Operations and Planning

The Arizona Department of Water Resources collaborates with the Bureau of Reclamation and representatives of the seven Colorado River Basin States to better prepare for Arizona’s long-term needs and by taking an active role in water use projections, monitoring of hydrologic conditions and Colorado River operations.  The Department also utilizes models prepared by Reclamation to evaluate various scenarios related to modifications in water use, hydrology, climate, water supply and demand and other factors within the Colorado River Basin.

The Colorado River system has experienced severe drought conditions for almost two decades. Further, the Basin runoff during this period is comparable with one of the lowest comparable periods in the paleo-hydrologic record that dates back over 1,200 years. As a result, water levels in Lake Mead, the primary storage reservoir for the Lower Basin states, and the entire Colorado River System reservoirs have been declining and projections indicate that this will continue into the foreseeable future.

As a result, water levels in Lake Mead, the primary storage reservoir for the Lower Basin states and largest of its kind in the United States, and reservoirs throughout the Colorado River System have been declining; projections indicate that this will continue into the foreseeable future. In addition, given the basic apportionments in the Lower Basin, the allotment to Mexico, and evaporation losses, Lake Mead annual outflow is about 1.2 million acre-feet more than the combination of annual releases from Lake Powell and local inflows between the two reservoirs.

Water deliveries to the Lower Basin States and Mexico are facilitated through releases from Lake Mead, while Lake Powell is operated to deliver water from the Upper Basin. As introduced under the 2007 Interim Guidelines below, water levels in these two reservoirs are coordinated to allow for better management of the Colorado River supply.

Three factors that significantly affect the water levels in lakes Powell and Mead are:

1. The hydrology of the Colorado River, such as the amount of precipitation (mostly as snowpack) that falls within the basin and the resulting runoff that flows into the river and reaches the reservoirs,
2. Colorado River water use, such as the amount of water needed for agricultural and urban purposes in both the Upper and Lower Basins, and
3. Colorado River reservoir operations per the "Law of the River."

As a result of these conditions, the Colorado River users have taken actions to protect Lake Mead’s elevation from dropping to critical levels.

Annual Operating Plans – In consultation with the representatives of the Governors of the seven Colorado River Basin States, Indian tribes, Upper Colorado River Commission, appropriate Federal Agencies and others interested in Colorado River Operations, the Bureau of Reclamation produces an Annual Operating Plan (AOP) for Colorado River Reservoirs that reports on both the past operations of the Colorado River reservoirs for the completed year as well as the projected operations and releases from these reservoirs for the coming year. Annual Operating Plans for Colorado River Reservoirs.

Colorado River Interim Guidelines for Lower Basin Shortages and Coordinated Operations – The 2007 Interim Guidelines were a product of direction to Reclamation from the Secretary of the Interior to develop additional strategies for improved coordinated management of Colorado River system reservoirs. Development of these guidelines was spurred by the current drought period, system storage volatility, and growing demands on the Colorado River.  Each year under the Guidelines, the Secretary is required to declare the Colorado River water supply availability conditions for the Lower Basin States in terms of Normal, Surplus, or Shortage. While regulations and operations criteria had been developed for Normal and Surplus conditions, robust protocol for operation during shortage were not established. These guidelines provide greater certainty to future annual water deliveries, particularly under drought conditions.