Incorporating Climate Change into the Precipitation-Frequency Curve at Taylor Park Dam

The Bureau of Reclamation uses precipitation-frequency estimates to characterize facility hydrologic loadings for evaluation of safety of dams. Currently, Dam Safety analyses include a qualitative climate change analysis based on bias corrected down scaled general circulation models. In the existing Dam Safety framework, it is often not clear how to include a more quantitative examination of climate non-stationarity due to large uncertainties in global climate models (GCMs). A stochastic storm transposition (SST) or weather generation technique, along with a stochastic hydrologic modeling process, can be used to modify the precipitation frequency curve in order to represent climate non-stationarity, and these modifications can then be used to determine how the flow frequency curve may change under future climatic conditions.

The approach described in Pennsylvania State's contribution to the 2022 NOAA Atlas 14 Estimates Assessment Report is used in this work. creating a modified precipitation frequency curve for Taylor Park Dam using the Generalized Maximized Likelihood Estimator. Several covariates are identified over the historical period, and the projections of these quantities in general circulation models are used to examine potential future precipitation-frequency curves. The results of this method are compared to the L-Moments methodology which is currently used in Reclamation’s Safety of Dams process.