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<br />February 27, 1998 <br /> <br />OD13U3 <br /> <br />· Calculate historical monthly average diversions for the average years within 1975- <br />1991, as well as monthly average diversions for wet years and dry years within 1975- <br />1991. This will be completed for each structure. <br />· Create a file of estimated diversions for 1929-1975 based on the type of runoff year <br />(wet, dry, or average) for the specified basin <br />· Adjust diversions for structures known to have come on-line within the period 1929- <br />1974, or known to change significantly over that period in accordance with the scale <br />factors developed in Task 11.4. <br /> <br />Deliverables: <br />· description of demandts enhancements <br />· input files as required by the new demandts for each basin <br />· Draft and Final task memoranda describing this task <br /> <br />11.6 Enhance Demandts <br />Primary Responsibility: State or Other Contractor <br /> <br />The OMI demandts will be modified per the description developed in Task 11.5. To test the <br />software, historical diversions (*.ddh) files for 1975-1991 will be developed for the Yampa <br />River and the San Juan River models, by modifying Phase IDa command files with calls to <br />the new options. <br /> <br />Deliverables: <br />· new version of demandts <br />· historic diversions files for the Yampa and San Juan basins <br /> <br />11.7 Verify Diversion Estimates <br /> <br />Primary Responsibility: Ayres <br /> <br />In this subtask, the San Juan and Yampa Phase IDa models will be executed in baseflow <br />generation mode for 1975-1991, using the historical diversions files developed in Task 11.6. <br />Baseflows at two gages in the LaPlata River and six gages in the Yampa River above the <br />Maybell gage will be compared to baseflows previously determined for the Phase IDa models <br />using actual diversion data. The objective is to verify that the selected approach to filling in <br />diversions records satisfies the data extension objectives. Note that the Phase IDa filled <br />streamgages will be used in this step. <br /> <br />In addition to comparing the new baseflows to Phase IDa baseflows, Ayres will also compare <br />baseflows to USBR natural flow estimates. Factors for comparison will be monthly and <br />annual flows, means and standard deviations. Also, magnitude and occurrence of negative <br />flows will be reviewed. If negative flows are more frequent or larger in magnitude than in <br />the Phase IDa models, recommendations will be made to further investigate and/or adjust for <br />negative flows differently. Efforts to address negative flows or general dissatisfaction with <br />the diversion estimates will require additional scope and contingency funding. A task <br />memorandum describing the approach and conclusions from this task will be prepared. <br /> <br />4 <br />