Blom, Tevis听1
1听University Colorado Boulder
April 1st Snow Water Equivalent (SWE) is a useful indicator of potential water resources along Colorado鈥檚 Front Range. This is especially so at altitude where snowpack serves as a seasonal storage reservoir. Climate change in the 20th century has the potential to alter presumed water resources. This has been evidenced by ecological changes at Indian Peaks sites (notably the Niwot Ridge long term ecological research site). Manually collected Snow Course(SC) and automated Snow Telemetry (SNOTEL) datasets extending to 1938 have been analyzed using a two period statistical breakdown. Period 2 means were generally near the lower limit of Period 1 Confidence intervals. The average trend of 5 sites for period 1 was -0.17, the average trend of 6 sites for period 2 was -0.049. Four out of five Eastern slope Indian Peaks SNOTEL data sets show decreasing April 1st SWE over the complete 70 year sequence (combined average trend slope is -0.11 for all 5 sites). Trends in El Nino-Southern Oscillation (ENSO) patterns using 鈥楳ultivariate ENSO Index鈥� (MEI) are plotted against combined average SWE for all 5 sites. Positive MEI scores relate to higher April 1st SWE at these sites (trend slope=0.2992). A fifty-nine year trend in MEI score is plotted against year; a trend toward higher MEI values exists in the time series (trendline slope= 0.0096). A discussion of Snow Course versus SNOTEL data follows; a -1.7% error exists in early Snow Course data based on early sampling. This bias would further inflate early values and correspondingly steepen decreasing trend slopes. This study indicates an increasing 59 year March/April MEI index, increasing temperatures, and decreasing April 1st SWE along Colorado鈥檚 Front Range.
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