Rainfall Pattern and Erosivity: A 90-Year Study in a Cropland Region of Argentina

Water soil erosion is a significant threat to agricultural sustainability and a key process of land degradation. Climate change is altering precipitation patterns and increasing rainfall erosivity globally, leading to more extreme hydrological conditions, yet many agriculturally significant regions lack detailed long-term analysis. This study addresses this gap by quantifying 90-year trends (1934–2023) in key precipitation metrics—total depth, number of rainy days, heavy rainfall (% of rainfall ≥ 50 mm), and rainfall erosivity (R-factor)—in a critical cropland region of Argentina. Analysis of daily data from the Paraná Agrometeorological Station revealed significant breakpoints in the 1970s. Post-breakpoint increases were observed for annual rainfall depth (+16% since 1975), rainy days (+19% since 1972), heavy rainfall events (+21% since 1971), and rainfall erosivity (+24% since 1977). On a monthly basis, March exhibited the highest erosivity. Despite a recent decrease in total monthly precipitation for March, its erosive potential appears to be sustained by a higher concentration of rainfall in intense events. Conversely, the period from May to September was characterized by lower and more stable erosivity values. Positives and significant correlations were established between the El Niño-Southern Oscillation (ENSO), measured by the Oceanic Niño Index (ONI), and all rainfall variables, with the strongest influence observed during the spring-summer seasons for rainfall depth (r= 0.24 to 0.51). Furthermore, the frequency of quarters classified as El Niño conditions has increased about 91% since the mid-1970s breakpoint. This study demonstrates a clear climatic shift towards conditions of higher precipitation and greater erosivity in the region. These findings underscore the urgent need for enhanced soil and water conservation policies to mitigate the increasing risk of land degradation.