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in that it is east of the Continental Divide however, because of the large mountain barriers to the east of the Divide (the Sangre de Cristo mountains) the climatology of the basin is much like that of the West Slope Basins. This interest has translated into several studies that related one or more hydro- climate indices to stream flow and drought occurrence. Lilies (2002) documented a strong relationship between the Pacific Decadal Oscillation (PDO) and New Mexico precipitation. Negative PDO years are associated with below normal precipitation years and positive PDO years are associated with above normal precipitation years. He also noted that these influences were much stronger in the southern third of the state than in the northern third. Since the PDO is entering a predominantly negative PDO cycle for the next 20-30 years, he concluded that New Mexico should receive 75 percent of wet cycle year annual precipitation into the 2020’s. In essence he predicted a continuing drought condition for most of New Mexico’s river systems including the Rio Grande system. Leeet al (2003) noted a strong ENSO influence on both the accumulation and melting of snow pack in the Upper Rio Grande basin. The strongest precipitation connection occurred between much lower than average March precipitation during La Nina years preceded by above normal temperatures from September to March. While he notes additional correlations between El Nino and wet summers and La Nina and dry summers his results are less strongly supported by the observations. Given the availability of precipitation data there were three divisions that were examined Districts 26 (Saguache Creek), 20 (Rio Grande main branch) and 35 (Sangre de Cristo/Ute Creeks). These Divisions are geographically diverse with respect to the basin with the western, northern and eastern parts of the basin represented. The key ‘inflow’ areas for storm systems to positively impact the basin with precipitation are quite varied given the roughly ‘semi-circular’ nature of the basin, with the San Luis Valley being the center of the basin. In essence the passage of general storms that create long periods of orographic upslope winds from the south west to northeast can produce significant snowfalls. Monsoon moisture surges from the south can have similar impacts by producing multiple days of thunderstorm rainfall during the summer. Figure 3 shows the topography of the basin. 8