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Stanislaus River basin suffering from its 5th driest year since 1901
New melones
New Melones Reservoir is at 25 percent of capacity for this time of year.

On any given day a small group of farmers gather behind Jimmy’s One Stop on Airport Way, kick back in resin patio chairs and shoot the breeze under a canopy of ragged trees.

If they glance to the east they can see the future of Manteca — as well as farmers in the South San Joaquin and Oakdale irrigation districts plus struggling Chinook salmon in the Stanislaus — flow by in the San Joaquin River.

The usually anemic mid-summer flow of the San Joaquin is being substantially augmented at the potential expense of sufficient water next year for 200,000 residents and 56,000 acres of ag land the SSJID serves.

The water joining the San Joaquin from the Stanislaus River at its confluence less than a quarter of a mile away at Vernalis is due to abnormally high seasonal releases from New Melones.

Releases from New Melones — the linchpin reservoir on the Stanislaus River watershed for storage and flood control with a 2.4 million acre foot capacity — are flowing at 1,500 cubic feet per second (cfs).

In water jargon that’s the equivalent of 1,500 basketballs filled with water passing a specific point in a second.

The normal outflow this time of year from New Melones is 350 to 400 cfs. While the Bureau of Reclamation plans to taper releases down to 400  to 600 cfs in the coming days, more water than usual will be sent out of the reservoir despite this year shaping up as the fifth driest in 120 years on the Stanislaus River watershed.

It sounds like pure madness unless you operate the Metropolitan Water District (MWD), the largest purveyor of water in the Los Angeles-San Diego region that relies heavily on water stored behind Shasta, Oroville, and Folsom dams where water levels are crashing fast.

Shasta and Oroville releases have been designated in agreements to address salinity issues in the Delta. Water stored at New Melones was legally committed only to address water quality and salinity issues at Vernalis.

How that benefits the MWD is simple. The more robust releases passing under the Airport Way Bridge 10 miles south of Manteca is helping keep saltwater intrusion at bay so water being pumped into the California Aqueduct to start its 444-mile journey as far south of San Diego doesn’t have its quality compromised with salt as it heads toward South State faucets and hose spigots.

It also means conserving water behind Shasta for the crucial Sacramento River salmon run in the fall.

What this means from the perspective of the SSJID that next year water cutbacks to Manteca, Tracy, Lathrop, and farmers could be in the works.

That wasn’t the outlook just five months ago.

New Melones had about 1.5 million acre feet with 68 percent storage placing it in the most robust position of the state’s eight largest reservoirs.

“Based on the hydrology at the time, it looked like we (SSJID and OID) would likely be OK for next year with our conservation account (the two district’s carry over),” SSJID General Manager Peter Rietkerk shared with the Manteca Rotary during their meeting at Mountain Mike’s.

That was before premature warm weather started melting the Sierra snowpack causing much of the moisture from snow to seep into the soil reducing the runoff in this second year of the current drought to 340,000 acre feet. The average year the Stanislaus River basin yields 1.1 million acre feet in runoff.

Then the Bureau shifted releases for Delta water quality to New Melones.

Rietkerk indicated it is now likely by the end of the water year New Melones will fall possibly significantly below 1 million acre feet. As of Wednesday it was at 1,438,694 acre feet that is 41 percent capacity and 68 percent of capacity of historic capacity for Aug. 11

As things stand now three of the six driest years on the Stanislaus River basin will have occurred during the current six year period stretching back to 2015. The fourth driest was in 2015, this year is expected to be the fifth driest and 2014 was the sixth driest.

Manteca, Lathrop, and Tracy all receive treated water from SSJID in addition to pumping water from aquifers. However, all areas in California are facing a looming mandate preventing them from taking more water out of the ground than they return in a given year.

SSJID officials have made it clear that if everyone uses water wisely — from farmers to urban users — that the district should be able to meet basic needs without imposing draconian cutbacks.

As things stand now the district will need to tap into 15,000 acre feet of its conservation account to meet this year’s water needs.

OID and SSJID have rights to the first 600,000 acre feet of water that flows into New Melones each year. That is based on a 1988 agreement that acknowledges the district’s historic water rights. Melones Reservoir the two districts built in 1925 was inundated in order to build New Melones with its 2.4 million acre feet of capacity.

 

To contact Dennis Wyatt, email dwyatt@mantecabulletin.com