The first water to irrigate South County orchards and farmlands will likely start flowing through South San Joaquin Irrigation District canals between Feb. 26 and March 5.
The SSJID board authorized Chairman Dale Kuil to make the call after consulting with staff on the progress of critical infrastructure work including in takes at Woodward Reservoir for the treatment plant supplying water to Manteca, Lathrop, and Tracy. The SSJID stressed Wednesday that no definite decision on the start of irrigation has been made.
The board Tuesday was updated on the water outlook for the 2018 season. Based on current conditions on the Tri-Dam Project on the Stanislaus River watershed there is a projected 275,000 acre feet of water that will come from the existing snowpack as it melts. Half of that water will go to Oakdale Irrigation District, SSJID’s Tri-Dam partner.
That water coupled with what is left in the conservation account at New Melones Reservoir after the Bureau of Reclamation responded to dry conditions in January and stopped flood control releases should provide the district with upwards of 240,000 acre feet of water.
The district last year used 200,000 acre feet of water thanks to conservation efforts by both farmers and the three cities. If use happens to go back to 2013 levels by agricultural, municipal users, or both the district could find itself in a precarious situation this year. SSJID in 2013 used 239,000 acre feet of water.
On Wednesday, SSJID General Manager Peter Rietkerk said the district is fairly confident they will be able to meet all water needs this year without an issue based on wise water use patterns for the past three years.
Rietkerk noted it always makes sense to use water wisely given California’s unpredictable hydrology. He noted the jury is still out as to whether California is slipping into another drought year. The latest drought monitor information compiled by the US Department of Agriculture rates 81.73 percent of the state as abnormally dry, 45.6 percent of the state in moderate drought, and 6.39 percent of the state — Los Angeles, Ventura, Santa Barbara, and part of Orange counties — in severe drought.
Updated National Weather Service models indicate there is a 90 percent possibility that the balance of winter and early spring will result in a snowpack on the Stanislaus River watershed that will produce a runoff of 410,000 acre feet into New Melones Reservoir. SSJID and OID are entitled to the first 600,000 acre feet of snowpack runoff each year that they split in half.
Assuming the NWS forecast is correct, SSJID would have 205,000 acre feet of runoff this year meaning they could meet all of their needs without dipping into the conservation account that has 103,000 acre feet left in it or 51,500 acre feet for each district.
“Based on hydrology we are expecting the runoff to come in at between 275,000 and 410,000 acre feet this year,” Rietkerk noted.
That means even of if the worst case scenario happens and it is on the low end, the water conservation account would allow the district to get by this year based on 2017 usage.
The current increased flow in the Stanislaus is to meet water flow requirements on the San Joaquin River at Vernalis south of Manteca.
Rietkerk expects the intake work at Woodward Reservoir to be done in time to allow the water season start call to be made by Kuil the week of Feb. 26.
The work on the intakes has been needed for a number of years but the district opted not to do it during the drought as it would have required reducing storage level causing the loss of water that might have been needed for irrigation or municipal uses.
The fickle California hydrology underscores how critical the SSJID being established 109 years ago and its decisions to build reservoirs in conjunction with OID has been to the ability to farm as well as urbanize the South County.
Without a steady water supply that reservoirs and secured water rights provide it is highly unlikely there would be significant orchards or vineyards in the region.
Orchards typically take three or so years to establish and vineyards longer. Unlike farming row crops that could go fallow in a drought, if enough water is not supplied during a dry year trees and vines die off.
Some farmers in the western end of the district around Manteca and Ripon where the soil has sandy loam and doesn’t hold as much moisture have been concerned about having water available after the almond blossoms set.
 
To contact Dennis Wyatt, email dwyatt@mantecabulletin.com