by Belize Lane, Sam Sandoval, and Sarah Yarnell Alterations to the natural flow regime for human water management activities have degraded river ecosystems worldwide.
To improve California’s water management, particularly around determining environmental flows for our diverse ecosystems, we needed a better method that addressed the diversity and scale of California’s streams.
UC Davis researchers recently developed a hydrologic classification for California that is specific enough to make critical distinctions between natural streamflow patterns (also called natural flow regimes), but general enough to support the development of environmental flow targets in altered stream reaches across the state.
The California hydrologic classification is based on available hydrologic and geospatial data.
This second model (Figure 1) was then used to predict the stream classes of all the reaches in California.
California’s Natural Stream Classes Snowmelt (SM): SM streams exhibit highly seasonal flow regimes with spring snowmelt peak flows, predictable recession curves, very low summer flows, and minimal winter rain influence.
Winter Storms (WS): WS streams, driven by winter rain storms, exhibit distinct duration, timing and magnitude of high flows during the rainy season.
For example, the SM flow regime exhibits a highly predictable spring snowmelt pattern with low interannual variability (<6) while the WS flow regime exhibits highly variable winter storm flows (<18) and very low summer flows.
The hydrologic classification provides a footprint of the locations of distinct natural stream classes which, combined with ecological and geomorphic information, can be used to design environmental flow targets.
Lane BA, Sandoval-Solis S, Yarnell SM, Stein ED (2017b) Characterizing diverse river landscapes using hydrologic classification and dimensionless hydrographs.