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<br />MWSI Project <br />Phase" Conjunctive Use Summary Report - DRAFT <br /> <br />August 22, 1995 <br /> <br />In the event that the conjunctive use program is implemented over existing groundwater <br />districlS, these districts would need to come together and agree to participate in the program and <br />reserve groundwater supplies for that purpose. For the groundwater portion of the plan to work <br />effectively, it is important that a large block of groundwater supply be identified, protected, and <br />utilized under the rules and regulations of the State, <br /> <br />Water rights would be a significant issue, The very essence of the conjunctive use <br />concept envisions a more intensive use of surface water rights including increased reservoir <br />drawdowns. It is unclear if the use of existing surface water rights for conjunctive use purposes, <br />particularly groundwater recharge, would be consistent with originally decreed purposes. It is <br />possible that changes of water rights or new water rights may be required, <br /> <br />In addition, as discussed previously, the groundwater portion of the conjunctive use plan <br />requires groundwater rights over an extensive area, These water rights would be purchased for <br />use in the plan from governmental or private entities, or might be dedicated to the plan for credits <br />on tap fees. <br /> <br />The other concern related to water rights is the State's Rules and Regulations for use and <br />ownership of recharged groundwater supplies, The State is in the process of developing new <br />Rules and Regulations with regard to recharge. In general, the rules being promulgated are <br />consistent with and allow recharge under the conjunctive use plan, particularly ifreusable <br />effluent can be used as an augmentation source for recharge of water stored under "one use" <br />water rights, The State would serve an important role in developing and administering these <br />regulations, <br /> <br />As discussed previously, a key component of the amount of firm yield that can be <br />developed under the plan relates to acceptable levels of aquifer decline, Under the assumptions <br />used in this study, no aquifer depletion would occur which should be acceptable to all parties. If, <br />however, a plan is selected to increase yield with aquifer declines, all parties would need to agree <br />upon an acccptable rate of decline, Clearly, this is a political issue that would need to be <br />addressed, perhaps by the Water Forum. <br /> <br />While development of a conjunctive use plan would not require construction of major <br />new surface storage facilities, the stream depletion and reservoir recreational level impacts <br />associated with a large scale conjunctive plan would be similar to those associated with new <br />surface reservoir development. Depending on the surface water systems involved, stream flow <br />depletions could occur during high flow periods in both the South Plane and Colorado River <br />basins. Greater drawdowns of existing major surface water reservoirs would occur, it may be <br />possible to manage the impact of these drawdowns to avoid prime recreational seasons. Both of <br />these types of impacts are potentially serious in nature and would probably act as major limiting <br />factors to the scale of any conjunctive use plan. <br /> <br />45 <br />