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I I I I I I I I I I I I I I I I I I I Chapter 11/ - AGUA Well Pumping and Replacement Requirements The second amended 1997 Plan provides for the replacement of depletions accruing to the Arkansas River and to Fountain Creek caused by the pumpil1g of 348 active AGUA member wells. The total annual amount of pumping requested in the plan was approximately 22,008 acre-feet (19,452 acre- feet by actual wells plus 2,556 by four dummy wells'). Pumping used in the plan is the annual estimate provided by each well owner. AGUA ma.kes replacements due to an additional 1 03 acre-feet of pumping by three AGUA members who are not eligible under the Rules and who have their own substitute water supply plans. Depending on the type of use, a presumed (provided in the Arkansas River Basin Rules) or estimated (provided by RMC) depletion factor is assigned to each well. According to the Arkansas River Basin Rules, wells using sprinkler irrigation are presumed to be 75 percent depletive, wells using flood or furrow irrigation with no other source of water.(sole source) are presumed to be 50 percent depletive, and supplemental wells for flood or furrow irrigation are presumed to be 30 percent depletive. Household and municipal uses are estimated to be 38.75 percent depletive based on previous engineering studies. The estimated annual pumpil1g for the well times the depletion factor is the wellhead depletion for the well. The annual wellhead depletions are distributed monthly using irrigation and municipal patterns based on historic use by others. The estimated 1997 plan year wellhead depletions of the AGUA wells was determined to be 10,254 acre-feet (8,933 acre-feet for actual wells under the Arkansas River Basin Rules, plus 1,220 acre-feet for the four dummy wells, plus 101 acre-feet for the substitute water supply plans). Because of the lagged patterns by which the return flows accrue, the strea.m depletions during the 1997 plan year are estimated to be approximately 7,603 acre-feet (RMC, September 8, 1997, Attachment A). After several years of pumping and operation of the plan, assuming the level of pumping stays the same as estimated for the 1997 plan year, the annual replacement requirement will approach 8,933 acre-feet. Table 111-1 shows AGUA's estimated mo(lthly replacement needs by river reach if pumping by actual wells continues in future years at the currently estimated level. Pumping by dummy wells is included in the plan to allow for the transfer of wellhead depletion credits among member wells without the need for a complete plan revision for each occurrence. -5-