MOUNTAIN ECOHYDROLOGY
Mountains serve as "water towers" for about one quarter of the global population. However, mountain regions are likely to see large changes in their hydrologic function as climate change leads to less snow and more rain in these critical water resource regions. These regions also have tight couplings between subsurface flow, the water available for plant use, and the energy available for plant growth which may make understanding their linkages more tractable. We need to better understand how complex mountain watersheds function to manage our water resources under climate change. The WRElab uses computational simulation constrained by novel measurements to build new understanding of and better predictive tools for mountain watersheds and their critical water resources.
Tracking water's flow
We are using dynamic-flux particle tracking to investigate the details of subsurface flow in two mountain watersheds: the Cosumnes Watershed in California and the East River Watershed in Colorado. Dynamic-flux particle tracking allows us to follow the detailed flow paths of water in the watershed from its source as rain or snow, through the subsurface, and to its exit via streamflow or evapotranspiration. With this approach we can both test our simulation's fidelity by comparing it to measurements sensitive to flow paths and better understand our measurements by representing the complex context in which they are taken at much higher resolution in a model. Dynamic-flux particle tracking elucidates previously opaque flow dynamics and process couplings in these complex watersheds; it can do so at extreme resolutions, representing water by hundreds of millions of particles flowing through the watershed at any given time.
In the Cosumnes Watershed we are developing these approaches to better understand mountain headwater/Central Valley groundwater connections and investigate the role of extreme storms called atmospheric rivers on groundwater storage. In the East River Watershed we are investigating the distinct role of rain and snow in leading to streamflow and evapotranspiration and doing the first comparisons of this technique with stable isotope measurements. In both places we are applying these analyses at very high resolution, representing water with hundreds of millions of particles to interrogate simulated flow paths in great detail.
Cumulative streamflow curves for each of 11 measured subwatersheds in Colorado's East River show how rain and snow contribute differently to streamflow and ET in a dynamic-flux particle-tracking simulation.
Recent papers & presenations
Siirila-Woodburn, E. R., P. J. Dennedy-Frank, A. Rhoades, P. Vahmani, F. Maina, B. Hatchett, Y. Zhou, & A. Jones. The Role of Atmospheric Rivers on Groundwater: Lessons Learned From an Extreme Wet Year. Water Resources Research 59, no. 6 (2023): e2022WR033061. https://doi.org/10.1029/2022WR033061.
Sprenger, M., R. W. H. Carroll, P. J. Dennedy‐Frank, E. R. Siirila‐Woodburn, M. E. Newcomer, W. Brown, A. Newman, C. Beutler, M. Bill, S. S. Hubbard, & K. H. Williams (2022), Variability of Snow and Rainfall Partitioning Into Evapotranspiration and Summer Runoff Across Nine Mountainous Catchments. Geophysical Research Letters, 49, e2022GL099324, https://doi.org/10.1029/2022GL099324
Dennedy-Frank, P. J., M. Sprenger, R. Carroll, K. Williams, S. Hubbard & E.R. Siirila-Woodburn (2021), Understanding Snow and Rain Partitioning into Runoff and Evapotranspiration in a Mountainous Watershed Using Dynamic-Flux Particle Tracking, Abstract H11A-07 presented at 2021 Fall Meeting, AGU, 13-17 Dec.
Dennedy-Frank, P.J., F.Z. Maina, A. Visser and E.R. Siirila-Woodburn (2020) Understanding Sierra Nevada-Central Valley Hydrologic Links by Combining Integrated Hydrologic Modeling, Remote Sensing, and Isotope Measurements, presented at Computational Methods in Water Resources 2020, 14-17 Dec.
Modeling mountain watersheds
Annual water budgets for the water that started in "atmospheric rivers" vs. non-atmospheric-river storms show that the latter lead to more groundwater storage in a simulation of California's Cosumnes Watershed.
We are using sophisticated watershed simulators that represent both integrated surface and groundwater flow and the surface energy balance to better understand how mountain watersheds function in the Cosumnes Watershed in California and the East River Watershed in Colorado. These applications leverage one of the ten biggest supercomputers in the world to represent these processes at resolutions and with process fidelity that cannot be achieved without such computing power.
In the Cosumnes watershed we have investigated how climate shifts affect hydrologic patterns at the end of the century and the particular role that large California storms, called atmospheric rivers, play in replenishing groundwater. In the East River we have investigated how subsurface flow alters the water available for evapotranspiration and how including that subsurface flow might change clustering approaches typically based solely on surface observations. Recently we have been using a new coupling of an integrated watershed model with a vegetation demography model to investigate watershed-scale feedbacks between water and plants.
Recent papers & presenations
Siirila-Woodburn, E. R., P. J. Dennedy-Frank, A. Rhoades, P. Vahmani, F. Maina, B. Hatchett, Y. Zhou, and A. Jones. “The Role of Atmospheric Rivers on Groundwater: Lessons Learned From an Extreme Wet Year.” Water Resources Research 59, no. 6 (2023): e2022WR033061. https://doi.org/10.1029/2022WR033061.
Maina, F. Z., A. Rhoades, E. R. Siirila-Woodburn, & P. J. Dennedy-Frank (2022), Projecting end-of-century climate extremes and their impacts on the hydrology of a representative California watershed. Hydrology and Earth System Science, 26, 3589-3609, https://doi.org/10.5194/hess-26-3589-2022
Maina, F. Z., H. M. Wainwright, P. J. Dennedy-Frank, & E. R. Siirila-Woodburn (2022), On the similarity of hillslope hydrologic function: a clustering approach based on groundwater changes. Hydrology and Earth System Science, 26, 3805-3823, https://doi.org/10.5194/hess-26-3805-2022
Dennedy-Frank, P.J., E.R. Siirila-Woodburn, P. Boutte, T. Powell, Y. Fang & L.M. Kueppers (2022). Lateral Flow, Evapotranspiration, and Vegetation Response in the Mountain Critical Zone, presented at 2022 Fall Meeting, AGU, 12-16 Dec.