| 1. |
- Montanari, A., et al.
(författare)
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"Panta Rhei-Everything Flows" : Change in hydrology and society-The IAHS Scientific Decade 2013-2022
- 2013
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Ingår i: Hydrological Sciences Journal. - : Taylor & Francis Group. - 0262-6667 .- 2150-3435. ; 58:6, s. 1256-1275
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Tidskriftsartikel (refereegranskat)abstract
- The new Scientific Decade 2013-2022 of IAHS, entitled Panta RheiEverything Flows, is dedicated to research activities on change in hydrology and society. The purpose of Panta Rhei is to reach an improved interpretation of the processes governing the water cycle by focusing on their changing dynamics in connection with rapidly changing human systems. The practical aim is to improve our capability to make predictions of water resources dynamics to support sustainable societal development in a changing environment. The concept implies a focus on hydrological systems as a changing interface between environment and society, whose dynamics are essential to determine water security, human safety and development, and to set priorities for environmental management. The Scientific Decade 2013-2022 will devise innovative theoretical blueprints for the representation of processes including change and will focus on advanced monitoring and data analysis techniques. Interdisciplinarity will be sought by increased efforts to connect with the socio-economic sciences and geosciences in general. This paper presents a summary of the Science Plan of Panta Rhei, its targets, research questions and expected outcomes.
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| 2. |
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| 3. |
- Jonker, L., et al.
(författare)
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A regional and multi-faceted approach to postgraduate water education - the WaterNet experience in Southern Africa
- 2012
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Ingår i: Hydrology and Earth System Sciences. - : Copernicus GmbH. - 1027-5606 .- 1607-7938. ; 16:11, s. 4225-4232
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Tidskriftsartikel (refereegranskat)abstract
- This paper reports the experience of a regional network of academic departments involved in water education that started as a project and evolved, over a period of 12 yr, into an independent network organisation. The paper pursues three objectives. First, it argues that it makes good sense to organise postgraduate education and research on water resources on a regional scale and presents the WaterNet experience as an example that a regional approach can work. Second, it presents preliminary findings and conclusions that the regional approach presented by WaterNet did make a contribution to the capacity needs of the region both in terms of management and research capacity. Third, it draws two generalised lessons from the WaterNet experience. Lesson one pertains to the importance of legitimate ownership and an accountability structure for network effectiveness. Lesson two is related to the financial and intellectual resources required to jointly developing educational programmes through shared experience.
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| 4. |
- Keys, Patrick W., et al.
(författare)
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Analyzing precipitationsheds to understand the vulnerability of rainfall dependent regions
- 2012
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Ingår i: Biogeosciences. - : Copernicus GmbH. - 1726-4170 .- 1726-4189. ; 9:2, s. 733-746
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Tidskriftsartikel (refereegranskat)abstract
- It is well known that rivers connect upstream and downstream ecosystems within watersheds. Here we describe the concept of precipitationsheds to show how upwind terrestrial evaporation source areas contribute moisture for precipitation to downwind sink regions. We illustrate the importance of upwind land cover in precipitationsheds to sustain precipitation in critically water stressed downwind areas, specifically dryland agricultural areas. We first identify seven regions where rainfed agriculture is particularly vulnerable to reductions in precipitation, and then map their precipitationsheds. We then develop a framework for qualitatively assessing the vulnerability of precipitation for these seven agricultural regions. We illustrate that the sink regions have varying degrees of vulnerability to changes in upwind evaporation rates depending on the extent of the precipitationshed, source region land use intensity and expected land cover changes in the source region.
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| 5. |
- Rockström, Johan, et al.
(författare)
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The unfolding water drama in the Anthropocene : towards a resilience-based perspective on water for global sustainability
- 2014
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Ingår i: Ecohydrology. - : Wiley. - 1936-0584 .- 1936-0592. ; 7:5, s. 1249-1261
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Tidskriftsartikel (refereegranskat)abstract
- The human influence on the global hydrological cycle is now the dominant force behind changes in water resources across the world and in regulating the resilience of the Earth system. The rise in human pressures on global freshwater resources is in par with other anthropogenic changes in the Earth system (from climate to ecosystem change), which has prompted science to suggest that humanity has entered a new geological epoch, the Anthropocene. This paper focuses on the critical role of water for resilience of social-ecological systems across scales, by avoiding major regime shifts away from stable environmental conditions, and in safeguarding life-support systems for human wellbeing. It highlights the dramatic increase of water crowding: near-future challenges for global water security and expansion of food production in competition with carbon sequestration and biofuel production. It addresses the human alterations of rainfall stability, due to both land-use changes and climate change, the ongoing overuse of blue water, reflected in river depletion, expanding river basin closure, groundwater overexploitation and water pollution risks. The rising water turbulence in the Anthropocene changes the water research and policy agenda, from a water-resource efficiency to a water resilience focus. This includes integrated land and water stewardship to sustain wetness-dependent ecological functions at the landscape scale and a stronger emphasis on green water management for ecosystem services. A new paradigm of water governance emerges, encouraging land-use practices that explicitly take account of the multifunctional roles of water, with adequate attention to planetary freshwater boundaries and cross-scale interactions.
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| 6. |
- Temesgen, Melesse, et al.
(författare)
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Assessment of strip tillage systems for maize production in semi-arid Ethiopia : effects on grain yield, water balance and water productivity
- 2012
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Ingår i: Physics and Chemistry of the Earth. - : Elsevier BV. - 1474-7065 .- 1873-5193. ; 47-48, s. 156-165
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Tidskriftsartikel (refereegranskat)abstract
- The Maresha, the traditional Ethiopian plow, requires repeated cross-plowing which causes increased surface runoff, less infiltration and hence lower water availability to crops. The main reasons for increased surface runoff and reduced infiltration are plowing along the slope and the formation of a plow pan at shallow depths. Conservation tillage is seen as a way to alleviate these problems. The widely advocated zero-tillage, however, is not feasible for smallholder farmers in semi-arid regions of Ethiopia because of difficulties in maintaining adequate soil cover, the practice of communal grazing, and high costs of herbicides. Strip tillage systems, on the other hand, may offer a solution. This study was initiated to test strip tillage systems and to evaluate the impacts of new tillage systems on the water balance and grain yields of maize. Experiments have been conducted in a semi-arid area called Melkawoba in the central Rift Valley of Ethiopia during 2003–2005. Strip tillage systems involved cultivation along planting lines at a spacing of 0.75 m using the Maresha plow followed by subsoiling along the same lines (STS) or without subsoiling (ST). Results have been compared with traditional tillage involving 3–4 overpasses with the Maresha plow (CONV). Soil moisture has been monitored to a depth of 1.8 m using a Time Domain Reflectometer (TDR) while surface runoff has been measured using a specially designed rectangular trough installed at the bottom of each plot. STS resulted in the least surface runoff (Qs = 18 mm season−1) and the highest grain yields (Y = 2130 kg ha−1) followed by ST (Qs = 26 mm season−1, Y = 1840 kg ha−1) and CONV (Qs = 43 mm season−1, Y = 1720 kg ha−1) provided sowing was carried out within a week after subsoiling. Thus, STS resulted in the highest water productivity, WP = 0.60 kg m−3, followed by ST (WP = 0.52 kg m−3) and CONV (WP = 0.48 kg m−3). The main conclusion of the paper is that even in dry areas reasonable yields can be obtained provided moisture conservation in the root zone is guaranteed. In this regard subsoiling is essential. Moreover, it is concluded that the time between subsoiling and planting is a key factor and should not exceed one week.
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| 7. |
- van der Ent, R. J., et al.
(författare)
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Contrasting roles of interception and transpiration in the hydrological cycle - Part 2 : Moisture recycling
- 2014
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Ingår i: Earth System Dynamics. - : Copernicus GmbH. - 2190-4979 .- 2190-4987. ; 5:2, s. 471-489
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Tidskriftsartikel (refereegranskat)abstract
- The contribution of land evaporation to local and remote precipitation (i.e. moisture recycling) is of significant importance to sustain water resources and ecosystems. But how important are different evaporation components in sustaining precipitation? This is the first paper to present moisture recycling metrics for partitioned evaporation. In the companion paper Wang-Erlandsson et al. (2014) (hereafter Part 1), evaporation was partitioned into vegetation interception, floor interception, soil moisture evaporation and open-water evaporation (constituting the direct, purely physical fluxes, largely dominated by interception), and transpiration (delayed, biophysical flux). Here, we track these components forward as well as backward in time. We also include age tracers to study the atmospheric residence times of these evaporation components. We present a new image of the global hydrological cycle that includes quantification of partitioned evaporation and moisture recycling as well as the atmospheric residence times of all fluxes. We demonstrate that evaporated interception is more likely to return as precipitation on land than transpired water. On average, direct evaporation (essentially interception) is found to have an atmospheric residence time of 8 days, while transpiration typically resides for 9 days in the atmosphere. The process scale over which evaporation recycles is more local for interception compared to transpiration; thus interception generally precipitates closer to its evaporative source than transpiration, which is particularly pronounced outside the tropics. We conclude that interception mainly works as an intensifier of the local hydrological cycle during wet spells and wet seasons. On the other hand, transpiration remains active during dry spells and dry seasons and is transported over much larger distances downwind, where it can act as a significant source of moisture. Thus, as various land-use types can differ considerably in their partitioning between interception and transpiration, our results stress that land-use changes (e.g. forest-to-cropland conversion) do not only affect the magnitude of moisture recycling, but could also influence the moisture recycling patterns and lead to a redistribution of water resources. As such, this research highlights that land-use changes can have complex effects on the atmospheric branch of the hydrological cycle.
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| 8. |
- Wang-Erlandsson, Lan, et al.
(författare)
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Contrasting roles of interception and transpiration in the hydrological cycle - Part 1 : Temporal characteristics over land
- 2014
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Ingår i: Earth System Dynamics. - : Copernicus GmbH. - 2190-4979 .- 2190-4987. ; 5:2, s. 441-469
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Tidskriftsartikel (refereegranskat)abstract
- Moisture recycling, the contribution of terrestrial evaporation to precipitation, has important implications for both water and land management. Although terrestrial evaporation consists of different fluxes (i.e. transpiration, vegetation interception, floor interception, soil moisture evaporation, and open-water evaporation), moisture recycling (terrestrial evaporation-precipitation feedback) studies have up to now only analysed their combined total. This paper constitutes the first of two companion papers that investigate the characteristics and roles of different evaporation fluxes for land-atmosphere interactions. Here, we investigate the temporal characteristics of partitioned evaporation on land and present STEAM (Simple Terrestrial Evaporation to Atmosphere Model) - a hydrological land-surface model developed to provide inputs to moisture tracking. STEAM estimates a mean global terrestrial evaporation of 73 900 km(3)year(-1), of which 59% is transpiration. Despite a relatively simple model structure, validation shows that STEAM produces realistic evaporative partitioning and hydrological fluxes that compare well with other global estimates over different locations, seasons, and land-use types. Using STEAM output, we show that the terrestrial residence timescale of transpiration (days to months) has larger inter-seasonal variation and is substantially longer than that of interception (hours). Most transpiration occurs several hours or days after a rain event, whereas interception is immediate. In agreement with previous research, our simulations suggest that the vegetation's ability to transpire by retaining and accessing soil moisture at greater depth is critical for sustained evaporation during the dry season. We conclude that the differences in temporal characteristics between evaporation fluxes are substantial and reasonably can cause differences in moisture recycling, which is investigated more in the companion paper (van der Ent et al., 2014, hereafter Part 2).
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