WATER SUPPLY REGULATIONS

Our present system of water law grew out of the intense competition for water among early American miners and settlers. People at that time were competing for surface water, and the laws that developed were intended to protect the rights of those who arrived first from the claims of those who arrived later. The law to determine surface water rights is called the prior appropriation doctrine. By the early 1880s, most of the surface water in the Tucson area was claimed for use.

Competition for groundwater developed much later when increasingly powerful pumps enabled pumpers to draw water from beneath lands owned by others. Groundwater laws were passed in the 1950s to protect existing farmers from being pumped dry by new farms. The laws, however, hardly take note of the fact that some groundwater and surface water are actually hydrologically connected. Pumping that affects surface water rights is therefore legal throughout most areas of the state because under Arizona law, surface water and groundwater are generally considered to be separate.

As more people moved to Arizona, the burgeoning urban areas competed with agriculture for groundwater. In 1980, the Legislature passed the Groundwater Management Act (GMA) which sets goals and policies for the most problem-plagued parts of the state. ADWR, which was established to administer the GMA, is responsible for allocation of both surface water and groundwater.

GROUNDWATER MANAGEMENT ACT

Central to the GMA was the establishment of four Active Management Areas (AMAs) in areas of the state with the greatest groundwater overdraft problems: the Phoenix, Prescott, Pinal and Tucson AMAs. A fifth, the Santa Cruz AMA, was created in 1994 when it was split off from TAMA. Some other areas were designated Irrigation Nonexpansion Areas (INAs). (See Figure 7-5.) In these areas, new pumping for agriculture is limited, but other pumping is not. Most of eastern Pima County is included within TAMA. There are no INAs within Pima County.

Each AMA must develop five successive plans for reaching its goal over the period 1980 to 2025. The first four plans each cover a ten-year period, while the last plan covers the final five years. The AMAs are currently preparing to enter the third management period, which covers the years 2000 to 2010. TAMA issued its draft Third Management Plan in the fall of 1998.

Safe Yield

The management goal designated for all AMAs except the Pinal AMA is that of reaching “safe yield” by the year 2025. Achieving safe yield involves reaching, and thereafter maintaining a long-term balance between the annual amount of groundwater withdrawn and the annual amount of natural and artificial recharge within an AMA. Each AMA has its own criteria for satisfying the requirements. For example, the Phoenix AMA allows 7.5 percent of the annual supply to be mined groundwater. In TAMA, as much as 15 percent can be mined groundwater. The balance must come from renewable supplies — CAP or other surface water. Therefore, even the GMA safe yield requirements allow depletion of groundwater, but over a long period of time. In the Draft Third Management Plan for TAMA, ADWR states that even with use of CAP water and conservation measures, the safe yield goal will not be met.

The ADWR water budget is calculated by estimating water use based on projected population, probable per capita water use, agricultural and industrial use and Indian use. Supply is based on assumptions about CAP use, recharge and effluent use. Estimating up to 45 years into the future is obviously difficult, and projections are revised in succeeding management plans. For example, population estimates for TAMA in the year 2025 have been revised downward, from 1,693,000 people in the Second Management Plan (SMP) to 1,266,500 in the Third Management Plan (TMP). These figures represent official state projections.

Assured Water Supply

New subdivisions are required to demonstrate that they have an “assured water supply” before being built. What counted as an “assured water supply” originally was very broad and included groundwater withdrawals that would lower the water table by as much as 1,000 feet. An assured water supply also could be demonstrated by contracting for CAP water or subcontracting with an entity that had contracts for CAP water, whether the CAP water ever reached the subdivision or not. Assured water supply rules have been revised and somewhat tightened to include the following criteria:

• Sufficient quantity of water is continuously available to satisfy the water demands of the development for 100 years;
• Water source meets water quality standards;
• Proposed use of water is consistent with conservation standards;
• Proposed use is consistent with water management goals; and
• Applicant is financially capable of installing the necessary water distribution and treatment facilities.
• The concept of assured water supply does not assure sustainability for more than 100 years, and the requirements can be met in some ways that do not assure sustainability. Participating in a recharge program or contracting for CAP water can be sufficient to meet the requirement.