Colorado River Water Use Highlights:

Arizona Colorado River Water Use:

From the 2018 Annual Report - View Full Report Here ⟶

2018 marked the 50th anniversary of the Colorado River Basin Project Act, which was signed into law by President Lyndon B. Johnson on Sept. 30, 1968.

The significance of the act is underscored not only by the fact that it authorized Central Arizona Project construction, but that this legislation also paved the way for growth and economic development in the West as we know it today. CAP celebrated this milestone by highlighting historic moments that paved the way for collaboration amongst diverse interests through partnerships with state, regional and national agencies.

Early in 2018

In response to ongoing historic drought conditions in the Colorado River Basin and to reduce the likelihood of Lake Powell and Lake Mead declining to critical elevations—the Arizona Department of Water Resources and the Central Arizona Water Conservation District announced they would work collaboratively to bring the Drought Contingency Plan to closure in Arizona by addressing a broad range of issues that reflect the concerns of all stakeholders across the state.

To launch the dialogue, ADWR and CAWCD, with the Bureau of Reclamation, hosted a public briefing and started discussions with stakeholders through a 40-member Steering Committee supported by smaller groups working on specific issues. A series of public Steering Committee meetings and work group meetings has been held as Arizonans work toward developing a consensus-based approach to implement the DCP in Arizona.

The winter of 2018 in Arizona turned out to be one of the driest in recent history. Runoff from the Salt and Verde watersheds was the lowest on record going back to 1913, with only 100,000 acre-feet (AF) of water flowing into the SRP reservoirs from January through May. This is more than 5 times lower than the median inflow and resulted in a decline in overall reservoir storage of 125,000 AF during a period that typically lake levels are being replenished and overall storage is increasing. Despite the dismal winter, the water stored in SRP reservoirs still remains greater than more than half of the years since 1950, and has adequate supplies to meet WY 2019 water demands.

SRP’s constant planning for drought and conjunctive use of surface water and groundwater has allowed SRP to continue to provide adequate and reliable water to its shareholders. During the previous winter in 2017, the system experienced above-median inflows of nearly 1 million AF of runoff, increasing storage in the reservoirs to 76% of capacity. Even though the reservoir levels were healthy, surface water supplies were supplemented with water from the groundwater system because of the conservative planning philosophy to operate the system under the assumption the coming year will experience lower quartile flows into the reservoirs. In midwinter 2018 that forecast held true and the runoff forecast was much lower than planned, the lowest ever recorded. Because of conservative planning and SRP’s capability to proactively adjust the water mix, groundwater pumping was immediately increased to ensure adequate storage remained in the reservoirs to meet future year’s demands. As of September 2018, SRP reservoirs were at just over 1 million AF of storage (46% of capacity).

The Yuma area irrigation districts and the Yuma Center for Excellence in Desert Agriculture (YCEDA) have teamed up on a multiyear irrigation and soil salinity management research project to quantitatively track water use and salt balance across typical crop production systems and rotations. Ongoing research thus far has focused on cool season produce grown in rotation with wheat and Sudan grass. Partners include University of Arizona and USDA researchers, the Arizona Department of Agriculture, USDA-ARS, USBR, NASA, Arizona Commodity Councils, and others. Technologies such as electromagnetic surveys (EM38), Eddy covariance (ECV) and large aperture scintillometry (LAS) instrumentation, UAV with remote sensors, and satellite will be deployed to measure evapotranspiration (ET) and soil salinity levels at multiple scales.

Data collection and analysis are ongoing, and opportunities for more efficient water and salt management outcomes will be identified. Ultimately, this data will be used to develop realtime management tools for most desert cropping systems to assist in making rotational management decisions that maximize irrigation efficiency, while precluding detrimental salt accumulations in the soil.