Climate and Land-cover Change in Dryland-Catchments, and their Effect on Spate-hydrology of Farming Community in Semi-arid Lowlands of Raya-Valley, Northern Ethiopia

Abstract

Spate-irrigation, a system foreseen as a potential means of improving agricultural production in rainfall deficit lowlands, is profoundly threatened by climate and land-cover change upstream. Yet, the actual implications of these changes on spate-hydrology has not been well studied. The objective of this study was thus to analyse the hydrological-response of dryland catchments to changing climate and land-cover in the Raya-valley. Longterm climate data were collected from National Meteorological Agency, and land-cover information extracted from Landsat satellite images. Soil Conservation Systems Curve-Number method was then employed to formulate the likely impacts of climate and land-cover dynamics on spate-hydrology. Average temperature, and evapotranspiration of the study area raised at a Coefficient of 0.13oC yr-1, and 16.43mm yr-1 respectively. Rainfall on the other hand dropped at a coefficient of 5.1mm yr-1. Land-cover change and Normalized Difference Vegetation Index analysis also showed improvement in vegetation-cover, enhancing water-retention capacity of the soil upstream. Declining rainfall, coupled with rising temperature and evapotranspiration on the top of increasing water-retention capacity of the soil aggravated moisture stress, thereby threatening spate-hydrology at a coefficient of 0.23x106m3 yr-1. Appropriate policies and strategies would therefore be desirable to address contesting interests on scarce water resources in the face of climate-change.