Laserfiche WebLink
Maximum loss constraints for the flow data are presented in Table 7. Results for the reaches <br />along the South Platte River varied between 81 cfs and 442 cfs, with the exception of a value of <br />1031 cfs for the South Platte 7 -Balzac to Julesburg reach. As discussed above, some of the <br />differences in flow are due to differing lengths of each reach. When converted to a loss per river <br />Hole, the maximum loss constraints range from 5 to 11 cfs/nine for the mainstem reaches (Table <br />7). Tl1e lower calculated loss rates in t11e mainstem are upstream of the Fort Lupton gage. h1 <br />general, it appears that the maximum loss constraint increases downstream. This maybe <br />because there is of more pumping in the downstream reaches wl1ic11 would induce more stream <br />loss. Additionally, the alluvial aquifer widens downstream which increases the flow and <br />transmissivity values used in the Glover calculations. Maximum loss constraints for the Cherry <br />Creek reach and the Cache la Poudre River reach were 314 cfs and 232 cfs, respectively, <br />equating to losses of 6 cfs/mile in for both reaches (Table 7). <br />Table 7 -Maximum Loss Constraints <br />Reach Name Total Q (cfs) Q (cfs) per River Mile <br />South Platte 1-Waterton to Denver 81 5 <br />South Platte 2 -Denver to Henderson 83 5 <br />South Platte 3 -Henderson to Fort Lu Eton 110 6 <br />South Platte ~ -Fort Lu Eton to Kerse 442 11 <br />South Platte 5 -Kerse to Weldona 413 9 <br />South Platte 6 -Weldona to Balzac 192 8 <br />South Platte 7 -Balzac to Julesbur r 1031 10 <br />Cache la Poudre - Ft Co]]ins to Greele 314 6 <br />Cherr Creek - Franktown to Denver 232 6 <br />The maximum loss constraints (Table 7) are smaller than the maximum gain constraints (Table <br />6). This is mainly due to t11e different methods of calculation for t11e two constraints, which <br />reflect the different flow situations when maximum gains and losses might occur. For the <br />maximum loss constraint the shorter duration of High flow, high stage events would likely <br />result in stream losses of lower magnitude than the maximum gains, which occur for a more <br />sustained period of time. <br />2.4 Long-Term Averaging <br />Due to the relatively slow rates of groundwater movement, it is expected t11at patterns of stream <br />gains and losses should be gradual w11en considered on a reach by reach basis. To better <br />represent the more gradual movement of groundwater and to produce again-loss curve that is <br />more smooth and gradual a long term averaging period was applied. The long-term averaging <br />consists of a 31-day moving average. This averaging period was selected because it produced a <br />reasonably smooth result that, based on engineering judgment, produced suitable results. By <br />comparison, the Pilot Point method applied in the RGDSS arrived at a 61-day long-term average <br />based on a trial and error approach $Zat produced suitable results for that basin. The stream <br />gains and losses resulting from the long-term averaging are called the estimated baseflow <br />values. These are discussed in Section 3. <br />SPDSS Phase 4 Task 46 Technical Memorandum -Final 13 <br />0~4i 10i0~ <br />