ABSTRACT:

Hydroclimatic extremes such as droughts and floods pose major challenges for water management across Kansas and the broader Great Plains. Climate models have limited ability to predict these extremes, making historical analysis essential for understanding how such events may evolve in the future. Compound extremes — including recurring wet or dry conditions across consecutive years and "weather whiplash" transitions between opposite extremes — add further complexity and uncertainty.
This project aimed to better understand historical patterns and trends in seasonal to annual hydroclimatic extremes in Kansas, organized around three objectives. The first objective focused on quantifying spatiotemporal patterns in compound extremes. Historical precipitation data from meteorological stations and the gridded PRISM dataset were compiled for Kansas and surrounding areas contributing to federal reservoirs. A comparison of these sources confirmed that PRISM accurately reproduces annual and seasonal precipitation totals, with minimal bias in identifying extremes. PRISM was therefore selected for statewide analysis across a 128-year period (1895–2023). A percentile-based classification system was developed to identify six types of extremes: isolated wet and dry events, recurring wet-to-wet and dry-to-dry sequences, and whiplash transitions in both directions, producing a 4 km resolution database of precipitation extremes.
The second objective analyzed changes in compound extremes across water management areas. Annual precipitation is increasing over much of Kansas, with significant long-term wetting trends across 40.3% of the state, driven primarily by increased spring rainfall. Both isolated wet and recurring wet-to-wet extremes have become more widespread since approximately 1980. Results were summarized for 148 management-relevant areas including federal reservoir watersheds, groundwater management districts, and Regional Advisory Committee boundaries. Western reservoirs show persistent drying, while eastern reservoirs exhibit increasingly wet conditions. Whiplash events occur most frequently in summer and are more common in northern and eastern reservoirs. The frequency of wet extremes since reservoir construction is significantly correlated with loss in reservoir storage capacity.
The third objective produced an interactive web-based tool built on ESRI Experience Builder, allowing users to explore visualizations of historical precipitation and extremes for all 148 management boundaries and download the underlying data for further use.

ABSTRACT:

Precipitation extremes, such as droughts and floods, are key stress points for water management, and challenges increase further when considering compound precipitation extremes, such as recurring extreme conditions (consecutive wet or dry periods) and ‘weather whiplash’ transitions from anomalously wet to anomalously dry conditions (or vice versa). Unfortunately, climate models struggle to predict extremes, and therefore understanding historical trajectories of change may offer one of the best clues for how precipitation extremes may persist or change in the future. Here, we investigated historical spatiotemporal dynamics in seasonal and annual precipitation extremes across the U.S. Great Plains (USGP) region, which spans ## km2 in parts of ## states. We developed a percentile-based approach to quantify six typologies of extremes (isolated wet/dry, recurring wet/dry, dry-to-wet and wet-to-dry whiplash) in a methodologically consistent manner across time and space. Each of these extreme types was identified at both annual and seasonal resolution from YYYY to YYYY. We found that annual and seasonal precipitation is increasing across the USGP, particularly during the spring, which is accompanied by significantly more frequent isolated wet and recurring wet extremes. These dynamics were correlated with El Nino-Southern Oscillation (ENSO) patterns, with extreme wet conditions 33% more frequent during El Nino conditions across the central and southern USGP. These changes in precipitation extremes can have impacts on diverse processes such as agriculture management and reservoir operations and the changes we document underscore the necessity of adaptive management strategies to improve climate resilience in agricultural and water resource sectors.