(Bloomberg) -- California regulators approved rules that for the first time require mandatory water reductions across the state as a historic drought gripping the region enters its fourth year and conservation efforts fall short of targets.

The state’s 411 urban water suppliers must cut use by 8% to 36%, with some of the deepest decreases imposed on wealthy communities that haven’t reduced their consumption enough. Those cities that have already cut back the most would face smaller restrictions.

The drought has forced farmers in the nation’s top agricultural state to fallow millions of acres while some rural communities are running out of water. The cost to drill wells has tripled because of demand and the below-ground aquifer in some parts of the state has sunk to the lowest level ever. The price of water is on the rise as utilities increase rates to make up for lost revenue.