No end in sight as repair work on California's sinking land costs billions

Historic pace of land subsidence in state's Central Valley, the most productive US agricultural region, drives need for extensive infrastructure fixes

A canal that delivers vital water supplies from northern California to southern California is sinking in places. So are stretches of a riverbed undergoing historic restoration. On farms, well casings pop up like mushrooms as the ground around them drops.

Four years of drought and heavy reliance on pumping of groundwater have made the land sink faster than ever up and down the Central Valley, requiring repairs to infrastructure that experts say are costing billions of dollars.