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miles. Assuming that water is diverted during the winter months (December- February), and an <br />average SDF of 100 days is used, the majority of the water which was placed into the alluvium <br />through natural seepage or through the use of recharge ponds, would be realized at the South Platte <br />River during the spring runoff period (March- June). Recharge to the river during the spring runoff <br />period, contributes very little towards the goals of this project. <br />Recharge reservoirs require the maintenance of the bottom interface with the alluvium to insure <br />maximum percolation. Silty water will tend to plug the voids which requires occasional scarification <br />of bottom and removal of fines. This is less of a problem with pumped groundwater than ditch <br />water. <br />The possibility of using the site as strictly a groundwater recharge project seems to be of limited <br />benefit. The timing of the return flows to the South Platte River will not provide the maximum <br />benefit in removing or preventing a call placed on the river. It is felt that the northern portion of the <br />site could be effectively utilized for a smaller recharge pond. Water could be diverted into the <br />recharge portion of the project when it was available during the spring runoff period. This area could <br />be developed into wetlands mitigation for the proposed reservoir. Diverting water into this site <br />during the spring runoff period would allow for flows to accrue to the river during the late summer <br />months. The limitation of utilizing a portion of the site for a recharge pond would be the availability <br />of capacity in the Peterson Ditch. Peterson Ditch shareholders may be diverting flows during the <br />spring runoff period, which could limit the amount of water available for recharge. <br />Table 3 is a summary representation of four different scenarios for the operation of a recharge pond. <br />The different operating scenarios represent two periods of diversion into the recharge area (Jan/Feb <br />A& & May /June) and are evaluated for SDF's of 100 and 200 days. Recharging during the spring runoff <br />(May /June) appears to have the greatest benefit towards achieving the project goal of increasing the <br />flows in the river in the late summer months. The location of the recharge area, within the project <br />site, is capable of achieving SDF's ranging from 100 to 200 days. The variation in the SDF does <br />change the proportion of the recharged water that is returned to the stream during each individual <br />month, but does not seem do have a drastic affect on the overall accretions back to the river during <br />the latter parts of the irrigation season. Diverting water for recharge during the spring runoff period <br />could return approximately 40% of the quantity recharged back to the South Platte River during the <br />late summer period. <br />The possibility of developing a portion of the site into a recharge project does seem to be feasible and <br />beneficial towards achieving project goals. Additional study would be recommended to compare the <br />effectiveness of recharge against development of additional reservoir storage. <br />Table 3 — Summary of Accretions to South Platte River from Recharge at Reservoir Site <br />Recharc <br />Stream Depletion Facto, January February <br /># of Da scrodeet acre-feet <br />a Period <br />Accretion To South <br />Platte River <br />*Effective Stream Recha e <br />May <br />acre -feet <br />June <br />acre feet <br />July <br />acre-feet <br />August <br />acre-feet <br />September <br />acre-feet <br />October Stream Accretions/ <br />acre-feet Recha e <br />100 500 <br />500 <br />0 <br />0 <br />34.9 <br />27.6 <br />22.6 <br />18.9 10.4% <br />100 0 <br />0 <br />500 <br />500 <br />168.5 <br />100.7 <br />6407 <br />46.0 38.0% <br />200 500 <br />500 <br />0 <br />0 <br />423 <br />34.3 <br />28.6 <br />24.3 13.0% <br />200 0 <br />0 <br />500 <br />500 <br />115.2 <br />97.1 <br />71.0 <br />53.7 33.7% <br />Effective Stream Recharge is dermed as the percent of recharge water that accrue to the stream during the late summer months (July -October) <br />All reservoirs will have a certain amount of natural seepage associated with normal operations. The <br />seepage will be dependent upon the native soils and the type of liner system that is constructed. <br />Depending upon what method of sealing the reservoir is opted for, consideration should be given to <br />attaining credit for the groundwater recharge and eventual stream accretion associated with the <br />seepage. See Appendix B for detailed calculations used in Table 3. <br />12 <br />