Additional complexity is displayed within the four pools of CAP's water supply. Unlike the remainder of CAP water supplies in the Fourth Priority, the first pool of Indian Rights Settlement Water (for the Ak-Chin Indian Community – 50,000 acre-feet [AF] and Salt River Pima-Maricopa Indian Community – 22,000 AF) is in the Third Priority, making it the highest priority in the CAP system. The Indian Settlement Water was obtained from the Yuma Mesa Irrigation and Drainage District (50,000 AF) and the Wellton-Mohawk Irrigation and Drainage District (22,000 AF), which are Priority 3 mainstem contractors. After accounting for CAP delivery system loss of 5%, the 72,000 AF is reduced to 68,400 AF.
The next pool is the CAP Priority 4 water allocated to Indian and municipal and industrial (M&I) subcontractors, which have the highest co-equal priority for CAP Priority 4 deliveries. The CAP Indian priority water totals 343,079 AF. The M&I priority water totals 638,823 AF through 2043. After 2043, the amount is 686,126 AF, due the conversion 47,303 AF of non-Indian agricultural (NIA) priority water to CAP M&I priority. Thus, the total amount of CAP Indian and M&I priority is 981,902 AF through 2043. After 2043, the amount is 1,029,205 AF.
The third pool, NIA “Relinquished Water” pool (hereafter referred to as the “NIA Priority Pool”), has been allocated 364,698 AF through 2043. In 2044, 47,303 AF converts to CAP M&I priority, leaving 317,395 AF for the NIA Pool. This pool was created as part of the 2004 Arizona Water Settlements Act (AWSA) when the CAP non-Indian-agricultural contractors relinquished their NIA priority water subcontracts (due to its high cost) for a pool of less costly CAP excess water.
The fourth pool is the remaining CAP supply, known as the “Excess Pool.” The priority of delivery within this pool is as follows: “Non-Indian Agriculture Settlement” water, which decreases according to the following schedule: 400,000 acre-feet through 2016; 300,000 acre-feet, from 2017 through 2023; and 225,000 acre-feet, from 2024 through 2030 (after 2030, the pool goes to zero); the Arizona Water Banking Authority (AWBA) and the Central Arizona Groundwater Replenishment District (CAGRD) replenishment reserve (they have co-equal priority) pool; and other excess water deliveries (i.e., short term contracts). The AWBA/CAGRD and short term contracts supplies are variable because they are dependent on CAP’s annual Priority 4 supply and on the total annual demand of the CAP’s higher priority users.
In general, excess water supplies will decrease over time as existing entitlement holders increase their water demands.