The first rain of fall forecast for Friday and Sunday is expected to drop between a half and three-quarters of an inch on various parts of the Stanislaus River watershed that South San Joaquin Irrigation District depends upon to supply water to farmers as well as the cities of Manteca, Lathrop, and Tracy.
That is welcome news — if it materializes.
But based on the National Weather Service (NWS) forecast modeling for the next three months and critical storage in the New Melones Reservoir, the odds of California — and particularly the Northern San Joaquin Valley — heading into a sixth straight year of drought are fairly strong.
“We are still well within the woods,” SSJID General Manager Peter Rietkerk noted Wednesday.
New Melones Reservoir storage as of Tuesday was at 527,559 acre feet of water or 22 percent of its 2.4 million acre foot capacity. More critical, though, is the storage is only at 39 percent of where it should be for Oct. 11 in a normal year for water. That makes New Melones the lowest reservoir based on time-of-year storage among the state’s eight largest water storage facilities.
Rietkerk noted the Stanislaus River watershed has arguably the heaviest regulatory flows — such as water released for fish and to combat salt water intrusion in the Delta — of any other major reservoir in the state. That puts additional pressure on SSJID water supplies.
The NWS is forecasting a drier October, November, and December than normal. Making matters worse the weather service expects temperatures to be higher than normal. In the past people have responded by not tapering off landscape irrigation as the calender rolls into winter. That would further stress carryover storage. When combined with less rain and snow — if that holds through April 1 — the drought’s grip won’t loosen and could actually get worse.
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It is against that backdrop the City of Manteca’s water conservation rule goes into effect if it rains Friday, Sunday or both days. The rule states no irrigation is allowed during or within 48 hours following measurable rainfall as defined by storms that generate run-off or puddles.
September marked the fifth consecutive month Manteca in month-to-month comparisons has seen a rise in water use from 2015 to 2016 as consumption rose 10 percent over last year.
Manteca in September used 21 percent more water than they did in the baseline year of 2013. Manteca’s target is to reduce water use 28% over 2013 levels
The upswing in Manteca water use comes as state officials are starting to talk about the possibility of re-imposing mandatory water restrictions after savings slid overall in August statewide. Forecasters are warning California could be headed into a sixth drought year this winter.
Manteca last year met the goal of reducing water 28 percent over 2013 levels despite adding more than 3,000 residents.
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