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So, why are those Stanislaus County canals filled with water?

Water flows through an irrigation canal off Virginia Avenue in Modesto on Thursday.
Water flows through an irrigation canal off Virginia Avenue in Modesto on Thursday. aalfaro@modbee.com

Why are some canals full of water if Modesto Irrigation District’s season doesn’t start for another week?

And why is the Stanislaus River brimming with water? Don’t the people who run those dams up in the hills know we’re facing one of the worst droughts in history?

Calm down, people. These questions have answers.

Let’s look first at MID canals. Water has been flowing into some canals for weeks, off and on. But it’s not melted snowpack from the Tuolumne River, which won’t start filling canals until Easter Sunday.

What you’re seeing is groundwater pumped from wells. A farmer whose crop can’t wait until after Easter can use an MID canal at no charge to carry groundwater from his private well to the point where he takes it out to put on that thirsty crop. Or he can rent a district pump and do the same.

Because of minerals in groundwater, it’s not as pure as surface water from the river, and the cost of electricity for pumping makes it far more expensive. But even in irrigation districts, groundwater often keeps trees and plants alive and plays a critical role during a drought. Outside of irrigation district boundaries, many nut orchards survive exclusively on groundwater.

During irrigation season, a constant flow of river-fed canals keeps them charged, or full enough to create the pressure that farmers need to take water when it’s their turn. In the off-season, they use weirs to book-end canal segments, creating a bay from which to pull water with a pump. Because of dry weather, some 200 MID wells rented by farmers have been going full-tilt.

Some country folks with domestic wells have questioned whether these huge, industrial-size wells suck from the aquifers they depend on, perhaps resulting in shallower wells going dry. Most complaints have not been within MID’s territory.

By the time people around Modesto read this, the canal they’re used to seeing is dry, or soon will be. That’s because MID crews need a few days between the end of groundwater pumping and the start of irrigation season to remove weirs, temporary blocks in the canal made of concrete or lumber.

Most farmers rely on a combination of water sources: private pumps, district pumps, surface water, transfer programs and what little rain fell in the winter. There is nothing unusual about canals transporting groundwater before or after the formal irrigation season, but heightened awareness of water issues in this fourth consecutive drought year prompts calls and emails from the curious, MID spokeswoman Melissa Williams said.

“And same as canals, people notice when the river’s up,” she added, leading to the second question.

‘Pulse flows’ aid fish

For this answer, we’ll turn to the Oakdale and South San Joaquin irrigation districts because they depend on the now-swollen Stanislaus. Actually, a three-day surge in dam releases was scheduled to end Thursday, so the river level might be about back to normal by the time people read this.

But many noticed, and some were angry – including those who could be affected if the partner districts were to drain Lake Tulloch this summer as a drought-coping strategy. Similar surges will follow mid-April to mid-May, and again in October, and it’s all part of a high-level effort to benefit migrating fish.

For several decades, foothill dams holding snowmelt have released it little by little throughout the year. The gradual flow enabled the Valley to blossom in agricultural glory, but environmental advocates blame the unnatural flow for nearly exterminating steelhead trout and salmon; they need bigger rivers in the spring to push them to the Delta and out to sea, and to return to spawn in the fall.

The Endangered Species Act of 1973 started changing things, resulting in so-called pulse flows of recent years, timed to best help fish. The flows can swell the Stanislaus from 150 cubic feet per second to 1,000.

“It’s a cookbook approach to fisheries management,” OID General Manager Steve Knell said of release tables proscribed by the federal government.

Unaltered, the mandatory fish flows might have reduced the Stanislaus to a trickle by fall. Negotiations involving OID, SSJID and federal officials a few days ago produced a tentative deal for relaxed fish-flow requirements while reserving enough for fall spawning, and at the same time keeping Tulloch full enough for tap water and recreation demands through September.

U.S. Reps. Jeff Denham and Tom McClintock and state legislators Kristin Olsen, Tom Berryhill and Adam Gray praised the deal, but it could fall apart if state water leaders don’t give it a green light in mid-April. That could provoke a lawsuit involving the districts, its officials said.

The congress members on Thursday sent a letter to the California State Water Resources Control Board saying they’re “adamantly opposed” to pulse flows “for the theoretical benefit of fish populations,” especially in time of drought, and calling the deal “a delicate balance between competing needs.”

Jack Cox of the Lake Tulloch Alliance said fish-flow policy “waste(s) enough water to supply the cities of Modesto and Stockton combined for one year.” The group will stage a Water Crisis Forum at 10 a.m. Saturday at 920 Black Creek Drive in Copperopolis. For more information, go to www.laketulloch.org/.

The Tuolumne – the source for MID and its larger partner, the Turlock Irrigation District – also is subject to federally ordered pulse flows. The next will begin Wednesday and last through April 11, peaking Friday at 1,222 cfs.

Bee staff writer Garth Stapley can be reached at gstapley@modbee.com or (209) 578-2390.

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