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0`25 <br />The unconfined alluvial aquifer associated with the Arkansas River <br />consists of from 0 to 300 feet (0 to 90 m) of gravel, sand, silt, and <br />clay. The average saturated thickness is 30 feet (9 m). The hydraulic <br />i <br />conductivity of the aquifer averages about 600 feet squared per day <br />(56 m /d) and the specific yield averages about 0.20. About 1.7 million <br />acre -feet (2.1x10 m of water is stored in this aquifer. In general, <br />the river acts as a drain to the aquifer, but it may supply water to the <br />aquifer in some areas. Recharge from applied irrigation water is the <br />primary source of recharge to the aquifer. The ground -water system was <br />extensively developed in the 1950's and 1960's as a supplemental <br />irrigation supply because of periodic water shortages. <br />John Martin Reservoir, which is about 90 miles (140 km) downstream <br />from Pueblo, *.•gas constructed to store irritation water and control floods <br />and began storing water in 1943. This reservoir is normally emptied <br />early in the irrigation season and remains dry until late fall. Under <br />the proposed change in water use, the Division of Wildlife would maintain <br />a permanent pool of about 10,000 acre -feet (1.2x1.0 m The current <br />capacity of the reservoir is a little more than 600,000 acre -feet (7.4x10 <br />m of which the first 351,000 acre -feet (4.3x10 m is reserved for <br />irrigation storage. The long -term mean annual storage in the reservoir <br />at the beginning of the irrigation season is 75,000 acre -feet (9.3x10 <br />m but the median storage for the same time is much lower. <br />7 <br />Ir.1 <br />