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1. Why is water being released from Lopez Dam?

There are four key reasons Lopez Dam releases water downstream:

1. The California Fish and Game Code, Section 5937, requires: “The owner of any dam shall allow sufficient water at all times to pass through a fishway, or in the absence of a fishway, allow sufficient water to pass over, around or through the dam, to keep in good condition any fish that may be planted or exist below the dam.” Since Lopez Dam does not have a fishway (fish ladder), downstream releases are made through pipes that pass through the dam.
2. The Federal Endangered Species Act. Federal Law prohibits any action that would result in the “take” ("The term 'take' means to harass, harm, pursue, hunt, shoot, wound, kill, trap, capture, or collect, or to attempt to engage in any such conduct."). Steelhead were declared a Threatened Species in 1995 and Arroyo Grande Creek supports a population of the fish. Shutting off downstream releases would dry up the upper part of the creek and result in harm to steelhead in the area, thereby violating federal law.
3. Downstream Water Rights. Landowners, primarily farmers, whose land abuts the creek have a legal right under section 10 of the California Constitution to the natural flow of water in the creek, so long as the farmers use the water for reasonable and beneficial uses. If flows from the dam are stopped, farmers and landowners in the upper portions of the Arroyo Grande Valley would not be able to exercise their water rights. In the winter, when flows in the creek are above the amount needed by the farmers, the “extra” water is stored in the reservoir above the dam.
4. In addition to the legal requirements, it is important to note that the water released from the dam increases the amount that recharges the groundwater basin below the dam. This groundwater is used by landowners as well as downstream municipalities in addition to supplies from Lopez Lake.

2. How much water is released downstream from Lopez Dam?

• The Lopez Project was designed to produce a long term annual average of 8,730 acre feet water per year (an acre-foot of water is 325,851 gallons). Of this 8,730 acre feet, 4,530 is contracted to municipal users in the five cities and Avila Beach area, the remaining 4,200 acre feet is for downstream uses. When the watershed produces more than 8,730 acre feet in a given year, the excess is stored in the lake and used in years when the watershed produces less than 8,730 acre feet. The rate at which water is released from the dam varies with the season. In winter months releases are reduced because downstream uses need less water, in summer releases increase to meet streamside and groundwater needs. In recent years, a typical winter release averages 3 cubic feet per second (1.9 million gallons or 5.95 acre feet per day), in the summer releases rise to as much 12 cubic feet per second (7.8 million gallons or 26 acre feet per day).
• Most recently, in the 15 days between January 4, 2017 and January 19, 2017 the reservoir inflow was 3,192.25 acre feet. At 3 cubic feet per second, 89.25 acre feet was released downstream and 3,103 acre 2 feet were kept in storage. That is, 97.2% of the inflow was kept in the lake, and 2.8% was released downstream.

3. Is there a plan to reduce releases if the water gets very low in the reservoir?

• Yes. In December of 2014 the Board of Supervisors and all the agencies that receive water from Lopez Lake adopted the Low Reservoir Response Plan. As levels in the lake drop, reductions are made in both municipal deliveries and downstream releases. In December of 2016 the lake was at a critical point, just 1,000 acre feet above the level that would trigger substantial reductions in downstream releases. These reductions are a key part of the emergency drought response actions reflected in the Low Reservoir Response Plan.

4. Do other reservoirs make similar releases?

• Yes. The Nacimiento Reservoir, operated by the Monterey County Water Resources Agency, for reasons similar to Lopez, releases a minimum of 60 cubic feet per second into the Nacimiento River, even during winter months. These minimum releases are a requirement of the Federal Endangered Species Act. In summer, when irrigation demands in the Salinas Valley increase, the releases increase substantially.
• The Salinas Reservoir (Santa Margarita Lake), operated by the County of San Luis Obispo, is allowed to divert water to storage only when the Salinas River is flowing on the surface between the Dam and the confluence of the Salinas and Nacimiento Rivers, a distance of about 40 miles. This requirement is part of the water rights permit issued for the building of the dam in the 1940’s and is intended to protect both downstream water rights and fish populations in the river.