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I I I I I I I I I I I GOHi33 Streamflow Estimates The Missouri region opted to use the Framework Report estimates of average natural streamflows, adjusted to reflect depletions in 1975; however, an exception was made for ASA 1008 (Platte-Niobrara) where it was decided to use the estimate shown in the recently completed Platte Level B Study which reflects the results of stream-aquifer modeling and projected surface water/ground water utilization and streamflow depletions. All of t~e MCC streamflow estimates were developed by the U.S. Geological Survey. The USGS stated that mean annual and monthly discharges were computed from the record and that the period of record used for all computations was that representative of 1975 storage and operational conditions. The discharges computed at the gaging stations were transferred to the outlets of the ASA's, generally on a drainage area basis. The MCC and SRF estimated average annual discharges are shown as present modified flow in the COMP-4 tables at the end of this section. The two sets of discharges used show differences of less than 10 percent except at Sioux City (ASA 1006) and for the Kansas Basin (ASA 1010). It is to be noted that the MCC used a discharge for ASA 1006 which is not at the outflow point of the ASA at Sioux City. Why this was done is not clear. Water Use and Requirements Water use and requirements projections are given in Table Series COMP-2 and COMP-3. Table Series COMP-2 shows water use and requirements in terms of withdrawals while Table Series COMP-3 presents the comparison in terms of water consumption. Within the Missouri region crop irrigation constitutes 92 percent of the total water consumed, excluding evaporation losses from man-made. impoundments. Differences between the MCC and SRF estimates for other uses are therefore relatively unimportant. Whereas the MCC shows 11 major functional uses, with manufacturing further broken down into seven uses and minerals into three, the SRF shows only five major functional uses. For the SRF, domestic central and non-central and manufacturing were lumped together. The SRF esti- mates are somewhat higher than the MCC, which is to be expected because of the procedure used in the MCC, which does not account for water use for public or institutions use from municipal systems. The minerals total for the SRF is somewhat under the MCC which is probably due to the fact that the SRF used a different approach in deriving estimates and some of this water use shows up in estimates for manufacturing. The MCC and SRF estimates for livestock water consumption are quite comparable; however, the SRF probably would have been somewhat higher had it included 20 percent of small farm pond evaporation as was done for the MCC. The SRF estimates for steam electric for 1975 are somewhat higher than those for the MCC. Water use on public lands was not included in the SRF estimates since the water used is minimal and certainly should not have included estimates of water consumed by wildlife. The Framework Report recognizes streamflow depletions resulting from watershed protection projects, In an agricultural area as large as the Missouri region conservation practices. do have a sizeable effect on average streamflow and should be worthy of recognition. For irrigation the Department of Agriculture estimated water requirements for the dry year condition (2 out of 10 years) in the annual water requirement tabulations. Estimates were also made for 1975 actual use for the average condition. This latter estimate was used to derive the total current water supply. However, actual use estimates were not included for the 1985 and 2000 projections, so that in the COMP-4 tables the actual water use estimates are high. It is also noted that the estimated ground water withdrawals are added to the total water supply available within the ASA and that these estimates are unchanged for the projections. For the SRF part of the ground water con- sumptions and all of the surface water consumptions are treated as a depletion flow. The treatment of ground and surface water withdrawals and consumptive use III-13