Hydrologic Region Colorado River
California’s Groundwater
Coachella Valley Groundwater Basin
Bulletin 118
Last update 2/27/04
Coachella Valley Groundwater Basin,
Indio Subbasin
• Groundwater Basin Number: 7-21.01
• County: Riverside, San Diego, Imperial
• Surface Area: 336,000 acres (525 square miles)
Basin Boundaries and Hydrology
Indio Subbasin is located northwest of the Salton Sea and receives low
precipitation, averaging about 6 inches per year, and a wide range of
temperatures. The Banning fault bounds the subbasin on the north and the
semi-permeable rocks of the Indio Hills mark the northeast boundary.
Impermeable rocks of the San Jacinto and Santa Rosa Mountains bound the
subbasin on the south. A bedrock constriction separates the Indio Subbasin
from the San Gorgonio Pass Subbasin on the northwest. The Salton Sea is
the eastern boundary and the subbasin’s primary discharge area. A low
drainage divide forms a short boundary with the West Salton Sea
Groundwater Basin in the southeast.
The Indio Subbasin is drained by the Whitewater River and its tributaries.
The Whitewater River rarely flows throughout the year and flow in
tributaries such as San Gorgonio River is intermittent. Surface flow is
southeastward to the Salton Sea. The Colorado River Aqueduct and the
Coachella Branch of the All-American Canal convey imported surface water
into the Coachella Valley which overlies the subbasin.
Hydrogeologic Information
Water Bearing Formations
Primary water-bearing materials in the subbasin are unconsolidated late
Pleistocene and Holocene alluvial deposits. These deposits consist of older
alluvium and the Ocotillo Conglomerate Formation, a thick sequence of
poorly bedded coarse sand and gravel. The Ocotillo Conglomerate is greater
than 1,000 feet thick in many places and is the primary water-bearing unit in
the subbasin (DWR 1964).
In the upper part of the subbasin, groundwater is unconfined, whereas to the
south and southeast groundwater is mostly conf