From drought to flood: A water balance analysis of the Tuolumne River Basin during extreme conditions (2015 – 2017)

Authors: Hedrick, Andrew; Marks, Daniel; MARSHALL, HANS-PETER - Boise State University; MCNAMARA, JAMES - Boise State University; Havens, Scott; TRUJILLO, ERNESTO - University Of California - Cooperative Extension Service; Sandusky, Micah; Robertson, Mark; Johnson, Micah; BORMANN, KAT - California Institute Of Technology; PAINTER, THOMAS - University Of California (UCLA)

Submitted to: Hydrological Processes
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 3/10/2020
Publication Date: 4/2/2020
Citation: Hedrick, A., Marks, D.G., Marshall, H., McNamara, J., Havens, S.C., Trujillo, E., Sandusky, M.L., Robertson, M.E., Johnson, M.J., Bormann, K., Painter, T.H. 2020. From drought to flood: A water balance analysis of the Tuolumne River Basin during extreme conditions (2015 – 2017). Hydrological Processes. 34(11):2560-2574. https://doi.org/10.1002/hyp.13749.
DOI: https://doi.org/10.1002/hyp.13749

Interpretive Summary: Basin annual evapotranspiration (ET) and runoff efficiencies (RE) are estimated using a water balance approach for three climatically dissimilar water years (2015-2017) in the snow-dominated Tuolumne headwater catchment. Surface water input (SWI) is highly constrained by a physics-based energy/mass balance model that is updated with periodic airborne lidar-derived snow depths. Results reveal that ET was similar year to year despite vastly different input precipitation amounts, while RE was nonlinearly related to both total annual SWI and snowfall fraction of precipitation.

Technical Abstract: The degree to which the hydrologic water balance in a snow-dominated headwater catchment is affected by climatic conditions is difficult to quantify, primarily due to uncertainties in measuring precipitation inputs and evapotranspiration losses. Over a recent three-year period, the snowpack in California’s Sierra Nevada fluctuated from the lowest in recorded history (2015) to historically large (2017), with a relatively average year in between (2016). This large dynamic range in climatic conditions presents a unique opportunity to investigate the correlation between annual water availability and runoff in a snow-dominated catchment. Here, we estimate evapotranspiration (ET) using a water balance approach where the water inputs to the system are constrained using a combination of remote sensing, physically based modeling, and in-situ observations. For all three years of this study, the NASA Airborne Snow Observatory (ASO) combined periodic high-resolution snow depths from airborne lidar with snow density estimates from a physically based energy balance model to produce spatial estimates of snow water equivalent (SWE) over the Tuolumne headwater catchment at 50-m resolution. Using the well-quantified hydrologic inputs from the snowmelt model along with periodic snow depth updates and observed streamflow from the basin outlet, we estimate annual ET and the associated uncertainty across these three dissimilar water years. Throughout the study period, estimated annual ET remained steady (222 mm in 2015, 151 mm in 2016, and 299 mm in 2017) relative to the large differences in basin input precipitation (547 mm in 2015, 1060 mm in 2016, and 2211 mm in 2017). Independent satellite-derived ET estimates and previously published studies in similar Sierra Nevada catchments are compared. Results reveal that ET in the Tuolumne does not scale linearly with the amount of available water to the basin, and that runoff efficiency (RE) primarily depends on total annual snowfall.