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Development of Estimated Daily Flows - Yampa River at Maybell DAilY MAYBEll FLOWS: FUTURE CONDITIONS WITH-PROJECT Estimated daily Maybell flows under future (year 2040) demand conditions .MID the enlargement of Elkhead Reservoir were developed by applying a set of differences to the daily depleted flows estimated for year 2040. This set of differences reflect the change in Maybell flow conditions, over the without-project case, caused by operation of the enlarged Elkhead Reservoir. The general pattern of these differences is that of storage (less flow) in the early spring and releases (more flow) in late July and early August. These monthly differences were derived using results from the Yampa River Basin Model developed in the Phase 2 study. Monthly differences in Maybell flows under the with- and without-Elkhead-enlargement model scenarios were converted to a set of daily differences using a simplified step function scheme. This scheme was designed to reflect that Elkhead Reservoir typically captures the majority of its annual storage volume from the early runoff of Elkhead Creek in April and the first part of May. During typical storage periods (April and May), the total monthly volume stored (as determined from model scenarios in the Phase 2 study) was distributed on a weekly basis as shown in Table 5. If storage occurred during the months of June and July, the total monthly volume stored was assumed to be a constant rate in the first two weeks of the month. Weekly volumes were then distributed uniformly into daily values.. Any storage occurring in the remaining months of the year was distributed on a daily basis evenly throughout the month. Table 5 Weekly Distribution of Monthly Storage Volumes from the Phase 2 Study Week 1 Week 2 Week 3 Week 4 April 0% 0% 20% 80% May 70% 20% 5% 5% June 70% 20% 5% 5% July 90% 10% 0% 0% Releases from the enlarged Elkhead Reservoir were handled in a slightly different manner. The majority of releases from the enlargement pool to meet assumed flow targets at Maybell typically occur in the later part of July and the early part of August as flow levels in the Yampa River decline. For these two months. the estimated daily 2040 flows without the project were compared to the flow targets assumed in the Phase 2 study (Table 6) to provide an indication of when daily "shortages" to the flow target occurred and when releases would be needed. A daily factor was then calculated as the difference between the estimated daily flow and the flow target, divided by the total shortage for the month. The daily factor was then multiplied by the monthly release volume determined from the Phase 2 study. In this way, total monthly release volumes from the Phase 2 study were preserved while the estimated 2040 daily flows without the project provided an indication of the daily distribution of the releases. During other months of the year. monthly release volumes from the Phase 2 study were generally distributed evenly over each day of the month. 12