Trends in rainfall and runoff in the Blue Nile Basin: 1964–2003

Tesemma, Zelalem; Mohamed, Yasir A.; Steenhuis, Tammo S.

doi:10.1002/hyp.7893

Cited by 136 publications

(113 citation statements)

References 36 publications

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“…In the more recent period (1995)(1996)(1997)(1998)(1999)(2000)(2001)(2002)(2003)(2004)(2005)) the 13% degraded area gives the best fit to the observed data (slope of the regression line close to 1) compared with the 5% degraded area that under predicted the sediment concentration. Similar analysis for the Blue Nile basin showed the same trends (Tesemma et al, 2010; Steenhuis and Tilahun, 2014) where direct runoff and sediment increased and sediment concentration with time that could be related to an increase in the proportion of degraded areas. This is strengthening this type of analysis.…”

Section: Saturation Excessmentioning

confidence: 59%

Improving efficacy of landscape interventions in the (sub) humid Ethiopian highlands by improved understanding of runoff processes

et al. 2015

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Despite millions of dollars invested in soil and water conservation (SWC) practices in the (sub) humid Ethiopian highlands and billions of hours of food-for-work farm labor, sediment concentration in rivers is increasing. This paper reports on the research to reverse the current trend. Based on the understanding of the hydrology of highlands, we provide evidence on sources of surface runoff and sediment and on mechanisms that govern the erosion processes and approaches and how they affect SWC practices. We suggest that priority in landscape interventions should be given to re-vegetation of the degraded areas so as to reduce the sediment concentration contributions originating from these areas. Additionally, efforts should be directed to gully rehabilitation in the saturated bottom landscape that may consist of vegetating shallow gullies and stabilizing head cuts of deeper gullies. Finally, rehabilitation efforts should be directed to increase the rain water infiltration in the upland areas through the hardpan layer by connecting the land surface to the original deep flow paths that exist below about 60 cm. It will reduce the direct runoff during the rainy season and increase baseflow during the dry season.

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Section: Saturation Excessmentioning

confidence: 59%

Improving efficacy of landscape interventions in the (sub) humid Ethiopian highlands by improved understanding of runoff processes

et al. 2015

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“…Conway and Hulme (1993) reported declining annual rainfall over the Blue Nile and Atbara basins, resulting in a reduction of river flows between 1945 and 1984. In contrast, recent investigations by Tesemma et al (2010), Tekleab et al (2013) and Gebremicael et al (2013) agreed that rainfall over the Upper Blue Nile Basin did not show a statistically significant trend for the last 40 years . Despite the fact that the pattern of rainfall remained constant, hydrological flows in the basin showed a heterogeneous trend.…”

Section: Introductionmentioning

confidence: 75%

“…Many studies (e.g. IPCC, 2013;Shi et al, 2013;Tekleab et al, 2013;Tesemma et al, 2010;Zhao et al, 2015) have shown that rainfall is the primary atmospheric factor that directly affects the streamflow patterns. The impact of climate change on hydrology varies from place to place.…”

Section: Introductionmentioning

confidence: 99%

Temporal and spatial changes of rainfall and streamflow in the Upper Tekezē–Atbara river basin, Ethiopia

Gebremicael

Mohamed

Zaag

et al. 2017

Hydrol. Earth Syst. Sci.

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Abstract. The Upper Tekezē-Atbara river sub-basin, part of the Nile Basin, is characterized by high temporal and spatial variability of rainfall and streamflow. In spite of its importance for sustainable water use and food security, the changing patterns of streamflow and its association with climate change is not well understood. This study aims to improve the understanding of the linkages between rainfall and streamflow trends and identify possible drivers of streamflow variabilities in the basin. Trend analyses and changepoint detections of rainfall and streamflow were analysed using Mann-Kendall and Pettitt tests, respectively, using data records for 21 rainfall and 9 streamflow stations. The nature of changes and linkages between rainfall and streamflow were carefully examined for monthly, seasonal and annual flows, as well as indicators of hydrologic alteration (IHA).The trend and change-point analyses found that 19 of the tested 21 rainfall stations did not show statistically significant changes. In contrast, trend analyses on the streamflow showed both significant increasing and decreasing patterns. A decreasing trend in the dry season (October to February), short season (March to May), main rainy season (June to September) and annual totals is dominant in six out of the nine stations. Only one out of nine gauging stations experienced significant increasing flow in the dry and short rainy seasons, attributed to the construction of Tekezē hydropower dam upstream this station in 2009. Overall, streamflow trends and change-point timings were found to be inconsistent among the stations. Changes in streamflow without significant change in rainfall suggests factors other than rainfall drive the change. Most likely the observed changes in streamflow regimes could be due to changes in catchment characteristics of the basin. Further studies are needed to verify and quantify the hydrological changes shown in statistical tests by identifying the physical mechanisms behind those changes. The findings from this study are useful as a prerequisite for studying the effects of catchment management dynamics on the hydrological variabilities in the basin.

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“…For studies in the Lake Tana basin we refer to Solomon et al (2010) who focused on hydrologic impacts of deforestation in the Koga catchment that directly neighbors the Gilgel Abbay catchment and to Tesemma et al (2010) who focused on trends in rainfall and runoff for selected areas in the Blue Nile. Part of the latter study focused on the Lake Tana basin area but establishing clear effects of land use changes was not possible since hydrologic assessments focused on the outflow of Lake Tana instead of stream flows from catchments that drain to the lake.…”

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confidence: 99%

Changes in land cover, rainfall and stream flow in Upper Gilgel Abbay catchment, Blue Nile basin – Ethiopia

Rientjes

Haile

Kebede

et al. 2011

Hydrol. Earth Syst. Sci.

168

140

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Abstract. In this study we evaluated changes in land cover and rainfall in the Upper Gilgel Abbay catchment in the Upper Blue Nile basin and how changes affected stream flow in terms of annual flow, high flows and low flows. Land cover change assessment was through classification analysis of remote sensing based land cover data while assessments on rainfall and stream flow data are by statistical analysis. Results of the supervised land cover classification analysis indicated that 50.9 % and 16.7 % of the catchment area was covered by forest in 1973 and 2001, respectively. This significant decrease in forest cover is mainly due to expansion of agricultural land.By use of a change detection procedure, three periods were identified for which changes in rainfall and stream flow were analyzed. Rainfall was analyzed at monthly base by use of the Mann-Kendall test statistic and results indicated a statistically significant, decreasing trend for most months of the year. However, for the wet season months of June, July and August rainfall has increased. In the period 1973-2005, the annual flow of the catchment decreased by 12.1 %. Low flow and high flow at daily base were analyzed by a low flow and a high flow index that is based on a 95 % and 5 % exceedance probability. Results of the low flow index indicated decreases of 18.1 % and 66.6 % for the periods 1982-2000 and 2001-2005 respectively. Results of high flows indicated an increase of 7.6 % and 46.6 % for the same periods. In this study it is concluded that over the period 1973-2005 stream flow has changed in the Gilgel Abbay catchment by changes in land cover and changes in rainfall.

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Trends in rainfall and runoff in the Blue Nile Basin: 1964–2003

Cited by 136 publications

References 36 publications

Improving efficacy of landscape interventions in the (sub) humid Ethiopian highlands by improved understanding of runoff processes

Improving efficacy of landscape interventions in the (sub) humid Ethiopian highlands by improved understanding of runoff processes

Temporal and spatial changes of rainfall and streamflow in the Upper Tekezē–Atbara river basin, Ethiopia

Changes in land cover, rainfall and stream flow in Upper Gilgel Abbay catchment, Blue Nile basin – Ethiopia

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