The MWA's boundaries encompasses approximately 4,900 square miles of the High Desert in San Bernardino County. As a state water contractor, MWA is entitled to receive an annual allotment of 75,800 acre feet of water from the State Water Project via the California Aqueduct. This facility extends south from the Sacramento Delta and runs locally through the communities of Baldy Mesa and Hesperia. The imported water supply is crucial to the area's survival, because local aquifers have been in overdraft since the early 1950's, according to recent studies. For the past four decades, residents have been using more water than is replaced naturally.

The Agency's essential mission was strongly reaffirmed with the conclusion of the Mojave River Adjudication. The Court's ruling notes that the Agency area continues to be in severe overdraft. The Court ordered the Agency to seek sources of water, including supplemental water, and to deliver that water in the most effective fashion to ensure the quality of life within its boundaries.