… To account for natural variability, CDFW uses functional flows. Functional flows are the key parts of a river’s natural yearly flow pattern that do a specific job for the ecosystem. Instead of asking only, “how much water does a river need?”, the approach also asks, “when, how fast, and for how long?” Scientists have found that California’s rivers and streams follow five main flow patterns, each linked to a different part of the year. The water year begins in fall with the fall pulse flow, a short burst of water that flushes out the stream and signals fish to migrate. This is followed by winter storms which bring peak flows, moving gravel and sediment, reshaping the channel, and moving water onto floodplains. Between storms, steady wet-season baseflows keep the habitat connected, allowing fish to move, feed, and grow.