Frequency and Duration of Drought in the Upper Green River Basin, Wyoming, USA

The limited length of instrumental streamflow data impacts the true magnitude of natural interdecadal variability of water delivered from the UGRB. This limited period of instrumental record can be expanded by utilizing proxy records (reconstructed streamflow) derived from tree rings. Two reconstructed streamflow datasets are now available for the Green River near Green River, UT, and a new preliminary reconstruction has been developed for the Green River near Green River, Wyoming. Also, recent research has resulted in the development of nine streamflow reconstructions spatially located throughout the UGRB. The proposed research would use these streamflow reconstructions to assess patterns (temporal and spatial) and sources of streamflow variability in the UGRB. An investigation of long-term streamflow variability, focusing on extreme events such as mega-droughts, will be performed. The research will result in the development of probabilistic drought forecasts. Salas et al. provides drought definitions and equations that can be utilized by water planners in storage dependent systems. Loaiciga utilized the compound renewal process, which generalizes the Poisson process, to calculate return periods for drought events. This may result in frequency — duration curves for UGRB drought. Such probability curves can then be analyzed in light of Compact agreements to answer questions such as, "How often might the outflow from the UGRB fail to meet 10-year delivery obligations?"