Why Water Conservation Officials are Intentionally Flooding Central Valley Vineyards

ACAMPO -- Flooding in a San Joaquin County vineyard is an odd sight before the beginning of the rainy season.

But the flooding in Al Costa’s stand of Zinfandel vines is entirely man-caused, with water being pumped from the adjacent Mokelumne River at the rate of 4,000 gallons per minute.

It's part of a pilot project using East Bay Municipal Utility District allotted water to replenish the groundwater in the region. The North San Joaquin Water Conservation District is working with EBMUD and the Sustainable Conservation to see how crops can withstand a soaking and to see how much of the water actually filters into the water table.

Costa says a levee break last winter flooded one of his vineyards but did not affect his vines at all. He says flooding often makes his yield better.

The project will determine how much water in the vineyard will actually affect nearby wells, which have been drying up, and how it might affect crops. Water engineers are relatively certain the water that sinks to the aquifer won’t flow back into the river, but that will be monitored as well.

There is pressure by state water regulators for agencies to replenish groundwater levels after years of over-pumping. Underground is a valuable resource when surface water is in short supply for growers.

EBMUD is also looking at the feasibility of pumping water for its needs during non-drought years. Replenishing strategies will rely on information collected from test flooding projects, which are taking place at various sites in the Central Valley.