Erosivity density as an indicator of soil erosion risk in South Asia

Abstract

Soil erosion presents substantial environmental issues, affecting agriculture, water quality, and biodiversity, with approximately 24 billion tonnes of productive soil lost annually worldwide. This is especially critical for South Asia, which is a hotspot for soil loss and has an economy dependent on agricultural productivity. Rainfall is a primary agent of erosion, and erosivity density (ED), which is the rainfall erosivity per unit of precipitation, is a measure of the interaction between the kinetic energy of rainfall and the soil surface. But a large-scale assessment of erosivity density currently doesn’t exist for South Asia. Using precipitation data from 1980 to 2018 and analytical techniques such as Mann-Kendall trend analysis and wavelet transform analysis, this study detects significant trends in erosivity density, highlighting regions most susceptible to soil erosion. Rainfall erosivity (R-factor) was calculated using high-resolution precipitation data (I60) and kinetic energy equations. Prominent areas with high erosivity density were detected in the Western Ghats and Northeastern Himalayas. Additionally, high ED values were observed in northeastern India, certain areas of Pakistan, and central and southern India. An increasing trend in ED was detected in the Indo-Gangetic plain, suggesting increased erosion risk. In contrast, declining patterns in certain regions of Pakistan and northern India indicated a decrease in rainfall intensity or frequency, potential impacting water availability. The wavelet transform analysis showed significant biennial and decadal patterns in ED, indicating climatic influences in South Asia. Biennial cycles showed variations in power levels, ranging from 0.75 to 1.05 in certain years, highlighting significant fluctuations in erosivity density intensity that result in substantial changes in soil erosion risk, demanding robust and adaptive conservation strategies. The study highlights the necessity for region-specific soil conservation techniques to mitigate erosion risks, providing a foundation for effective soil conservation and land management strategies in South Asia.