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Strengthening Streams in California

The State of California employs EPA's causal assessment CADDIS tool to identify and treat problems in waterways

Photo of the Salinas River in California

The Salinas River in California, one of three causal case studies in freshwater streams.

Thriving aquatic life--fish, insects, plants, algae and invertebrates--is a good indication that a stream or other watery ecosystem is healthy. On the other hand, aquatic life that is unhealthy or dying off is a strong signal that there is a problem. But beyond that initial diagnosis, deciphering the cause of the trouble can be a serious challenge. In such situations, scientists conduct a causal assessment to discover the cause of the problem and develop solutions to remedy it.

A causal assessment uses a variety of techniques to evaluate data and other information to identify probable culprits, much like a doctor conducts exams and tests to diagnose illnesses or injuries in a patient.

Over the last 15 years, EPA has honed its causal assessment process, an effort that culminated in the Causal Analysis/Diagnosis Decision Information System (CADDIS), a valuable tool that water managers and others from states and tribes rely on to identify problems in their local waterways. Named for caddisflies, an order of insects whose larvae live in flowing waters on the bottom of high quality streams, CADDIS provides a step-by-step framework to help conduct causal assessments, mainly in streams.

Recently, the State of California began using CADDIS as a way to find the causes of unhealthy streams and identify solutions. The EPA, the Southern California Coastal Water Research Project, the California Department of Fish and Game, and several stakeholder groups, have collaborated to conduct causal assessment case studies for three freshwater streams: the Santa Clara and San Diego Rivers, the Salinas River, and the Garcia River.

These three case studies capture the diversity of California's geography, land use characteristics, and stressors. Each examines evidence to identify the cause(s) of unhealthy aquatic life and provides recommendations for future causal assessment efforts.

The goal of the collaboration is to help California protect the health of state streams and, ultimately, the people who depend on them.

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EPA Rivers & Streams Research

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