The Perennial Streams Assessment (PSA): An Assessment of Biological Condition using the New California Stream Condition Index (CSCI)

PSA stream surveys found that the majority of stream length in the Sierra Nevada and North Coast is in good biological condition, while the majority of stream length in the South Coast, Chaparral and Central Valley is in poor or very poor condition. Similarly, most of the stream length draining forested watersheds is in good condition, while most of the stream length draining watersheds dominated by agricultural and urban land use is in poor or very poor condition. On average, stream condition showed no directional change over time, either for better or for worse. Streams where phosphorous concentration or riparian disturbance exceeded thresholds had the greatest relative risk of biological impairment.