How is the quantity of water necessary to protect wild and scenic river values determined?

A variety of methodologies are used to determine instream flows necessary to protect flow-dependent outstandingly remarkable values for a specific wild and scenic river. Methodologies can range from staff/expert opinions (e.g., flows necessary for boating) to complicated hydraulic models (e.g., Instream Flow Incremental Methodology and Physical Habitat Simulation Models) used to simulate fish habitat requirements.

Water law is a complex legal area, and water rights are a highly contentious issue. Whenever a water allocation issue arises, a river manager should consult with staff with water rights expertise and, as necessary, seek legal counsel.