The effect of climate and land‐cover changes on runoff response in Guguf spate systems, northern Ethiopia

Abstract

Irrigated agriculture in the rainfall‐deficit semi‐arid lowlands of the Raya valley rely on spate systems to produce food crops. Climate and land‐cover dynamics upstream are, however, threatening runoff response reaching these spate systems. The objective of this study was thus to analyse the hydrological response of dryland catchments to changing climate and land cover in Guguf spate systems. Thirty‐six years of climate data were analysed using Mann–Kendall, Pettitt's test and linear regression methods, and time‐series land‐cover information extracted from Landsat satellite images in a remote‐sensing interface. The Soil Conservation Systems curve number method was then employed to formulate the likely impact of climate and land‐cover changes on runoff response, and trends analysed. Results showed that temperature, evapotranspiration and rainfall varied at least by 0.11°C, 15.2 mm and −5.1 mm yr−1 respectively, intensifying moisture stress. Moreover, improving vegetation cover in the highlands enhanced the water‐abstraction capacity of the soil, impeding the runoff curve number by 9.2%. Thus, the combined effects of climate induced moisture stress and land cover led water abstraction upstream has threatened runoff response at a rate of 0.23 × 106 m3 yr−1. In other words, the runoff response reaching Guguf spate systems degenerated by 7.96 × 106 m3 over 36 years. Such unusual highland–lowland hydrological linkage has therefore endangered the availability of surplus water to irrigate spate‐based farms downstream. Appropriate policies and strategies would therefore be desirable to address conflicting interests in scarce water resources in the face of climate change. © 2019 John Wiley & Sons, Ltd.

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