The Corps Water Management System (CWMS) includes four interrelated models to assist with water management for the basin:

- GeoHMS (Geospatial Hydrologic Modeling Extension)
- ResSIM (Reservoir System Simulation)
- RAS (River Analysis System)
- FIA (Flood Impact Analysis)

The Gila River Basin has a drainage area totaling 57,807 square miles. It includes most of southern Arizona and also extends into New Mexico, Mexico, and California. Principle tributaries to the Gila River Basin include the Gila River, Salt River, Verde River, Agua Fria River, Santa Rosa Wash, and Santa Cruz River. Queen Creek is also included to account for the Corps project along this channel.

The counties which are affected and directly benefit by the operation of the reservoirs within the Gila Basin include a small part of Maricopa County along the Gila River, a major part of Yuma County along the Lower Gila River and Colorado River, and a part of Imperial County in California west of the Colorado River. The properties encompassed in these areas include residential developments, agricultural farmlands, industrial operations, commercial outfits, irrigation and drainage works, transportation facilities (roads, highways and railroads), and important defense installations. In addition to the Yuma Metropolitan area, other cities and towns protected by Painted Rock Dam include Tacna, Wellton, Gadsden, Somerton, San Luis, Winterhaven, and Andrade. Much of the northern part of the Gila River Basin is irregular and rugged, with the boundary elevations ranging from about 7,000 feet, NAVD to more than 12,000 feet, NAVD. This part of the basin is mostly drained by the Salt River, which joins the Gila River at river mile 198 near Phoenix. The southeastern part of the basin consists largely of long desert valleys lying between north-south ranges of rugged mountains; the elevations are generally lower but in places are above 10,000 feet, NAVD. The southwestern third of the basin consists essentially of broad, flat, low-lying desert valleys and isolated mountains of relatively low relief; comparatively few localities are more than 4,000 feet, NAVD in elevation, and a large part is below 1,000 feet, NAVD; the elevation of the river mouth near Yuma is approximately 130 feet, NAVD. The Painted Rock Dam site is in the lower part of the basin at river mile 126, with its invert elevation at 530.0 feet, NAVD.

Soils and vegetative types vary widely throughout the basin. In general, the mountains in the Gila River basin are of igneous rock, mostly granitic, schistose, or volcanic. The valleys along the Gila River and its tributaries are alluvial fills of varying depths. The soil in the valleys is fertile, and where water without a high saline content is available for irrigation, the crop yields are high. The type, density, and distribution of vegetation in the Gila River basin reflect the differences in elevation, temperature, and precipitation. The desert vegetation is sparse and composed principally of cacti, creosote bush, and sagebrush. Mesquite, salt cedar, and arrow-weed grow in dense thickets in stream bottoms and other areas where the water table is near the ground surface. Grasses interspersed with desert and semidesert shrubs grow at elevations ranging from 3,000 to 8,000 feet, NAVD. Chaparral, oak, pinion, and juniper grow at elevations ranging from 4,000 to 7,000 feet, NAVD. Aspen and conifers, such as fir, spruce, and pine are common above elevations of 6,000 feet, NAVD.