2021 Fiscal Year Annual Research Report
Development of precision estimation method of rainfall erosivity for better understanding of soil erosion in data-sparse regions
| Project/Area Number |
19K13434
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| Research Institution | Tottori University |
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Principal Investigator |
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| Project Period (FY) |
2019-04-01 – 2022-03-31
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| Keywords | Rainfall intensity / Rainfall erosivity / Satellite rainfall / Soil erosion |
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| Outline of Annual Research Achievements |
Rainfall erosivity (R‐factor) was estimated based on a relationship established between the long-term (1981－2016) gauge-based erosivity values and Climate Hazards Group InfraRed Precipitation with Stations (CHIRPS)‐derived erosivity index for the East Africa region. The mean annual R‐factor in the region was estimated at 3,246 ± 1,895 MJ mm ha－1 h－1 yr－1. The mean annual gross soil loss by water erosion amounts to 4 billion t, with a mean soil erosion rate of 6.3 t ha－1 yr－1, of which ca. 50% was found to originate in Ethiopia. Nearly 10% of East Africa is subject to moderate or elevated water erosion risks (>10 t ha－1 yr－1), that require priority management intervention. Soil erosion and the potential of different watershed management practices in reducing soil erosion were investigated in detail taking Ethiopia as a case study. The mean rate of soil erosion by water in Ethiopia was estimated at 16.5 t ha－1 yr－1, with an annual gross soil loss of ca. 1.9 × 109 t, of which the net soil loss was estimated at ca. 410 × 106 t (22% of the gross soil loss). The results further showed that ca. 25% of Ethiopia (28 × 106 ha) has soil erosion rates above 10 t ha－1 yr－1, which is higher than the tolerable soil erosion limits estimated for Ethiopia. Ex-ante analysis revealed that implementation of proper land management practices in such areas could reduce the mean soil erosion rate from 16.5 t ha－1 yr－1 to 5.3 t ha－1 yr－1 (mean, by ca. 68%; range, 65-70%).
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