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SPDSS Task 4 Memorandum <br />November 23, 2004 <br />4. Determine the most reliable estimates and fill any missing data using the <br />techniques adopted for Colorado River Decision Support System (CROSS) and <br />Rio Grande Decision Support System (RGDSS). <br />Approach -Data Collection and Filling Process <br />The following approach was taken for the data collection and filling of each <br />transmountain diversion structure: <br />1) Daily and/or monthly diversion records were collected from the available information <br />sources. Unless otherwise indicated, continuously monitored USGS and DWR <br />streamflow records and DWR administrative records were obtained from HydroBase. <br />HydroBase is the State of Colorado's relational database, containing streamflow, <br />diversion, water rights, and other water related data. <br />2) Diversions from the available sources were summarized on an annual basis. For <br />years with annual discrepancies among data sources, diversions were reviewed on a <br />monthly or daily basis. <br />3) Where annual discrepancies were identified, discussion between responsible parties <br />was initiated to identify the cause of the discrepancies and to resolve the conflicting <br />records. <br />4) From inspection of the resolved diversion data, the best available data source for each <br />year was selected. Initial selection was based on the source with the longest period of <br />record, the most complete set of data throughout the period of study, the availability <br />of corresponding monthly and daily diversion data, and continuing operation of the <br />recording device. In those cases where data provided by the owner and data available <br />from the State both met the initial selection criteria and were similar within <br />approximately one percent, State records were selected as the best available data <br />source. <br />5) When reliable data was found from USGS Water Supply Papers or project owners for <br />periods missing in HydroBase, work was conducted with State hydrographers and <br />other DWR personnel to determine if it was appropriate to use the data to fill <br />HydroBase gaps. DWR approved data was digitized and formatted for easy <br />incorporation into HydroBase. <br />6) If data from multiple sources was required to develop a complete set of data for the <br />SPDSS study period, the best available data sources were combined into a monthly <br />tabulation of estimated diversions for the transmountain diversion structure and a <br />StateMod format file was developed. <br />7) When required, filling techniques developed during CROSS and RGDSS were <br />applied. <br />Page 2 of 19 <br />