CRDSS_Task10-2_EvaluateExtensionHistoricalData

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county and HLJC 14020001 combination has two temperature stations in it: the Crested Butte station, weighted at 61 %, and the Gunnison station, weighted at 39%. The temperature stations are located in the Gunnison River basin. In order to establish the number of temperature and precipitation gages in each basin, the county/HiJC combinations were identified. Next, the number of stations in each county/HUC combination were identified. Finally, the county/HUC combinations were located by river basin. The streamflow and climatological data used in the Water Resources Planning and Consumptive Use Models were reviewed to evaluate the feasibility of extending the data records to various dates. Exhibit 3 lists the five river basins used in the Water Resources Planning and Consumptive Use Models. It also presents six different possible data extension dates (from 1960 to 1910), and the corresponding number of gages and percent of the total that would be useful in extending the data in each case. These are listed according to streamflow, precipitation, and temperature data. The gages were plotted using the tstool option in the CRDSS model to compile this information. A cursory review was also performed to determine if there were gages with significant record that were not included in the Phase IIIa and IIIb Water Resources Planning Models because they did not fit the model study period from 1975 to 1991. Exhibit 4 lists the five models and gages, if any, that were not included. There is potential to use these gages as part of the extension process, since the data-centered approach and baseflow component of StateMod make the addition of new streamflow data relatively easy. Estimating Diversion Data Before beginning a discussion on diversions, it is necessary to define the difference between demands, diversions, and depletions. Demands are the quantities of water requested by the users; diversions are the quantities of water allocated; and depletions are diversions minus any return flow, or the combination of consumptive use, evaporation, and trans-basin diversions (water taken from the basin). A cursory review of the diversion data in each of the five Water Resources Planning Models was performed. Amore detailed review was not performed due to the high number of diversions present in each model. The Yampa River basin had the greatest number of digitized diversion data records extending back prior to the 1975 - 1991 calibration period. A good portion of the records extended back to the 1930s, with some as far back as the 1910s. The White River basin had many of its records extending back to the 1960s. The Colorado, San Juan, and Gunnison River basins all had some records extending to the 1950s. Based on this review, a significant amount of diversion data would need to be digitized or estimated, depending upon the desired extension period. This data will be required for estimation of natural flows from gaged data prior to filling missing streamflow data. Diversion data from three senior ditches were reviewed to determine if there were any relationships between diversions and streamflows. The ditches were the Grand Valley Canal, the Fire Mountain Canal, and the Maybell Canal from the Colorado, Gunnison, and Yampa basins, respectively. Exhibits 5, 6, and 7 summarize the data for the three canals, and indicate very little correlation between the streamflows and the diversions. In general, during summer months (June, July, and August) the diversions were independent of streamflows, indicating that the priorities of the canals are not called out and they can divert as much water as desired. The diversions, in fact, show less variation than the streamflows. For months in the early and late season (April, May, September, and October), the diversions appear to be governed by the climate and are still a function of water needed. Diversions are Appendix E E-16