A record Sierra snowpack and above normal rainfall on the valley floor is unlikely to ease the need for the City of Manteca — and most over California cities — to watch their water use.

That’s because the day is coming when Manteca and other jurisdictions cannot take out more water from the groundwater basin than is replenished in a given year under a new state mandate for groundwater sustainability.

At the same time regulatory pressures for surface water from the Stanislaus River for fish flows and to combat Delta salinity poses a threat to water supplies that Manteca has been counting on through senior secured rights held by South San Joaquin Irrigation District to provide the bulk of municipal water in the coming years.

Two new city water

wells costing $7.9M

Also entering into the equation is the cost of drilling new wells and paying for Manteca’s share of the second phase of the SSJID operated surface water treatment plant to increase the city’s water supplies. Manteca us currently in the process of drilling two new wells — one at Yosemite Park southeast of the Union and Yosemite intersection and the other at Shasta Park next to Shasta School — at a cost of $7.9 million.

City officials have repeatedly warned that stepped up conversation is likely here to stay. 

That means requirements for new construction to use landscaping using less water will probably stay In place or even be stepped up. Most of Manteca’s existing water conservation rules that are being enforced had been on the books years before the current drought.

In addition to putting teeth into them by issuing warnings and citations the city eliminated one day of watering allowing residents and businesses to irrigate landscaping three days a week based on odd and even address system. They also banned watering within 48 hours following measurable rainfall as defined by storms that generate run-off or puddles.

Manteca exceeding

state targets for

water conservation

Water conservation efforts continue to meet or exceed state targets based on 2013 levels.

Manteca used 157.5 million gallons of water in February.

The last time Manteca used less water than it did last month was 13 years ago in February 2004. Back then 154.5 millions of gallons of water were used. Manteca had 60,958 residents in 2004. Today there are 76,000 residents for an increase in population of 25 percent.

While a rainy February helped cut Manteca’s water consumption by 35 percent from baseline levels established in 2013 and 12 percent from 2016, a concerted effort to educate people to conserve water plus more water miserly homes have helped the cause.

Manteca ended 2016 using 27 percent less water than the city did in 2016. The state selected 2013 as the baseline year to set community-level conservation goals aimed at reducing overall water use in California by 20 percent. Manteca just missed its state assigned goal of a 28 percent cutback.

Manteca has reduced water consumption by 20% since 2006 despite adding 12,000 residents. The city used 4,675 millions of gallons of water in 2006 compared to 3,759 million of gallons in 2016.

While part of the savings is reflected in low-flow, high-efficiency toilets as well as water efficient washing machines that are among the top three residential indoor uses of water along with showers and baths, the bulk came from the city’s effort to switch irrigation of its 300 plus acres of parkland from the domestic water system to shallower wells that tap non-potable water. The primary driving force was to reduce the water bill the parks department incurs from the inter-department charges for treated water.  It also reduced the need for dropping deeper and more expensive drinking water wells and expanding the portion of Manteca’s water from the surface water treatment plant. It also had the bonus impact of increasing water pressure given park irrigation takes place over night and also during early morning hours when people are hitting bathrooms preparing for the day.

Groundwater pumping

at a third of peak

level in 2004

The year-end water consumption report showed another favorable trend for Manteca. Since Manteca started using treated surface water from the Stanislaus River Basin in 2005 the reliance on groundwater that is now targeted for by the state to keep at a set level has continually dropped. During the last three years surface water has accounted for nearly 60 percent of overall use.

Groundwater pumping is almost at a third of what it was in the peak year of 2004.

Having surface water allowed Manteca to avoid installing several specialized treatment plants on well heads after federal standards on lead — which occurs naturally in water — were tightened significantly. The much cleaner surface water is blended with the well water to exceed the new federal standards, besides avoid upfront costs it also eliminated a $500,000 charge per well every two years to replace elaborate filters.

Conserving is also paying dividends financially for Manteca residents. Reduced water use during the first eight months of 2016 kept $1.8 million in the pockets of Manteca residents and business. That is based on roughly a 28 percent water savings over the water consumption level for the same January through August period of 2013.

An update of the city’s state-mandated water management plan in September showed Manteca has already met a pre-drought mandate set by the state to reduce per capita water consumption to 179 gallons by 2020. Water use in 2015 was 139 gallons per capita, down from an average of 223 gallons per capita between 1996 and 2005. 

To contact Dennis Wyatt, email dwyatt@mantecabulletin.com