The Ventura River was once home to of one the largest southern steelhead runs on the south coast, and is considered one of the four major steelhead-bearing watersheds in Southern California. The Ventura River is also one of five priority stream systems selected as part of the California Water Action Plan effort. The Ventura River watershed may experience long periods of dry conditions with little to no measurable precipitation, resulting in mainstem reaches becoming seasonally and even annually intermittent. In addition, moderate to extremely high episodic precipitation patterns and flow events may also occur in the winter months. This unpredictability in the timing, magnitude, frequency and duration of river flows limits the hydrologic connectivity of the riverine habitat for southern steelhead migrating to and from upstream spawning and rearing habitats.
The goal of this study is to develop streamflow versus habitat relationships in the mainstem Ventura River, and San Antonio Creek, a primary tributary. This information will be used to enhance flows in the watershed in several ways, including the development of flow criteria and identification of important flow thresholds for conservation, restoration, and protection of southern steelhead in the Ventura River watershed. Some key questions include:
- What flows are required to maintain hydrologic connectivity for steelhead lifestages throughout the mainstem and typically intermittent reaches of the Ventura River?
- What flows are required for survival and movement of southern steelhead, as well to promote productive riffle habitat for benthic macroinvertebrates, in San Antonio Creek?
- What are the appropriate flows for maintaining important fluvial geomorphic conditions in the watershed?
To answer these questions, surveys must be performed and data collected. The Instream Flow Program anticipates performing various actions at locations within the Ventura River watershed including evaluating existing data and habitat conditions, performing riverine topographical surveys, constructing hydraulic-habitat models, measuring streamflows, and conducting data analyses.
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