SIMULATION OF SEDIMENT YIELD AT THE UPSTREAM WATERSHED OF JEBBA LAKE IN NIGERIA USING SWAT MODEL
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Date
2015
Journal Title
Journal ISSN
Volume Title
Publisher
Malaysian Journal of Civil Engineering
Abstract
In this study, we focused on the applicability and suitability of Soil and Water
Assessment Tool (SWAT) embedded in Geographical Information Systems (GIS) environment in
the prediction of sediment yield of a watershed (12,992km2). The watershed is drained by
Rivers Niger, Kontagora, Awun and Eku and is located at the upstream of Jebba Reservoir in
north central Nigeria . SWAT was run daily for 26 years (1985 to 2010 ) using climatic data
representing three weather stations located within the watershed. The model was calibrated and
validated using measured flow data from 1990 to 1995. Also due to the unavalilability of
observed sediment data for the area, sediment samples were collected from three locations in the
watershed from May to December, 2013 using suspended sediment sampler USDH-2A. The
sediment samples were analysed and used to spatially calibrate and validate the model. The
model was statistically evaluated using coefficient of determination, R2 and Nasch-Sutcliffe
Efficiency, NSE. Evaluation of the model revealed that it performed satisfactorily for stream
flow and sediment yield predictions in the watershed. The model predicted the annual sediment
yield in the watershed as 255.8 tons/ha/yr producing about 8.31x 109 tons of sediment between
1985 and 2010. Sediment concentration (mg/l) in the reach during the period of simulation
showed that the highest sediment concentration was obtained in subbasins 29, 20 and 19 with
values 446.3, 376.8 and 365.4 mg/l respectively. However, lowest sediment concentration
occurred in subbasin 73 with a value of 108.6 mg/l. The results from the study showed that a
properly calibrated SWAT embedded in GIS environment is suitable for modelling the hydrology
and predicting the sediment yield in a watershed. In the light of this, SWAT can be adopted by
water engineers and hydrologists in Nigeria and other sub sahara Africa countries in the region
as a decision support tool to assist policy makers in achieving sustainable sediment and water
management at watershed level.