A step towards mapping rainfall erosivity for India using high-resolution GPM satellite rainfall products

The R-factor is a multi-annual average index that measures the climatological potential of rainfall and its kinetic energy. It is used to evaluate the effect of rainfall on sheet and rill-erosion. A continuous record of 30-minute resolution pluviograph data is required to compute rainfall erosivity. However, due to the limited availability of short interval precipitation data, rainfall erosivity mapping involves interpolation from point-rainfall erosivity values. This study attempts to prepare the first-ever rainfall erosivity map from high-resolution satellite precipitation data for India. We used the IMERG final run 30-minute precipitation data from 2001 to 2018 to compute spatially distributed rainfall erosivity for India. We also correlated rainfall erosivity with daily rainfall data using a power equation. We presented the calibrated parameter values of the developed power equation as maps at 0.1 degrees x 0.1 degrees spatial resolution. The mean annual rainfall erosivity value ranges from 77 to 20,662 MJ mm ha(-1) h(-1) yr(-1). The summer monsoon is the most erosive season, accounting for about 85% of the annual rainfall erosivity. We compared the rainfall erosivity map computed in this study with the previously available rainfall erosivity map produced from very few gauged point rainfall data. It is found that the spatial pattern of erosivity between the two maps matches very well. However, the erosivity map produced using satellite data exhibits slightly lower erosivity values in areas receiving very low and very high rainfall than the previously available erosivity map. We also computed erosivity density maps of India to identify the hotspot areas prone to erosion and landslide. Northeast and the Western Ghats of India receive high-intensity rainfall in the summer monsoon and have significantly high erosivity density. This study's outcome could serve as the primary source of information by the policymakers to take appropriate catchment management measures to reduce soil erosion.

Automated summary

This study prepared the first-ever rainfall erosivity map for India using high-resolution satellite precipitation data, finding that the most erosive season is the summer monsoon, and identifying erosion hotspot areas in India.