper soil layers, with much (33-71%) of the total discharge of the hillslope originating from deeper water flow below the fragipan. During storm events with wet antecedent conditions and large rainfall amounts, shallow lateral flow of event and pre-event water above the fragipan occurred and was one magnitude greater than the deeper water flow contribution. Spatial surface and subsurface water quality observations indicate that water from a distance of up to 56 m contributed runoff from the hillslope during storm events. In addition, mobilization of total dissolved phosphorus (TDP) with subsurface flow played a greater role than with overland or near-surface flow. During all events TDP loads were highest in the total discharge during peak flows (8-11.5 kg ha(-1) d(-1)), except during the largest storm event, when TDP concentrations were highly diluted. These results have implications for strategies to protect streams and other downstream water recipients from waterborne nutrient and pollutant loading.
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| 9. |
- Dahlke, Helen E., et al.
(författare)
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Early melt season snowpack isotopic evolution in the Tarfala valley, northern Sweden
- 2013
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Ingår i: Annals of Glaciology. - 0260-3055 .- 1727-5644. ; 54:62, s. 149-156
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Tidskriftsartikel (refereegranskat)abstract
- This study investigated the stable water isotopic (delta O-18 and delta D) evolution of two snowpacks located at the same elevation on a north-facing (Nf) and a south-facing (Sf) slope within the Tarfala research catchment, northern Sweden, and the potential impact of pre-freshet snowpack melt on streamflow. Our results indicate that over the study period the Sf snowpack showed a more enriched isotopic composition, especially in the top of the profile, and contributed more snowmelt to streamflow than the Nf slope. The Sf snowpack also showed a significantly higher variability in snowpack delta O-18 levels and snowpack snow water equivalent (SWE) over time. Comparing snowpack and snowmelt isotopic values it was seen that the Sf slope experienced earlier snowmelt from upslope positions due to greater insolation that subsequently enhanced the meltwater flux at the base of downslope snowpacks. In contrast, the Nf slope primarily underwent changes within the snowpack and experienced relatively minimal melt. Detailed field-based isotopic snowmelt studies such as this highlight the potential importance of incorporating spatio-temporal runoff generation concepts into distributed energy-balance models, which could allow for more accurate prediction with regard to the spatio-temporal dynamics associated with the snowmelt ion pulse.
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| 10. |
- Dahlke, Helen E., et al.
(författare)
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Isotopic investigation of runoff generation in a glacierized catchment in northern Sweden
- 2014
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Ingår i: Hydrological Processes. - : Wiley. - 0885-6087 .- 1099-1085. ; 28:3, s. 1383-1398
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Tidskriftsartikel (refereegranskat)abstract
- In this study, summer rainfall contributions to streamflow were quantified in the sub-arctic, 30% glacierized Tarfala (21.7km(2)) catchment in northern Sweden for two non-consecutive summer sampling seasons (2004 and 2011). We used two-component hydrograph separation along with isotope ratios (O-18 and D) of rainwater and daily streamwater samplings to estimate relative fraction and uncertainties (because of laboratory instrumentation, temporal variability and spatial gradients) of source water contributions. We hypothesized that the glacier influence on how rainfall becomes runoff is temporally variable and largely dependent on a combination of the timing of decreasing snow cover on glaciers and the relative moisture storage condition within the catchment. The results indicate that the majority of storm runoff was dominated by pre-event water. However, the average event water contribution during storm events differed slightly between both years with 11% reached in 2004 and 22% in 2011. Event water contributions to runoff generally increased over 2011 the sampling season in both the main stream of Tarfala catchment and in the two pro-glacial streams that drain Storglaciaren (the largest glacier in Tarfala catchment covering 2.9km(2)). We credit both the inter-annual and intra-annual differences in event water contributions to large rainfall events late in the summer melt season, low glacier snow cover and elevated soil moisture due to large antecedent precipitation. Together amplification of these two mechanisms under a warming climate might influence the timing and magnitude of floods, the sediment budget and nutrient cycling in glacierized catchments.
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| 11. |
- Dahlke, Helen E., et al.
(författare)
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Modelling variable source area dynamics in a CEAP watershed
- 2009
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Ingår i: Ecohydrology. - : Wiley. - 1936-0584 .- 1936-0592. ; 2:3, s. 337-349
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Tidskriftsartikel (refereegranskat)abstract
- In the Northeast US, saturation excess is the most dominant runoff process and locations of runoff areas, typically called variable source areas (VSAs), are determined by the available soil water storage and the landscape topographic position. To predict runoff generated from VSAs some water quality models use the Soil Conservation Service Curve Number equation (SCS-CN), which assumes a constant initial abstraction of rainfall is retained by the watershed prior to the beginning of runoff. We apply a VSA interpretation of the SCS-CN runoff equation that allows the initial abstraction to vary with antecedent Moisture conditions. We couple this modified SCS-CN approach with a semi-distributed water balance model to predict runoff, and distribute predictions using a soil topographic index for the Town Brook watershed in the Catskill Mountains of New York State. The accuracy of predicted VSA extents using both the original and the modified SCS-CN equation were evaluated for 14 rainfall-runoff events through a comparison with average water table depths measured at 33 locations in Town Brook from March-September 2004. The modified SCS-CN equation captured VSA dynamics more accurately than the original equation. However, during events with high antecedent rainfall VSA dynamics were still under-predicted suggesting that VSA runoff is not captured solely by knowledge of the soil water deficit. Considering the importance of correctly predicting runoff generation and pollutant source areas in the landscape, the results of this study demonstrate the feasibility of integrating VSA hydrology into water quality models to reduce non-point source pollution.
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| 12. |
- Dahlke, Helen E., et al.
(författare)
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Using concurrent DNA tracer injections to infer glacial flow pathways
- 2015
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Ingår i: Hydrological Processes. - : Wiley. - 0885-6087 .- 1099-1085. ; 29:25, s. 5257-5274
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Tidskriftsartikel (refereegranskat)abstract
- Catchment hydrology has become replete with flow pathway characterizations obtained via combinations of physical hydrologic measurements (e.g. streamflow hydrographs) and natural tracer signals (e.g. stable water isotopes and geochemistry). In this study, we explored how our understanding of hydrologic flow pathways can be improved and expanded in both space and time by the simultaneous application of engineered synthetic DNA tracers. In this study, we compared the advective-dispersive transport properties and mass recovery rates of two types of synthetic DNA tracers, one consisting of synthetic DNA strands encapsulated into biodegradable microspheres and another consisting of `free' DNA, i.e. not encapsulated. The DNA tracers were also compared with a conservative fluorescent dye. All tracers were injected into a small (3.2-km(2)) valley glacier, Storglaciaren, in northern Sweden. Seven of the nine DNA tracers showed clear recovery during the sampling period and similar peak arrival times and dispersion coefficients as the conservative fluorescent dye. However, recovered DNA tracer mass ranged only from 1% to 66%, while recovered fluorescent dye mass was 99%. Resulting from the cold and opaque subglacial environment provided by the glacier, mass loss associated with microbial activity and photochemical degradation of the DNA is likely negligible, leaving sorption of DNA tracers onto suspended particles and loss of microtracer particles to sediment storage as probable explanations. Despite the difference in mass recovery, the advection and dispersion information derived from the DNA tracer breakthrough curves provided spatially explicit information that allowed inferring a theoretical model of the flow pathways that water takes through the glacier.
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| 13. |
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| 14. |
- Destouni, Georgia, et al.
(författare)
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Hydro-Biogeochemical and Environmental-Management Functions of Wetland Networks in Landscapes
- 2012
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Ingår i: 9th INTECOL International Wetlands Conference, Wetlands in a Complex World. ; , s. 915-
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- A main application goal of ecohydrological science is to amplify opportunities of achieving water quality improvements, biodiversity enhancements and sustainable development, by improved understanding and use of ecosystem properties as a management tool. This paper draws on and synthesizes main result implications for the function and possible enhanced use of wetland networks in the landscape as such a tool, from a series of hydro-biogeochemical and environmental economics studies of nutrient/pollutant loading and abatement in different Swedish hydrological catchments. Results show large potential of wetland networks to reduce the cost of abating nutrient and metal loads within and from hydrological catchments, and emphasize some main research questions for further investigations of actual possibilities to realize this potential. The questions regard in particular the ability of wetland networks to extend the travel times and reduce the uncertainty of hydrological nutrient/pollutant transport through catchments.The paper further presents and discusses some main joint conclusions of the participants in a recently held International Workshop on Ecohydrology and Integrated Water Resource Management (1) at the Navarino Environmental Observatory in Messinia, Greece (2), regarding essential goals for collaborative international efforts in wetland network research. The goals include to investigate on different spatiotemporal scales and in different world regions: a) the dynamics of natural and managed wetland networks across a gradient of different climate, human disturbance, energy and organization conditions; b) the reciprocal interactions between wetland networks and associated hydrological catchments; c) how climate change and different human activities in the wetland network catchments influence these interactions (in b) and generally the ecohydrology of individual wetlands and the whole wetland networks; and d) the ecosystem services provided by networks of wetlands.
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| 15. |
- Elmhagen, Bodil, et al.
(författare)
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Interacting effects of change in climate, human population, land use, and water use on biodiversity and ecosystem services
- 2015
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Ingår i: Ecology and Society. - 1708-3087. ; 20:1
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Tidskriftsartikel (refereegranskat)abstract
- Human population growth and resource use, mediated by changes in climate, land use, and water use, increasingly impact biodiversity and ecosystem services provision. However, impacts of these drivers on biodiversity and ecosystem services are rarely analyzed simultaneously and remain largely unknown. An emerging question is how science can improve the understanding of change in biodiversity and ecosystem service delivery and of potential feedback mechanisms of adaptive governance. We analyzed past and future change in drivers in south-central Sweden. We used the analysis to identify main research challenges and outline important research tasks. Since the 19th century, our study area has experienced substantial and interlinked changes; a 1.6 degrees C temperature increase, rapid population growth, urbanization, and massive changes in land use and water use. Considerable future changes are also projected until the mid-21st century. However, little is known about the impacts on biodiversity and ecosystem services so far, and this in turn hampers future projections of such effects. Therefore, we urge scientists to explore interdisciplinary approaches designed to investigate change in multiple drivers, underlying mechanisms, and interactions over time, including assessment and analysis of matching-scale data from several disciplines. Such a perspective is needed for science to contribute to adaptive governance by constantly improving the understanding of linked change complexities and their impacts.
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| 16. |
- Eriksson Hägg, Hanna, et al.
(författare)
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Future nutrient load scenarios for the Baltic Sea due to climate and lifestyle changes
- 2014
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Ingår i: Ambio. - : Springer Science and Business Media LLC. - 0044-7447 .- 1654-7209. ; 43:3, s. 337--351
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Tidskriftsartikel (refereegranskat)abstract
- Dynamic model simulations of the future climate and projections of future lifestyles within the Baltic Sea Drainage Basin (BSDB) were considered in this study to estimate potential trends in future nutrient loads to the Baltic Sea. Total nitrogen and total phosphorus loads were estimated using a simple proxy based only on human population (to account for nutrient sources) and stream discharges (to account for nutrient transport). This population-discharge proxy provided a good estimate for nutrient loads across the seven sub-basins of the BSDB considered. All climate scenarios considered here produced increased nutrient loads to the Baltic Sea over the next 100 years. There was variation between the climate scenarios such that sub-basin and regional differences were seen in future nutrient runoff depending on the climate model and scenario considered. Regardless, the results of this study indicate that changes in lifestyle brought about through shifts in consumption and population potentially overshadow the climate effects on future nutrient runoff for the entire BSDB. Regionally, however, lifestyle changes appear relatively more important in the southern regions of the BSDB while climatic changes appear more important in the northern regions with regards to future increases in nutrient loads. From a whole-ecosystem management perspective of the BSDB, this implies that implementation of improved and targeted management practices can still bring about improved conditions in the Baltic Sea in the face of a warmer and wetter future climate
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| 17. |
- Fazey, Ioan, et al.
(författare)
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Ten essentials for action-oriented and second order energy transitions, transformations and climate change research
- 2018
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Ingår i: Energy Research and Social Science. - : Elsevier BV. - 2214-6296 .- 2214-6326. ; 40, s. 54-70
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Forskningsöversikt (refereegranskat)abstract
- The most critical question for climate research is no longer about the problem, but about how to facilitate the transformative changes necessary to avoid catastrophic climate-induced change. Addressing this question, however, will require massive upscaling of research that can rapidly enhance learning about transformations. Ten essentials for guiding action-oriented transformation and energy research are therefore presented, framed in relation to second-order science. They include: (1) Focus on transformations to low-carbon, resilient living; (2) Focus on solution processes; (3) Focus on ‘how to’ practical knowledge; (4) Approach research as occurring from within the system being intervened; (5) Work with normative aspects; (6) Seek to transcend current thinking; (7) Take a multi-faceted approach to understand and shape change; (8) Acknowledge the value of alternative roles of researchers; (9) Encourage second-order experimentation; and (10) Be reflexive. Joint application of the essentials would create highly adaptive, reflexive, collaborative and impact-oriented research able to enhance capacity to respond to the climate challenge. At present, however, the practice of such approaches is limited and constrained by dominance of other approaches. For wider transformations to low carbon living and energy systems to occur, transformations will therefore also be needed in the way in which knowledge is produced and used.
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| 18. |
- Fazey, Ioan, et al.
(författare)
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Transforming knowledge systems for life on Earth : Visions of future systems and how to get there
- 2020
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Ingår i: Energy Research & Social Science. - : Elsevier. - 2214-6296 .- 2214-6326. ; 70
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Tidskriftsartikel (refereegranskat)abstract
- Formalised knowledge systems, including universities and research institutes, are important for contemporary societies. They are, however, also arguably failing humanity when their impact is measured against the level of progress being made in stimulating the societal changes needed to address challenges like climate change. In this research we used a novel futures-oriented and participatory approach that asked what future envisioned knowledge systems might need to look like and how we might get there. Findings suggest that envisioned future systems will need to be much more collaborative, open, diverse, egalitarian, and able to work with values and systemic issues. They will also need to go beyond producing knowledge about our world to generating wisdom about how to act within it. To get to envisioned systems we will need to rapidly scale methodological innovations, connect innovators, and creatively accelerate learning about working with intractable challenges. We will also need to create new funding schemes, a global knowledge commons, and challenge deeply held assumptions. To genuinely be a creative force in supporting longevity of human and non-human life on our planet, the shift in knowledge systems will probably need to be at the scale of the enlightenment and speed of the scientific and technological revolution accompanying the second World War. This will require bold and strategic action from governments, scientists, civic society and sustained transformational intent.
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| 19. |
- Fischer, Benjamin M. C., et al.
(författare)
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Improving agricultural water use efficiency with biochar - A synthesis of biochar effects on water storage and fluxes across scales
- 2019
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Ingår i: Science of the Total Environment. - : Elsevier BV. - 0048-9697 .- 1879-1026. ; 657, s. 853-862
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Tidskriftsartikel (refereegranskat)abstract
- There is an urgent need to develop agricultural methods that balance water supply and demand while at the same time improve resilience to climate variability. A promising instrument to address this need is biochar - a charcoal made from pyrolyzed organic material. However, it is often unclear how, if at all, biochar improves soil water availability, plant water consumption rates and crop yields. To address this question, we synthesized literature-derived observational data and evaluated the effects of biochar on evapotranspiration using a minimal soil water balance model. Results from the model were interpreted in the Budyko framework to assess how climatic conditions mediate the impacts of biochar on water fluxes. Our analysis of literature-derived observational data showed that while biochar addition generally increases the soil water holding capacity, it can have variable impacts on soil water retention relative to control conditions. Our modelling demonstrated that biochar increases long-term evapotranspiration rates, and therefore plant water availability, by increasing soil water retention capacity - especially in water-limited regions. Biochar amendments generally increased crop yields (75% of the compiled studies) and, in several cases (35% of the compiled studies), biochar amendments simultaneously increased crop yield and water use efficiencies. Hence, while biochar amendments are promising, the potential for variable impact highlights the need for targeted research on how biochar affects the soil-plant-water cycle.
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| 20. |
- Fischer, Benjamin M. C., et al.
(författare)
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Investigating the impacts of biochar on water fluxes in a rice experiment in the dry corridor of Central America, Costa Rica
- 2022
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Ingår i: Hydrological Processes. - : Wiley. - 0885-6087 .- 1099-1085. ; 36:12
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Tidskriftsartikel (refereegranskat)abstract
- Amending soils with biochar, a pyrolyzed organic material, is an emerging practice to potentially increase plant available water and reduce the risks associated with climatic variability in traditionally-rainfed tropical agricultural systems. To investigate the impacts of biochar amendment on soil water storage relative to non-amended soils, we performed an upland rice field experiment in a tropical seasonally dry region of Costa Rica consisting of plots with two different biochar amendments and a control plot. Across all plots, we collected hydrometric and isotopic data (δ18O and δ2H of rain, mobile soil, ground and rice xylem water). We observed that the soil water retention curves for biochar treated soils shifted, indicating that rice plants had 2% to 7% more water available throughout the growing season relative to the control plots and thus could withstand dry spells up to seven extra days. Furthermore, the isotopic composition of plant water in biochar and control treatments were rather similar, indicating that rice plants in different treatments likely consumed similar water. Hence, we observed that biochar amendments can stabilize water supplies for the rice plants; however, still supplemental irrigation was required to facilitate plant growth during extended dry periods. Ultimately, our findings indicate, that biochar amendments can complement, but not necessarily replace, other water management strategies to help reduce the threat of rainfall variability to rainfed agriculture in tropical regions.
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| 21. |
- Fischer, Benjamin M. C., et al.
(författare)
-
Mojito, Anyone? An Exploration of Low-Tech Plant Water Extraction Methods for Isotopic Analysis Using Locally-Sourced Materials
- 2019
-
Ingår i: Frontiers in Earth Science. - : Frontiers Media SA. - 2296-6463. ; 7
-
Tidskriftsartikel (refereegranskat)abstract
- The stable isotope composition of water (delta O-18 and delta H-2) is an increasingly utilized tool to distinguish between different pools of water along the soil-plant-atmosphere continuum (SPAC) and thus provides information on how plants use water. Clear bottlenecks for the ubiquitous application of isotopic analysis across the SPAC are the relatively high-energy and specialized materials required to extract water from plant materials. Could simple and cost-effective do-it-yourself MacGyver methods be sufficient for extracting plant water for isotopic analysis? This study develops a suite of novel techniques for plant water extraction and compares them to a standard research-grade water extraction method. Our results show that low-tech methods using locally-sourced materials can indeed extract plant water consistently and comparably to what is done with other state-of-the-art methods. Further, our findings show that other factors play a larger role than water extraction methods in achieving the desired accuracy and precision of stable isotope composition: (1) appropriate transport, (2) fast sample processing and (3) efficient workflows. These results are methodologically promising for the rapid expansion of isotopic investigations, especially for citizen science and/or school projects or in remote areas, where improved SPAC understanding could help manage water resources to fulfill agricultural and other competing water needs.
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| 22. |
- Frampton, Andrew, et al.
(författare)
-
Non-isothermal, three-phase simulations of near-surface flows in a model permafrost system under seasonal variability and climate change
- 2011
-
Ingår i: Journal of Hydrology. - : Elsevier BV. - 0022-1694 .- 1879-2707. ; 403:3-4, s. 352-359
-
Tidskriftsartikel (refereegranskat)abstract
- Permafrost responses to a changing climate can affect hydrological and biogeochemical cycling, ecosystems and climate feedbacks. We have simulated a model permafrost system in the temperature range associated with discontinuous permafrost focusing on interactions between permafrost and hydrology using a non-isothermal, three-phase model of water migration coupled to heat transport in partially frozen porous media. We explore the subsurface hydraulic property controls on the formation and dynamics of permafrost, and how this impacts seasonal variability of subsurface runoff to surface waters. For all subsurface conditions considered, the main common hydrological signal of permafrost degradation in a warming trend is decreasing seasonal variability of water flow. This is due to deeper and longer flow pathways with increasing lag times from infiltration or thawing through subsurface flow to surface water discharge. These results show how physically based numerical modelling can be used to quantitatively and qualitatively improve the understanding of how permafrost thawing relates to, and may be detected in, hydrological data. This is advantageous since hydrological data is considerably easier to obtain, may be available in longer time series, and generally reflects larger-scale conditions than direct permafrost observations.
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| 23. |
- Giesler, Reiner, et al.
(författare)
-
Catchment-scale dissolved carbon concentrations and exportestimates across six subarctic streams in northern Sweden
- 2014
-
Ingår i: Biogeosciences. - : Copernicus GmbH. - 1726-4170 .- 1726-4189. ; 11:2, s. 525-537
-
Tidskriftsartikel (refereegranskat)abstract
- Climatic change is currently enhancing permafrost thawing and the flow of water through the landscape in subarctic and arctic catchments, with major consequences for the carbon export to aquatic ecosystems. We studied stream water carbon export in several tundra-dominated catchments in northern Sweden. There were clear seasonal differences in both dissolved organic carbon (DOC) and dissolved inorganic carbon (DIC) concentrations. The highest DOC concentrations occurred during the spring freshet while the highest DIC concentrations were always observed during winter baseflow conditions for the six catchments considered in this study. Long-term trends for the period 1982 to 2010 for one of the streams showed that DIC concentrations has increased by 9% during the 28 yr of measurement while no clear trend was found for DOC. Similar increasing trends were also found for conductivity, Ca and Mg. When trends were discretized into individual months, we found a significant linear increase in DIC concentrations with time for September, November and December. In these subarctic catchments, the annual mass of C exported as DIC was in the same order of magnitude as DOC; the average proportion of DIC to the total dissolved C exported was 61% for the six streams. Furthermore, there was a direct relationship between total runoff and annual dissolved carbon fluxes for these six catchments. These relationships were more prevalent for annual DIC exports than annual DOC exports in this region. Our results also highlight that both DOC and DIC can be important in high-latitude ecosystems. This is particularly relevant in environments where thawing permafrost and changes to subsurface ice due to global warming can influence stream water fluxes of C. The large proportion of stream water DIC flux also has implications on regional C budgets and needs to be considered in order to understand climate-induced feedback mechanisms across the landscape.
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| 24. |
- Giesler, Reiner, et al.
(författare)
-
Spatiotemporal variations of pCO(2) and delta C-13-DIC in subarctic streams in northern Sweden
- 2013
-
Ingår i: Global Biogeochemical Cycles. - : American Geophysical Union (AGU). - 0886-6236 .- 1944-9224. ; 27:1, s. 176-186
-
Tidskriftsartikel (refereegranskat)abstract
- Current predictions of climate-related changes in high-latitude environments suggest major effects on the C export in streams and rivers. To what extent this will also affect the stream water CO2 concentrations is poorly understood. In this study we examined the spatiotemporal variation in partial pressure of CO2 (pCO(2)) and in stable isotopic composition of dissolved inorganic carbon (delta C-13-DIC) in subarctic streams in northern Sweden. The selected watersheds are characterized by large variations in high-latitude boreal forest and tundra and differences in bedrock. We found that all streams generally were supersaturated in pCO(2) with an average concentration of 850 mu atm. The variability in pCO(2) across streams was poorly related to vegetation cover, and carbonaceous bedrock influence was manifested in high DIC concentrations but not reflected in either stream pCO(2) or delta C-13-DIC. Stream water pCO(2) values were highest during winter base flow when we also observed the lowest delta C-13-DIC values, and this pattern is interpreted as a high contribution from CO2 from soil respiration. Summer base flow delta C-13-DIC values probably are more affected by in situ stream processes such as aquatic production/respiration and degassing. A challenge for further studies will be to disentangle the origin of stream water CO2 and quantify their relative importance.
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| 25. |
- Grabs, Thomas, et al.
(författare)
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Riparian zone hydrology and soil water total organic carbon (TOC) : implications for spatial variability and upscaling of lateral riparian TOC exports
- 2012
-
Ingår i: Biogeosciences. - : Copernicus GmbH. - 1726-4170 .- 1726-4189. ; 9:10, s. 3901-3916
-
Tidskriftsartikel (refereegranskat)abstract
- Groundwater flowing from hillslopes through riparian (near-stream) soils often undergoes chemical transformations that can substantially influence stream water chemistry. We used landscape analysis to predict total organic carbon (TOC) concentration profiles and groundwater levels measured in the riparian zone (RZ) of a 67 km2 catchment in Sweden. TOC exported laterally from 13 riparian soil profiles was then estimated based on the riparian flow-concentration integration model (RIM). Much of the observed spatial variability of riparian TOC concentrations in this system could be predicted from groundwater levels and the topographic wetness index (TWI). Organic riparian peat soils in forested areas emerged as hotspots exporting large amounts of TOC. These TOC fluxes were subject to considerable temporal variations caused by a combination of variable flow conditions and changing soil water TOC concentrations. Mineral riparian gley soils, on the other hand, were related to rather small TOC export rates and were characterized by relatively time-invariant TOC concentration profiles. Organic and mineral soils in RZs constitute a heterogeneous landscape mosaic that potentially controls much of the spatial variability of stream water TOC. We developed an empirical regression model based on the TWI to move beyond the plot scale and to predict spatially variable riparian TOC concentration profiles for RZs underlain by glacial till.
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| 26. |
- Griffiths, PG, et al.
(författare)
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Spatial precipitation frequency of an extreme event: the July 2006 mesoscale convective complexes and floods in southeastern Arizona
- 2009
-
Ingår i: Water resources research. - 0043-1397 .- 1944-7973. ; 45:W07419
-
Tidskriftsartikel (refereegranskat)abstract
- An extreme, multiday rainfall event over southeastern Arizona during 27–31 July 2006 caused record flooding and a historically unprecedented number of slope failures and debris flows in the Santa Catalina Mountains north of Tucson. An unusual synoptic weather pattern induced repeated nocturnal mesoscale convective systems over southeastern Arizona for five continuous days, generating multiday rainfall totals up to 360 mm. Analysis of point rainfall and weather radar data yielded storm totals for the southern Santa Catalina Mountains at 754 grid cells approximately 1 km 1 km in size. Precipitation intensity for the 31 July storms was not unusual for typical monsoonal precipitation in this region (recurrence interval (RI) < 1 year), but multiday rainfall where slope failures occurred had RI > 50 years and individual grid cells had RI exceeding 1000 years. The 31 July storms caused the watersheds to be essentially saturated following 4 days of rainfall.
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| 27. |
- Hamisi, Rajabu, 1978-
(författare)
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Modelling phosphorus dynamics in constructed wetlands upgraded with reactive filter media
- 2017
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Licentiatavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Developing low-cost and effective technologies to upgrade phosphorus (P) removal from the catchment runoffs and rural wastewater treatment facilities is one of the main research agendas to save the Baltic Sea from eutrophication. In Sweden, the construction of the constructed wetlands has been one of the environmental objectives for wastewater quality improvement in the small communities. However, the insufficiently understanding of the mechanisms underlying the process of phosphorus mobility and sorption in the constructed wetlands has limited design of the effective constructed wetlands. To provide the better understanding of sorption process in the catchment and constructed wetland system, this thesis used the GIS-based Soil and Water Assessment Tool (SWAT) to predict phosphorus mobility and identify the critical diffusing sources of phosphorus loss in the Oxunda catchment (Paper I). Then, the study developed the three-dimensional numerical Reactive TRAnsPort Model (RETRAP - 3D) in the COMSOL Multiphysics® for evaluating the long - term sorption processes and removal efficiencies of the porous reactive media for upgrading the performance of constructed wetlands (Paper II and III). The latter model coupled many physics equations to solve process of water flow, reaction kinetics and solute transport in the porous reactive adsorbent media for application in the constructed wetlands. The data from the field measurements and column experiments have been used to demonstrate the model simulation accuracy to capture the process of phosphorus sorption in the real environment. Modeling results ranked the phosphorus removal efficiency of the adsorbent media as follows: Polonite® (88 %), Filtralite P® (85%), BFS (62%), Wollastonite (57 %). The satisfactory agreement which obtained between the simulated outputs and measured data confirmed that the SWAT and RETRAP-3D are useful tools for describing various processes in the complicated system. However, further study is required to generate and validate more experimental data to evaluate the sensitivity of local parameters.
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| 28. |
- Harpold, A. A., et al.
(författare)
-
Laser vision : lidar as a transformative tool to advance critical zone science
- 2015
-
Ingår i: Hydrology and Earth System Sciences. - : Copernicus GmbH. - 1027-5606 .- 1607-7938. ; 19:6, s. 2881-2897
-
Tidskriftsartikel (refereegranskat)abstract
- Observation and quantification of the Earth's surface is undergoing a revolutionary change due to the increased spatial resolution and extent afforded by light detection and ranging (lidar) technology. As a consequence, lidar-derived information has led to fundamental discoveries within the individual disciplines of geomorphology, hydrology, and ecology. These disciplines form the cornerstones of critical zone (CZ) science, where researchers study how interactions among the geosphere, hydrosphere, and biosphere shape and maintain the 'zone of life', which extends from the top of unweathered bedrock to the top of the vegetation canopy. Fundamental to CZ science is the development of transdisciplinary theories and tools that transcend disciplines and inform other's work, capture new levels of complexity, and create new intellectual outcomes and spaces. Researchers are just beginning to use lidar data sets to answer synergistic, transdisciplinary questions in CZ science, such as how CZ processes co-evolve over long timescales and interact over shorter timescales to create thresholds, shifts in states and fluxes of water, energy, and carbon. The objective of this review is to elucidate the transformative potential of lidar for CZ science to simultaneously allow for quantification of topographic, vegetative, and hydrological processes. A review of 147 peer-reviewed lidar studies highlights a lack of lidar applications for CZ studies as 38 % of the studies were focused in geomorphology, 18 % in hydrology, 32 % in ecology, and the remaining 12 % had an interdisciplinary focus. A handful of exemplar transdisciplinary studies demonstrate lidar data sets that are well-integrated with other observations can lead to fundamental advances in CZ science, such as identification of feedbacks between hydrological and ecological processes over hillslope scales and the synergistic co-evolution of landscape-scale CZ structure due to interactions amongst carbon, energy, and water cycles. We propose that using lidar to its full potential will require numerous advances, including new and more powerful open-source processing tools, exploiting new lidar acquisition technologies, and improved integration with physically based models and complementary in situ and remote-sensing observations. We provide a 5-year vision that advocates for the expanded use of lidar data sets and highlights subsequent potential to advance the state of CZ science.
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| 29. |
- Harpold, A, et al.
(författare)
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Effects of preferential hydrological pathways in a galciated watershed in the Northeastern USA
- 2010
-
Ingår i: Vadose Zone Journal. - : Wiley. - 1539-1663. ; 9:2, s. 397-414
-
Tidskriftsartikel (refereegranskat)abstract
- Despite observational evidence of lateral preferential flow paths in northeastern U.S. watersheds, their effects on the sources of runoff remain unclear. An intense field survey was undertaken during the 2007 growing season to determine the sources of stream runoff from a 2.51 km2 watershed in the Catskill Mountains, New York State. Lateral preferential flow paths are caused by groundwater springs and soil piping in this region. A two-component hydrograph separation using δ18O showed that event water (rain water) was a significant source of runoff during nine rainfall events (from July to October). With these rainfall events, 14 to 37% of the volume and 18 to 49% of the peak streamflow was attributable to event water. Further, end-member mixing analysis (EMMA), using δ18O, Si, and dissolved organic carbon (DOC), showed that saturated areas accounted for 2 to 24% of the total volume and 4 to 59% of peak streamflow but that groundwater was the dominant source of runoff volume during all events. Field surveys of saturated areas also suggested that near-stream areas were insufficient to generate the observed stream chemistry during rainfall events larger than 8 mm. A connection with the hillside saturated areas was therefore required to explain the results of the hydrograph separations, which were corroborated by the timing of the transient (perched) groundwater and overland flow. The hydrometric measurements confirmed that hillside lateral preferential flow paths rapidly transported water to near-stream saturation areas during runoff events under relatively dry antecedent conditions. A qualitative comparison with conventional techniques for distributing variable saturation areas (VSA) using surface topography and soil transmissivity (i.e., topographic index and soil topographic index), which do not consider the effects of lateral preferential flow paths, demonstrated that typical parameterizations (on the order of <10−1 m) would not have the spatial resolution to represent the measured lateral preferential flow paths (on the order of <10−3 m). Overall, the results suggest that the lateral redistribution of water from hillside areas reduces the influence of surface topography and channel topology on the sources of stream runoff, a finding that is consistent with recent ones from other landscapes where glacial soils have coevolved with the terrestrial hydrology.
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| 30. |
- Heidbuechel, Ingo, et al.
(författare)
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Separating physical and meteorological controls of variable transit times in zero-order catchments
- 2013
-
Ingår i: Water resources research. - 0043-1397 .- 1944-7973. ; 49:11, s. 7644-7657
-
Tidskriftsartikel (refereegranskat)abstract
- We observed water fluxes and isotopic compositions within the subsurface of six small nested zero-order catchments over the course of three North American monsoon seasons and found that mean transit times (mTTs) were variable between seasons and different spatial patterns of mTTs emerged each year. For each monsoon season, it was possible to correlate mTTs with a different physical catchment property. In 2007, mTTs correlated best with mean soil depth, in 2008 soil hydraulic conductivity gained importance in explaining the variability and in 2009 planform curvature showed the best correlation. Differences in meteorological forcing between the three monsoon seasons explained the temporal variability of mTTs. In 2007, a series of precipitation events caused the storage capacity of the soils of some of the zero-order catchments to be exceeded. As a result those catchments started producing quick runoff (overland and macropore flow). In 2008, precipitation events were more evenly distributed throughout the season, soils did not saturate, runoff coefficients decreased because more water left the catchment via evapotranspiration and soil hydraulic conductivity became a stronger control since matrix flow dominated. The 2009 monsoon was unusually dry, the soil storage became depleted and water flowed mainly through bedrock pathways. Therefore, topographic parameters gained importance in determining how quickly water arrived at the catchment outlet. In order to improve our understanding of what controls mTTs we suggest a dimensionless number that helps identifying partitioning thresholds and sorts precipitation events into one of the three response modes that were observed in our zero-order catchments.
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| 31. |
- Heidbuechel, Ingo, et al.
(författare)
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The master transit time distribution of variable flow systems
- 2012
-
Ingår i: Water resources research. - 0043-1397 .- 1944-7973. ; 48, s. W06520-
-
Tidskriftsartikel (refereegranskat)abstract
- The transit time of water is an important indicator of catchment functioning and affects many biological and geochemical processes. Water entering a catchment at one point in time is composed of water molecules that will spend different amounts of time in the catchment before exiting. The next water input pulse can exhibit a totally different distribution of transit times. The distribution of water transit times is thus best characterized by a time-variable probability density function. It is often assumed, however, that the variability of the transit time distribution is negligible and that catchments can be characterized with a unique transit time distribution. In many cases this assumption is not valid because of variations in precipitation, evapotranspiration, and catchment water storage and associated (de) activation of dominant flow paths. This paper presents a general method to estimate the time-variable transit time distribution of catchment waters. Application of the method using several years of rainfall-runoff and stable water isotope data yields an ensemble of transit time distributions with different moments. The combined probability density function represents the master transit time distribution and characterizes the intra-annual and interannual variability of catchment storage and flow paths. Comparing the derived master transit time distributions of two research catchments (one humid and one semiarid) reveals differences in dominant hydrologic processes and dynamic water storage behavior, with the semiarid catchment generally reacting slower to precipitation events and containing a lower fraction of preevent water in the immediate hydrologic response.
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| 32. |
- Ijumulana, J.
(författare)
-
Spatial variability of geogenic contaminants in drinking water sources : Insights into hydrogeological controls, geospatial data for safe water supply and groundwater resource management
- 2022
-
Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- The presence of geogenic contaminants in drinking water is a major health concern in many parts of the world. The interaction of groundwater with different rock types and sediments in the natural geochemical environment play an important role in controlling their mobility. Due to limited resource allocations, water quality investigations are mostly limited only to the drinking water sources serving the communities. As a consequence, most aquifer systems remain unexplored in terms of groundwater quality through conventional methods. The present study aims to investigate the status of groundwater quality in the nine drainage basins of Tanzania focusing on the occurrence of fluoride (F¯) and other potentially toxic elements especially in the northern development zone (NDZ). The specific objectives were to model the spatial distribution of geogenic F¯- in groundwater systems and the health risk among the population as well as to evaluate the key influencing hydrogeological factors for the observed variability in F¯ concentrations in water sources using modern geospatial methods and technologies. Both literature and community perspectives indicate a serious problem in terms of F¯ in the Internal, Pangani, and Lake Victoria basins in the NDZ where the prevalence of mild to severe fluorosis is a health risk among the communities dependent on groundwater for drinking. In order to understand the spatial variability, machine learning methods were developed during this research by applying a combination of the concepts of spatial statistics, geostatistics, different Geographical Information Systems (GIS) tools as well as non-parametric methods to study the occurrence of geogenic contaminants in groundwater systems. Spatial statistical methods such as Moran’s I statistics and GIS tools revealed two positive significant high-high spatial patterns along the Pliocene-recent volcanic and the Mozambique belt as well as around Meru and Hanang’ stratovolcanoes in the northeast and southwestern part of the study regions, respectively. The positive low-low spatial patterns were determined around the major and minor rift valley escarpments both in the west and east of the East African Rift Valley (EARV) graben and around the stratovolcanoes within the graben. Other potentially toxic elements were found in elevated concentration around the Meru stratovolcano creating another risk of health concern to the communities which depend on such sources of drinking water. Factors controlling the spatial variability of fluoride in groundwater included, in the descending order, the mineralization, topography, tectonic processes, pH and water exchange between hydrogeological units during water movement. Other factors included depth to groundwater, well depth, screen depth and irrigation practices in the Sanya alluvial plain. The spatial heterogeneity of geological characteristics may lead to the spatial variability of various geogenic contaminants at spatial scales besides several other factors like topography, soil type, surface water-groundwater interaction, climate, volcanic activities, tectonic processes.The results of this study are important to the water safety planning implementation in the naturally contaminated aquifer systems especially in the EARV regions and volcanic areas.
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| 33. |
- Jantze, Elin J., 1983-, et al.
(författare)
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Spatial Variability of Dissolved Organic and Inorganic Carbon in Subarctic Headwater Streams
- 2015
-
Ingår i: Arctic, Antarctic and Alpine research. - 1523-0430 .- 1938-4246. ; 47:3, s. 529-546
-
Tidskriftsartikel (refereegranskat)abstract
- The subarctic landscape is composed of a complex mosaic of vegetation, geology and topography, which control both the hydrology and biogeochemistry of streams across space and time. We present a synoptic sampling campaign that aimed to estimate dissolved C export variability under low-flow conditions from a subarctic landscape. The results included measurements of stream discharge and concentrations of both dissolved organic carbon (DOC), dissolved inorganic carbon (DIC), and carbon dioxide (CO2) for 32 subcatchments of the Abiskojokka catchment in northern Sweden. For these subarctic headwater streams, we found that DOC, DIC and CO2 concentrations showed significant variability (p < 0.05) relative to catchment size, discharge, specific discharge, lithology, electrical conductivity, weathering products, and the estimated travel time of water through the subcatchment. Our results indicate that neither vegetation cover nor lithology alone could explain the concentrations and mass flux rates of DOC and DIC. Instead, we found that mass flux rates of DOC, DIC, and CO2 depended mainly on specific discharge and water travel time. Furthermore, our results demonstrate the importance of studying lateral carbon transport in combination with hydrological flow paths at small scales to establish a knowledge foundation applicable for expected carbon cycle and hydroclimatic shifts due to climate change.
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| 34. |
- Jantze, Elin J., et al.
(författare)
-
Subsurface release and transport of dissolved carbon in a discontinuous permafrost region
- 2013
-
Ingår i: Hydrology and Earth System Sciences. - : Copernicus GmbH. - 1027-5606 .- 1607-7938. ; 17:10, s. 3827-3839
-
Tidskriftsartikel (refereegranskat)abstract
- Subsurface hydrological flow pathways and advection rates through the landscape affect the quantity and timing of hydrological transport of dissolved carbon. This study investigates hydrological carbon transport through the subsurface to streams and how it is affected by the distribution of subsurface hydrological pathways and travel times through the landscape. We develop a consistent mechanistic, pathway- and travel time-based modeling approach for release and transport of dissolved organic carbon (DOC) and dissolved inorganic carbon (DIC). The model implications are tested against observations in the subarctic Abiskojokken catchment in northernmost Sweden (68 degrees 21'N, 18 degrees 49'E) as a field case example of a discontinuous permafrost region. The results show: (a) For DOC, both concentration and load are essentially flow-independent because their dynamics are instead dominated by the annual renewal and depletion. Specifically, the flow independence is the result of the small characteristic DOC respiration-dissolution time scale, in the range of 1 yr, relative to the average travel time of water through the subsurface to the stream. (b) For DIC, the load is highly flow-dependent due to the large characteristic weathering-dissolution time, much larger than 1 yr, relative to the average subsurface water travel time to the stream. This rate relation keeps the DIC concentration essentially flow-independent, and thereby less fluctuating in time than the DIC load.
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| 35. |
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| 36. |
- Jantze, Elin, 1983-
(författare)
-
Waterborne Carbon in Northern Streams : Controls on dissolved carbon transport across sub-arctic Scandinavia
- 2015
-
Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Waterborne carbon (C) forms an active and significant part of the global C cycle, which is important in theArctic where greater temperature increases and variability are anticipated relative to the rest of the globe withpotential implications for the C cycle. Understanding and quantification of the current processes governing themovement of C by connecting terrestrial and marine systems is necessary to better estimate future changes ofwaterborne C. This thesis investigates how the sub-arctic landscape influences the waterborne carbon exportby combining data-driven and modeling methods across spatial and temporal scales. First, a study of the stateof total organic carbon monitoring in northern Scandinavia was carried out using national-scale monitoringdata and detailed data from scientific literature. This study, which highlights the consistency in land cover andhydroclimatic controls on waterborne C across northern Scandinavia, was combined with three more detailedstudies leveraging field measurements and modeling. These focused on the Abisko region to provide insightto processes and mechanisms across scales. The thesis highlights that the governing transport mechanismsof dissolved organic and inorganic carbon (DOC and DIC respectively) are fundamentally different due todifferences in release rates associated with the nature of their terrestrial sources (geogenic and organic matterrespectively). As such, the DIC mass flux exhibits a high flow-dependence whereas DOC is relatively flowindependent.Furthermore, these investigations identified significant relationships between waterborne C andbiogeophysical as well as hydroclimatic variables across large to small spatial scales. This thesis demonstratesthat both surface and sub-surface hydrological processes (such as flow pathway distributions) in combinationwith distributions of C sources and associated release rates are prerequisite for understanding waterborne Cdynamics in northern streams.
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| 37. |
- Jaramillo, Fernando, et al.
(författare)
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Multimethod assessment of evapotranspiration shifts due to non-irrigated agricultural development in Sweden
- 2013
-
Ingår i: Journal of Hydrology. - : Elsevier BV. - 0022-1694 .- 1879-2707. ; 484, s. 55-62
-
Tidskriftsartikel (refereegranskat)abstract
- During the 20th century, Sweden underwent a persistent agricultural development. In this study, we use and combine historical hydroclimatic and agricultural data to investigate how this large scale change of land use, and subsequent intensification of crop production, affected regional hydrology in two adjacent Swedish drainage basins. We find a main increase of evapotranspiration (ET) as cultivated area and/or crop production increased during the period 1901-1940. Thereafter, ET stabilized at a new higher level. Comparison between the data given, water balance constrained ET quantification (ETwb), and a range of different comparative estimates of purely climate driven ET (ETclim) shows that only 31% of the steep 1901-1940 increase of ETwb can be explained by climate change alone. The remaining 69% of this ETwb shift, which occurred in both investigated drainage basins, is instead explainable to large degree by the regional land use conversion from seminatural grasslands to cultivated land and associated enhanced productivity of herbaceous species.
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| 38. |
- Jin, Hongxiao, et al.
(författare)
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Drone-Based Hyperspectral and Thermal Imagery for Quantifying Upland Rice Productivity and Water Use Efficiency after Biochar Application
- 2021
-
Ingår i: Remote Sensing. - : MDPI AG. - 2072-4292. ; 13:10
-
Tidskriftsartikel (refereegranskat)abstract
- Miniature hyperspectral and thermal cameras onboard lightweight unmanned aerial vehicles (UAV) bring new opportunities for monitoring land surface variables at unprecedented fine spatial resolution with acceptable accuracy. This research applies hyperspectral and thermal imagery from a drone to quantify upland rice productivity and water use efficiency (WUE) after biochar application in Costa Rica. The field flights were conducted over two experimental groups with bamboo biochar (BC1) and sugarcane biochar (BC2) amendments and one control (C) group without biochar application. Rice canopy biophysical variables were estimated by inverting a canopy radiative transfer model on hyperspectral reflectance. Variations in gross primary productivity (GPP) and WUE across treatments were estimated using light-use efficiency and WUE models respectively from the normalized difference vegetation index (NDVI), canopy chlorophyll content (CCC), and evapotranspiration rate. We found that GPP was increased by 41.9 +/- 3.4% in BC1 and 17.5 +/- 3.4% in BC2 versus C, which may be explained by higher soil moisture after biochar application, and consequently significantly higher WUEs by 40.8 +/- 3.5% in BC1 and 13.4 +/- 3.5% in BC2 compared to C. This study demonstrated the use of hyperspectral and thermal imagery from a drone to quantify biochar effects on dry cropland by integrating ground measurements and physical models.
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| 39. |
- Juston, John, et al.
(författare)
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Data-driven Nutrient-landscape Relationships across Regions and Scales
- 2016
-
Ingår i: Water environment research. - 1061-4303 .- 1554-7531. ; 88:11, s. 2023-2031
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Tidskriftsartikel (refereegranskat)abstract
- Previous studies have identified relationships between nutrient exports and upstream conditions, but have often disconnected interpretations from hydrological flows and changes. Here, we investigated basic relationships between largely flow-independent nutrient concentrations and two key descriptors of upstream landscape and human activity: population density and arable land cover. Consistent data were gathered from previous studies of the Baltic Sea and Mississippi River basins. These data span wide ranges of subcatchment scales, hydroclimatic conditions, and landscape characteristics. In general, investigated relationships were stronger in the Baltic than in the Mississippi region and stronger for total nitrogen (TN) than total phosphorous (TP) concentrations. However, TN concentration was both highly and consistently correlated to arable land cover across all scales and both regions. These findings support that TN export from catchments is dictated principally by retention and slow release from subsurface legacy stores while export TP concentrations appear to be dictated more by faster particulate surface transport.
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| 40. |
- Kalantari, Zahra, et al.
(författare)
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A method for mapping flood hazard along roads
- 2014
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Ingår i: Journal of Environmental Management. - : Elsevier BV. - 0301-4797 .- 1095-8630. ; 133, s. 69-77
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Tidskriftsartikel (refereegranskat)abstract
- A method was developed for estimating and mapping flood hazard probability along roads using road and catchment characteristics as physical catchment descriptors (PCDs). The method uses a Geographic Information System (GIS) to derive candidate PCDs and then identifies those PCDs that significantly predict road flooding using a statistical modelling approach. The method thus allows flood hazards to be estimated and also provides insights into the relative roles of landscape characteristics in determining road-related flood hazards. The method was applied to an area in western Sweden where severe road flooding had occurred during an intense rain event as a case study to demonstrate its utility. The results suggest that for this case study area three categories of PCDs are useful for prediction of critical spots prone to flooding along roads: i) topography, ii) soil type, and iii) land use. The main drivers among the PCDs considered were a topographical wetness index, road density in the catchment, soil properties in the catchment (mainly the amount of gravel substrate) and local channel slope at the site of a roadstream intersection. These can be proposed as strong indicators for predicting the flood probability in ungauged river basins in this region, but some care is needed in generalising the case study results other potential factors are also likely to influence the flood hazard probability. Overall, the method proposed represents a straightforward and consistent way to estimate flooding hazards to inform both the planning of future roadways and the maintenance of existing roadways.
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| 41. |
- Kalantari, Zahra
(författare)
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Adaptation of road drainage structures to climate change
- 2011
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Licentiatavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Climate change is expected to lead to more frequent extreme precipitation events, floods and changes in frost/thawing cycles. The frequency of road closures and other incidents such as flooding, landslides and roads being washed away will probably increase. Stronger demands will be placed on the function of road drainage systems. The overall aim of this thesis was to produce scientifically well-founded suggestions on adaptation of road drainage systems to climate change involving more frequent floods. The work began by examining current practice for road drainage systems in Sweden and gathering experience from professionals working with various problems concerning surface and subsurface drainage systems. Various hydrological models were then used to calculate the runoff from a catchment adjacent to a road and estimate changes in peak discharge and total runoff resulting from simulated land use measures. According to these survey and hydrological modelling studies, adaptation of road drainage systems to climate change can be grouped into two categories: i) institutional adaptation; and ii) technical adaptation. The main approaches in institutional adaptation are to: i) raise the awareness of expected climate change and its impact on drainage systems in transport administration and relevant stakeholders; ii) include adaptation measures in the existing funding programme of the transport administration; and iii) develop an evaluation tool and action plans concerning existing road drainage systems. Technical adaptation will involve ensuring that road constructions are adapted to more frequent extreme precipitation events and responsive to changes in activities and land use in areas adjacent to roads. Changes in climate variables will have effects on watershed hydrological responses and consequently influence the amount of runoff reaching roads. There is a great need for tools such as hydrological models to assess impacts on discharge dynamics, including peak flows. Improved communication between road managers and local actors in the forestry and agriculture sectors can be a means to reduce the impacts of, e.g., clear-cutting or badly managed farmland ditches.
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| 42. |
- Kalantari, Zahra, et al.
(författare)
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Modeller subjectivity and calibration impacts on hydrological model applications : an event-based comparison for a road-adjacent catchment in South-East Norway
- 2015
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Ingår i: Science of the Total Environment. - : Elsevier BV. - 0048-9697 .- 1879-1026. ; 502, s. 315-329
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Tidskriftsartikel (refereegranskat)abstract
- Identifying a ‘best’ performing hydrologic model in a practical sense is difficult due to the potential influences of modeller subjectivity on, for example, calibration procedure and parameter selection. This is especially true for model applications at the event scale where the prevailing catchment conditions can have a strong impact on apparent model performance and suitability. In this study, two lumped models (CoupModel and HBV) and two physically-based distributed models (LISEM and MIKE SHE) were applied to a small catchment upstream of a road in south-eastern Norway. All models were calibrated to a single event representing typical winter conditions in the region and then applied to various other winter events to investigate the potential impact of calibration period and methodology on model performance. Peak flow and event-based hydrographs were simulated differently by all models leading to differences in apparent model performance under this application. In this case-study, the lumped models appeared to be better suited for hydrological events that differed from the calibration event (i.e., events when runoff was generated from rain on non-frozen soils rather than from rain and snowmelt on frozen soil) while the more physical-based approaches appeared better suited during snowmelt and frozen soil conditions more consistent with the event-specific calibration. This was due to the combination of variations in subsurface conditions over the eight events considered, the subsequent ability of the models to represent the impact of the conditions (particularly when subsurface conditions varied greatly from the calibration event), and the different approaches adopted to calibrate the models. These results indicate that hydrologic models may not only need to be selected on a case-by-case basis but also have their performance evaluated on an application-by-application basis since how a model is applied can be equally important as inherent model structure.
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| 43. |
- Kalantari, Zahra, et al.
(författare)
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On the utilization of hydrological modelling for road drainage design under climate and land use change
- 2014
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Ingår i: Science of the Total Environment. - : Elsevier BV. - 0048-9697 .- 1879-1026. ; 475, s. 97-103
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Tidskriftsartikel (refereegranskat)abstract
- Road drainage structures are often designed using methods that do not consider process-based representations of a landscape's hydrological response. This may create inadequately sized structures as coupled land cover and climate changes can lead to an amplified hydrological response. This study aims to quantify potential increases of runoff in response to future extreme rain events in a 61 km(2) catchment (40% forested) in southwest Sweden using a physically-based hydrological modelling approach. We simulate peak discharge and water level (stage) at two types of pipe bridges and one culvert, both of which are commonly used at Swedish road/stream intersections, under combined forest clear-cutting and future climate scenarios for 2050 and 2100. The frequency of changes in peak flow and water level varies with time (seasonality) and storm size. These changes indicate that the magnitude of peak flow and the runoff response are highly correlated to season rather than storm size. In all scenarios considered, the dimensions of the current culvert are insufficient to handle the increase in water level estimated using a physically-based modelling approach. It also appears that the water level at the pipe bridges changes differently depending on the size and timing of the storm events. The findings of the present study and the approach put forward should be considered when planning investigations on and maintenance for areas at risk of high water flows. In addition, the research highlights the utility of physically-based hydrological models to identify the appropriateness of road drainage structure dimensioning
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| 44. |
- Kalantari, Zahra, et al.
(författare)
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Quantifying the hydrological impact of simulated changes in land use on peak discharge in a small catchment
- 2014
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Ingår i: Science of the Total Environment. - : Elsevier BV. - 0048-9697 .- 1879-1026. ; 466, s. 741-754
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Tidskriftsartikel (refereegranskat)abstract
- A physically-based, distributed hydrological model (MIKE SHE) was used to quantify overland runoff in response to four extreme rain events and four types of simulated land use measure in a catchment in Norway. The current land use in the catchment comprises arable lands, forest, urban areas and a stream that passes under a motorway at the catchment outlet. This model simulation study demonstrates how the composition and configuration of land use measures affect discharge at the catchment outlet differently in response to storms of different sizes. For example, clear-cutting on 30% of the catchment area produced a 60% increase in peak discharge and a 10% increase in total runoff resulting from a 50-year storm event in summer, but the effects on peak discharge were less pronounced during smaller storms. Reforestation of 60% of the catchment area was the most effective measure in reducing peak flows for smaller (2-, 5- and 10-year) storms. Introducing grassed waterways reduced water velocity in the stream and resulted in a 28% reduction in peak flow at the catchment outlet for the 50-year storm event. Overall, the results indicate that the specific effect of land use measures on catchment discharge depends on their spatial distribution and on the size and timing of storm events.
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| 45. |
- Kalumanga, Elikana, 1975-
(författare)
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How elephants utilize a miombo-wetland ecosystem in Ugalla landscape, Western Tanzania
- 2015
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- African elephants are ‘keystone’ species with respect to biodiversity conservation in Africa since they maintain habitats that support several animal communities by changing vegetation structure through foraging and by dispersing seeds between landscapes. Elephants are also ‘flagship’ species because, given their impressive size, they can make people sympathetic and stimulate local and international concerns for their protection. Economically, elephants contribute to national revenues as tourists are willing to pay to watch them. Despite all these factors, little is known however about elephant movement and how they utilize resources, especially in miombo-wetland ecosystems. This thesis investigates how elephants utilize resources in a miombo-wetland ecosystem in the Ugalla landscape of Western Tanzania over different protected areas containing different resource users. Using Global Positioning System (GPS) collars fitted to six elephants, it was observed that some elephant families are not confined in one protected area in the Ugalla landscape. Rather, they moved readily between different protected areas. Elephant movements were restricted to areas near the rivers, especially the Ugalla River, during the dry season and were dispersed widely during the wet season. As they move, elephants in the miombo woodlands of Ugalla selected the most abundant woody plants for browsing. Common to many woody plants, the browsed plants were short of mineral nutrients (e.g., sodium, calcium). Elephants obtained additional minerals by eating soils from certain termite mounds. Soils from termite mounds are richer in mineral elements (e.g., sodium, calcium, iron) compared to soils from the surrounding flood plain or compared to the browsed plants. However, the recorded termite mounds from which elephants eat soils were not evenly distributed in the landscape but confined mainly to the flood plains in the Ugalla Game Reserve. The Ugalla River, which is the main source of water for the elephants and other animals and also supports fishing activities by the local people in Ugalla during the dry seasons, is infested by the water hyacinth (Eichhornia crassipes). Such infestation potentially limits access to these precious surface water supplies. In addition at the regional level, the Ugalla River is among the major rivers that flow into the Lake Tanganyika which is shared by the countries of Tanzania, Burundi, Democratic Republic of Congo and Zambia. Thus, the spread of water hyacinth if left unchecked threatens to impact Lake Tanganyika, affecting many countries and ecosystem services. This thesis highlights that sustainable conservation of biodiversity in different protected areas in the Ugalla landscape requires an integrated management approach that will embrace conservation of different interrelated landscape resources required by both wildlife and the rural poor populations for their livelihoods. Regular coordinated wildlife anti-poaching patrols should be initiated across the entire Ugalla landscape because the elephants, among other wildlife, utilize different protected areas in Ugalla. Local communities should also be engaged in conservation initiatives (e.g., controlling the spread of the water hyacinth) as these directly impact local livelihoods.
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| 46. |
- Karlsson, Caroline, 1984-, et al.
(författare)
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Natural hazard susceptibility assessment for road planning using spatial multi-criteria analysis
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Annan publikation (övrigt vetenskapligt/konstnärligt)abstract
- Inadequate infrastructural networks can be detrimental to a society if transport between locations becomes hindered or delayed, especially due to natural hazards which are more difficult to control. Thus determining natural hazard susceptible areas and incorporating them in the initial planning process, may reduce infrastructural damages in the long run. The objective of this study was to evaluate the usefulness of expert judgements for assessing natural hazard susceptibility through a spatial multi-criteria analysis (SMCA) approach using hydrological, geological and land use factors. To utilize SMCA for decision support, an analytic hierarchy process (AHP) was adopted where expert judgements were evaluated individually and in an aggregated manner. The estimates of susceptible areas were then compared with the methods Weighted linear combination (WLC) using equal weights and Factor interaction method (FIM). Results showed that inundation received the highest percentage of susceptibility. Using expert judgement showed to perform almost same as Equal weighting where the difference (i.e. average) in susceptibility between the two for inundation was around 4%. Results also showed that downscaling could negatively affect the susceptibility assessment and be highly misleading. Susceptibility assessment through SMCA is useful for decision support in early road planning despite its limitation to selection and use of decision rule and criteria. A natural hazard SMCA could be used to indicate areas where more investigations need to be undertaken from a natural hazard point of view, and to identify areas thought to have higher susceptibility along existing roads where mitigation measures could be targeted after in-situ investigations.
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| 47. |
- Karlsson, Caroline, 1984-, et al.
(författare)
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Natural Hazard Susceptibility Assessment for Road Planning Using Spatial Multi-Criteria Analysis
- 2017
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Ingår i: Environmental Management. - : Springer Science and Business Media LLC. - 0364-152X .- 1432-1009. ; 60:5, s. 823-851
-
Tidskriftsartikel (refereegranskat)abstract
- Inadequate infrastructural networks can be detrimental to society if transport between locations becomes hindered or delayed, especially due to natural hazards which are difficult to control. Thus determining natural hazard susceptible areas and incorporating them in the initial planning process, may reduce infrastructural damages in the long run. The objective of this study was to evaluate the usefulness of expert judgments for assessing natural hazard susceptibility through a spatial multi-criteria analysis approach using hydrological, geological, and land use factors. To utilize spatial multi-criteria analysis for decision support, an analytic hierarchy process was adopted where expert judgments were evaluated individually and in an aggregated manner. The estimates of susceptible areas were then compared with the methods weighted linear combination using equal weights and factor interaction method. Results showed that inundation received the highest susceptibility. Using expert judgment showed to perform almost the same as equal weighting where the difference in susceptibility between the two for inundation was around 4%. The results also showed that downscaling could negatively affect the susceptibility assessment and be highly misleading. Susceptibility assessment through spatial multi-criteria analysis is useful for decision support in early road planning despite its limitation to the selection and use of decision rules and criteria. A natural hazard spatial multi-criteria analysis could be used to indicate areas where more investigations need to be undertaken from a natural hazard point of view, and to identify areas thought to have higher susceptibility along existing roads where mitigation measures could be targeted after in-situ investigations.
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| 48. |
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| 49. |
- Karlsson, Johanna Mård, 1979-, et al.
(författare)
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Temporal Behavior of Lake Size-Distribution in a Thawing Permafrost Landscape in Northwestern Siberia
- 2014
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Ingår i: Remote Sensing. - : MDPI AG. - 2072-4292. ; 6:1, s. 621-636
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Tidskriftsartikel (refereegranskat)abstract
- Arctic warming alters regional hydrological systems, as permafrost thaw increases active layer thickness and in turn alters the pathways of water flow through the landscape. Further, permafrost thaw may change the connectivity between deeper and shallower groundwater and surface water altering the terrestrial water balance and distribution. Thermokarst lakes and wetlands in the Arctic offer a window into such changes as these landscape elements depend on permafrost and are some of the most dynamic and widespread features in Arctic lowland regions. In this study we used Landsat remotely sensed imagery to investigate potential shifts in thermokarst lake size-distributions, which may be brought about by permafrost thaw, over three distinct time periods (1973, 1987-1988, and 2007-2009) in three hydrological basins in northwestern Siberia. Results revealed fluctuations in total area and number of lakes over time, with both appearing and disappearing lakes alongside stable lakes. On the whole basin scales, there is no indication of any sustained long-term change in thermokarst lake area or lake size abundance over time. This statistical temporal consistency indicates that spatially variable change effects on local permafrost conditions have driven the individual lake changes that have indeed occurred over time. The results highlight the importance of using multi-temporal remote sensing data that can reveal complex spatiotemporal variations distinguishing fluctuations from sustained change trends, for accurate interpretation of thermokarst lake changes and their possible drivers in periods of climate and permafrost change.
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| 50. |
- Keys, Patrick W.
(författare)
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Probing the Precipitationshed : A quantification of the biophysical dimensions of terrestrial moisture recycling
- 2015
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Licentiatavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Terrestrial moisture recycling is the phenomena whereby water evaporates from the land surface, travels through the atmosphere, and fall as precipitation downwind. The interaction of societies with this branch of the hydrological cycle, though critical to the productive functioning of ecosystems around the planet, remains poorly understood. With this thesis, I aim to improve our understanding of terrestrial moisture recycling by exploring two dimensions of the phenomena. First, I build on earlier work that quantified terrestrial moisture recycling relationships using precipitationsheds, defined as the upwind land surface and atmosphere that contributes evaporation to downwind precipitation. In other words, the precipitationshed can be thought of as a watershed of the sky. In this thesis, I quantify the variability of the spatial pattern of the precipitationshed in order to understand whether the same or different regions recycle moisture every year (Paper 1). The key finding from this analysis is that there is high overall stability in the regions that provide evaporation to the downwind precipitationshed, such that there is a core area of evaporation contribution that provides a significant volume of moisture to downwind areas, every year. Second, I synthesize terrestrial moisture recycling insights using an ecosystem services framework, by defining and quantifying the biophysical structure, function, and ecosystem service of terrestrial moisture recycling (Paper II). I define terrestrial moisture recycling as a regulating ecosystem service, with the vegetation in upwind areas providing the critical role of regulating the amount of evaporation that enters the atmosphere, and that is available downwind for precipitation. My key findings are that vegetation provides important regulation of terrestrial moisture recycling in certain areas globally, but less so in others, as well as there being a clear and well-defined decreasing importance of terrestrial moisture recycling with distance from the evaporation source region. Since we know from Paper 1 that terrestrial moisture recycling relationships are persistent in time, it implies that there is a relatively stable set of upwind social-ecological systems that provide terrestrial moisture regulation to downwind social-ecological systems. Thus, using the classification of terrestrial moisture recycling as an ecosystem service, we can begin to unpack the social dimensions of the robust biophysical relationships between these upwind and downwind systems. The key next steps in this research will be to further characterize the providers and beneficiaries of terrestrial moisture recycling, the value of these services, and how, if at all, terrestrial moisture recycling may be governed.
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