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DATA PRODUCTS effects. RTi also obtained historical climate data for the Alamosa, San Luis Valley Regional Airport weather station (KALS) to identify periods of high wind and low humidity that might be conducive to sublimation losses. The KALS station is part of the F AA/NWS MET AR network. 3. Data Products In May and June 2008, RTi produced weekly summaries of SNODAS SWE for the project area and delivered the data products to the steering committee. The weekly products included a map of the project area that overlays the most recent SNODAS SWE grid onto the key index basins. Each index gage was annotated with the cunent SWE volume above the gage and the change in SWE volume from the preceding week. Attachment 1 includes an example of the weekly map. RTi distributed an Excel workbook containing historical and cunent SNODAS information for the key index basins. The SNODAS data included daily values of average SWE depth and SWE volume for each basin, allowing a comparison of how snowpack accumulation and ablation for WY 2008 compared to recent years. The workbook also contained SWE estimates normalized using the maximum snow accumulation for each water year to facilitate comparison across the years. Attachment 2 contains an example of the summary SNODAS information submitted by RTi each week. Finally, RTi submitted an Excel workbook that contained all historical and current SWE and soil moisture data collected for SNOTEL gages. This product allows the team members to compare SNODAS SWE estimates and accumulation and melt patterns against nearby SNOTEL stations. Attachment 3 contains an example of the SNOTEL data submitted. During the course of the project, updated data products were distributed to the project steering committee nine times. The project steering committee provided feedback on the weekly products. For example, RTi added the one-week SWE volume change to the map labels at the suggestion of the steering committee. Committee members also expressed interest in calculating weekly runoff coefficients (ROCs) to compare streamflow volumes to the changes in the snowpack SWE volume for the same period. RTi began calculating these values but did not distribute them to the group. The nudging procedures used in SNODAS to adjust SWE complicate short-term comparisons with other data. During the WY 2008 melt season, NOHRSC performed several nudging procedures to adjust the amount of snow. SWE values increased due to storms that generated more snow than indicated by the RUC2 numerical weather prediction model that produces precipitation estimates for SNODAS. SWE values decreased due to under-simulated snowmelt. These data assimilations frequently caused larger-than-normal SWE changes within a 24-hour peliod. Daily changes may represent adjustments for gradual, long-term deviations of SNODAS from reality or sudden changes in SWE from weather conditions. In either case, the nudging procedures obscure the timing of SWE accumulation or melt required for short-term comparisons, resulting in anomalous ROC values. 4. Forecast Comparison RTi performed a limited investigation into recent NRCS water supply forecasts for the RIODELCO gage that differed significantly from observed seasonal runoff volumes. The April-September water supply forecasts at RIODELCO showed large deviations from actual runoff volumes in WY 2005 and WY 2007. In WY 2005, the NRCS forecast was significantly higher than the actual seasonal runoff volume despite a large snowpack. In WY 2007, the NRCS forecast was lower than actual seasonal runoff volumes. The forecasting equations developed by the NRCS utilize first-of-the-month SWE observations and WY-to- date precipitation totals at six SNOTEL stations (i.e., Lily Pond, Middle Creek, Molas Lake, Upper Rio Grande, Upper San Juan, Wolf Creek Summit). 3 ~Riverside Technology, inc.