Tulare Lake now has more water than some California reservoirs. Efforts made to slow flow

About 160 square miles of the historic Tulare Lake basin are under water as a result of flooding from a combination of this winter’s atmospheric river storms and a record snowpack that continues to melt in the southern Sierra Nevada.

Much of the submerged area is farmland that in most years is high and dry. But the ongoing flow of runoff from melting snow is anticipated to drive the amount of land that’s inundated by floods higher, to between 182 and 260 square miles.

The figures come from an update presented Monday afternoon from the California Office of Emergency Services and the state Department of Water Resources, both of which are monitoring flows on the Kings, Kaweah and Tule rivers that feed the Tulare Lake basin and managing efforts to prevent flooding from encroaching on communities including Corcoran.

To minimize the risk of flooding, state water officials took the rare step of opening a connection from a flooded river into the California Aqueduct — one of the latest measures to divert water from reaching Tulare Lake in the first place.

“There are multiple concurrent efforts under way … to move water around and ultimately protect communities in the Central Valley,” said Brian Ferguson, a spokesperson for the state Office of Emergency Services. “We are in significantly better shape than we were several weeks ago. We … are not forecasting nearly as severe damage as perhaps we were several weeks ago.”

That does not mean the flood risk for Corcoran or other communities from flooding has fully abated.

“We are not out of the woods by any stretch of the imagination,” Ferguson added. “While perhaps the most serious risk may have been averted, we don’t know what we don’t know yet in terms of how fast the water comes down the mountain, what levee may have squirrels in it that we’re not aware of or a million other things that we don’t necessarily control as human beings.”

“The public in these communities should continue to be aware of the challenges that lie ahead and we’ll continue to be in this situation at least through the month of July.”

Mehdi Mizani, deputy state flood plain manager for the Department of Water Resources, estimated that the volume of water in Tulare Lake is likely to approach or exceed 620,000 acre-feet by the end of May. By the time the flooding reaches its peak — and various computer models put that at anywhere between the end of May and mid-July — there is a 50% likelihood of about 700,000 acre-feet, and a 10% chance of as much as 931,000 acre-feet.

The staggering growth of Tulare Lake can be put into perspective by comparing it with the capacities of nearby reservoirs. Millerton Lake, for example, has a storage capacity of 520,500 acre-feet. Lake Kaweah can store 185,000 acre-feet. Lake Success can store 82,000 acre-feet.

An acre-foot amounts to about 326,000 gallons, or enough to flood an acre of land under one foot of water.

The state has already put up more than $17 million to raise about 14.5 miles of levees standing between the flooded lakebed and the city of Corcoran. But there are other measures being taken, both upstream on the rivers and to the south in Kern County, to divert floodwater before it even gets to the lake.

Letting water flow into the California Aqueduct

Over the past weekend, gates were opened at the Kern River Intertie, a connection at the terminus of the Kern River in western Kern County that allows excess water to flow into the the California Aqueduct to be carried south and out of the San Joaquin Valley, said Daniel Wisheropp, a scientist with the state Department of Water Resources.

“We started up the operation of the intertie, opened up the gates and started taking Kern River water into the aqueduct this past Saturday,” Wisheropp said. It’s the first time in 17 years that the intertie has been opened. Since the intertie was built by the U.S. Army Corps of Engineers in 1977, it had only been used in nine prior years.

“The last time we used it was in 2006, and that was to help move water during an emergency release period out of (Lake) Isabella” in mountains northeast of Bakersfield, Wisheroff said.

“The water that makes it into the Kern River basin from this point,” he added, “typically would either enter the California Aqueduct or it would go out (an) outlet canal toward Tulare Lake, about 45 miles to the north. “So any water that’s brought into the aqueduct is less water that would be traveling north” to Tulare Lake.

The intertie has a maximum flow to the aqueduct of 3,500 cubic feet per second, but Wisheropp said the agency does not expect to exceed 1,500 cubic feet per second this spring and summer.

Diverting water to recharge underground aquifers

State and local water officials are also scrambling to siphon as much of a record snowmelt as they can from from the Kings, Kaweah and Tule rivers before that water even reaches Tulare Lake. Some of that water is being used by irrigation districts for farming purposes, but there’s also a concerted effort to use water that would otherwise add to flooding in the lake to recharge groundwater aquifers to the east, said Paul Gosselin, deputy director of the state water agency’s groundwater management office.

That involves flooding empty fields with water and letting it soak into water tables that have been depleted by overpumping during years of drought.

To date, Gosselin said Monday, almost 92,000 acre-feet of water has been captured and used for groundwater recharge, “and that’s just beginning.”

Some water agencies would be able to take more water — as much as 50,000 more acre-feet, he added — but they don’t have the necessary infrastructure, including pumps, to move the water to areas where it can best be allowed to soak back into the ground. Gosselin said the state is working to provide pumps for local irrigation districts.

So far, the Fresno Irrigation District has received pump and siphon equipment to take water from the Kings River and is examining where orchards can be cleared for recharge uses.

At least 14 more pumps are planned to be provided to the Kings County Water District, Consolidated Irrigation District and the North Fork Kings Groundwater Sustainability Agency to pull water from the Kings River; the Tulare Irrigation District to divert water from the St. John’s and Kaweah rivers; the city of Visalia and the Kaweah Delta Water Conservation District to divert Kaweah River water; and Kern County water districts yet to be determined to pump and siphon water from the Kern River.

Those pumps “are going to be deployed in the next week or two weeks,” Gosselin said, “and that is really going to advance a lot of the diversion off of the rivers and reduce the amount getting into the lake while keeping the water locally.”

“In terms of diversion, if the pumps current and planned run for four months, approximately 192,000 acre-feet will have been diverted “ from Tulare Lake, Gosselin added.