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Show The spatial distribution of drawdown for the first two runs, 100% uniform demand pattern specified for 1982 pumping rates and for the average annual historical pumpage ( 1969- 1982), is quite similar. In both cases the maximum drawdown ( 100 feet) occurs at nodes ( 24,19) and ( 26,20), and a high drawdown occurs at nodes ( 28,22) and ( 27,20). The drawdown is fairly evenly distributed over the rest of the county as shown in Figures 3.10 and 3.11. The highest pumping occurs in areas of the county with lower pumping lifts, even after significant drawdowns at the sites. Comparing Tables 3.5 and 3.9, we observe that the average drawdown over the county is reduced from 30.785 feet that would result in 10 years with the historical pumping record from 1973 to 1982 ( run 1) , to an average of 13.73 feet for the optimized condition ( run 2) for the same demand condition. This is consistent with the expectation from optimization. It is interesting to note from Table 3.9 that in the optimal solution for run 2 ( 100% of average annual demand), the optimal pumping in areas 2,4,7, and 10 ( Murray, South Salt Lake, Granger, and Magna) exceeds the demand specified for these areas. While this appears contrary to the expectation for cost minimization, it is a direct consequence of the water rights specification through the boundary flow constraints. These areas have the lowest unit costs for pumping in the county. While Salt Lake County, Murray, Salt Lake City, South Salt Lake City and Granger are neighbors, demands for Salt Lake County and Salt Lake City are twice more than the others. The model relocates the concentration of pumping in the areas with the higher unit pumping costs to wells with lower unit costs. The optimal solution for run 2 indicated that the boundary flows for boundaries between Salt Lake City and Granger, Salt Lake County and Granger, Salt Lake County and Murray, South Salt Lake and Granger, and Murray and Sandy were at their bounds with significant values of the associated dual variables. None of the contamination constraints were active at the optimal solution for this run. In order to still satisfy the water rights structure and maintain the same flow across interagency boundaries, pumping in the areas with low costs exceeds the demands of these areas. While this adds to their pumping cost, the system cost is still lower. A case for export of water from these areas to the areas with higher costs, instead of groundwater pumping in the more expensive areas, such as White City, Sandy and Salt Lake County may thus be made, where distribution system costs are not considered. For the Salt Lake County Water Conservancy District, the background lifts ( prior to optimization) range from 101 feet to 260 feet, except at node ( 24,19) where the lift is 43 feet. The model consistently selected this node for high pumping rates. In Sandy, lifts range from 115 feet to 383 feet except at node ( 26,20) which has a 71 foot lift. This node is also consistently selected for high pumping rates. The same situation holds for the nodes ( 28,22) and ( 27,20). At node ( 19,19) a high pumping rate in the first few years, is followed by a drastic reduction in pumping in the last few years. This reduction of pumping leads to only a moderate drawdown at this node at the end of year 10, since natural recharges in the latter years alleviates the drawdown from the first few years. 67 |