| 1. |
- Darracq, Amelie, et al.
(författare)
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Scale and model resolution effects on the distributions of advective solute travel times in catchments
- 2010
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Ingår i: Hydrological Processes. - : John Wiley & Sons, Ltd.. - 0885-6087 .- 1099-1085. ; 24:12, s. 1697-1710
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Tidskriftsartikel (refereegranskat)abstract
- Advective solute travel times and their distributions in hydrological catchments are useful descriptors of the dynamics and variation of the physical mass transport among and along the different source-to-recipient pathways of solute transport through the catchments. This article investigates the scale dependence and the effects of model and data resolution on the quantification of advective travel times and their distributions in the Swedish catchment areas of Norrström and Forsmark. In the surface water networks of the investigated (sub)catchments, the mean advective travel time increases with (sub)catchment scale, whereas the relative travel time variability around the mean value (coefficient of variation, CV) is scale-invariant and insensitive to model resolution. In the groundwater and for the whole (sub)catchments, both the mean value and the CV of travel times are scale-invariant, but sensitive to model resolution and accuracy. Such quantifications and results of advective travel times constitute important steps in the development of improved understanding and modelling of nutrient, pollutant and tracer transport through catchments.
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| 2. |
- Li, Meijun, et al.
(författare)
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Evidence of field-scale shifts in transpiration dynamics following bark beetle infestation : Stomatal conductance responses
- 2024
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Ingår i: Hydrological Processes. - 0885-6087 .- 1099-1085. ; 38:5
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Tidskriftsartikel (refereegranskat)abstract
- Amplified eruptive outbreaks of bark beetles as a consequence of climate change can cause tree mortality that significantly affects terrestrial water and carbon fluxes. However, the lack of field-scale observations of underlying physiological mechanisms currently hampers the expression of such ecosystem disturbances in predictive modelling. Based on a unique flux tower dataset from a subalpine forest located in the Rocky Mountains, mechanisms of stomatal response to an extensive bark beetle outbreak were investigated using various models and parametrizations. The datasets cover a decade, including the periods of pre-infestation, infestation, and post-infestation. Field measurements showed considerable decreases in evapotranspiration (ET), transpiration (T), and leaf area index (LAI) during the two-year infestation period compared to the pre-infestation period. Model interpretations of observed water and carbon fluxes indicated that the overall reductions in T were not solely due to decreased LAI, but also to changes in physiological behaviours. The summer season's canopy-scale stomatal conductance was significantly reduced during the infestation period, from 0.0018 to 0.0011 m s−1. One primary reason for the observed variations is likely that the bark beetle infestation hampers the water transport in the xylem. The damage of xylem has important implications for water use efficiency (WUE), which also significantly influences the parameterization of stomatal conductance. When using stomatal conductance models to forecast ecosystem dynamics, it is crucial to recalibrate the model's parameters to ensure the accurate depiction of stomatal dynamics during various infestation periods. The neglect of the temporal variability of canopy-scale stomatal conductance under ecosystem disturbances (e.g., bark beetle infestations) in current earth system models, therefore, requires specific attention in assessments of large-scale water and carbon balances.
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| 3. |
- Lyon, Steve W., et al.
(författare)
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Interpreting characteristic drainage timescale variability across Kilombero Valley, Tanzania
- 2015
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Ingår i: Hydrological Processes. - : Wiley. - 0885-6087 .- 1099-1085. ; 29:8, s. 1912-1924
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Tidskriftsartikel (refereegranskat)abstract
- We explore seasonal variability and spatiotemporal patterns in characteristic drainage timescale (K) estimated from river discharge records across the Kilombero Valley in central Tanzania. K values were determined using streamflow recession analysis with a Brutsaert-Nieber solution to the linearized Boussinesq equation. Estimated K values were variable, comparing between wet and dry seasons for the relatively small catchments draining upland positions. For the larger catchments draining through valley bottoms, K values were typically longer and more consistent across seasons. Variations in K were compared with long-term averaged, Moderate-resolution Imaging Spectroradiometer-derived monthly evapotranspiration. Although the variations in K were potentially related to evapotranspiration, the influence of data quality and analysis procedure could not be discounted. As such, even though recession analysis offers a potential approach to explore aquifer release timescales and thereby gain insight to a region's hydrology to inform water resources management, care must be taken when interpreting spatiotemporal shifts in K in connection with process representation in regions like the Kilombero Valley.
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| 4. |
- Pietroń, Jan, et al.
(författare)
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Sedimentation patterns in the Selenga River delta under changing hydroclimatic conditions
- 2018
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Ingår i: Hydrological Processes. - : Wiley. - 0885-6087 .- 1099-1085. ; 32:2, s. 278-292
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Tidskriftsartikel (refereegranskat)abstract
- The Selenga River delta (Russia) is a large (>600km(2)) fluvially dominated fresh water system that transfers water and sediment from an undammed drainage basin into Lake Baikal, a United Nations Educational, Scientific, and Cultural Organization World Heritage Site. Through sedimentation processes, the delta and its wetlands provide important environmental services, such as storage of sediment-bound pollutants (e.g., metals), thereby reducing their input to Lake Baikal. However, in the Selenga River delta and many other deltas of the world, there is a lack of knowledge regarding impacts of potential shifts in the flow regime (e.g., due to climate change and other anthropogenic impacts) on sedimentation processes, including sediment exchanges between deltaic channels and adjacent wetlands. This study uses field measurements of water velocities and sediment characteristics in the Selenga River delta, investigating conditions of moderate discharge, which have become more frequent over the past decades (at the expense of peak flows, Q>1,350m(3)s(-1)). The aims are to determine if the river system under moderate flow conditions is capable of supporting sediment export from the main distributary channels of the delta to the adjacent wetlands. The results show that most of the deposited sediment outside of the deltaic channels is characterized by a large proportion of silt and clay material (i.e., <63m). For example, floodplain lakes function as sinks of very fine sediment (e.g., 97% of sediment by weight<63m). Additionally, bed material sediment is found to be transported outside of the channel margins during conditions of moderate and high water discharge conditions (Q1,000m(3)s(-1)). Submerged banks and marshlands located in the backwater zone of the delta accumulate sediment during such discharges, supporting wetland development. Thus, these regions likely sequester various metals bound to Selenga River sediment.
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| 5. |
- Thorslund, Josefin, et al.
(författare)
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Solute evidence for hydrological connectivity of geographically isolated wetlands
- 2018
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Ingår i: Land Degradation and Development. - : Wiley. - 1085-3278 .- 1099-145X. ; 29:11, s. 3954-3962
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Tidskriftsartikel (refereegranskat)abstract
- Hydrological connectivity describes the water-mediated transfer of mass, energy, and organisms between landscape elements and is the foundation for understanding how individual elements such as wetlands and streams integrate to support ecosystem services and nature-based solutions in the landscape. Hydrological connectivity of geographically isolated wetlands (GIWs)-that is, wetlands without persistent surface water connections-is particularly poorly understood. To better understand GIW hydrological connectivity, we use a novel chloride mass-balance approach to quantify the local runoff generation (defined as precipitation minus evapotranspiration, assuming negligible long-term water storage) for 260 GIW subcatchments across North America. To evaluate hydrological connectivity, we compare the estimated local runoff from GIW subcatchments with the catchment-average runoff. These comparisons provide three novel insights regarding the magnitude and variability of GIW hydrological connectivity. First, across 10 study regions, GIW subcatchments generate runoff at 120% of the mean catchment rate, implying they are well-connected elements of the larger hydrologic landscape. Second, there is substantial heterogeneity in runoff generation among GIW subcatchments, which may enable support for a wide array of ecosystem functions and services. Finally, observed heterogeneity in runoff generation was largely uncorrelated to simple linear geographic predictors, indicating that GIW landscape position cannot reliably predict hydrological connectivity. In stark contrast to a priori legal assumptions that GIWs exhibit low or no hydrological connectivity, our results suggest that GIW subcatchments are active landscape features in runoff generation.
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