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John A Dracup

Linkages between tropical Pacific Ocean monthly climatic variables and the Upper Colorado River basin (UCRB) hydroclimatic variations from 1909 to 1998 are analyzed at interseasonal timescales. A study of the changes in these linkages through the years and their relationship to the Pacific Decadal Oscillation (PDO) is also investigated. Tropical Pacific climate variations were represented by atmospheric/oceanic ENSO indicators. For the UCRB, warm season (April–September) streamflow totals at Lee’s Ferry, Arizona, and precipitation averages at different periods (cold season: October–March; warm season: April–September; and annual: October– September) were used to study the UCRB’s response to tropical Pacific climatic...
The flooding in the lower basin of the Colorado River during the spring and summer of 1983 led to discussion of the management of the heavy spring runoff from the upper basin. This analysis stresses that the reasons for the flooding go beyond the climatic events of the year and the U.S. Bureau of Reclamation's response to them. It is argued that the flooding is the result of the convergence of three factors: 1) the 17-year period of filling Lake Powell (Glen Canyon Dam) has ended and the system of water storage reservoirs on the river now considered full; 2) during the filling period, physical encroachment into the lower basin flood plain accelerated; and 3) the climatic variability experienced in the Colorado River...
Many water agencies in California and the rest of the United States utilize sequences of wrapped historic hydrology rather than synthetic streamflows in their simulation models. The wrapped historic procedure is also known as the index-sequential method. This paper compares results from an annual regulation model of the Colorado River system which used both historic hydrologic sequences generated by the index-sequential method, and autoregressive, order 1 (AR(1)) synthetically generated streamflows as inputs. The synthetic AR(1) log normal model also included parameter uncertainty. Reservoir storage exceedance probabilities developed for Lake Powell and Lake Mead from a 32-year simulation show that AR(1) model generated...
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