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<br />Colorado Drou ht Watch <br /> <br />April 16. 2002 <br /> <br />About SNOTEL <br /> <br />The ~alural Resources Comen'alion Sen'ice (NRCS) inslalls, operates, and maintains an extensive, automated <br />system to collect snowpack and related climatic data in the \Vcstem United Slates called. SNOv.'P3Ck TELemetry <br />(SNOTEL). The syslem evolved from NRCS's congressional mandate in the mid-1930's "to measure snowpack in <br />the mountains or the West and forecast the waler supply." The programs began with manual measurements of <br />snow courses: since 1980. SNOTEL has reliably and cfliciently collected the data needed to produce water supply <br />forecasts and to suppon the resource management activities ofNRCS and others. <br /> <br />The sites are generally located in remote high-mountain watersheds where access is often dillicu[1 or restricted. <br />Acc<..'Ss for maintenance by NRCS includes various modes from hiking and skimg to helicopters. <br /> <br />Sites arc desi!,'lled to operate unattended and without maintenance for a year. 'Illey arc battery powered with solar <br />cell recharge. The condition of each site is monitored daily when it repons on 8 operational funclions. Serious <br />problems or deteriorating performance trigger a response from the NRCS electronic technicians located in six data <br />collection offices. <br /> <br />Common Drought and Moisture Indexes <br /> <br />. Surface W;dter Suppl~' Index (SWSI) is a weighted index of snow pack, stream flow. precipitation and res. <br />ervoir stornge. <br /> <br />. Standardized I'recipit;dtion Index (S!>I) is considered to be the simplest and most robust index for describ- <br />ing drought patterns. It is based on CUrTent and histonca] precipitation data for a particular location. <br /> <br />. I'almer f)rou~ht Index is a complex soil moisture calculation used by federal agricultural agencies in deter. <br />mining drought assistance to local famlers and ranchers. <br /> <br />. Crop :\Inhturc Index, developed from the Palmer Drought Index. evaluates shon-teml moisture conditions <br />across major crop producing regions of the U.S. <br /> <br />. Resen'oir len.'ls indicates the amount of,vafcr in storage at various water supply reservoirs. <br /> <br />About the U.S. Drought Monitor <br /> <br />111e Drought Monitor map identifies general drought areas. labeling droughts by IIltensity. with [) I being the least <br />intense and D-J being the most intense. DO drought watch areas, arc either drying out and possibly heading for <br />drought. or are recovering from drought but not yet back to normal. and arc sutTering long-ternl impacts such as low <br />reservoir le\'Cls. <br /> <br />Droughl intensity categories are ba~ed on six key indicators and numerous supplementary indicators. B<..'Cause the <br />ranges of the various indicators onen don't coincide, the final drought category tends to be based on ,..'hat the major~ <br />it)' of the indicators show. The analysts prooucing the map also weigh the indices according to how well they per- <br />form in various pans of the country and at dille-rent times ofrhe year. Also. additional indicators are ollen needed in <br />the West. where winter snowfall has a strong bearing on water supplies. <br /> <br />A pannership consisting of the U.S. Depanmem of Agriculture. the National Weather Service's Climate Prediction <br />Cemer. and the National Drought ~litigation Center at the University of Nebraska Lincoln produces the Drought <br />lVlonitor. Howe"er. advice from many other sources is incorporated in the pnxlucl. including ,-inually every gO\'em- <br />ment agency dealing with drought. <br /> <br />7 <br />