With the filling of Lodi Lake, the Woodbridge Irrigation District Fish Screen is now up and running to keep fish from entering the irrigation canal and continue their swim upstream. (Courtesy photograph/Alan Macisaac)

$3.5 million project finished

Fish screen provides elaborate way for fish to return to Mokelumne

Bet you didn't know that a baby salmon could squeeze through a metal screen with slots as wide as the depth of a penny.

That's why the screens of the new Woodbridge Irrigation District fish screen have holes you can't even slide a penny through. Instead, they're 1.75 mm thick — about seven-tenths of an inch, or the depth of a dime, said John Wookey, assistant to Woodbridge Irrigation District Manager Andy Christensen.

The irrigation district has just completed the elaborate $3.5 million fish screen project that will keep salmon and other fish out of the irrigation canal system and in the Mokelumne River where they belong, Christensen said.

"It's allowing Woodbridge to take its (water) diversion and protect the fish," he added.

It finally allows farmers to get the irrigation water they need after a threeto four-week delay. Water normally begins flowing to farmers in Woodbridge and areas to the west and south of the community in the second half of March, but this year, the spigot didn't get turned on until April 15.

"'There are some very thirsty lands out there," Christensen said.

But the Woodbridge Irrigation District needed to finish the fish screen before releasing irrigation water for the year, Christensen said.

The fish screen, which replaces a smaller worn-out 40-year-old screen between Lodi Lake and Woodbridge Dam, was constructed in six-and-a-half months, beginning Oct. 1.

Some of the 50 kinds of fish that swim through the main part of the Mokelumne River head through an opening at Woodbridge Dam toward the Delta and San Francisco Bay. Other fish make a detour through Lodi Lake and through a waterway west of the main part of the river and back to the dam and down the river.

But some of the wayward fish that go through the adjacent waterway make a sudden left turn toward the irrigation canal delivering water to farmers west and south of Woodbridge. That's where the fish screen comes in.

The fish first swim underneath two 47-foot-high concrete walls connecting a service road and into a separate canal just for them. The canal gets very narrow, and after going about 200 feet west of the river, the fish canal makes a 180-degree turn and goes 100 feet east — back toward the river, Christensen said.

But before it reaches the river, the pipeline turns north and goes another 1,800 feet. The fish exit into the river, just downstream from Woodbridge Dam, Christensen said.

So why must fish take such a circuitous route to be navigated back to the river?

"You're providing a safe, proven method of transporting fish and taking them back to the river," Christensen said. "It gives the fish the right cues."

There are 30 fish screens at the Woodbridge site, with each one costing $10,000, Christensen said. They're stainless steel so that they can withstand exposure to water, he said.

The $3.5 million has been completely financed by the Woodbridge Irrigation District, Christensen said. There was no financial contribution by the state or federal governments, he said. However, the district borrowed $13.3 million, which is being paid off by ratepayers and by the cities of Lodi and Stockton, which are buying water from the irrigation district, Christensen said.

Contact reporter Ross Farrow at rossf@lodinews.com.