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<br />MWSI Project <br />Phase" Conjunctive Use Summary Report - DRAFT <br /> <br />August 22, 1995 <br /> <br />Under a conjunctive use plan, there would be additional benefits to recharge. The facility <br />cost of recharge would consist of the marginal cost of outfitting a well to allow for injection <br />since the well field infrastructure necessary to produce the groundwater would already be <br />required as a part of the plan, Under this conjunctive use plan formulation, well field <br />infrastructure would be better utilized with recharge included since these wells would otheIWise <br />remain essentially idle during periods of sufficient flow from surface water sources. <br /> <br />Ullimale Use of Addilional Waler Supplies Developed <br /> <br />Another dimension of conjunctive use plan formulation relates to the ultimate use of the <br />developed supply, and has major implications with respect to the groundwater facilities included <br />in the plan, <br /> <br />In one scenario, a conjunctive use plan could be designed solely to develop new yield for <br />future growth in the metropolitan area, This would likely require purchasing or otheIWise <br />securing the water rights for a large block of groundwater, preferably groundwater that is <br />virtually untapped, as the groundwaler supply, This plan would also req\lire the development of <br />new well field infrastructure necessary to meet demands and to provide for surface system <br />paybacks, One advantage of this plan would be that it could allow for phased investment in <br />infrastructure over time as development occurs and demands are realized, A hypothetical <br />example of this formulation would be if a municipality were to develop new well fields within its <br />groundwater control area and implement a conjunctive use plan in order to develop new yield <br />from its unused divertible surface water supplies, <br /> <br />Another option would be to formulate a conjunctive use plan for the pUIJlose of reducing <br />or eliminating aquifer depletions from already developed groundwater systems, Under this <br />option, existing surface water and groundwater systems would be interconnected, and surface <br />water would be provided in most years to meet demands in the groundwater area and for <br />recharge, Groundwater use on a regular basis would be halted and the groundwater supply <br />would be used only in drought periods, both to meet the groundwater area demands and for <br />surface system payback. The main advantage of this plan would be the controlled reduction or <br />elimination of groundwater depletion and the development of new yield for use within the <br />groundwater area without the need for major new surface reservoir construction, <br /> <br />The advantage of reducing existing groundwater use would be that current annual <br />depletions of the groundwater would be slowed or halted thereby relieving pressure on these <br />underground aquifers and preserving this water supply. Additionally, in the case of Arapahoe <br />and Douglas Counties the well field infrastructure for conjunctive use is already largely in place <br />and could be utilized with little modification, Existing well field infrastructure could meet <br />existing demands and significant excess capacity already exists to meet future demands, <br /> <br />The disadvantage ofreplacing existing groundwater use is that new yield would be <br />reduced by the amount of groundwater supply that is replaced. <br /> <br />31 <br />