WaterSim examines water sustainability challenges in the Phoenix Metropolitan Area (PMA).
The model explores the impacts of climate change, drought, agriculture to municipal transfers, reclaimed water, water for the environment, etc. on water supply. For water demand, WaterSim considers population growth and water policy for 33 municipal water providers in the PMA.
WaterSim 5.0 will have a state-of-the-art web-based user interface scheduled for release in fall 2014.
Water Rights to Salt and Verde Rivers
Entitlements to Salt-Verde River water are defined in a legal ruling known as the Kent Decree that established “Member and Non-Member Class A” land is entitled to “normal flow” water, which is river water that would have been available for irrigation in the Valley in the absence of upstream reservoirs. (Salt River Valley Water Users Association, 1910).
The building of Roosevelt Dam was the impetus for a lawsuit that was settled by the Kent Decree.
The Kent Decree establishes the amount and priority of use for daily flows from the Salt-Verde River. These are based on the notion that “the first in time of appropriation is the first in right to appropriate” with ownership and “reasonably continuous beneficial use” as the two criteria needed to establish rights (Salt River Valley Water Users Association, 1910).
Entitlements to Salt-Verde River water are still calculated using the “Trott Table”, a tabular system developed in 1910 by Frank P. Trott who was the Water Commissioner at the time.
The Colorado River watershed encompasses an area of about 640,000 km2 (246,000 mi2) covering parts of seven U.S. states and two Mexican states. The Central Arizona Project (CAP) administers and conveys Colorado River water to Phoenix.
The CAP is designed to bring about 1.6 million acre-feet of Colorado River water per year to Pima, Pinal and Maricopa counties. A typical family of four may use about ½ acre-feet of water annually.
The CAP carries water from Lake Havasu near Parker on the California-Arizona border to the southern boundary of the San Xavier Indian Reservation southwest of Tucson. It is a 336-mile long system of aqueducts, tunnels, pumping plants, and pipelines. It is the largest single resource of renewable water supplies in the state of Arizona. Approximately 41% of this water stays in the Phoenix Metropolitan Area.
During the early 1900′s, the seven states of the Colorado River Basin: Arizona, California, Nevada, New Mexico, Wyoming, Colorado, and Utah negotiated for shares of Colorado River water. In 1922, representatives from the seven states and the United States government created the Colorado River Compact, which divided the states into lower and upper basins and gave each basin 7.5 million acre-feet of water to apportion.
Population Water Demand
Four out of the five counties in the planning area have requirements under the Growing Smarter Plus Act of 2000 (GSP Act). The GSP Act requires that counties with a population greater than 125,000 (2000 Census) include planning for water resources in their Comprehensive Plans.
Counties in the planning area that must meet this requirement are Maricopa, Pinal, Pima and Yavapai. Santa Cruz is the only county in the planning area with a population less than 125,000 residents.
Salt & Verde Rivers
The Salt River is fed by numerous perennial streams that seep along the Mogollon Rim in Central Arizona. The river is formed by the confluence of the White River and the Black River in the White Mountains of eastern Gila County.
The Salt River is perennial from its tributary headwaters to Granite Reef Diversion Dam near Mesa. Deliveries of stored water and runoff from the Salt-Verde watershed are managed by the Salt River Project (SRP).
There are four dams on the Salt River that are used to manage the release and use of water downstream in the Salt River Valley.
The Verde River is a major tributary of the Salt River. It is one of the largest perennial streams in Arizona. The river begins below the dam at Sullivan Lake, and is fed by the Big Chino Wash and the Williamson Valley Wash in Yavapai County.
The Verde flows freely for about 125 miles through private, state, tribal, and U. S. Forest Service lands before entering the first of two dams on the river that form man-made reservoirs; Horseshoe Lake and Bartlett Lake.