The week of March 10-16 was national Groundwater Awareness Week. Riverside Public Utilities gets 100% of its drinking water from local groundwater basins, and Western Water gets about 40% from local groundwater.
Like a surface reservoir, groundwater can be pumped in dry years and replenished in wet ones. The wet winter of 2023 and the heavy rains so far this year have allowed California to refill its surface water reservoirs and begin to replenish over-drafted groundwater basins throughout the state. Some good progress was made on replenishing groundwater this year, but the process of getting water into the ground is slower than filling a surface reservoir. The basins in the San Bernardino area, where Riverside gets most of its water, and Western gets some of it, remain below desirable levels.
Significant efforts are being made to store more groundwater, including the construction of more facilities to inject and percolate water into underground basins. Locally, water agencies are capturing more stormwater and local runoff and increasing the use of treated wastewater to replenish groundwater.
As we all saw, California, and particularly Southern California, had heavy rain in the first part of this year, but Northern California did not get as much rain as the south, and snow was generally less than in an average year. That has changed with recent storms that dumped much snow in Central and Northern California. At the end of February, the statewide snowpack was only 80% of the average. As of March 11, that had increased to 100% of average, and overall precipitation was at 107% of average.
California went into this year cautiously from a water forecasting perspective. The water year begins October 1, and the period from October through New Year’s Day was relatively dry. The State Department of Water Resources operates the State Water Project, which brings water 700 miles from Lake Oroville to Southern California, dropped the allocation of State Water project water available from 100% in 2023 to just 10% to conserve water in Northern California Reservoirs in case the water year stayed below normal. In February, the allocation was increased to 15%, and that will be updated on April 2. Most observers anticipate the allocation will be increased – perhaps substantially.
The Metropolitan Water District (MWD) provides imported water to most of Southern California to supplement local water sources. MWD is the source of the imported water Western serves and, should Riverside need it, would provide imported water to Riverside. The level of State Water Project allocation is important because it determines whether imported water is available for groundwater recharge. Generally, if the allocation is below 30%, State Water Project water is not available for recharge. If it is above 30%, it is available for recharge. Long-range weather forecasts suggest there will continue to be significant precipitation in much of California, and most observers believe the State Water Project will go above 30%. Local water agencies are hopeful this will be the case and that we can continue replenishing local groundwater basins.
As was mentioned in an earlier article, water from the Colorado River is being restricted, and those that divert water from the Colorado River are all cutting back. The wet year in 2023 and good precipitation in the Colorado River Basin this year have allowed water levels in Lakes Powell and Mead to increase significantly, but they are still far below full. Southern California will continue to get Colorado River water, but the amount will decrease over time rather than increase. As with State Water Project water, Colorado River water can be used to replenish groundwater in wet years, but little will be available for this purpose in dry years.
Overall, the water picture for California and the Inland Empire is good for the next couple of years, and we are positioning ourselves for the next drought, which will surely come. You can help by continuing to use water wisely, even in wet periods, so that we will have supplies to carry us through the dry periods.
