Lower Colorado River Water Resource Issues - Colorado River

Water resource issues in the Lower Colorado River Planning Area have been identified in regional studies primary involving Colorado River water supplies, through the distribution of surveys and from other sources. There are no ADWR Rural Watershed Initiative Groups in the planning area. Colorado River and groundwater transportation issues, planning and conservation activities and results from water provider surveys are discussed in this section. Environmental protection and restoration, and local management of water resources to meet the needs of growing communities while maintaining the agricultural economy are important considerations in the planning area. 

Mexican Treaty

Compliance with conditions of the delivery of 1.5 maf of water to Mexico under the 1944 Treaty and Minute 242 have required significant investments and actions within the U.S. and in the planning area.  In the 1960s, salinity associated with irrigation return flows from the Wellton-Mohawk Irrigation and Drainage District (WMIDD) to the Colorado River coupled with reduced flows in the river system developed into a major international issue. To address this issue, Minute 242 to the Treaty was negotiated. This Minute requires that the Treaty water delivered to Mexico will be of nearly the same quality as that which is diverted at Imperial Dam and delivered to U.S. water users.  To comply with this requirement, the U.S. implemented a number of measures including re-routing drain water from the WMIDD to the Cienega de Santa Clara in Mexico.  The U.S. also built a $250 million dollar desalination plant in Yuma to treat WMIDD drain water, so that it could be returned to the mainstream for delivery to Mexico.  The facility was completed in 1992, operated briefly in 1993 and then placed in standby status. 

A consequence of continuing to annually bypass the approximately 100,000 acre-feet of saline irrigation return flow to the Cienega de Santa Clara was the reestablishment of a rich, ecologically important wetland in the Mexican Delta.  Currently, there is significant interest on both sides of the border to continue to maintain the area in its present condition.  However, bypassing this water to Mexico each year without crediting it against the U.S. Treaty obligation requires the U.S. to release an equal amount of water from storage in Lake Mead. As a result, the risk of shortage is increased, particularly to the Central Arizona Project and other equal priority water users in Arizona. After more than a decade of drought, the potential for shortage has been further amplified. 

Reactivation of the Yuma Desalination Plant to treat and discharge this water to the Colorado River to meet U.S. Treaty obligations with Mexico, would impact the Cienega.  In recognition of this concern, the Yuma Desalination Plant/Cienega de Santa Clara Workgroup was formed in 2004 to identify and discuss potential solutions that would preserve the Cienega and make the treated bypass flows available for use under the Treaty. Workgroup recommendations were released in April, 2005.

In 2007, Reclamation conducted a pilot run of the Yuma Desalting Plant by operating it at about ten percent capacity for three months.  The purposes of the run were to test new equipment, acquire current operational data, and identify design deficiencies to better determine whether the facility could reliably and efficiently be operated on a long-term basis.  Results from this study were favorable.  However, it was determined that to obtain more conclusive information, the plant needed to be operated at a scale and for a duration which covers seasonal variations associated with chemical use and power consumption. As a result, Reclamation will conduct a second pilot run of the facility.  During this pilot run, which is scheduled to be initiated in May 2010, the plant will operate at up to one-third capacity for 365 operating days during a 12- to 18-month period. Components of the project will include a commitment to offset the reduced bypass flows with up to 30,000 acre-feet of Colorado River water and an extensive monitoring program for the Cienega.

Shortage Sharing

As mentioned in Section 7.0.6, Reclamation issued a Record of Decision (ROD) in December, 2007 on interim operating criteria (2008-2026).  The elements of the ROD, which include rules for shortages and surpluses, coordinated operation of Lake Powell and Lake Mead, and water conservation have implications for water supply availability in the planning area.

The shortage recommendation implements water supply reductions when Lake Mead water storage is depleted to key surface water level elevations. In Arizona, hydrologic modeling indicates that shortage reductions will impact 4th, 5th and 6th priority water users, including on-river municipal, industrial and agricultural contractors and to the Central Arizona Project excess pool.  During a shortage, the available water supply is sufficient to meet all higher priority water users.

Currently, Arizona and the other Colorado River Basin States, Reclamation and federal and state water organizations in Mexico have been engaging in discussions regarding the development of cooperative, innovative and holistic measures that will ensure that the Colorado River will continue to be able to meet environmental, agricultural and urban water demands in both countries.  To further this effort, the U.S., Mexico and the Basin States are working to develop a policy framework.

Salinity and Other Water Quality Issues

Increased salinity levels in the Colorado River affect agricultural, municipal and industrial uses.  Damages in the U.S. are estimated at $330 million per year, and while economic damage in Mexico is not quantified, it also poses a significant concern. The EPA approved salinity standards proposed by the Colorado River Basin Salinity Control Forum for three locations in Arizona, including two in the planning area. The water quality standards establish a flow-weighted average annual salinity standard that must be maintained on the lower Colorado River at the following locations in the planning area: Below Parker Dam (to Imperial Dam) - 747 mg/L and at Imperial Dam - 879 mg/L.

In 2005, the Governor of Arizona appointed The Clean Colorado River Alliance (Alliance) stakeholder group to address water quality issues for the Colorado River.  In addition to salinity, the Alliance identified several other water quality concerns including nutrients, metals, endocrine disrupting compounds, perchlorate, bacteria and pathogens, and sediment.  In 2006, the Alliance issued a report titled Clean Colorado River Alliance Recommendations to Address Colorado River Water Quality. The report includes a number of recommendations to monitor and mitigate the impacts of these pollutants.

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