Water Use and Water Law: Mining, Agriculture, and the CAP (A History)

In November 1993, Tucson's Mayor and City Council directed the City of Tucson to contract with a consultant to study alternative uses for Central Arizona Project (CAP) water. A comprehensive Alternative Use Study was conducted during 1994. One of the four primary issues examined is the use of CAP water by mines and agriculture.

Arizona's Water Laws

The State of Arizona manages all the groundwater in Arizona and determines how that water is used. Therefore, all water users in Arizona, including the City of Tucson, must conform to the direction of the State of Arizona in water use and water management.

In 1980, the Arizona Legislature passed the Groundwater Management Act (GMA) pdfexiting Tucson Water website, a law that regulates our current and future water use and requires water resource planning. A part of the Act, called "Safe Yield", requires that a balance be achieved between the amount of groundwater we pump and the amount that's naturally replaced. The Act also requires progressively stricter conservation requirements for water use by all water users.

Another important part of the GMA is the requirement of an "Assured Water Supply". This means that Tucson and other central Arizona cities must be able to prove that they have enough water of satisfactory quality to meet their needs of projected growth and development for the next 100 years. In order to meet the GMA's "Assured Water Supply" requirements, the City of Tucson will use a combination of groundwater, water recharge programs, continued development of our reclaimed water system, conservation, and CAP water.

The Original Plan for the Central Arizona Project

When the Central Arizona Project was first planned, it was anticipated that Arizona's farmers would use the majority of the water from the Colorado River during the early years after the project was completed. Then, as agricultural areas were retired and incorporated into growing urban areas, use of CAP water by expanding cities would increase. Examples of this process are the former Cortaro Farms north of Tucson that is now the Continental Ranch development and the former Midvale Farms southwest of Tucson that is now the Midvale Park development. In addition, as farmers developed better conservation methods and improved technology for irrigation, their use of CAP water would continue to decrease. From the beginning, it was anticipated that cities eventually would become the major users of Arizona's allocation of CAP water.

Changes in Arizona's Agriculture

Many farmers and cities in Maricopa, Pinal, and Pima Counties signed contracts for CAP water. But Arizona's agricultural industry faltered, crop prices fell, and many farms closed. As of 1994, many farmers are facing bankruptcy and find they can not afford to purchase the more expensive CAP water they had hoped to use.

The Cities' CAP Water Agreement

The use or non-use of CAP water by agriculture does not change the requirement that the cities of central Arizona, including Tucson, meet "Safe Yield" and "Assured Water Supply" rules as mandated by Arizona water law. Unlike the Phoenix area which has surface water resources with the Salt, Verde, and Gila Rivers, Tucson's only source of water has been groundwater. The only new water resource we can use to meet the requirements of State water law is water delivered via the CAP.

Use of CAP Water by Mines

Mines in Arizona are not required to use CAP water. Instead, they are subject to strict water conservation requirements. Use or non-use of CAP water by Arizona's mines does not change the requirements that Tucson and the other cities of central Arizona meet "Safe Yield" and "Assured Water Supply" rules as mandated by Arizona water law.

Agriculture's Use of CAP Water -
Legal, Technical and Economic Issues

Tucson is committed to its allocation of 148,420 acre feet per year of CAP water and must use it to meet the requirements of Arizona water law. However, the City is working with and encouraging CAP water use by Pima County mines and agriculture .

For example, the City of Tucson is "exchanging" CAP water with some local farms for the right to pump an equal amount of groundwater. This exchange process is called indirect recharge credits. Unlike Pinal and Maricopa Counties, there is relatively little agriculture in Pima County. An exchange agreement between Tucson and all agricultural interests in Pima County would account for only a portion of Tucson's CAP water allocation.

Arizona water law allows Tucson to perform a CAP water for groundwater credit exchange outside our area if we can find solutions to economic and technical issues. Arizona water law states that in the event of an indirect recharge credit agreement, the groundwater that is exchanged for CAP water must be pumped from the area where the CAP water is used. That means that if Tucson had such an agreement with farmers in Pinal County, we would have to pump the groundwater in Pinal County and then move it to Tucson. The transportation of water in that case would be a problem. Similarly, the lack of a delivery system is an important technical and economic issue in exchanging water with mines or farms located at a distance from the CAP canal.

The issue surrounding CAP water use by other entities is extremely complex. CAP water will remain critical to Tucson as we work to meet the requirements of the Groundwater Management Act.