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Applying pressure to conserve

Plan would reduce overall SSJID water use by 10%

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Applying pressure to conserve

Farmers inspect the Division 9 SSJID reservoir that is used to pressurize water deliveries to crops south of Manteca and west of Ripon.

HIME ROMERO/The Bulletin

POSTED August 27, 2014 12:48 a.m.

The South San Joaquin Irrigation District is studying a pressurized water system between Woodward Reservoir and the Van Groningen Road reservoir near Escalon that could save enough water to supply all of the current needs of Manteca and Lathrop.

The SSJID board Tuesday was told a pressurized line replacing the district’s main canal that is uncovered and unlined is feasible. Engineers estimate such a pressurized system would save 26,400 acre feet of water a year or roughly 10 percent of the water the district currently uses for all urban and farm uses.

An acre-foot translates into 325,851 gallons. Manteca’s water use in July — the peak month for water consumption — was 557.4 million gallons. Based on annual water use by Manteca and Lathrop the savings from the proposed pressurized system is equivalent to the combined current use of water in the two cities.

SSJID General Manager Jeff Shields noted that doesn’t include savings that could occur if the entire delivery system for the 72,000 acres in the district is switched to a pressurized system such as has happened in Division 9 south of Manteca and west of Ripon.

The board directed staff to continue working with Stantec Davis Engineering to study the next milestone in the extensive study.

The results to date indicated a gravity flow pressurized system without the need for energy to run pumps is feasible. The 130-foot drop from Woodward Reservoir to the district’s main reservoir within its service boundaries is enough to deliver 50 to 55 pound pressure. That will allow the operation of drip irrigation that can save additional water when orchards and vineyards — the primary use of farmland in the SSJID territory — are irrigated.

“It would also save us a lot of cost in the chemicals we have to use to keep the water clean,” Shields said noting water flowing from Woodward Reservoir in an enclosed pressurized system would not be subject to evaporation loss and would “stay clean.”

The next milestone involves looking at specific costs as well as the impacts on groundwater.

The seepage from the canal has been recharging underground water tables for over 100 years. 

Shields said that may not be an issue if what happens elsewhere in the district follows the Division 9 experience. 

Once the pressurized system was in place, all farmers in the Division 9 area that could access the system stopped underground pumping and to end a big drain on the aquifer.

Shields noted the cost drops significantly for farmers as they are not paying massive PG&E power bills to run pumps. It brings the use and cost of water down significantly.

At the same time pressurized drip systems allow fertilizers and other crop maintenance to be delivered with the water further reducing costs and increasing the efficiency of applications.

The Division 9 pressurized system has been lauded by federal and state water officials as the most cutting edge system of its kind in the nation in terms of efficiency and technology. The system is controlled by ditch tenders and farmers through the use of apps on smartphones or tablets.

The potential construction of a pressurized system would be bankrolled from proceeds of SSJID’s share of Tri-Dam Project power sales. Tri-Dam is a joint venture with the Oakdale Irrigation District.

Shields has indicated the revenue from the electrical sales will allow the district to pursue both additional water conservation projects such as the pressurized system and implement a retail power system that will lower rates by 15 percent.

The San Joaquin County Local Agency Formation Commission next month is expected to determine when hearings will take place for the district’s request to takeover the PG&E system.

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