Colorado River Project
The Colorado River Aqueduct brings water 242 miles through deserts and over mountain ranges to its terminal reservoir, Lake Mathews, in Riverside County. The aqueduct system includes five pumping plants which lift the water 1,617 feet in elevation.

State Water Project
The State Water Project, also known as the California Aqueduct, transports water 600 miles from Northern California. Owned and operated by the State of California, this is the longest aqueduct system in the world. The system includes 23 dams and reservoirs, 22 pumping plants which lift the water to heights of 3,500 feet in elevation, and six power plants. The aqueduct is comprised of 473 miles of canals, 175 miles of pipeline and 20 miles of tunnels.

Local Groundwater
For many years, IRWD received all of its water from the imported sources mentioned above. To alleviate its total dependency on imported water, the District in 1979 began to develop a series of local wells called the Dyer Road Wellfield Project. These wells are located in Santa Ana, range from 400 to 2,000 feet in depth, and extract high quality water from the Orange County Groundwater Basin. IRWD also has wells located in the Irvine sub-basin and in Lake Forest. Groundwater now makes up approximately 65 percent of IRWD's total potable water supply.

These sources of water, or blending of multiple sources, varies according to the time of year and your geographic location within the District.

In general, most areas of the District receive mostly groundwater from mid-April through mid-October and mostly imported water from mid-October through mid April. Some areas such as Lake Forest receive a majority of imported water year-round.