C150243 feas study - Laserfiche WebLink

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the demand rates to calculate total treated water demands. Population projections, based on an annual growth rate of 1.7 percent, indicate that Aurora's current population of approximately 300,000 will increase to over 600,000 by 2050. Water Supply and Water Rights Aurora Water, through the PWP, will re-divert legally re-usable water. As a general rule in Colorado, appropriators are allowed one use of water and the water left over after that use goes downstream to the next user. The exception to this rule is legally re-usable water. Legally re-usable water is water from trans-basin sources (Aurora's Colorado River and Arkansas River water rights), deep wells (Aurora's Denver Basin wells) or previously court changed water rights (Aurora's South Park water rights). Colorado water law does not require approval to re-divert legally re-usable water if the water is withdrawn through a ditch diverting from a stream (excerpted from BHF, 2006). To maximize the natural purification processes that occur in the river s alluvium, Aurora Water plans to divert its legally re-usable water through tributary wells consiructed close to the South Platte River, rather than through ditches. Tributary wells affect stream flow on a delayed basis, and as a result, Colorado water law requires all tributary wells in over- appropriated basins (the South Platte River is over-appropriated) to obtain water court approved plans for augmentation. The water court will approve a plan for Augmentation if Aurora Water demonstrates that the time, location, and amount of well depletions equal the re-usable water sources Aurora Water has available at the same location on the stream. Aurora Water has ample re-usable water resources to obtain the plan for augmentation, and its counsel anticipates water court approval of the augmentation and pumping plan. There are no legal impediments to obtaining the required water court approvals to operate the Prairie Waters Project (excepted from BHF, 2006). Water Storage Storage within the raw water supply system is extremely important to meet annual operational needs as well as demands during extended dry periods. Aurora Water utilizes its storage facilities annually to meet fall and winter water demands. The need to use reservoirs for annual operation will continue into the future and will become even more critical with additional City growth. During dry years when direct diversions do not satisfy annual water demands, water demands are met by water delivered from long-term reservoir storage. A review of supplies versus demands shows that this hydrologic situation occurs about 15-percent of the time, or on average about once every seven years. Development of the Prairie Waters Project In development of the PWP, Aurora Water initially considered 37 raw water supply project elements. These elements were screened down to 24 potential project components, and subsequently evaluated using a decision analysis tool. Evaluation criteria used in the decision analysis tool included permitting, institutional, public, schedule, cost, yield, flexibility, and sustainability considerations. The criteria were assigned a weight and each project component was scored and ranked.