In California, our weather patterns can quickly shift from one extreme to another.  Just look at the last 10 years.  We’ve had five dry years—2014, 2015, 2020, 2021 and 2022—where the state and federal water supply were greatly reduced. Local aquifers pumped down water to help meet demands, reservoir levels fell, and river flows were low.

There have been two very wet years—2017 and 2019—where water was abundant, the rivers and creeks experienced flood flows, groundwater was recharged, reservoirs filled, and our system of rivers ran with natural, good quality water. We have had three average years wherein the present regulatory system in California made water supplies a challenge for many in California. 

We have started 2023 with the promise of another wet year. Since Christmas, California has experienced a series of storms, or “Atmospheric Rivers” in the modern vernacular, which has resulted in as much as 25 inches of precipitation in some Northern California and Sierra Mountain locations, and over five inches locally. As of the writing of this article, more significant rainfall is in the forecast.

What a difference a few weeks make can make in California. The local creeks are suddenly back flowing, providing many benefits while, at the same time, risking damage to property. Los Banos Creek flows have filled the Los Banos Creek Detention Dam which has been releasing flood flows down the creek providing the City of Los Banos and the local area with significant groundwater recharge.

This is important because the creek recharge is a significant contributor to the long-term water supply of Los Banos. The flood control project that built the Los Banos Creek Detention Dam in the early 1960s has provided additional indirect water supply benefits to the area. Detention Dams by design store the peak of storm runoff events and then release them later, after the storm peak has passed. In other words, creek flows stay in the creek longer that they would have naturally, creating even more recharge benefits.  

In just these few weeks, San Joaquin River flows into Millerton have forced flood releases into the river.  The flood flows from Millerton Lake flow down the river through areas under the watch of our local water districts and flood control districts. We work to coordinate flood flow operations through the Mendota Pool and downstream. In fact, the local Central California Irrigation District, San Luis Canal Company, Firebaugh Canal Company, Columbia Canal Company and San Luis Water District are in flood watch operations along the river, and on the local westside creeks working with our local communities to safely pass flood flows through the system while maximizing recharge to groundwater for water supply benefits.

Stepping back and looking at the bigger picture, flood flows from the Sacramento and San Joaquin River systems are flowing into the Delta. In Fact, Delta outflow has averaged about 85,000 cubic feet per second (cfs) over the last seven days. To put it in plain English, that is enough water to fill the entire 2 million acre-feet San Luis Reservoir in about twelve days.

The present circumstance certainly reinforces the need for additional storage facilities for this region to take advantage of wet periods like these. Projects like the proposed raising of San Luis Reservoir or the construction of the Del Puerto Canyon Reservoir near Patterson combined would provide about 220,000 acre-feet of additional storage. That is water that could be stored now and used in the next drought period.

In the meantime, we will track the hydrology and water operations as they continue to develop this spring. It is nice to be working with a promising beginning to the water year, but we will continue to diligently monitor water operations to ensure that the state and federal operations maximize water supply to provide a much better water supply year in 2023. After the last couple of years, this is a major relief.

Chris White

Executive director. San Joaquin River Exchange Contractors Water Authority