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1 White, E. D.; Easton, Z. M.; Fuka, D. R.; Collick, A. S.; McCartney, Matthew; Awulachew, Seleshi Bekele; Steenhuis, T. S. 2009. A water balance-based Soil and Water Assessment Tool (SWAT) for improved performance in the Ethiopian highlands. In Awulachew, Seleshi Bekele; Erkossa, Teklu; Smakhtin, Vladimir; Fernando, Ashra (Comps.). Improved water and land management in the Ethiopian highlands: its impact on downstream stakeholders dependent on the Blue Nile. Intermediate Results Dissemination Workshop held at the International Livestock Research Institute (ILRI), Addis Ababa, Ethiopia, 5-6 February 2009. Colombo, Sri Lanka: International Water Management Institute (IWMI). pp.152-158.
Hydrology ; Simulation models ; Water balance ; Soil water ; Infiltration ; Runoff ; Highlands / Africa / Ethiopia / Blue Nile River Basin / Abay Blue Nile / Gumera Basin / Laka Tana
(Location: IWMI HQ Call no: IWMI 333.9162 G100 AWU Record No: H042515)
(0.62 MB)
The Soil Water Assessment Tool (SWAT) is a watershed model widely used to predict water quantity and quality under varying land use and water use regimes. To determine the respective amounts of infiltration and surface runoff, SWAT uses the popular Curve Number (CN). While being appropriate for engineering design in temperate climates, the CN is less than ideal when used in monsoonal regions where rainfall is concentrated into distinct time periods. The CN methodology is based on the assumption that Hortonian flow is the driving force behind surface runoff production, a questionable assumption in many regions. In monsoonal climates water balance models generally capture the runoff generation processes and thus the flux water or transport of chemicals and sediments better than CN-based models. In order to use SWAT in monsoonal climates, the CN routine to predict runoff was replaced with a simple water balance routine in the code base. To compare this new water balance-based SWAT (SWAT-WB) to the original CN-based SWAT (SWAT-CN), several watersheds in the headwaters of the Abay Blue Nile in Ethiopia were modeled at a daily time step. While long term, daily data is largely nonexistent for portions of the Abay Blue Nile, data was available for one 1,270 km2 subbasin of the Lake Tana watershed, northeast of Bahir Dar, Ethiopia, which was used to initialize both versions of SWAT. Prior to any calibration of the model, daily Nash-Sutcliffe model efficiencies improved from -0.05 to 0.39 for SWAT-CN and SWAT-WB, respectively. Following calibration of SWAT-WB, daily model efficiency improved to 0.73, indicating that SWAT can accurately model saturation-excess processes without using the Curve Number technique.
2 Steenhuis, T.; Taylor, J.; Collick, A.; van de Giesen, N.; Liebe, J.; Andreini, Marc; Easton, Z. 2009. Rainfall-discharge relationships for monsoonal climates. In Andreini, Marc; Schuetz, Tonya; Harrington, Larry (Eds.). Small reservoirs toolkit, theme 2 b: hydrology and physical measures of performance. Colombo, Sri Lanka: CGIAR Challenge Program on Water and Food (CPWF); Colombo, Sri Lanka: International Water Management Institute (IWMI); Brasilia, DF, Brasil: Brazilian Agricultural Research Corporation (Embrapa Cerrados Center); Harare, Zimbabwe: University of Zimbabwe (UZ); Accra, Ghana: Ghana Water Research Institution (WRI); Delft, The Netherlands: Delft University of Technology (TUD); Stockholm, Sweden: Stockholm Environment Institute (SEI); Marseille, France: Institut de Recherche pour le Developpement (IRD); Bonn, Germany: Center for Development Research, University of Bonn; Ithaca, NY, USA: Cornell University. 10p.
Rivers ; Discharges ; Water balance ; Simulation models ; Watersheds ; Climate ; Rain ; Evapotranspiration / Africa / Abay Blue Nile / Volta Basin
(Location: IWMI HQ Call no: e-copy only Record No: H042665)
Methods for estimating runoff that have been developed for temperate climates may not be suitable for use in the monsoonal climates of Africa, where there is a distinct dry season in which soils dry out to a considerable depth. Water balance models have been shown to better predict river discharge in regions with monsoonal climates than alternative methods based on rainfall intensity, or on the USDA-SCS curve number. This tool can be used to develop a simple water balance model for predicting river discharge.
3 Steenhuis, T. S.; Collick, A. S.; Awulachew, Seleshi B.; Adgo, E.; Ahmed, A. A.; Easton, Z. M. 2008. Modelling erosion and sedimentation in the Upper Blue Nile. 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.200-212.
Erosion ; Sedimentation ; Simulation models ; Rainfall-runoff relationships ; Rivers ; Flow discharge / Ethiopia / Upper Blue Nile / Abay Blue Nile
(Location: IWMI HQ Call no: 551.48 G136 ABT Record No: H044323)
(0.82 MB)
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