Water Resources


Freshwater will always be a precious commodity in southern California.  Although Los Angeles County is home to six groundwater basins covering 800,000+ acres that potentially yield over 35,000 gpm, demand from the County’s almost 10 million residents far outstrips the local groundwater supply.  Depending on precipitation levels, local aquifers meet only 30-40% of current regional demand.  Water providers must turn to external sources to make up the difference, and have constructed elaborate and extensive conveyance systems to import water from the distant Sierra Nevada Mountains and Colorado River.   However, the heavy reliance on imports means that Los Angeles County now competes with agricultural interests in the San Joaquin and Coachella valleys, environmental interests in the Owens Valley, and others.

            The effects of climate change are predicted make the procurement of freshwater from both local and external sources all the more challenging.  Model simulations indicate both a continued high degree of variability of annual precipitation (and subsequent vulnerability to drought) and a decided drying tendency throughout California.  Recharging of local aquifers would decrease in both frequency and amount.  Projected temperature increases during winters in the eastern Sierra Nevada would increase the ratio of rain vis-à-vis snow, decrease snowpack, and initiate earlier melt, leaving fewer reserves for the summers.  Projections for the Colorado River point to decreased mean natural flow, continued drying along the entire river basin, and increases in drought frequency and duration.

Why It Matters


Flooding and heavy storms

  • Injuries/Death
  • Home and property destruction
  • Public infrastructure damage
  • Chemical and sewage overflow
  • Contaminated drinking water
  • Increase in vector-borne diseases (very sensitive to rainfall, temperature and humidity)


  • Disruption of food supply/food shortage
  • Drinking water availability and costs