ABSTRACT:

The model presented here was developed by applying a diagnostic approach to modeling watersheds with human interference. This mixed methods approach is informed by the case history and builds on the top-down hydrological modeling approach where process complexity is incrementally added with changing timescales to identify and respond to changing dominant hydrological processes in any given watershed. Here we implement this modeling approach in the East Fork of the Upper Russian River in California, USA for which data on changes in water imports, withdrawals, irrigation and agriculture land cover is available from the early 1940’s, making it an ideal case to demonstrate this method. In the East Fork watershed, we find that incorporation of water imports and water rights are sufficient to replicate annual patterns of runoff variability, and that adding crop water demand and irrigation enables replication of monthly and daily patterns, while incorporation of groundwater pumping results in negligible improvements.