5 things to know about the plan to ship water to Southern California

Earlier this week, KPCC learned Southern California's largest water importer, the Metropolitan Water District, was considering more than doubling its investment in a plan to reconfigure how supplies are diverted from one of the region's most important sources of water: the Sacramento-San Joaquin River Delta just east of San Francisco.

Three MWD board members have floated the idea of spending an additional $6 billion to revive a plan to build two giant tunnels under the delta. The idea behind the plan, called the California WaterFix, is to minimize disruptions to water deliveries to Southern California when there isn’t enough water in the delta to sustain its ecosystem.

Southern California gets about one-third of its water from the delta. MWD had already pledged about $4 billion out of the $16 billion needed to build both tunnels. But last week, state officials scaled the project back to a single tunnel because they could not get funding commitments from all the water agencies that would benefit.

Proponents say two tunnels are needed to ensure reliable water supplies to cities and farms in the southern half of the state. Opponents say construction will irreparably harm the environment of the delta and enable Southern California to siphon away ever greater supplies of water from the north.

We've put together this FAQ to catch you up on why this development is important to Southern California.

What is the Sacramento-San Joaquin River Delta?

The delta is wetland area east of the San Francisco Bay where salty bay water mixes with freshwater to form the largest estuary on the West Coast. Covering more than 1,000 square miles, the delta is considered the hub of the California water system. Rivers with headwaters in the Sierra Nevada bring fresh water to the delta. Much of that water is then diverted into two water conveyance projects -- one state, the other federal -- that provide water to two-thirds of the state's population and millions of acres of farmland, according to the California Department of Water Resources.

What is the California WaterFix?

Right now, water diverted from the delta is funneled into pumping stations on its south end near the city of Tracy. But environmental law sometimes forces the pumping to slow or stop because too many endangered fish get caught in the flow. Dry winters and lower river flows into the delta also trigger reduced pumping because delta managers are required to make sure the estuary doesn't become too salty from bay water. Highly saline water can damage the delta's fragile ecosystem. 

In an effort to reduce those disruptions, state officials devised the California WaterFix. It envisions diverting water on the north end of the delta into two 30-mile tunnels that would run underneath it, providing freshwater flows evenly across the estuary. The project would halt the direct pumping on the south end that kills fish. The project is also meant to protect water supplies from contamination if the delta's aging system of levees were to crumble under a major earthquake. 

Why are some at MWD wanting to put more money into this project?

MWD Director Brett Barbre is one of those who supports MWD closing the funding gap to build the two-tunnel project. He said two tunnels could carry more water, a combined 9,000 cubic feet per second, than a single tunnel carrying 6,000 cfs. A second tunnel also provides an extra measure of reliability in case one of the tunnels is damaged or taken off line for repairs.

"You always want to have that redundancy and reliability," Barbre said.

Who would pay for MWD's additional funding? Would it be SoCal households?

The two-tunnel project as originally envisioned would add about $2 to the monthly bills of some 19 million water customers, said MWD General Manager Jeffrey Kightlinger. Some Southern Californians would pay more, depending on how much imported MWD water their local water district relies on to supplement the locally sourced supply.

Kightlinger said MWD's stepping in to guarantee an added $6 billion of project costs should not increase what local water customers pay by very much because the agency would require other project participants to cover the cost.

What is the timeline for MWD board to decide on whether to make this investment?

MWD staff is expected to present its analysis of the added investment by about mid-April, Kightlinger said. That analysis would spell out who, ultimately, will end up paying the cost of the added investment.

This story is part of Elemental: Covering Sustainability, a new multimedia collaboration between Cronkite News, Arizona PBS, KJZZ, KPCC, Rocky Mountain PBS and PBS SoCal.