By Edward Ring, Director of Water and Energy Policy at the California Policy Center
With another series of drenching storms about to hit California, now is a good time to ask what has become a perennial question: why can’t we harvest more of this massive runoff and reserve it for our farms and cities? California must periodically cope with multi-year droughts, but these droughts are usually preceded by years with above average rainfall. And yet we not only fail to save water from wet years to sustain us through dry years, we aren’t even saving enough water during wet years to sustain us through wet years.
There is plenty of water to work with. Publicly accessible reports available from the California Data Exchange Center provide comprehensive information on water management in the state. It is updated daily and goes back several years. Three variables are particularly revealing: (1) How many acre feet were pumped into the Delta-Mendota Canal, (2) how many acre feet were pumped into the California Aqueduct, and (3) how many acre feet ran through the delta and into the ocean. To update any of these three direct links, just change the characters at the end of the URLs, i.e., update “&End=2025-11-30” to reflect the current date.
Let’s take a look at what happened during the peak four weeks of rain over the last three years.
This past winter, over four weeks from 2/03 through 3/02, over 6.8 million acre feet of freshwater flowed through the Sacramento San Joaquin Delta and out to the ocean. During that exact same period of time, 233,692 acre feet of water was pumped into the Delta-Mendota Canal, and 156,322 acre feet was pumped into the California Aqueduct.
What these numbers tell us is that during that period of huge storm runoff that had swelled every tributary in the entire Sacramento-San Joaquin watershed, and strained the delta’s levees to their limits, California’s water managers had 7,130,336 acre feet of runoff to work with, and they allocated just 358,732 to farms and cities in Southern California. Only 5.0 percent of the product of this winter deluge was deemed acceptable to allocate for food and people.
The high water in February 2025 was not an isolated case. The winter of 2025 was our third wet winter in a row. During the four weeks between 2/07 and 3/05 in 2024, 389,955 acre feet were pumped into the aqueducts, and 5.6 million acre feet went through to the ocean. During the four weeks between 3/11 and 4/07 in 2023, 560,429 acre feet were pumped into the aqueducts, and 6.8 million acre feet went through to the ocean.
The biggest nodes in California’s massive, manmade plumbing system are the two pumping stations on the south end of the delta. The bigger one, part of the California State Water Project and feeding the California Aqueduct, is the Banks Pumping Plant, it was constructed in the 1960s and began operating in 1969. The capacity of this pumping plant is 20,430 acre feet per day. The other one is the Jones Pumping Plant, a federally owned facility that feeds the Delta-Mendota Canal. Construction began in the late 1940s and it began operating in 1951. At full capacity, it can move 8,500 acre feet of water per day.
The big challenge in California, whether or not our long-term destiny will shift us to less snow and more erratic rainfall, is to have the capacity to take the so-called “big gulp” when excess water is transiting the Sacramento-San Joaquin Delta. There is no single alternative source of fresh water in the state of comparable magnitude. And to move water out of the delta during high flows, these two pumps, with a combined capacity of 28,930 acre feet per day, are all we’ve got. But we don’t use them at capacity even during periods with extremely high flows.
Returning to the example from earlier this year, if the state and federal pumps had operated at capacity during the four weeks from 2/03 through 3/02 in 2025, 810,040 acre feet could have been diverted into the aqueducts. This would still only represent 11.4 percent of the total water that flowed through the delta during that period, and more important than the percentage that could have been withdrawn by these pumps, is the absolute quantity of water that still would have passed through the delta and out to the ocean, 6.3 million acre feet in just four weeks.
Why in wet winters during periods with the highest flow are we moving water into the aqueducts at only around half our pumping capacity? Why aren’t the existing pumps being utilized to their full capacity when there are high winter flows through the delta, and why, since even these pumps at full capacity are nowhere near capable of safely withdrawing even more water from the delta during high flows, haven’t we built additional infrastructure to remove and store much more than 28,930 acre feet per day in order to ensure multi-year water security for our farms and cities?
Efforts to improve fisheries in California at the expense of water for food and people have been ineffective and wasteful. The politicians and agency appointees who persist in viewing water volume – no matter how voluminous it may be – as the prevailing metric affecting the health of fisheries need to be aggressively challenged. The biased studies they cite require expert rebuttals, and their failed policies need to be replaced with balanced, results oriented management.
When it comes to California’s future, we are told to expect erratic weather that whipsaws between consecutive years of severe drought, followed by winters characterized by shrinking snowpacks and drenching rain. The only way to be ready is to change our water management priorities, while also building new facilities that permit a far greater percentage of the delta’s winter flood runoff to be captured and stored.
