Extreme Daily Rainfall Event Distribution Patterns in Kansas

Abstract

The Rainfall Frequency Atlas (TP40) was last updated for Kansas in 1961, using weather data from 1911 to 1958. Rainfall information contained in the atlas is the basis for important engineering and hydrologic design decisions in the state. With growing concern about the effects of global climate change and predictions of more extreme weather events, it is necessary to explore rainfall distribution patterns using the most current and complete data available. In this study, extreme rainfall frequency was analyzed using daily precipitation data (1920–2009) from 24 stations in Kansas and 15 stations from adjacent states. The Weibull distribution was used to calculate the precipitation probability distribution frequency at each station. Weather station point data were spatially interpolated using kriging. The overall analysis showed an increase in extreme precipitation events in Kansas with extreme event values tending to increase in magnitude from the northwest to southeast part of the state. Comparing results of the original TP40 analysis to the last of three study periods (1980–2009) showed that approximately 84% of the state had an increase in short-term rainfall event magnitudes. Long-term event magnitudes were predicted to be less than those reported earlier, but have increased over time, most likely because of the short data period used to calculate the TP40 precipitation probability distribution frequency. Results show a shift in rainfall distribution patterns in Kansas across both time and space. This shift changes the design criteria for water management systems, both in runoff control and storage structures.