Submitted to: Journal of Theoretical and Applied Climatology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 7/13/2026
Publication Date: N/A
Citation: N/A

Interpretive Summary: The Missouri and Mississippi River basins comprise the largest river basin in the continental United States. Further, the river basins are relied upon by a large portion of the United States agricultural industry. Thus, knowledge of the past and present extremes in water are important to the success of this large watershed. To this end, this study uses station data to investigate extreme precipitation events and how they are shifting from the past to the present. The area studied is the entire Missouri River basin across the north central United States and the upper Mississippi River basin, covering the western Midwest states. Results show that impactful precipitation events are becoming more frequent and more intense when comparing past events to current extreme precipitation events. These results even extend to multi day rainfall extremes, thus underlying a shift towards more extreme precipitation when the present and past datasets are compared. Overall, this study shows that large magnitude precipitation events in the Missouri and upper Mississippi River basins are becoming more impactful as time has progressed, underlying the need for more awareness of the impacts of these intense precipitation events and the adoption of strategies to mitigate their effects in agricultural areas near the watersheds.

Technical Abstract: This study investigates long-term changes in extreme precipitation trends across the Missouri River Basin (MORB) and Upper Mississippi River Basin (UMSRB) over two separate multi-decadal periods: 1950–1986 (Period I) and 1987–2023 (Period II), each spanning 37 years. The combined study area covers approximately 1,888,311 km2, focusing on the U.S. portion of the basins. Daily precipitation from 322 high-quality Global Historical Climatology Network (GHCN) stations, with less than 2% missing values, were examined to explore shifts in extreme precipitation trends. The analysis utilizes nine precipitation indices developed by the Expert Team on Climate Change Detection and Indices (ETCCDI), including PRCPTOT, Rx1day, Rx3day, Rx5day, R20mm, R95pTOT, Rainy days, SDII and CWD. To identify statistically significant trends, the non-parametric Mann-Kendall test and Sen’s slope estimator were applied. Additionally, Return Level (RL) magnitudes were estimated using the Gumbel distribution to evaluate change in extreme event frequency and intensity.Results indicate an intensification of extreme precipitation during Period II, particularly across southeastern and northeastern parts of the MORB and UMSRB. Statistically significant increases were observed in high-intensity, short-duration events, along with a rise in multi-day rainfall extremes. The identified changes reflect a shift toward more frequent and severe precipitation events, consistent with a warming climate and amplified precipitation trends. These findings underscore the growing need for adaptive water resource management and enhanced flood risk mitigation strategies.