The University of Arizona

Background | CLIMAS

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Background

The Southwest is one of the most rapidly growing areas of the United States and also one of the most arid. Conflicts over scarce water resources have a long history in the region. In order to efficiently utilize this precious resource in a sustainable manner, a complex set of physical structures—including dams, reservoirs, and interconnected groundwater pumping and delivery systems—have been built. Likewise, over the years, an increasingly complex institutional structure has emerged to mediate competition over water allocation and use.

Water Supplies Vary

Surface water accounts for more than half of Arizona's water supplies. The Central Arizona Project—a 335 mile long canal and series of pumping stations and reservoirs—delivers water from the Colorado River to parts of the state, including the large urban areas of Phoenix and Tucson. Groundwater resources in the Southwest are unevenly distributed, with some areas having large volumes of groundwater and some having very little.

Climate variability directly affects many of the region's water resources, as surface water supplies are dependent on annual rainfall amounts and minimization of evaporative loss. Groundwater supplies in many areas also depend on rainfall that infiltrates back into the ground.

Water Policy and Population Growth

In 1980, Arizona's Groundwater Management Act established "Active Management Areas" (AMA) within the state where groundwater withdrawals are closely regulated. The Arizona Department of Water Resources estimates that more than 80 percent of the state's water use occurs within the five AMAs. While much of this goes to agriculture, the demand for water in urban areas is increasing as Arizona cities grow. Projections by the Arizona Department of Economic Security indicate that both the Phoenix and Tucson metropolitan areas will grow by about 40 percent by 2025.

Climate Variability and Information Use

The urban water sector is one of the more climate-sensitive sectors in the Southwest. Water managers and other decision makers must balance the needs of exponentially expanding populations with the physical reality of limited water supplies. Weather- and climate-related events, such as unusually hot weather, prolonged drought, or flood events frequently add additional stress to urban water systems.

One way that water managers and other decision makers may prepare for and cope with such events is through expanding their use of climate information and forecasts. However, the climate research community lacks sufficient knowledge about the use of information by local water managers, exactly which types of weather and climate events managers find most difficult to contend with, and what their specific information needs are. Water managers, on the other hand, may have limited knowledge of what products are available, where to access them, and how to apply them to their decision-making processes.