Probable Maximum Precipitation in a Changing Climate: Implications for Dam Design

Abstract

Modern dams are overwhelmingly designed under the assumption of climatic stationarity by using a static design value known as probable maximum precipitation (PMP). Therefore, it is worthwhile to explore the impact of relaxing the assumption of stationarity and recalculating design PMP values by using currently practiced procedures enhanced by numerical modeling or observational climate trends. This study reports the findings of nonstationary PMP recalculations at three large dam sites in the United States (South Holston Dam in Tennessee, Folsom Dam in California, and Owyhee Dam in Oregon). The results indicate that currently accepted PMP values are significantly increased when future changes in dew points from observational trends or numerical models are taken into account. It is plausible that such future changes in these meteorological thresholds, had they been known among the engineering community when PMPs were designed, would have received the necessary attention regarding the future uncertainty of stationary PMP values as a dam ages.