Publication Date: 
December 2013
Emmons, JD, SM Yarnell, A Fryjoff-Hung, JH Viers.. Quantifying the Restorable Water Volume of California’s Sierra Nevada Meadows EOS TRANS. AGU, 93(53): H31H-1298

The Sierra Nevada is estimated to provide over 66% of California's water supply, which is largely derived from snowmelt. Global climate warming is expected to result in a decrease in snow pack and an increase in melting rate, making the attenuation of snowmelt by any means, an important ecosystem service for ensuring water availability. Montane meadows are dispersed throughout the mountain range and can act like natural reservoirs, and also provide wildlife habitat, water filtration, and water storage. Despite the important role of meadows in the Sierra Nevada, a large proportion is degraded from stream incision, which increases volume outflows and reduces overbank flooding, thus reducing infiltration and potential water storage. Restoration of meadow stream channels would therefore improve hydrological functioning, including increased water storage. The potential water holding capacity of restored meadows has yet to be quantified, thus this research seeks to address this knowledge gap by estimating the restorable water volume due to stream incision. More than 17,000 meadows were analyzed by categorizing their erosion potential using channel slope and soil texture, ultimately resulting in six general erodibility types. Field measurements of over 100 meadows, stratified by latitude, elevation, and geologic substrate, were then taken and analyzed for each erodibility type to determine average depth of incision. Restorable water volume was then quantified as a function of water holding capacity of the soil, meadow area and incised depth. Total restorable water volume was found to be 120 x 10^6 m3, or approximately 97,000 acre-feet. Using 95% confidence intervals for incised depth, the upper and lower bounds of the total restorable water volume were found to be 107 - 140 x 10^6 m3. Though this estimate of restorable water volume is small in regards to the storage capacity of typical California reservoirs, restoration of Sierra Nevada meadows remains an important objective. Storage of water in meadows benefits California wildlife, potentially attenuate floods, and elevates base flows, which can ease effects to the spring recession curve from the expected decline in Sierran snowpack with atmospheric warming.