Why does Sierra rain, snow help Modesto but not Turlock?

While it did not turn out to be a Miracle March, the rain and snow that walloped the Sierra Nevada this month bolstered what had been a paltry water year.

But the storms will have different impacts in the Northern San Joaquin Valley.

Modesto — which relies on wells and the Tuolumne River for its water — will increase the watering of lawns and other landscaping from twice to three days a week effective April 1.

That's because the city is receiving its full allotment of Tuolumne River water from the Modesto Irrigation District, a benefit of last year's record rain and snow that recharged groundwater and filled reservoirs, after several years of severe drought.

Still, the recent storms are good news for the city and others that rely on Sierra Nevada rain and snow.

"We are very fortunate to have these late-season rains, and we are getting our full allotment," Modesto Utilities Director Will Wong said. But customers who rely only on wells, including those in Del Rio and Grayson, will be limited to twice-a-week watering.

It's a different story for Turlock and other Valley cities that draw on wells for their water.

Municipal Services Director Michael Cooke said Turlock is in its third year of allowing once- or twice-a-week watering, depending upon the time of year. He said the city switched to twice a week March 1.

Cooke said six of Turlock's 24 wells are not in use, primarily because of contaminants. He said the city is working with consultants to get at least three wells operating by summer.

But Turlock and Ceres are working to secure their water future through building a treatment plant near the Fox Grove Fishing Access on the Tuolumne River. The cities are partnering with the Turlock Irrigation District on this.

Cooke said the initial estimate for the project is $277 million, and the goal is for the plant to open in September 2022. He said construction of a structure that would draw water from the river before it is pumped to the plant is expected to start in July.

Cooke said the treatment plant will provide the two cities with about half of their water and offer a more reliable and better water source. It also will help recharge groundwater.

The Modesto Irrigation District reported that downtown received about a half-inch of rain in the last seven days, bringing its seasonal total to 5.45 inches. Modesto's historical average is 12.23 inches in a normal water year, which is Oct. 1 through Sept. 30.

The National Weather Service in Sacramento said the Sierra Nevada received 3 to 5 inches of rain over the seven days, with higher elevations receiving 7 to 9 inches of water in the snow that fell.

As of midnight Sunday, Don Pedro Reservoir on the Tuolumne River was at 89 percent capacity, which was 122 percent of its average for this time of year, according to the state Department of Water Resources. New Melones Reservoir on the Stanislaus River was at 83 percent capacity, which was 133 percent of its average.

Don't expect a repeat of these storms. The National Weather Service's Climate Predication Center says the outlook for April is for above-normal temperatures and below-normal precipitation for the southern two-thirds of California, including Modesto.

This story was originally published March 26, 2018 at 4:58 PM with the headline "Why does Sierra rain, snow help Modesto but not Turlock?."