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Show APPENDIX XII XII-61 Colorado Region's Comprehensive Framework Studies. The sources of readily available and published data are essentially the same for both reports. The report relies, in some cases, on the results of special studies prepared for the framework study. UPPER COLORADO RIVER Irrigation Consumptive Use: Annual irrigated acreage and cropping patterns are the most important items of data required for a proper determination of consumptive uses and losses in the Upper Colorado River Basin. The annual State agricultural statistics reports of Wyoming, Colorado, and New Mexico provide good estimates of irrigated harvested cropland. (This item of data is not collected or reported on in the Utah statistics report.) These data are presented on a county basis and must be disaggregated into tributary basins. Generally, this does not present too much of a problem except in Wyoming, where county lines and the Colorado River Basin divide are considerably dissimilar. More timely issuance of the reports would be helpful. The determination of irrigated nonhar-vested cropland (mostly irrigated pasture lands) is ah area of data collection which needs to be considerably strengthened. This item is not reported on in the State statistics reports. The acreage used to develop the estimates of irrigated pasture consumptive use for this Study are based very strongly on acreage values reported in the 1969 National Census of Agriculture. Other areas of data collection which need to be improved are (1) the determination of irrigated lands which receive less than a full seasonal supply of irrigation water and improvement of techniques for estimating water use on these lands, and (2) up-to-date inventories of seeped and phreatophyte areas associated with irrigated lands. The present level of climate data acquisition is adequate for the proper application of the evapotranspiration formula. Reservoir Evaporation: The techniques and data used to compute reservoir evaporation were generally satisfactory. Of course, additional pan evaporation and reservoir content records would strengthen the estimates. Other Uses: The records of transbasin exports and thermal powerplant uses are excellent. The estimates of municipal and mineral resource uses could be enhanced through the collection of additional diversion and return flow records. However, extensive data acquisition programs for these items do not seem warranted in light of their small magnitude in comparison to the possible error of estimate of the larger water-use items (e.g., irrigation, evaporation). LOWER COLORADO RIVER Mainstream: The annual land use, water supply, and water use information being gathered for the operation, maintenance, and administration of the Colorado River mainstream below Lee Ferry is believed to be generally adequate in quantity, quality, and extent. Under more or less constant review, these data are being continually upgraded wherever deficient. Studies and programs are in progress to remedy a lack of data on return flows from mainstream diversions and to correct the apparent inaccuracies of the recorded releases from Hoover Dam. Tributaries: For the purpose of this report, there are adequate data, for the most part, in the tributary areas of the Lower Colorado River system to make reasonably accurate estimates of the overall beneficial consumptive use of water by the major types of use. Major uses are agriculture, municipal and industrial, and reservoir evaporation. Although most of the data could be enhanced to some extent, upgrading would entail the collection of supplementing data which would be both expensive for f ieldwork and instrumentation and for the office work to assimilate these additional data. Whether supplementing data would actually improve the accuracy of the net water use must be carefully weighed, since most theoretical techniques consider only a small fraction of the factors involved. Agriculture: County information is available in most of the area to aid in the estimation of irrigated crop acreage. In general, these data are adequate although some difficulty is encountered in disaggregating the data into 15 |
