Detecting the Causes of Stream Flow Change and its Implication for Water Management in the Upper Blue Nile River Basin: Case of Jedeb Catchment.

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Date

2020-06

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Addis Ababa University

Abstract

Jedeb River is one of the major tributary of Blue Nile River. However, the stream flow trend of Jedeb River has been decreased specially in dry seasons. Climate variability and human activity had been identified as the two main reasons for the decrease in stream flow. Here, climate variability refers to variability in precipitation and temperature and human activity is the activities which includes direct withdrawal of water (for irrigation, domestic and non-domestic use) and land use land cover change. Understanding the individual contributions of climate variability and human activities to changes in runoff is important for sustainable management of regional water resources. To detect the cause of stream flow change, the temporal trends of seasonal stream and annual flow (Dry, less rainy, rainy and annual) during 1980–2014 were first explored by modified Mann-Kendall trend. Annual, less rainy and rainy season’s display slightly decreasing trend but not significant, but in dry season significant decreasing trend occur in Jedeb River. Change points from 1980 to 2014 are detected by pittitt test. From the result, the year 1998 is identified as abrupt change year. So that, the stream flow data set is divide into two periods as the pre-change period and post-change period. Three methods including climate elasticity, hydrological sensitivity and hydrological model method was used to detect and quantify the hydrological runoff response to climate variability and human activities, based on the assumption that climate variability and human activities are the only drivers for stream flow. We found that human activities has 75.8% ,73% and 77.4% contribution for stream flow change by using climate elasticity, hydrological sensitivity and hydrological model method respectively. Whereas climate variability has 24.2%, 27% and 22.6% contribution for decreasing stream flow by using climate elasticity, hydrological sensitivity and hydrological model respectively. From all method human activity was detected as the dominant factor for decreasing stream flow. The study provides scientific foundation to the stakeholder to understand the causes of water resources redaction and useful information for the planning, management and development of water resources.

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Keywords

Climate elasticity, Hydrological sensitivity, Hydrological model, Modified MannKendall, Pettitt test, Jedeb River

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