EVALUATION OF STREAM FLOW UNDER LAND USE LAND COVER CHANGE AND ASSESSMENT OF SUITABLE LAND RESOURCES FOR SURFACE IRRIGATION; CHEMOGA CATCHMENT, ABAY BASIN, ETHIOPIA

Abstract

To stay alive in earth surface, land and water are indispensible. To enhance the agricultural productivity and socioeconomic development in agricultural catchment, irrigation development is an important issue. The initiation of this study was to evaluated stream flow under land use land cover change and assessment of suitable land resources for surface irrigation. The methods used include desk study of the previous studies related to present study. Data were collected from MOWIE, MOA, ENMA and other related institutions. After collecting the necessary data, filling of missed data and quality checking was made. The land use land cover classification was performed using ERDAS imagine 2014 which was used for further analysis of GIS and SWAT. To estimate surface water of the catchment was using SWAT model after calibration and validation. CROPWAT 8 was used to determine the water requirement of the dominant crops grown in the catchment. Surface water availability was assessed in sub-watersheds of river catchments. In Chemoga catchment various factors effects resource bases like expansion of residential area, deforestation and increase of agricultural land and this depict that change of land use land cover in the catchment. The selected land use land cover years of 1994 and 2013 were used for evaluation of land use land cover change impact on seasonal stream flow and to the major components of stream flow as well as the current land use land cover map was used as a factor for land suitability evaluation. Due to the land use land cover change the catchment hydrology was affected. The result depicts that in wet season (surface runoff) the stream flow increase due to this rugged land surface occur so hinder the sustainability surface irrigation and in dry season (lateral flow & ground water flow) the stream flow decreases so connate water stress to the irrigated crops. So watershed management approach should be done in the catchment. The coefficient of determination (R 2 ), nash-sutcliff efficiency (ENS), and relative volume error (RVE) were used for evaluating the model performance. The flows in the catchment are able to satisfy gross irrigation water requirements of one variate crops in each catchment to the irrigable areas but to satisfy irrigation demand to the whole crop, with the help of semi-detailed to detailed design document analysis construct water harvesting structures. The land suitability was evaluated using factors such as slope, land use land cover, and soil physical properties (soil depth, soil texture and soil drainage) and finally overall suitability map of the catchment was produced using weighted overlay analysis tool on Arc GIS. In the weighted overlay analysis; high weightage was given for slope, since it is the high determinant factor in the evaluation of the given area. Other suitability factors like socioeconomic, environmental issues, and soil chemical properties should be studied for sustainable irrigation development in catchment.