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SUMMARY AND RECOMMENDATIONS WY 200S The summer precipitation in WY 2004 was lower than average, resulting in drier soil conditions at the beginning of WY 2005. (Relatively dry soil moisture conditions were also recorded at the Upper San Juan and Upper Rio Grande SNOTEL stations at the beginning of WY 2005). WY 2005 was characterized by a large snowpack but also by a late melt-out (see Figure 4-1). The SWE change of 5A inches in June is much higher than in other years. Melt OcculTing this late in the year can be subject to significant evapotranspiration. Our estimates indicate that approximately 3.85 inches of the June snowmelt were lost to AET. Additional snowmelt was likely lost to moisten dry soils that resulted from the previous dry summer. The sum of these effects is evident in the low ROC value of 0.58. In addition, the April-September precipitation was below average in WY 2005. Overall, a combination of a larger soil moisture deficit, late snowmelt, and below-average summer precipitation appear to have resulted in lower seasonal runoff volumes than were forecasted. WY 2007 The initial soil moisture for WY 2007 was wet based on above-average precipitation in July-October 2006. (Relatively wet soil moisture conditions were also recorded at the Upper San Juan and Upper Rio Grande SNOTEL stations between October and December 2007). The snowpack began to melt relatively early, with a one-inch SWE change in March and most of the remaining snowmelt occuning in May, months that have considerably less ET-demand than June. WY 2007 had the smallest losses from sublimation, particularly in April and May. Much like WY 2006, WY 2007 had very high precipitation from April to September of almost 16 inches. Overall, a combination of wet soil moisture, early snowmelt, low sublimation losses, and large amounts of summer precipitation appear to have caused higher seasonal runoff volumes than predicted. WY 200S WY 2008 started with wet soil moisture conditions based on above average precIpItation during the preceding summer. Large precipitation totals were also recorded from December to February 2008. The large snowpack accumulation is comparable to WY 2005 but is melting out earlier (see Figure 4-1). The sublimation losses are the highest of the available years, particularly in April. The runoff in WY 2008 has been less than that recorded in WY 2005 despite more snowpack. However, nearly II inches of SWE change occuned in May that should cause streamflow to be higher than average in June. The 4 inches of SWE remaining on the ground on June 1st are expected to melt during that month and will likely be subject to significant evapotranspiration. The Climate Prediction Center (CPC) is forecasting average precipitation over the next three months (CPC 2008). As of the end of May 2008, temperature forecasts are average for June 2008 but above average over the next three months. The net impact of lower runoff in April and May, large May snowmelt, and average summer precipitation should be a water supply for WY 2008 that is similar to WY 2005. 5. Summary and Recommendations The work performed during this project indicates that the SNODAS data products have the potential to add value to the snowpack assessments and water supply forecasts in the Upper Rio Grande basin. The SNODAS SWE estimates were consistent with SNOTEL gages in the area as judged by the magnitude of snow accumulation across the years examined and the snow accumulation and ablation patterns. Unlike point observations, the SNODAS provides spatially continuous estimates of snowpack characteristics. The SNODAS data products were useful in conjunction with SNOTEL information to characterize the areal extent of snow cover and melt out patterns across the years and project area. The surface sublimation and condensation product from SNODAS shows potential for predicting snow losses that do 8 ~Riverside Technology, inc.