How does land use affect the health of our streams?
This map shows data generated by:
The health of our rivers and streams is influenced by their surroundings. Streams that run through industrial corridors may be subject to increased stress relative to pristine streams in the Sierra. Streams in agricultural areas can be subject to contaminants from pesticide applications. Streams in cities may be littered with trash.
This map shows the distribution of sites sampled under the Perennial Streams Assessment (PSA) Program between 2000 and 2007 coded by biological condition.
The Perennial Streams Assessment (PSA) looked at the relationship between the condition of our streams and nearby land uses. The PSA study sites were classified based on the dominant land use in the upstream watershed. Stream condition was then compared across these land use classes. Land use appears to be strongly related to stream condition. A higher proportion of stream miles are impaired in agricultural and urban landscapes. In fact, 100% of streams draining agricultural and urban landscapes sampled in the PSA survey had degraded or very degraded biological condition, whereas about 30% of streams draining forested landscapes had degraded biological condition.
Streams draining agricultural areas tended to have high levels of agriculture related contaminants (phosphorous, nitrogen, chloride). In addition, almost all of these streams exhibited some form of habitat disturbance, both instream and riparian. Urban streams had high levels of nutrients and very high levels of chloride. Habitat degradation was common in most urban streams where instream habitat was especially degraded. Poor water quality and habitat degradation observed in forested areas was less pervasive than for either agricultural or urban areas.
* Please Note: some specific fish or aquatic insect species pictured & described here may not occur in California streams
* Source of these stream diagrams: