An alternative soil erodibility estimation approach for data-scarce regions: a case study in Ethiopian Rift Valley Lake Basin

Abstract

Soil erodibility (K) is an essential factor for erosion prediction, conservation planning and assessment of sediment related environmental problems. K estimation methods have been developed in many soil erosion and water quality models, which are developed for soil data rich areas and pose a challenge for areas with limited data. Unlike others, by using the erosion productivity impact calculator (EPIC) model, the required soil parameters for calculating K can be extracted from the Food and Agricultural Organization (FAO) world database. In order to verify the FAO soil database and develop an alternative K method (KET) by mimicking the equation of K used in the EPIC model, we collected 203 soil samples from different soil units in the Ethiopian Rift Valley Lake Basin (ERVLB). Unlike the K of EPIC model, KET is developed based on the physical properties of soils that can be easily measured in a laboratory. The results from KET were compared with those from the EPIC-K. Statistically, the performance of KET is excellent and the soil analysis result of ERVLB deviates from the FAO soil database on lower altitude areas of the basin. When KET is projected for overall soil units of the country, it predicts 35.7% of the country soil with less than ±5% relative error. On average, the KET can be applied to overall country soils with a relative error of −9.88% with a standard deviation of 6.4. By applying KET, the ERVLB and the country K map were produced. We recommend that the K map developed for ERVLB can be confidently used since it is validated using field data.