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- McDonnell, J.J., et al.
(författare)
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How old is streamwater? : Open questions in catchment transit time conceptualization, modelling and analysis
- 2010
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Ingår i: Hydrological Processes. - : John Wiley & Sons. - 0885-6087 .- 1099-1085. ; 24:12, s. 1745-1754
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Tidskriftsartikel (refereegranskat)abstract
- The time water spends travelling subsurface through a catchment to the stream network (i.e. the catchment water transit time) fundamentally describes the storage, flow pathway heterogeneity and sources of water in a catchment. The distribution of transit times reflects how catchments retain and release water and solutes that in turn set biogeochemical conditions and affect contamination release or persistence. Thus, quan- tifying the transit time distribution provides an important constraint on biogeochemical processes and catchment sensitivity to anthropogenic inputs, contamination and land-use change. Although the assumptions and limitations of past and present transit time modelling approaches have been recently reviewed (McGuire and McDonnell, 2006), there remain many fundamental research challenges for understanding how transit time can be used to quantify catchment flow processes and aid in the development and testing of rainfall–runoff models. In this Commen- tary study, we summarize what we think are the open research questions in transit time research. These thoughts come from a 3-day workshop in January 2009 at the International Atomic Energy Agency in Vienna. We attempt to lay out a roadmap for this work for the hydrological commu- nity over the next 10 years. We do this by first defining what we mean (qualitatively and quantitatively) by transit time and then organize our vision around needs in transit time theory, needs in field studies of tran- sit time and needs in rainfall – runoff modelling. Our goal in presenting this material is to encourage widespread use of transit time information in process studies to provide new insights to catchment function and to inform the structural development and testing of hydrologic models.
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| 2. |
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| 3. |
- Peralta Tapia, Andres, et al.
(författare)
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Connecting precipitation inputs and soil flow pathways to stream water in contrasting boreal catchments
- 2015
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Ingår i: Hydrological Processes. - : Wiley-Blackwell. - 0885-6087 .- 1099-1085. ; 29:16, s. 3546-3555
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Tidskriftsartikel (refereegranskat)abstract
- Stable isotopes of water are one of the most widely used tools to track the pathways of precipitation inputs to streams. In the past, soils have often been treated as black-boxes through which precipitation is routed to streams without much consideration of how, when, and where water is transported along soil and groundwater flow paths. Here, we use time series of stable isotopes (O-18) in precipitation, soil/groundwater, and stream water to evaluate how landscape structure and heterogeneity influence seasonal hydrological patterns characteristic of boreal headwater catchments. To do this, we collected water throughout a full year at three adjacent catchments draining forest, mire, and mire/lake ecosystems within the Krycklan Experimental Catchment of northern Sweden. Isotope time series from forest and mire groundwater piezometers showed spatial and temporal heterogeneity in the dominant hydrologic flow pathways connecting precipitation to stream flow at different sites. The isotopic signature of stream water suggested strong connections to the dominant landscape elements within each catchment. These connections translated into greater temporal variability in the isotopic response of streams draining lake and wetland patches, and a much more attenuated pattern in the forest-dominated catchment. Overall, seasonal changes in the isotopic composition of streams and groundwater illustrate how differences in landscape structure result in variable hydrological patterns in the boreal landscape.
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| 5. |
- Soulsby, C., et al.
(författare)
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Catchment-scale estimates of flow path partitioning and water storage based on transit time and runoff modelling
- 2011
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Ingår i: Hydrological Processes. - : Wiley. - 0885-6087 .- 1099-1085. ; 25:25, s. 3960-3976
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Tidskriftsartikel (refereegranskat)abstract
- Tracer-derived mean transit times (MTT) and rainfallrunoff modelling were used to explore stream flow generation in 14 Scottish catchments. Both approaches conceptualise the partitioning, storage, and release of water at the catchment scale. The study catchments were predominantly upland and ranged from 0.5 to 1800?km2. Lumped convolution integral models using tracer inputoutput relationships generally provided well-constrained MTT estimates using a gamma function as the transit time distribution. These ranged from 60?days to >10?years and are mainly controlled by catchment soil cover and drainage density. The HBV model was calibrated using upper and lower storage layers to conceptualise rapidly responding near-surface flow paths and slower groundwater contributions to runoff. Calibrated parameters that regulate groundwater recharge and partitioning between the two storages were reasonably well-identified and correlations with MTTs. The most clearly identified parameters and those with the strongest correlations with MTT and landscape controls (particularly soil cover) were the recession coefficients which control the release of water from the upper and lower storage layers. There was also strong correlation between the dynamic storage estimated by HBV and the total catchment storage inferred by tracer damping, although the latter was usually two orders of magnitude greater. This is explained by the different storages estimated: while the total storage inferred by tracers also includes the passive storage involved in mixing, the model estimates dynamic storage from water balance considerations. The former can be interpreted as relating to total porosity, whereas the latter rather corresponds to the drainable porosity. As MTTs for Scottish the uplands can be estimated from catchment characteristics, landscape analysis can be used to constrain sensitive model parameters when modelling in ungauged basins. Furthermore, the dynamic storage inferred by HBV may also be used to provide a first approximation of minimum total catchment storage. Copyright (c) 2011 John Wiley & Sons, Ltd.
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| 6. |
- Tetzlaff, D., et al.
(författare)
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How does landscape structure influence catchment transit time across different geomorphic provinces?
- 2009
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Ingår i: Hydrological Processes. - : Wiley. - 0885-6087 .- 1099-1085. ; 23:6, s. 945-953
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Tidskriftsartikel (refereegranskat)abstract
- Despite an increasing number of empirical investigations of catchment transit times (TTs), virtually all are based on individual catchments and there are few attempts to synthesize understanding across different geographical regions. Uniquely, this paper examines data from 55 catchments in five geomorphic provinces in northern temperate regions (Scotland, United States of America and Sweden). The objective is to understand how the role of catchment topography as a control on the TTs differs in contrasting geographical settings. Catchment inverse transit time proxies (ITTPs) were inferred by a simple metric of isotopic tracer damping, using the ratio of standard deviation of delta O-18 in streamwater to the standard deviation of delta O-18 in precipitation. Quantitative landscape analysis was undertaken to characterize the catchments according to hydrologically relevant topographic indices: that could be readily determined from a digital terrain model (DTM). The nature of topographic controls on transit times varied markedly in different geomorphic regions. In steeper montane regions. there are stronger gravitational influences on hydraulic gradients and TTs tend to he lower in the steepest catchments. In provinces where terrain is more subdued, direct topographic control weakened; in particular, where flatter areas with less permeable soils give rise to overland How and lower The steeper slopes within this flatter terrain appear to have a greater coverage of freely draining soils, which increase sub-surface flow, therefore increasing TTs. Quantitative landscape analysis proved a useful tool for intercatchment comparison. However, the critical influence of sub-surface permeability and connectivity may limit the transferability of predictive tools of hydrological function based on topographic parameters alone. Copyright (C) 2009 John Wiley & Sons, Ltd.
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