MODELING CLIMATE AND LAND-USE CHANGE IMPACTS ON STREAMFLOW AND SEDIMENT YIELD OF AN AGRICULTURAL WATERSHED USING SWAT

Abstract

Quantifying the hydrological response due to changes in climate and land-use is imperative for the proper management of water resources within a watershed. The impact of climate and land-use changes on the hydrology of the Upper Ebonyi river (UER) watershed, South East Nigeria, was studied using the Soil and Water Assessment Tool (SWAT) hydrological model. A climatological time series analysis from 1985-2014 using non-parametric test showed significant negative trends in precipitation and relative humidity trend while minimum and maximum temperature, solar radiation and wind speed showed significant positive trends. Future hypothetical land-use change scenarios representing urbanization and conversion of forest to agricultural land were combined with future downscaled climate model (CSIRO-Mk3-6-0) and simulated in SWAT model. Scenario 1 represents urbanization and climate data of 2020-2030; Scenario 2 represents urbanization and climate data of 2040-2050; Scenario 3 represents conversion of forest to agricultural land and climate data of 2020-2030 and Scenario 4 represents conversion of forest to agricultural land and climate data of 2040-2050 while the Baseline Scenario is the present land-use and climate data of 2005-2014. Relative to the Baseline (2005-2014), the results showed a decrease in streamflow by 10.29%, 26.20%, 11.80% and 26.72% for Scenarios 1, 2, 3, and 4 respectively, while sediment yield decreased by 8.2%, 19.4%, 11.1% and 9.1% for Scenarios 1, 2, 3, and 4 respectively. The results suggest development of adaptation strategies to cope with the predicted hydrological conditions under future climate and land-use change in the watershed.