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<br />MWSI Project <br />Phase II Conjunctive Use Summary Report - ORAFT <br /> <br />August 22, 1995 <br /> <br />Surface Water Availability <br /> <br />General Categories of Potentially Available Surface Water <br /> <br />One basic purpose of any conjunctive use plan is to maximize the use of surface water <br />supplies through the coordinated use of surface water and groundwater resources. The surface <br />supplies that could potentially be used in a conjunctive use plan include virtually any surface <br />supplies. Critical to the operation of any conjunctive use plan is a surface water supply that is <br />available for use, <br /> <br />Options for providing surface water for conjunctive use were examined in Task 4E. Four <br />potential options were initially identified: ]) unused supplies divertible by the Oenver Water <br />system, 2) unused divertible Windy Gap water, 3) additional surface water borrowed from <br />reservoir systems and requiring payback, and 4) surface water captured on local tributaries <br />during precipitation events. Ouring subsequent MWSI investigations additional sources of <br />potential surface water for conjunctive use were identified including divertible surface supplies <br />from other South Plane and Clear Creek providers, and surface supplies derivable by exchange of <br />reusable effluent. <br /> <br />Surface Water Supplies Assumed For Illustrative Purposes <br /> <br />In this Phase II study of conjunctive use options, the Oenver Water system was used as an <br />example source of potentially available divertible surface supplies and "borrowed" water, OW's <br />system was selected for illustrative purposes because it includes surface water supply sources <br />from both the South Platte and Colorado basins, and it contains significant carryover storage, In <br />addition, planning level operations data on OW's system was easily obtainable, Other surface <br />supplies may be obtainable from other providers. <br /> <br />OW's unused divertible surface supplies were initially estimated through the use of <br />Hydrosphere's OWOSYM model. These initial estimates were replaced by estimates obtained <br />from OW staff, These laner estimates were considered to be rough approximations of OW's <br />unused divertible surface supplies assuming an annual demand level of approximately 335,000 <br />acre-feet per year. These were obtained by OW from previous model runs of their TSM model, <br />which is being replaced by their P ACSM model. These unused divertible surface supplies are <br />comprised of South Plane, Blue River and Fraser River flows divertible under OW's water rights <br />in excess of OW's system needs at a demand level of 335,000 acre-feet per year. These unused <br />supply estimates are illustrated in summary form in Figure II. <br /> <br />These estimates overstate the ultimate availability of surface supplies from the OW <br />system, since they include all of OW's unused supplies under its current system configuration at <br />a demand level that is below its projected "build-out" demands, In order to meet its build-out <br />demands, OW will have to implement some combination of supply-side water development <br />, measures and/or demand management measures. As a result of these future measures and to the <br />degree that OW's water demands grow to its build-out levels, these estimates ofDW's unused <br /> <br />36 <br />