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in the South Platte River and its tributaries. The alluvial aquifer is an important source for <br />irrigation supply. <br />The Denver Basin bedrock aquifers include the Dawson, Denver, Arapahoe, and Laramie-Fox <br />Hills sedimentary rock formations (see Figure 1-2). The Denver Basin aquifer system contains <br />approximately 470 million acre-feet of water (Robson 1988) with 300 million acre-feet of <br />drainable storage. Estimated total pumping of groundwater from the Denver Basin aquifers in <br />1996 was 56,000 acre-feet (Colorado Water Conservation Board and State Engineers Office <br />1998). Natural recharge for these deep aquifers is minimal with the majority originating from <br />outcrop areas. The Denver Basin aquifers are important sources of supply for municipal and <br />industrial purposes. <br />1.3 WATER ADMINISTRATION AND MANAGEMENT ISSUES <br />Colorado administers water rights according to the prior appropriation doctrine (first in time, first <br />in right). The decreed appropriation and adjudication dates are the basis for determining which <br />users are entitled to river flow during periods when there is insufficient water for all <br />appropriators. The Colorado State Engineer and staff administer water rights to both surface <br />water and groundwater within the State and the South Platte River basin as decreed by the <br />Division One Water Court in Greeley. Administration in the North Platte River basin of <br />Colorado is divided between Division 1 (South Platte River) and Division 6 (Yampa and White <br />Rivers). The Laramie River and Sand Creek are administered as part of Division One and the <br />North Platte River is administered as part of Division 6. <br />Water management and administration in the study area have become more challenging in the <br />past few years, due to several factors: <br />• Increased demand for municipal and industrial water supply along the Front Range has <br />emphasized the need for efficient and effective management and administration <br />• Difficulty and expense of developing new reservoir storage given today's environmental <br />regulations <br />• Transfers of water from agriculture to municipal uses. These and other water rights <br />transfers are becoming increasingly complex in order to fulfill the demand of growing <br />urban areas and industry. Augmentation plans, water exchanges and substitutions have <br />added to the complexity of administration. <br />• Recent years of seasonal low flow in the South Platte River (e.g., summer 2000) have <br />increased the competition for water supplies for both direct use and for augmentation <br />purposes <br />The increasing complexity of water administration requires efficient access to real-time diversion <br />and streamflow data together with effective analysis tools. <br />p:data\gen\spdss\final report\chapter l.doc 1-S <br />October 31, 2001 <br />