An Assessment of ENSO-Induced Patterns of Rainfall Erosivity in the Southwestern United States

Microerosion processes due to the impact of raindrops on the soil (rainsplash) represent an important mechanism of detachment and removal of soil parcels. The annual and interannual patterns of rainsplash erosion are controlled by the variability of rainfall, vegetation cover, and land-use practice. This paper presents a study of the interannual variability of rainfall erosivity (which is an indicator of the erosive power of rainfall) due to winter precipitation in the southwestern United States and its connection to the El Niño–Southern Oscillation (ENSO). A remarkable degree of dependence was found between the values of winter erosivity and the Southern Oscillation index (SOI) in the months proceeding and during each winter. In general, it was observed that the erosive power of rainfall is stronger during El Niño years and weaker during the La Niña phase in the U.S. southwest, as is the rainfall itself. It was also observed that the erosivity and SOI are nonlinearly related. This dependence of rainfall erosivity on the ENSO signal suggests a potential short-term predictability of the erosive phases and could be useful in the implementation of new strategies of soil conservation.