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<br />Colorado Drou ht Watch <br /> <br />May 8. 2002 <br /> <br />About SNOTEL <br /> <br />The ~atural Rc!'>ources Consen'alion Seryice (NRCS) installs. operates. and maintains an extensive. automated <br />system to collect slIO\vpack and related climatic data in the Western United Stales called. SNO\.\!pack TELemetry <br />(SNOTEL). The system evolved from NRCS's congressional mandale in the mid. 1930's "10 measure sno....'Pack in <br />the mounlains aflhe West and forecast the water supply." The programs began with manual measurements of <br />snow courses; since 1980. SNOTEL has reliably and efiiciently collected the data needed to produce water supply <br />forecasts and to suppon the resource management activities ofNReS and others. <br /> <br />The sites are gcncmlly located in remole high-mountain \vatersheds where access is ollell dillicult or restricted. <br />Access tor maintenance by NRCS includes various modes from hiking and skiing to helicopters. <br /> <br />Sites are designed to opcrnte unattended and without maintenance for a year. lbey are baltery powered with solar <br />cell recharge. Tbe condition of each site is monitored daily when it reports 011 8 operational functions. Serious <br />problems or deteriorating pcrfonnance trigger a response from the NRCS electronic technicians located in six data <br />collection olliccs. <br /> <br />Common Drought and Moisture Indexes <br /> <br />. Surface Waler Supply Index (SWSI) is a weighted index ofsllOw pack. stream !low. precipitation and res- <br />ervoir storage. <br /> <br />. Standardi.led Precipitation Index (SPI) is considered to be the simplest and most robust index lor describ- <br />ing drought patterns. II is based on CUlTCnt and historical precipitation data lor a particular locatioll. <br /> <br />. I'lllmer Drought Index is a complex soil moisture calculation used by federal agriculturnl agencies in deter- <br />mining drought a'isistance to local farolers and ranchers. <br /> <br />. Crol) ~llIhtllrc Index, developed from the Palmer Drought Index. evaluates short-tenn moisture conditions <br />across major crop producing regions of the U.S. <br /> <br />. H.escnoir ICHls indicatcs the amount of water in storage at various water supply reservoirs. <br /> <br />About the U.S. Drought Monitor <br /> <br />The Drought Monitor ITklp identifies general drought ar(,,<iS. labeling droughts by intensity, with DI being the least <br />intense and D-l. being the most intense. DO drought watch areas. are either drying out and possibly heading for <br />drought. or arc recovering from drought but not yet back to nomla!. and are suffering long.tenn impacts such as IO\\" <br />reservoir levcls. <br /> <br />Drought intensity categories are based on six key indicators and numerous supplementary indicators. Bl.'Causc the <br />ranges of the various indicators ollen don't coincide, the linal drought category tends to be based on what the major- <br />ity of the indicators show. The analysts producing the map also weigh the indices according to how well they per. <br />fonn in various parts oflhe country and at ditTerenttimes of the year. Also. addilional indicators are ollen needed in <br />the West. where winter snowfall has a strong bearing on \vater supplies. <br /> <br />A partnership consisting of the U.S. Depanment of Agriculture. the National Weather Service's Climate Prediction <br />Center. and the National Drought Mitigation Center at the University of Nebraska Lincoln produces the Drought <br />!\.1onitor. II0we\"er. advice from many other sources is incorpomtcd in the product, including virtually every govern. <br />ment agency dealing \\;th drought. <br /> <br />7 <br />