Modelling of Streamflow of a Catchment in Kenya
- 1
- 2
- 3
Abstract
Modeling stream flow forms a basis upon which policy makers, watershed planners and managers make ap- propriate decisions consistent with sustainable management of land and water resources in the watershed. The aim of this research is to provide a preliminary assessment of the performance of a complex watershed model in predicting stream flow on the Naro Moru river catchment in Ewaso Ng’iro river basin, Kenya. The research involved model input data preparation, model set up and test running, sensitivity analysis and cali- bration of the Soil Water Assessment Tool (SWAT) model. Preliminary evaluation of the model performance involved the use of known quantitative evaluation statistics that included correlation coefficient, Nash Sut- cliffe efficiency (NSE), Deviation Volume (D<sub>v</sub>) and a graphical technique for comparing observed and simu- lated flows. Initial model runs yielded poor daily flow simulations compared to monthly simulations. Poor daily simulation was attributed to differences in the timing of observed and simulated hydrographs. The model was calibrated for a three year period followed by a three year validation period based on monthly flows. Calibration results indicated an acceptable, but modest, agreement between observed and simulated monthly stream flows with a correlation coefficient (r) of about 0.7, NSE = 5%, and D<sub>v</sub>= 61.7%. After vali- dation, the model performance was satisfactory with the coefficient of determination (R<sup>2</sup> ≈ 0.6), Nash-Sut- cliffe efficiency (NSE) of 0.51 and a deviation volume (D<sub>v</sub>) value of 24.7%. The modest model performance was associated with input data deficiencies and model limitations. Even then, the results indicate that the model can possibly be adapted to the local conditions in the catchment for which it is being applied but with improvements involving better parameter calibration techniques, and collection of better quality data. Such a study may be used to predict the effect of climate change on river flows as well as the effect of land use changes on the hydrologic response of a catchment.
- E. G. Bekele and H. V. Knapp, “Hydrologic Modeling of Fox Watershed: Model Development, Calibration, and Validation,” Proceedings of the World Environmental and Water Resources Congress, Honolulu, Hawaii, 12-15 May 2008, pp. 1-10. doi:10.1061/40976(316)588
- S. K. Jain, and K. P. Sudheer, “Fitting of Hydrologic Models: A Close Look at the Nash-Sutcliffe Index,” Journal of Hydrologic Engineering, Vol. 13, No. 10, 2008, pp. 981-986. doi:10.1061/(ASCE)1084-0699(2008)13:10(981)
- B. Schmalz, F. Tavares and N. Fohrer, “Modeling Hydrological Processes in Mesoscale Lowland River Basins with SWAT-Capabilities and Challenges,” Hydrological Sciences Journal, Vol. 53, No. 5, 2008, pp. 989-1000. doi:10.1623/hysj.53.5.989
- S. N. Ngigi, “Hydrological Impacts of Land Use Changes on Water Resources Management and Socio-economic Development of Upper Ewaso Ng’iro River Basin in Kenya,” PhD Thesis, Delft University of Technology, Netherlands, 2006.
- M. K. Thomas, H. P. Liniger and F. N. Gichuki, “Development of a Stream flow Model for Rural Catchments in Kenya,” Proceedings of the Fourth National Workshop on Land and Water Management in Kenya: Towards Sustainable Land Use, Kikuyu, Kenya, 15-19 February 1993, pp. 191-202.
- J. M. Gathenya, H. P. Liniger and F. N. Gichuki, “Problems of River-Water Management for a Basin West of Mount Kenya: Challenge to Water Resource Planners,” Proceedings of the Fourth National Workshop on Land and Water Management in Kenya: Towards Sustainable Land Use, Kikuyu, Kenya, 15-19 February, 1993, pp 175-180.
- S. L. Neistsch, J. G. Arnold, J. R. Kiniry and J. R. Williams, “Soil Water Assessment Tool Theoretical Documentation (version 2005),” Grassland Soil and Water Research Laboratory, Temple, Texas, 2005, pp. 1-27.
- P. M. Ndomba and B. Z. Birhanu, “Problems and Prospects of SWAT Model Applications in NILOTIC Catchments: A Review,” Nile Water Engineering Scientific Magazine, Vol. 1, 2008, pp. 41-52.
- A. Stehr, A. P. Debeles, F. Romero and H. Alcayaga, “Hydrological Modeling with SWAT under Conditions of Limited Data Availability: Evaluation of Results from Chilean Case Study,” Hydrological Sciences Journal, Vol. 53, No. 5, 2008, pp. 588-601. doi:10.1623/hysj.53.3.588
- G. Andualem and M. Yonas, “Prediction of Sediment Inflow to Legedadi Reservoir Using SWAT Watershed and CCHELD Sediment Transport Models,” Nile Basin Water Engineering Scientific Magazine, Vol. 1, 2008, pp. 66-74.