Deaths of endangered fish curtail water exports

In a step that has become more routine over the last decade, water exports to the San Joaquin Valley and Southern California have been reduced to avoid killing endangered delta smelt.

State and federal water managers said Tuesday that early winter pumping from the Sacramento-San Joaquin River Delta has been curtailed because too many of the native fish were dying at the delta’s export pumps.

At this point it is difficult to say what effect the pumping cutbacks could have on water deliveries. December storms have left crucial Northern California reservoirs with slightly more water than usual for this time of year, although after a dry January, statewide snowpack is below normal for the date.

Proponents of a controversial proposal to change the way water supplies are conveyed through the delta immediately cited the export reductions, arguing that the cuts could have been avoided with the new system.

“This is all too familiar a story,” said Mark Cowin, director of the state Department of Water Resources. “This conflict will continue to play out year after year until we make fundamental changes in the way we manage the delta.”

State and federal water officials — along with the biggest urban water and irrigation districts in California — are advocating the construction of two massive tunnels that would carry supplies beneath the delta to southbound aqueducts from a new diversion point on the Sacramento River. That would mean less water is pumped directly from the south delta, avoiding harm to the smelt and, backers hope, the accompanying pumping restrictions.

Cowin said computer modeling shows an additional 700,000 acre-feet of water could have been sent south and to the Bay Area since Nov. 1 if the new diversion had been in place, enough to irrigate more than 200,000 acres or supply 1.4 million homes.

Opponents of that plan warn that taking large volumes of water from the Sacramento River could create problems for another fish, the endangered salmon that migrate up the river to their spawning grounds. Delta farmers also worry that with less fresh water flowing through the delta, their irrigation supplies could grow saltier, hurting crops.

State and federal officials also acknowledge that even with the tunnel system, they will not be able to guarantee a certain level of water deliveries to farms and cities south of the delta.

It was probably the big December storms that drew smelt in the direction of the pumps. The finger-sized fish likes muddy water. When winter rains flush runoff into the delta, the increased turbidity acts as a signal to the smelt to swim to the interior — closer to the pumps — as they prepare to spawn.

At the same time state officials were discussing the water cutbacks, Southern California environmentalists who oppose the $14-billion tunnel project announced an advertising campaign in which they portray the proposal as a costly boondoggle that would drive up water rates.

bettina.boxall@latimes.com