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FINAL REPORT- HYDRO-CLIMATE INDEX PROJECT FOR THE <br />COLORADO RIVER WATER CONSERVATION DISTRICT <br />Introduction <br />A study was conducted by HDR Engineering – Atmospheric Sciences Group to <br />assess basin and sub-basin impacts of Hydro-Climate Indices (HCI) on various seasonal <br />components of precipitation, temperature and stream flow in a number of basins and sub- <br />basins in Colorado. The purpose was to attempt to gain insight into examining the key <br />relationships between various HCI and single and multi-year relationships of key <br />components of the meteorological/hydrological cycle of the San Juan-Dolores (Division <br />7), Rio Grande (Division 3) and the upper portions of the Arkansas River basin (Division <br />2- above Pueblo Reservoir). <br />In addition, multi-year relationships of precipitation, stream flow and temperature <br />were determined for the Upper Colorado (Division 5), Gunnison (Division 4) and the <br />Yampa-White (Division 6) as well. Some guidelines have been provided to assist in <br />using this study for input to a decision-making tool. <br />Background <br />Over the past 10-15 years, extensive research has been performed on <br />understanding seasonal outlooks of large-scale oscillations in variables in the atmosphere <br />and ocean systems around the world. These oscillations occur with variability that can <br />range from month-to-month to seasonal to multi-seasonal, depending on the temporal and <br />spatial scale of analysis. A sizable number of scientific studies have been conducted <br />comparing these climatic indices to seasonal impacts of sensible weather including <br />precipitation and temperature. <br />Examples of well documented seasonal oscillations include the El Nino/Southern <br />Oscillation (ENSO) and the Pacific Decadal Oscillation (PDO) with numerous regional <br />and hemispheric impacts being observed. A generalized example of ENSO’s impacts on <br />Figure 1 <br />North America in the January to March time frame can be seen in . The actual <br />HCI values assessed within the scope of this study were the Multi-Variate ENSO Index <br />(MEI), the Southern Oscillation Index (SOI), the PDO, the Atlantic Multi-Decadal <br />Oscillation (AMO) and the North Atlantic Oscillation (NAO). <br />A number of the scientific studies published on this topic were initiated by <br />correlating the calculated values of these indices to the seasonal temperature impacts in a <br />concurrent fashion. <br />1 <br />