Case Study of Drought Frequency and Risk Analysis in the Upper Green River Basin, Wyoming

Abstract

The limited length of instrumental streamflow data impacts the true magnitude of natural interdecadal variability of water delivered from the Upper Green River Basin (UGRB). This limited period of instrumental record can be expanded by utilizing proxy records (reconstructed streamflow) derived from tree rings. Recent research has resulted in the development of nine streamflow reconstructions spatially located throughout the UGRB. This paper utilizes four of those nine reconstructed streamflow records and instrumental records to compare and analyze differences between the two streamflow records—human and natural. Three approaches were used for comparison and analysis: (1) Weibull distribution, (2) compound renewal, and (3) drought risk using bivariate probability distribution functions. This analysis has resulted in magnitude-duration-frequency curves for UGRB drought. Such probability curves and stochastic analysis can then be utilized in light of compact agreements and system storage to answer questions such as “How bad is it right now and what can we expect to happen next year?” This case study is intended to show statistical and observed differences between human (short-term) and natural (long-term) streamflow records and specifically target differences in long-term drought characteristics for this drainage basin.