California Water Blog –
Alterations to the natural flow regime for human water management activities have degraded river ecosystems worldwide. Such alterations are particularly destructive in regions with highly variable climates like California, where native riverine species are highly adapted to natural ﬂooding and drought disturbances. In California, less than 2% of the total streamﬂow remains unaltered, while over 80% of the native ﬁsh species are now imperiled or extinct .
Determining the natural flow regime for altered stream reaches is difficult as unimpaired streamﬂow records are unavailable for many locations of interest. Where data is available, previous methods distinguished such specific stream types that their application was limited and unhelpful for regional management. 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.
Hydrologic classiﬁcation is a strategy for distinguishing groups of stream reaches with similar streamflow characteristics for regional water management efforts. 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.