In June 2021, the DWR completed an update of statewide Probable Maximum Precipitation (PMP) data through a two-year PMP study.
The 2021 study supersedes Hydrometeorological Reports (HMRs) HMR-48, HMR-51, and HMR-52, which were derived in the 1970s and 1980s by the National Ocean and Atmospheric Administration, as best available PMP data in North Dakota.
Results of the 2021 PMP study reflect the current standard of practice used for defining PMP and incorporate snowmelt along with both temporal and spatial distributions of PMP rainfall events.
The PMP study includes three GIS-based tools to allow evaluation of the PMP for individual basins: a PMP tool, a Snowmelt Tool, and a Spatial Distribution Tool. Application of the PMP study to dam design in North Dakota is outlined in the Dam Safety Standards. The final report of the PMP study and the accompanying GIS tools are below:
Download GIS Tools, Manuals, and Scripts
Probable Maximum Precipitation Study For North Dakota Final Report (PDF)