The central San Joaquin Valley is fortunate to have a variety of water sources – such as the Sierra snow pack, rivers and groundwater – all of which are affected by the hydrologic cycle.

Water is dynamic. It is always on the move, by sea, by air, by land and underground. In the process, water provides life for all of us.

With its typically hot and dry summers, the Valley may seem well removed from the ocean, but the Pacific is the source of storm events that spread rain over the Valley and its foothills while draping blankets of snow across the high Sierra Nevada.

Sierra Snow

Sierra snow is the most dramatic and best-known source of the Valley’s water supply. Our “wet season” begins in the fall when snow accumulates at higher elevations. Usually in April, warmer weather unleashes the snowmelt season, swelling flows in the rivers and canals that reach into the Valley.

The Kings and San Joaquin Rivers

Snowmelt runoff and flood flows that are spawned occasionally by heavy rains are captured behind Pine Flat Dam on the Kings River, Friant Dam on the San Joaquin River and in other Valley reservoirs. These big flows are managed and stored for flood control as well as for spring and summer irrigation use by tens of thousands of valley farmers.

The cities of Fresno and Clovis have both developed surface water treatment plants to further tap into these resources. Treated surface water is already used beneficially in Coalinga, Huron, Avenal, Friant, Brighton Crest, Orange Cove, Lindsay, Strathmore and Terra Bella.


Surface water supplies can vary radically, but the Valley is fortunate to have a supply of groundwater. Pumping water from the aquifer is vital for sustaining crops in places and at times when surface water is not available. Groundwater is also a main source of our drinking water. However, the aquifer isn’t a limitless resource. Due to our heavy water use, more groundwater is being pumped out than is being replenished & pointing to the importance of conservation.