Why is hydrologic sufficiency important?

Streams in California have a wide variety of natural flow patterns. In some streams, water flows for only a few days a year (intermittent streams), while others maintain flow year round (perennial streams) or become dry during late summer and early fall (ephemeral streams). The amount of water flowing through a stream and the length of time that a stream carries flow are relevant to overall stream health because they control the types of plants and animals that can survive in and around a particular stream. Minimum flows are required to sustain pools, recharge groundwater, transport sediment, provide fish passage, and feed springs.

Goals for a particular stream dictate the amount of flow that is seen as sufficient. If flows are reduced or increased so that they differ significantly from natural patterns, overall stream health may be reduced.

How do we measure hydrologic sufficiency?

Investigators can use a stream gauge, field measures, and hydrologic models to determine the amount of flow in a stream.