Characterizing Precipitation Extremes to Support Flexible Water Management and Planning

Precipitation and flow extremes are critical parameters for water resources planning, due to both the management threats and opportunities for water supply that they provide. MMM scientists have been working with colleagues at the Bureau of Reclamation (funding sponsor) to better characterize precipitation extremes now and in the future. This research identifies and incorporates dominant weather patterns associated with precipitation anomalies into a statistical model that characterizes precipitation extremes in the context of water management. A clustering algorithm identified distinct atmospheric circulation patterns, or weather types (WTs), associated with precipitation, including extremes. A statistical model based on Extreme Value Theory (EVT) was then used to describe the frequency and magnitude of extreme precipitation events, how they vary with WTs, and how they are likely to change over time. The solution was applied in New Mexico (NM), with a focus on the Rio Grande and Pecos River basins, where there may be opportunities to exploit changes in warm season extreme rainfall for water supply.

Projected changes in the number of days in which precipitation in the New Mexico Rio Grande Basin exceeds 6.5mm during the monsoon season. The statistical extremes model was driven with weather-type count projections from the Community Earth System Model Large Ensemble. The blue envelope is the ensemble 25th-75th percentile and the white line is the ensemble average.
Figure: Projected changes in the number of days in which precipitation in the New Mexico Rio Grande Basin exceeds 6.5mm during the monsoon season. The statistical extremes model was driven with weather-type count projections from the Community Earth System Model Large Ensemble. The blue envelope is the ensemble 25th-75th percentile and the white line is the ensemble average.

Acknowledgements

  • This work was supported by the Bureau of Reclamation Science & Technology award No. 1782: “Detecting, Interpreting, and Modeling Hydrologic Extremes to Support Flexible Water Management and Planning.” This material is based upon work supported by the National Center for Atmospheric Research (NCAR), which is a major facility sponsored by the National Science Foundation (NSF) under Cooperative Agreement No. 1852977.