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Show Final Report Hydrologic Model Analysis of the Provo River Basin 2.3.1 Meteorological Analysis PROSIM requires representative precipitation and temperature data for each agricultural water user. Precipitation and evaporation data are required for each modeled reservoir. A single set of precipitation and temperature data were developed from the Heber City gages for modeling consumptive use on irrigated land areas above Deer Creek Reservoir. For areas downstream of Deer Creek, the Utah Lake at Lehi precipitation record was used. For reservoir accounting at Deer Creek and Jordanelle reservoirs, the Deer Creek precipitation record was used. Lake evaporation data were developed from the Morton equation for Utah Lake evaporation, with an 86 percent coefficient applied for Jordanelle and Deer Creek. The Utah Lake data are documented in the Draft Preliminary Planning Report - Utah Lake Salinity Control Studies ( CUWCD, 1992b). 2.3.2 Water Use Data River diversion and agricultural water use data were used in calculating natural flows, a critical component of the PROSIM hydrological database. The available historic data consisted of River Commissioner's records for each of the major diversion points on the Provo River. Data for the years 1950 through 1989 were available from the Utah Department of Natural Resources. Data previous to 1950 are only available in unprocessed form in the River Commissioner's annual reports. Significant checking, processing, and adjustment were required to make the diversion records complete and consistent. This was largely because the accuracy of flow measuring devices is low, and because the data were not intended for use in a comprehensive hydrologic analysis of the system. However, these data were the best available information for estimating historic withdrawals from the river, and historic withdrawals were required to estimate the natural flow of the river. The recorded data were adjusted where obvious inconsistencies were noticed, or where incompatibilities existed with respect to the other water balance elements. However, the errors in the diversion estimates are expected to be significant at times, and it is understood that the magnitude of these errors may prevent accurate estimation of return flow timing and volume. 2.3.3 Streamflow Data Historical streamflow data were required for each model node in the basin, and for each significant tributary. However, measured streamflow data were only available at selected points on the river, and in most cases, only for portions of the study period. Streamflow correlations and water balance calculations were used extensively to estimate missing streamflows and to develop flows at ungaged January 1998 Page 12 |