"Efforts are under way to reverse the deterioration of a major water source, the Sacramento-San Joaquin Delta in California, which is sinking." The drainage of Delta marshlands for agriculture "allowed oxygen to penetrate the soil, permitting microbes to consume organic detritus that had lain undisturbed for millenniums, and to churn out carbon dioxide. As the soil deflated, the land sank as much as two inches per year."
"California'S Sinking Delta"
Source: Christian Science Monitor, 12/04/2009