Spatially explicit knowledge of the origins of water resources for ecosystems and rivers is challenging when using tracer data alone. We use simulations from a spatially distributed model calibrated by extensive ecohydrological data sets in a small, energy-limited catchment, where hillslope-riparian dynamics are broadly representative of humid boreal headwater catchments that are experiencing rapid environmental transition. We hypothesize that in addition to wetness status, landscape heterogeneity modulates the water pathways that sustain ecosystem function and streamflows. Simulations show that catchment storage inversely controls stream water ages year-round, but only during the drier seasons for transpiration and soil evaporation. The ages of these evaporative outputs depend much less on wetness status in the oft-saturated riparian soils than on the freely draining hillslopes that subsidize them. This work highlights the need to consider local dynamics and time-changing lateral heterogeneities when interpreting the ages, and thus the vulnerability, of water resources feeding streams and ecosystems in landscapes.
This work was supported by the European Research Council (ERC, project GA 335910 VeWa). M.P. Maneta acknowledges support from the NASA Ecological Forecasting Program Award #80NSSC19K00181 and NASA EPSCoR #80NSSC18M0025M. The authors are thankful to V. Ivanov, two anonymous reviewers, and E. Anguelova, whose comments and suggestions considerably improved the manuscript. Open access funding enabled and organized by Projekt DEAL.
EC | FP7 | FP7 Ideas: European Research Council (FP7 Ideas). Grant Number: GA 335910 VeWa National Aeronautics and Space Administration (NASA). Grant Numbers: #80NSSC19K00181, #80NSSC18M0025M NASA EPSCoR. Grant Number: #80NSSC18M0025M NASA Ecological Forecasting Program. Grant Number: #80NSSC19K00181 European Research Council. Grant Number: GA 335910 Open access funding enabled and organized by Projekt DEAL.