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