United States: Finding the sweet spots for managed aquifer recharge

Much of California's $50 billion agricultural industry depends on groundwater. We typically see only what this water makes possible above the soil: almond and pistachio groves, citrus orchards, rows of lettuce and grapevines and cattle herds in a valley that supplies a quarter of the nation's food even when surface water is scarce. But a lot is happening below the surface. Deep underground, intricate channels of sand and gravel weave through tightly packed clays and silts, allowing Earth to hold water like a sponge.Excessive pumping can squeeze out the sponge, permanently depleting an aquifer's storage capacity and releasing toxic arsenic into water supplies. In California's fertile Central Valley, years of rampant overdraft have led to shortages in many low-income, ...