Assessing Dry Winter

SONORA, CA: Tuolumne Utilities District (TUD) staff is faced with the challenge of trying to forecast the remaining winter season and to project its water supply should the county not receive any significant rain or snow. Precipitation and snowfall are relied upon to replenish the main water supply for the county with water storage at Pinecrest and Lyons Reservoirs. PG & E owns and operates Pinecrest and Lyons Reservoirs, and the 15.7 mile Main Canal. In an agreement with PG & E, TUD receives its water supply from Lyons Reservoir through the Main Canal.

District Associate Engineer, Glen Nunnelley, tracks the lake level and water flows in and out of Lyons Reservoir. “Looking at today’s information, we can see that the current winter conditions are shaping up to be a very unusual dry winter weather pattern with conditions being consistent to one of the driest winter’s on record. One of the driest years on record was 1977. By the end of January in 1977, the Sonora area had received a total rainfall accumulation of 5.9 inches,” states Nunnelley. According to TUD sources, as of this January, the Sonora area has received a total of only 3.2 inches of accumulated rainfall. Comparatively, normal accumulated rainfall totals at this time should be about 17
inches. The National Weather Service has no rain predicted for the area in the next seven days.

Eric Hall, District Water Master, said “The District is taking the lack of water so far this season seriously.” Hall states, “In order to hold on to what water we have in storage, the District has turned down its water intake in the ditch system from Lyons Reservoir.” Hall’s crews are also constantly walking all 57 miles of the ditch system to make sure no water is wasted, checking for leaks and ditch services to insure that all water is being stored where it can. Hall also stated, “Typically the winter season is when the District does its annual water flushing of its treated water distribution system. Due to the current dry weather conditions most water flushing has been suspended.” The flushing of water lines typically occurs every year between the months of January and March. The reason for the flushing
is to clear out any sediment or minerals that may accumulate in pipes on an annual basis and to ensure quality water is delivered to customers. Hall encourages all customers to be on alert for the appearance of any unusual water occurrence that may appear to be a leak in the system whether it’s a home, business or ditch and to notify the District as soon as possible to investigate.

Peter Kampa, District General Manager, states “When you look at the large reservoirs below us (New Melones and Don Pedro) and can see those reservoirs are above average on water storage, it can be confusing to our customers if they are requested to conserve water. Especially frustrating is when the state announces that there is plenty of stored water available. Unfortunately, the reservoirs owned by PG & E which serve TUD are much smaller.”

Kampa continues, “The District is keeping in close contact with PG & E and with National Oceanic and Atmospheric Administration (NOAA) regarding the predicted weather forecast for this region. The District will also continue to monitor the lake levels at Pinecrest and Lyons Reservoirs to better estimate if and when water conservation from our customers is needed.”

The Tuolumne Utilities District currently serves over 44,000 Tuolumne County residents. The District currently owns and operates 15 water treatment plants, 71 treated water storage tanks, two wastewater treatment plants, approximately 57 miles of open ditches and 330 miles of treated water pipeline.

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