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Manteca: Reliance on SSJID water growing
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Manteca’s municipal water fortunes will become more and more reliant on how well the South San Joaquin Irrigation District protects and manages its water rights to the middle fork of the Stanislaus River watershed.

The Kennedy/Jenks Consultants update costing $190,000 for the state-mandated urban water management plan that is before the City Council Tuesday for adoption notes the city’s groundwater supply will top out at 13,570 acre feet of water in 2020. Meanwhile demand will grow from an estimated 14,307 acre feet for the current year to 20,250 acre feet by 2020 and 29,770 acre feet by 2040. That means more than half of the city’s water will come from the SSJID.

Currently the city relies on a mixture of groundwater and treated surface water from the SSJID to meet the needs of municipal users. The city goes exclusively to well water during the winter months and takes surface water as the weather warms up. Manteca currently has 21,647 water service connections and uses 12,000 acre feet of water per year.

The study bases needs on a population of 72,169 in 2015 growing to 127,740 residents by 2040.

Another state mandate regarding water consumption requires Manteca’s per capita water use not to exceed 179 gallons on a daily basis by 2020. 

The average daily per capita use has been dropping. From 1996 to 2005, the average use was 223 gallons and from 2003 to 2007 it was 221 gallons. The 2015 interim target was 201 gallons per capita that the city exceeded significantly due to the 28 percent cutbacks driven by conservation efforts during the fifth year of California’s drought. The per capita use in 2015 was 139 gallons per day or 40 gallons less than the 2020 target.

The realities of the state groundwater management mandate means the city needs to rely on surface water more and more as the years go by. It is the same surface water the Department of Water Resources now wants to take from the SSJID and Oakdale Irrigation District to almost double water flows for fish in the Stanislaus River from January through June.

It is the same plan the state concedes will fallow 240,000 acres of farmland in San Joaquin, Stanislaus, and Merced counties as well as cost at least 6,756 jobs throughout the 209 region.

The city’s urban water plan calls for an increase in the use of treated recycled wastewater. Currently 1,030 acre feet are used to irrigate crops on land leased by farmers around the treatment plant site. By 2035 the use of treated water for agriculture will be nearly eliminated as the treatment plant site is developed as part of the family entertainment zone and envisioned business parks along the future extension of Milo Candini Drive that now ends at the northern edge of the Big League Dreams sports complex parking lot. By 2035, 410 acre feet of treated wastewater is expected to irrigate the golf course while another 40 acre feet will irrigate landscaping. Five years later in 2040 some 1,700 acre feet of treated recycled wastewater is anticipated to irrigate landscaping throughout Manteca.

The report notes that while Manteca has not studied the feasibility of the city utilizing storm water to meet municipal needs it does own infrastructure needed to store and treat storm runoff. The city has 170 miles of pipeline, 36 pump stations, and 35 detention basins to move and collect water that is eventually sent into SSJID canals and out to the San Joaquin River.