Water shortages vary widely from region to region.
For example, the North Coast and San Francisco Bay Regions are not expected to experience future shortages during average years, but will see shortages in drought years. Most of the State's remaining regions experience average year and drought year shortages now, and are forecasted to experience increased shortages in 2020. The largest average year shortages are forecasted for the Tulare Lake and South Coast Regions, areas that rely heavily on imported water supplies. Future average year shortages in the Tulare Lake Region reflect groundwater overdraft. Future average year shortages in the South Coast Region reflect forecasted population growth, plus lower Colorado River supplies as California reduces its use of Colorado River water to the State's basic apportionment.