Hydrologic Study of Large Basin in Eastern Wyoming

Abstract

A case study of the Horse Creek basin in eastern Wyoming is presented. The study involved calculating the 100‐year frequency and the probable maximum flood at several potential dam locations using a deterministic hydrologic model. The basin drains 1,560 sq mi. The basin has a long‐record gage near the point of interest, but the record is suspect due to irrigation diversion and return flows. Therefore, a flood flow frequency analysis from a hydrologically similar basin was performed. This included peak discharge and high volume‐duration‐frequency derivations. The model allows centering of a storm over a critical portion of the basin, with residual rainfall over the remainder. The study concludes that generation of rare‐event and probable‐maximum‐flood (PMF) design discharges at gaged locations requires careful analysis of the basin and gaged data. This includes review of hydrologically similar basins to allow generation of appropriate statistical parameters for calibration of a deterministic model.