Hydrological Response to Land Use and Land Cover Changes of Ribb Watershed, Ethiopia

Abstract

The study analyzed the present land covers that have taken place in the catchment and its effect on the hydrological responses of the catchment. The Soil and Water Assessment Tool (SWAT2009) model was used to investigate the impact of land cover change on hydrological responses of the study area. Sensitivity analysis result shown SCN curve number (CN), Soil Evaporation Compensation Factor (ESCO), Soil Depth (m) (Sol_Z), Threshold water depth in the shallow aquifer for flow (GWQMN), Base flow alpha factor (Alpha_Bf), (REVAPMN) and Soil Available Water Capacity (SOL_AWC) were found the most influential parameters affecting flow and USLE equation support practice (USLE_P), Linear parameter for maximum sediment yield (SPCON), Exponential parameter for maximum sediment yield in channel sediment routing (SPEXP), Cropping practice factor (USLE_C), channel cover factor (CH_COV1), channel erodiability factor (CH_ERODMO) were the most sensitive parameters affecting sediment yield of the catchment respectively. Scenarios were developed to analyze the impact of land use/cover changes to the hydrological regime. Base scenario: current land use practices has cultivated land, grass land, shrub and bush land, forest land, built up area and water body, scenario1: shrub and bush lands completely changed to forest land and scenario2: Grass land changed to cultivated land. The result for different land use scenarios show that: conversion of shrub land to forest area reduced surface runoff, reduced the amount of sediment transported out and increase base flow but conversion of grass land in to cultivated land areas increased surface runoff during wet seasons and reduced base flow during the dry seasons and also as the peak flow increases it is suspected of carrying more sediment.