Effect of conservation structures on curbing rill erosion in micro-watersheds, northwest Ethiopia

Abstract

Accelerated soil erosion by water is a critical problem in Ethiopia, where population is rapidly growing and extensive farming systems are very common with no or less preventive measures. The study aimed to evaluate effects of conservation structures (terraces) in reducing the magnitude of rill erosion by using rill survey technique at cultivated field scales in relation to crop type and location in hill slope direction of the fields in the Beribere micro-watershed (catchment), northwest Ethiopia. The study assessed factors accelerating rill erosion in the micro-watershed. Rill erosion in the terraced fields was reduced by 53.5% as compared to the non-terraced control fields. In the terraced areas, terracing damage is the main contributing factor to soil loss due to rills. In the non-terraced fields, entering of high erosive runoff from uphill areas and damage of drainage ditches were observed as the principal accelerating factors for initiation and development of rill erosion, whereas these processes had insignificant effect on rill erosion in the terraced fields. Moreover, rill erosion shows spatial differences in terms of crop covers and location in hill slope direction of the study site. Hence, there should be adequate criteria for effective communication between farmers and extension staff to design site-specific erosion control practices for addressing the problem. The study verifies that rill surveying is a significant method to pragmatic assessment of the effectiveness of terracing practices in controlling soil erosion by water. Keywords: Rill erosion, Conservation structures, Rill surveying, Micro-watersheds, Ethiopian highlands