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An example of this is in the accompanying charts and figures in the body of this <br />report where the `yellow' regions attempt to delineate the neutral mode of these <br />indices. In many of these defined two- dimensional relationships the values near <br />the `neutral' area of an index are very scattered and other index relationships <br />should be examined. <br />4) If an HCI is outside one of these `zones' it is recommended that the user consider <br />the segment that the current or expected HCI values resides in and not <br />immediately adjacent values. <br />5) In the body of this report the most relevant HCI variable that apply to given <br />variable and season are outlined. These indices should be examined first <br />however, other variables maybe examined as well. <br />Division 3 (Rio Grande Basin) <br />The Rio Grande Basin, in Colorado, is unique from a number of standpoints both <br />administratively and climatologically. A map of Division 3 and the administrative <br />boundaries of the Divisions can be found in Figure 3. The unique nature of this basin is <br />in that it is east of the Continental Divide however, because of the large mountain barriers <br />to the east of the Divide (the Sangre de Cristo mountains) the climatology of the basin is <br />much like that of the West Slope Basins. <br />This interest has translated into several studies that related one or more hydro - <br />climate indices to stream flow and drought occurrence. Lilies (2002) documented a <br />strong relationship between the Pacific Decadal Oscillation (PDO) and New Mexico <br />precipitation. Negative PDO years are associated with below normal precipitation years <br />and positive PDO years are associated with above normal precipitation years. <br />He also noted that these influences were much stronger in the southern third of the <br />state than in the northern third. Since the PDO is entering a predominantly negative PDO <br />cycle for the next 20 -30 years, he concluded that New Mexico should receive 75 percent <br />of wet cycle year annual precipitation into the 2020's. In essence he predicted a <br />continuing drought condition for most of New Mexico's river systems including the Rio <br />Grande system. <br />Lee et al (2003) noted a strong ENSO influence on both the accumulation and <br />melting of snow pack in the Upper Rio Grande basin. The strongest precipitation <br />connection occurred between much lower than average March precipitation during La <br />Nina years preceded by above normal temperatures from September to March. While he <br />notes additional correlations between El Nino and wet summers and La Nina and dry <br />summers his results are less strongly supported by the observations. <br />VA <br />