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Development of Estimated Daily Flows - Yampa River at Maybell Aggregation of Irrigated Areas The current distribution of irrigated land in the basin was examined from the perspective of climatic zone, distance from the Maybell gage, and irrigation practice. From these considerations, eight groupings of lands were defined for consumptive use estimation purposes (Table I). All lands within each group were treated as if they constituted a single parcel of irrigated land. Potential consumptive use rates for each of the eight land groupings were developed in consideration of each area's proximity to one of the four climate stations. Furthermore, cropping type was considered to appropriately weight PCU for differences in crop proportions between land groups. The PCU rates were then applied to the number of acres in each grouping to estimate monthly potential consumptive use. in acre-feet; over the study period. Table 1 Designation of Irrigated land Groupings for Estimation of Agricultural Depletions Group Irrigated Area Included in Grouping Climate Station 1 2 3 4 5 6 7 8 Yampa River/Tribs. ab. Steamboat and Elk River/Tribs. ab. Mad Creek Yampa River/Tribs. between Milner and Steamboat Springs Yampa River/Tribs. between Mount Harris and Milner Trout Creek/Tribs. and Williams Fork ab. Hamilton Yampa River/Tribs. between Mount Harris and Elkhead Creek Elkhead Creek/Tribs. Yampa River/Tribs. between Elkhead Creek andWilliams Fork Yampa River/Tribs. bel. Craig and Morapos Creek Yampa Steamboat Steamboat Steamboat Hayden Hayden Craig Craig Historical Diversions Records of historical diversions by all irrigation ditches in the Yampa River Basin were supplied by the Office of the State Engineer, Division of Water Resources. This data was available in both daily format and as monthly totals for each diversion structure. With the exception of the Maybell Canal, only monthly totals were examined. Diversion data was provided in electronic DBase format and was systematically filtered to develop a set of diversion records for only those ditches upstream of the Maybell Gage. The Maybell Canal was excluded from this subset (discussed below). The data were then cross referenced with data on irrigated lands to develop eight sets of diversion data which were geographically consistent with the geographic groupings shown in Table I. Each of the data sets consisted of 33 years of monthly diversion volumes (acre-feet). Irrigation Depletion Analysis Potential consumptive use is an upper-bound estimate of actual consumptive use. Actual consumptive use will generally be less than potential consumptive use because of water supply shortages and irrigation and harvesting practices. Furthermore, the temporal pattern of actual stream depletion is different irom that of actual consumptive use because of the lagging of 5