As California’s population grows and our weather patterns change, there is an increasing urgency to update the state’s water supply system. New Melones Reservoir was the last major state water infrastructure, and it was completed in 1979. At that time, California’s population was just over 23 million. In 2021, it was just over 39 million, an increase of about 16 million or about 70% more people now than then. It is true that both agricultural and urban water uses are much more efficient today than four decades ago, but our water shortage is not something we can conserve our way out of. We must improve the state’s water system to avoid future drastic shortages.
The population increase is just part of the problem. California’s weather is changing, and we have longer dry periods and more intense wet periods. We saw this over the last four years, with 2020 through 2022 being among the driest years on record and 2023 being among the wettest. Our reservoirs went from mostly full in 2019 to critically low in 2022. Although harder to see, our storage in groundwater basins fell dramatically in the dry years also.
A nuance of this latest drought was that both California and the Colorado River Basin were critically dry at the same time. In most past droughts, the Metropolitan Water District has been able to cover a shortage of water from Northern California with water from the Colorado River and vice versa. This time both were critically dry at the same time. This resulted in draconian water cutbacks in significant parts of the state, with large areas of agriculture taken out of production, banning of watering medians and landscaping, and in some areas without alternate supplies, a limit of one day a week of outdoor watering for residential customers.
California still has enough water to supply its needs, but it comes all at once, and we lack the ability to capture, transport and store water in wet years for use in dry years. We need to improve our capabilities of capturing stormwater and spring snowmelt runoff, transporting it to storage, and then transporting it to where it is needed in dry years. Constructed and operated properly, an improved state water system can provide sufficient water for agricultural, urban, and environmental purposes. If we have sufficient stored water, it can be released into waterways to support fish spawning and habitat preservation and moved to where it is needed for irrigation and urban uses.
This is not a problem we can solve with a single type of project. We will need to use everything at our disposal. Obviously, we must continue conservation and use water wisely. We also need to ensure that treated wastewater is beneficially reused rather than needlessly discharged to our waterways and, ultimately, to the ocean. Some wastewater discharge is necessary for riparian habitat preservation and for aquatic life, but in California, far too much is just gotten rid of rather than used beneficially for irrigation, groundwater recharge, or ultimately for direct urban reuse.
There are a number of brackish groundwater basins where water can be pumped, desalted, and used for beneficial purposes. In our area, this is already happening with the Arlington and Chino Desalters, which provide thousands of acre-feet of high-quality water annually. Ocean desalination is a proven technology that can be used to provide fresh water in the right circumstances.
With our wet winter in 2023, California’s surface reservoirs will be full this year. The groundwater basins are slower to fill, though, even though water is available to refill them, if we could capture and store it until it can be recharged into the ground. As an example, in December of 2022, 230,000 acre-feet of stormwater flowed into the ocean from the Sacramento San Joaquin delta that could have been put to beneficial use had we been able to capture and store it. Lake Mead and Lake Powell on the Colorado River are also recovering more slowly. They are likely to end the water year at less than 50% of capacity.
We need a state and local partnership to address our water supply problem. At the state level, we need more large surface reservoirs and the infrastructure to capture storm and snowmelt water and move it to the new storage. These will be big, expensive projects local water agencies, and even the Metropolitan Water District, cannot afford to construct. At the local and regional levels, we need to continue expanding our ability to capture and store storm runoff water. A number of new recharge basins have been recently completed, and a very large project is under construction below Seven Oaks Dam above Mentone on the Santa Ana River.
We also need to work to change the operation of flood control dams to allow water storage so long as that does not conflict with flood control. This has been done in partnership with the Army Corps of Engineers at Prado Dam near Corona. Except in very high water flows or a forecast of major rainfall with an already partly full reservoir, the Corps of Engineers releases water from Prado Dam only as fast as Orange County water agencies can percolate it into the underground water basins. Western Water and San Bernardino Valley Water District are currently working with the Corps of Engineers to change the operation of Seven Oaks Dam to allow storage of water behind the dam with the release of water consistent with the ability to percolate it into the water basins in the San Bernardino Valley and for habitat maintenance and aquatic species enhancement in the Santa Ana River. This is important to Riverside as the majority of Riverside Public Utility’s water comes from these basins, and the water level has declined significantly over the years.
We can all encourage our local elected officials and state legislators to support legislation and funding for important new state-level projects. With sufficient planning and investment, we can make our state and local water systems much more resilient to drought for the benefit of urban uses, agriculture, and the environment.