Dry year water impacts weighed

By Chris Caskey, The Union Democrat April 24, 2013 01:30 pm

While snow levels from winter indicate that this summer’s local water supply should be better than last year, that could still change, according to leaders with the Tuolumne Utilities District.

On Tuesday, TUD engineers gave an update to the district Board of Directors on the district’s supply. Though the winter saw below-average precipitation, district engineer Glen Nunnelley said the snow is melting quickly as we head into a possible warm spell. 

When coupled with weather forecasts predicting above-average temperatures in the coming weeks and months, he said there are some concerns about the quicker runoff.

“We’re going to watch how fast this melts off,” he said.

The rate of snowmelt is especially crucial in dry years, as the water supply for TUD depends heavily on when water stops spilling over the dam at Pinecrest. Called the “end of spill,” the point when the reservoir is full but not overflowing.

A relatively new state regulation setting the elevation of the lake level at 5,608 feet above sea level through Labor Day means local water officials use the “end of spill” date to gauge how tight the summer supply will be.

Nunnelley said this year’s predicted end of spill will likely be “an improvement over last year” — one of the earliest on record. Last year’s dry winter led to district-wide water conservation even after the district and Pacific Gas and Electric Co. took measures to control waste.

“We can get through these conditions, but they’re tight,” he said.

TUD, the county’s largest water agency, gets most of its water from Pinecrest and Lyons reservoirs through a contract with PG&E, which operates hydroelectric dams on the South Fork Stanislaus River. The district also draws water from Phoenix Lake Reservoir.

Most of the water comes from snowmelt off the Central Sierra Nevada mountains.

The most recent snowpack survey, taken at the beginning of the month by the Department of Water Resources, found the water content was 58 percent of average for this time of year.

The summertime level of Pinecrest is a bone of contention. The California Water Resources Control Board set a minimum level through the end of the summer for recreational purposes.

Recreation and environmental advocates say TUD needs to fix leaks and water loss issues in its own system, which includes 19th century open canals known as ditches, before drawing down the lake. But TUD says the district and PG&E have historically had more flexibility with the lake level in dry years, and say the restriction is unwieldy and will negatively impact customers in the long run.

The state water board is still considering a final decision on the Pinecrest lake level.