A vanishing lake figures large in a court battle over how Southern California gets it water, a high-stakes dispute with consequences that could ripple throughout the western United States.

A California appeals court is considering whether to overturn a landmark 2003 agreement that created the nation's largest farm-to-city water transfer and set new rules for dividing the state's share of the Colorado River. A three-judge panel of the 3rd Appellate District in Sacramento will hear arguments Monday and is expected to rule within three months.

Farmers and environmentalists involved in the lawsuit argue the pact is deeply flawed, while California water agencies say it is critical to keeping an uneasy peace on the river. The court has given each side 45 minutes to make its case and asked lawyers to focus on whether the state of California violated its constitution by essentially writing a blank check to restore the shrinking Salton Sea.

California long used more of the Colorado River than it was granted under agreements with Arizona, Colorado, Nevada, New Mexico, Utah, Wyoming and Mexico. Its overindulgence was never a big problem until Sunbelt cities like Phoenix witnessed explosive growth and other states clamored for their full share. Drought only exacerbated tensions.