The Metropolitan Water District of Southern California (MWD) is a water wholesaler, not a retailer. The MWD covers six counties in southern California, spanning over 5200 square miles, and imports water into the southern California area because southern California does not have enough of its own locally-supplied water for the needs of the people. (See figures below.)
The MWD is represented by the yellow area in the figure below. Where does the water come from? The portfolio includes local water with small surface diversions, recycling, water from the Sierra Mountains and the Colorado River, and local groundwater. The latter makes up a significant part of the overall portfolio, approximately 1.2 million acre-feet (1 acre-foot is about 326,000 gallons.)
The MWD developed an Integrated Water Resources Strategy (or Integrated Resources Plan, IRP) in 1996 and included stakeholder involvement in the work. A major outcome of the IRP was recognizing the MWD could invest in a diversified supply mix (next figure). This mix could include imported water, buying water on a voluntary basis, transfers, or exchanges from other entities. It could involve building either surface or groundwater storage, manage groundwater recovery, or even to clean up contaminated water and use some of that supply, recycling, or conservation.