Methodology and Data for Quantifying Extreme Precipitation Events in a Changing Climate

Project ID: 1385
Principal Investigator: John England
Research Topic: Managing Hydrologic Events
Priority Area Assignments: 2012 (Climate Change and Variability Research), 2013 (Climate Change and Variability Research)
Funded Fiscal Years: 2012 and 2013
Keywords: extreme precipitation events, data, watersheds, climate change

Research Question

What are the spatial and temporal characteristics of individual recent extreme precipitation storm events in orographic regions that have occurred since data used for Probable Maximum Precipitation (PMP) estimates were last collected?

Are recent individual extreme storms characteristics, including rainfall rates and spatial distributions at fine temporal and spatial scales, larger than those past events used in PMP estimates?

How can future climate projection information be used to potentially adjust the recent and past individual extreme storms underlying PMP, possibly affecting PMP in orographic regions?

This research is intended to address, in part, High Priority Gap No. 3.06 "Method and basis for estimating extreme meteorological event possibilities, deterministically or probabilistically, in a changing climate."

A major goal of this work is to develop a methodology and initial dataset of individual extreme precipitation events, in the form of gridded datasets at fine temporal and spatial scales (~hourly, 4 km) based on gage and radar data, to address the research questions.

Need and Benefit

Updated datasets and analyses of individual extreme storm events are needed for flood control rule curves, reservoir operations, and critical infrastructure (dams and nuclear reactors) assessments. For example, Dworak (2010) performed flood frequency analyses based on streamflow and paleoflood data to assess the probability of the required winter flood control space at Rire Reservoir in Idaho. The frequency curve was subsequently used by Mellema and McGrane (2010) to assess winter reservoir rule curve alternatives. The proposed research would benefit this type of study by providing extreme precipitation datasets that could be used to estimate flood probabilities because current U.S. Army Corps of Engineers' "Standard Project Flood" techniques to estimate flood control space are typically based on synthesis of record storms or PMP percentages. It would also provide a basis to potentially adjust these relationships to account for climate change of the extremes. A second example is to assess potential increased reservoir storage. A decision was made by the Bureau of Reclamation (Reclamation) in 2010 to allow for a 3-foot seasonal increase in storage at Lake Cachuma (Bradbury Dam). This proposed research and datasets could be used to investigate increases at other sites (such as Trinity) and incorporate climate change effects on extremes into the analysis.

Individual extreme storm datasets are old and outdated. The Extreme Storm Events Work Group, under the Subcommittee on Hydrology, (, is coordinating efforts to update the databases, and this proposed work would begin to meet that need for new datasets.

Kunkel et al. (2010) suggest that there may be changes in extreme storms and PMP due to climate change. They have analyzed point datasets to date. This proposed work would complement their work by focusing on the extreme precipitation data and estimates over storm areas, which are needed to estimate volumes over watersheds. The proposed work can also be used in hydrologic hazard assessments for dam safety.

This research is also a complementary effort to Proposal Project ID 6917, "Ingredients-based climatology and future projections of extreme precipitation events using a numerical weather prediction (NWP) framework." The development of new extreme precipitation datasets using surface observations and radar-based multisensor precipitation estimation (MPE) can subsequently be used to compare dynamically downscaled events with these observations. In addition, we can eventually use the Weather Research and Forecasting model (WRF) and statistics-based storm potential index ingredients to perturb the individual extreme precipitation events.

Dworak, F. 2010. Ririe Dam Flood Frequency Study, Bonneville County, Idaho. Bureau of Reclamation, Denver, CO, June, 26 p. and appendices.

Kunkel, K., K.T. Redmond, T.R. Karl, D.R. Easterling, And X. Liang, 2010. The Challenges of Producing Societally-useful Projections of Future Changes in Extreme Precipitation Events. Abstract GC33B-06, presented at 2010 Fall Meeting, AGU, San Francisco, CA, 13-17 Dec.

Mellema, M. and P. McGrane, 2010. Phase 1 Study of Proposed Modifications of Flood Control Operations, Ririe Dam and Reservoir, Ririe Project, Bonneville County, Idaho. Bureau of Reclamation, Pacific Northwest Regional Office, Boise, ID, September, 44 p. and appendices.

Contributing Partners

Contact the Principal Investigator for information about partners.

Research Products

Bureau of Reclamation Review

The following documents were reviewed by experts in fields relating to this project's study and findings. The results were determined to be achieved using valid means.

Will extreme rainfall change in Colorado's future? (final, PDF, 236KB)
By John England
Publication completed on September 30, 2013

This bulletin summarizes the research results and potential application to Reclamation's mission.

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Last Updated: 6/22/20