Your search found 3 records
1 McCartney, Matthew P.; Shiferaw, A.; Seleshi, Y. 2008. Estimating environmental flow requirements downstream of the Chara Chara weir on the Blue Nile River. In Abtew, W.; Melesse, A. M. (Eds.). Proceedings of the Workshop on Hydrology and Ecology of the Nile River Basin under Extreme Conditions, Addis Ababa, Ethiopia, 16-19 June 2008. Sandy, UT, USA: Aardvark Global Publishing. pp.57-75.
Water management ; River basin management ; Ecology ; Rivers ; Environmental flows ; Environmental effects ; Downstream ; Weirs ; Hydrology ; Models ; Ecosystems ; Water power / Africa / Ethiopia / Sudan / Blue Nile River / Abay River / Chara Chara Weir / Lake Tana
(Location: IWMI HQ Call no: IWMI 577.64 G100 MCC Record No: H041346)
(1.27 MB)
Over the last decade flow in the Abay River (i.e., the Blue Nile) has been modified by operation of the Chara Chara weir and diversions to the Tis Abay hydropower stations, located downstream of the rivers source, Lake Tana. The most conspicuous impact of these human interventions has been significantly reduced flows over the Tis Issat Falls. This paper presents the findings of a hydrological study conducted to estimate environmental flow requirements downstream of the weir. The South African desktop reserve model was used to determine both high and low flow requirements in the reach containing the Falls. The results indicate that to maintain the basic ecological functioning in this reach requires an average annual allocation of 862 Mm3 (i.e. equivalent to 22% of the mean annual flow). Under natural conditions there was considerable seasonal variation, but the absolute minimum mean monthly allocation, even in dry years, should not be less than approximately 10 Mm3 (i.e. 3.7 m3s-1). These estimates make no allowance for maintaining the aesthetic quality of the Falls, which are popular with tourists. The study demonstrated that, in the absence of ecological information, hydrological indices can be used to provide a first estimate of environmental water requirements. However, to ensure proper management, much greater understanding of the relationships between flow and the ecological condition of the riverine ecosystem is needed.
2 Shiferraw, A.; McCartney, Matthew. 2008. Investigating environmental flow requirements at the source of the Blue Nile River. Paper presented at the International Nile Basin Development Forum, Khartoum, Sudan, 3-5 November 2008. 14p.
Lakes ; Rivers ; Flow ; Hydrology ; Ecosystems ; Ecology ; Water allocation ; Weirs ; Water power ; Models / Ethiopia / Lake Tana / Blue Nile River / Abay River / Chara Chara Weir / Tis Abay Hydropower Station / Tis Issat Falls
(Location: IWMI HQ Call no: e-copy only Record No: H041853)
(0.06 MB) (0.06 MB)
3 Steenhuis, T. S.; Collick, A. S.; Easton, Z. M.; Leggesse, E. S.; Bayabil, H. K.; White, E. D.; Awulachew, Seleshi Bekele; Adgo, E.; Ahmed, A. A. 2009. Predicting discharge and sediment for the Abay (Blue Nile) with a simple model. Hydrological Processes, 23:3728-3737. [doi: https://doi.org/10.1002/hyp.7513]
Simulation models ; Forecasting ; Erosion ; Sedimentation ; Calibration ; Water balance ; Rainfall-runoff relationships ; River basins ; Climate / Ethiopia / Sudan / Egypt / Abay River / Blue Nile River
(Location: IWMI HQ Call no: e-copy only Record No: H042576)
(0.28 MB)
Models accurately representing the underlying hydrological processes and sediment dynamics in the Nile Basin are necessary for optimum use of water resources. Previous research in the Abay (Blue Nile) has indicated that direct runoff is generated either from saturated areas at the lower portions of the hillslopes or from areas of exposed bedrock. Thus, models that are based on infiltration excess processes are not appropriate. Furthermore, many of these same models are developed for temperate climates and might not be suitable for monsoonal climates with distinct dry periods in the Nile Basin. The objective of this study is to develop simple hydrology and erosion models using saturation excess runoff principles and interflow processes appropriate for a monsoonal climate and a mountainous landscape. We developed a hydrology model using a water balance approach by dividing the landscape into variable saturated areas, exposed rock and hillslopes. Water balance models have been shown to simulate river flows well at intervals of 5 days or longer when the main runoff mechanism is saturation excess. The hydrology model was developed and coupled with an erosion model using available precipitation and potential evaporation data and a minimum of calibration parameters. This model was applied to the Blue Nile. The model predicts direct runoff from saturated areas and impermeable areas (such as bedrock outcrops) and subsurface flow from the remainder of the hillslopes. The ratio of direct runoff to total flow is used to predict the sediment concentration by assuming that only the direct runoff is responsible for the sediment load in the stream. There is reasonable agreement between the model predictions and the 10-day observed discharge and sediment concentration at the gauging station on Blue Nile upstream of Rosaries Dam at the Ethiopia–Sudan border.
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