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<br />I <br />I <br />I <br />I <br /> <br />Using the emergency operational guidelines described above, the HEC-5 model was <br /> <br />started with releases matching inflow until the rain began. There is a lag tine of approximately 6- <br /> <br />8 hours between the start of heavy rainfall and a dramatic incTCase in reservoir intlow. Once the <br /> <br />heavy rainfall began, the rale ofrclcasc was ramped up by 1,000 cfs per hour to Ihe channel <br /> <br />capacity of 5,000 cfs. The release of 5,000 cfs was continued until storage began to fall below <br /> <br />gross pool, and then the release was set aboul equal to inllow. Using the emergency operational <br /> <br />criteria lor the simulation, gross pool storage was not exceeded; all releases were made using the <br /> <br />river outlet gates, and storage was allowed to gradually level out to just bclo\v gross pool. Table <br /> <br />22 presents infonnation on the simulated McPhee Reservoir routing, while reservoir inllow, <br /> <br />outllo\',,', and storage arc graphically presented on Platc 26. The computed maximum reservoir <br /> <br />stage for this simulalcd operation is 6.924.00 fecI, \....hich is non-damaging 10 the city of Dolores <br /> <br />(damaging stage is 6,930 feet). <br />I L Conclusions <br /> <br />The 1976 hydrology for the upper Dolores River basin has been re4analyzed. As part of this <br /> <br />analysis: (1) new melhodologies were used to develop a more detailed computer modcl of the <br /> <br />rainlall-runolTrelationship for the upper Dolores River dminage basin; (2) raintlood and <br /> <br />~mowmclt relationships have been developed for the below Rico and Lost Canyon Creek gages; <br /> <br />(3) the streamflow record at Dolores has been rc-analyzcd and flow frequency curves updated: <br /> <br />and (4) the f1EC-IIMS watershed computer model has been calibrated and used 10 generate <br /> <br />hydrographs in the basin for the I % general rainflood event. For Ihe hydraulic modeling phase of <br /> <br />the upper Dolores study. the subbasin hydrographs will be routed along the study reach. using the <br /> <br />FLO-2D model or IIEC-RAS, as appropriate. to map the 1% chance lloodplain. The study reach <br /> <br />is from the upper end of McPhee Reservoir to the connuencc of the upper mainstem and WCSI <br /> <br />43 <br />