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<br />· WET: 1905-1931, 1941-1951, 1957-1959, 1965-1975, 1979-1996 <br /> <br /> <br />· DRY: 1893-1905, 1931-1941, 1951-1957, 1963-1965, 1975-1978 <br /> <br />These periods indicate several aspects of climate during nearly a centruy. Two long wet periods <br /> <br />(1905-1931 and 1979-1996 and continuing) are longer than any dry periods. Two dry period of <br /> <br />1931-1941 and 1951-1957 had severe short term (3 month) and long term (48 month) drought. <br /> <br /> <br />No long term drought has occurred since the 1950s but short term drought has been as severe in <br /> <br /> <br />the recent years as during the major dry periods. <br /> <br />When the state is divided into river basins, the dry and wet mostly agree with the analysis <br /> <br />from the percentage of sites. Major exceptions were that the Y ampa- White basin was mixed in <br /> <br />the 1940s and 1950s, the western slope had a dry period in the later 1980s into 1990s and plains <br /> <br /> <br />portions of the South Platte and Arkansas were mixed in the period 1965-1975. <br /> <br />The worst dry and wet periods at individual locations have a wide variety of years of <br /> <br />occurrence and magnitudes. Regionally the magnitude (accumulated precipitation deficit) of the <br /> <br />worst periods increase with increasing time scale to 24 months and at 24 months lead to deficiets <br /> <br />(surpluses) of1 to 2 times the annual precipitation. Periods during the 1930s and 1950s were <br />common for drought. <br /> <br />Correlation coefficients of water year precipitation (October through September) between <br /> <br /> <br />river basins is above 0.50 for basins on the same side of the Continental Divide and much lower <br /> <br /> <br />for basins on opposite sides. Precipitation in the Rio Grande basin does not correlate well with <br /> <br />other basins. Correlation relationships of 12 month precipitaiton and the 12 month SPI are <br /> <br />27 <br />