The string of wet storms that have blanketed the Sierra with a snowpack with water content almost 200 percent above normal and drenched sections of California with as much as 10 inches of rain wasn’t supposed to happen.
Meteorologists were expecting a relatively dry winter.
And while the water outlook for summer is strong especially for the South County, state water authorities are carefully monitoring how the weather unfolds for the next few months as the snowpack could diminish before the spring run-off.
They are also concerned about flood control. There is precedent for unusually heavy snow fall in early winter to be followed by unseasonably warm weather in the higher elevations triggering extensive flooding. That is what happened in January of 1997 when heavy run-off from a warm spell overtaxed levees southwest of Manteca. The end result was 35 square miles flooded, $100 million in property damages, 2,000 people evacuated, 20,000 head of cattle relocated, and 800 homes and other structures sustaining some form of water damage.
The flooding occurred even though it hadn’t rained in the South County for more than two weeks.
“It (the weather pattern) was expected to be relatively dry this winter,” noted South San Joaquin Irrigation District General Manager Jeff Shields. “No one anticipated it to be similar to El Niño conditions.”
Shields noted there is less of a concern this winter should things heat up with unseasonably warm temperatures since New Melones Reservoir on the Stanislaus River has well over a million acre feet of storage capacity left. The overall capacity is 2,419,500 acre feet.
That is even with a massive flow of 16,500 acre feet into the reservoir on a daily basis during the storms. By comparison, Woodward Reservoir 16 miles northwest of Manteca has a capacity of 36,000 acre feet.
New Melones’ water elevation was much higher during the events that led up to 11 breaks in the levees along the San Joaquin and Stanislaus rivers in early 1997. As a result, the Bureau of Reclaimation had to release water aggressively from the reservoir. Higher flows from New Melones hit the confluence of the Stanislaus and San Joaquin rivers southwest of Manteca at the same time as heavier releases from other dams on the San Joaquin River watershed did. It was the pressure of the water that triggered the boils that led to the levee failures.
At the same time, the current high water content in the snow doesn’t necessarily translate into full deliveries for those who rely on the state and federal reservoir systems in California. However, SSJID along with Oakdale Irrigation District, have rights to the first 600,000 acre feet of water that flows into New Melones each year. That has already happened assuring 100 percent water deliveries.
“We’ve had 100 percent water deliveries for the past three dry years,” noted Shields.
How SSJID has been able to do that is the fact voters in the two districts back in 1926 secured the rights to additional Stanislaus River water with the building of the original Melones Dam.
Melones Dam was credited with saving farmers in the SSJID several times over the next 20 years when drought periods devastated farm production in other parts of California.
The Bureau of Reclamation built the 2.4 million acre-foot capacity New Melones Dam at the site of the original Melones Reservoir. Part of the agreement for the two districts giving up the dam site was to assure them of a set amount of water – 300,000 acre feet in a typical year – based on their historic superior water rights on the Stanislaus River.
And even though the district has ample water they are undertaking what Shields called “an extremely aggressive” water conservation effort working with farmers starting in January.
The SSJID board has set aside $1.5 million for the first year to partner with growers to implement water conservation programs.
Besides supplying 72,000 acres of farmland in the triangle of Manteca, Ripon, and Escalon with irrigation water the district also provides domestic water supplies for Manteca, Lathrop, and Tracy.