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. . . "'j~''''~7 ;~ '~~.u . J expected or desired. but it could be used in the future if certain assumptions are changed and virgin flows have to be redone) throughout the Gunnison Basin creating a set of error files for each sub-basin. An error analysis could be done for the Gunnison Basin by trying different values for acreages, consumptive use, and any other factors that were in question. By analyzing the effect substituting these different values had on the error files, possibly better estimates for these things could be obtained. When the mass balance was done using the Gunnison at Crystal as a Base, the negative errors were distributed amoung the upstream stations giving revised virgin flow files for these. Two of these upstream stations (Gunnison River at Gunnison and Tomichi Creek near Gunnison) were then used in upstream mass balances against other stations. According to the writeup, however, the revised files were not used for the two upstream mass balance Base Stations (is this correct?). Doesn't this mess up the balance amoung some of the upstream stations when the two revised upstream Base Stations are used in the model along with the other stations that were balanced against the original unrevised stations? Correlation Procedure to Extend Virqin Flow Record - Three of the fourteen "Core Stations" in the Upper Gunnison Basin have historical records less than ten years. These are Cimarron River at Cimarron (8.3% of Gunnison River at Crystal), Cochetopa Creek near Parlin (3.3% of Gunnison River at Crystal), and Ohio Creek near Gunnison (6.4% of Gunnison River at Crystal). Also, some of the other stations that were used in the Mean Elevation vs. Flow per Square Mile plots had records that were less than ten years and used ratio and proportion instead of doing a correlation (is this right?). Because of this, the correlations that were performed on these stations may have produced extended virgin flow records that are suspect. Possibly such things as snow, precipitation, and temperature could be used to improve correlations. Also, it is possible that they could be used to improve or help develop a correlation (instead of using ratio and proportion) for the other stations having a longer period of record available. Some stations may have additional flow records available now; however, none of the above three Core Stations appear to. Consideration should be made, however, whether the increased accuracy that would be produced would justify the extra work involved. Estimation of Shortages - 1- the Phase I Upper Gunnison Basin computation of virgin flows: shortages to irrigation were estimated using (How was this done? Page B-9 infers they were taken from operation studies from the Water Supply Appendix for the Upper Gunnison Project. If so maybe they are pretty good). Because shortages occur in critical years, errors in their estimation could produce appreciable errors in the results of the operation study model using these virgin flows.