Modelling of Streamflow of a Catchment in Kenya

John P. O. Obiero, Mohammed A. Hassan, Lawrence O. M. Gumbe

.

DOI: 10.4236/jwarp.2011.39077                

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_v) 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_v= 61.7%. After vali- dation, the model performance was satisfactory with the coefficient of determination (R² ≈ 0.6), Nash-Sut- cliffe efficiency (NSE) of 0.51 and a deviation volume (D_v) 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.

Keywords

Stream Flow Simulation, Model Evaluation, Prediction, Calibration and Validation

Conflicts of Interest

The authors declare no conflicts of interest.

References

[1]	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
[2]	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)
[3]	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
[4]	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.
[5]	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.
[6]	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.
[7]	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.
[8]	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.
[9]	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
[10]	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.
[11]	E. Levesque, F. Anctil and A. Van Griensven, “Evaluation of the Streamflow Simulation by SWAT Model for Two Small Watersheds under Snowmelt and Rainfall,” Hydrological Sciences Journal, Vol. 53, No. 5, 2008, pp. 961-976. doi:10.1623/hysj.53.5.961
[12]	R. Rostamian, A. Jaleh, M. Afyuni, S. F. Mousavi, M. Heidarpour, A. Jalalian and K. C. Abbaspour, “Application of a SWAT Model for Estimating Runoff and Sediment in Two Mountaneous Basins in Central Iran,” Hydrological Sciences Journal, Vol. 53 No. 5, 2008, pp. 977-988.
[13]	P. W. Gassman, M. R. Reyes, C. H. Green and J. G. Arnold, “The Soil Water Assessment Tool: Historical Development, Applications and Future Research Directions,” Transactions of the ASABE, Vol. 5, No. 4, 2007, pp. 1211-1250.
[14]	P. M. Ndomba, “Modelling of Sediment Upstream of Nyumba Ya Mungu Reservoir in Pangani River Basin,” Nile Basin Water Science & Engineering Journal, Vol. 3, No. 2, 2010, pp. 25-38.
[15]	S. G. Setegen, R. Srinivasan and Bijan Dargahi, “Hydrological Modelling in Lake Tana Basin, Ethiopia Using SWAT Model,” The Open Hydrology Journal, Vol. 2, 2008, pp. 49-62.
[16]	P. M. A. Odira, M. O. Nyadawa, B. Okello, N. A. Juma and J. P. O. Obiero, “Impact of Land Use/Cover dynamics on Stream flow: A Case Study of Nzoia River Catchment, Kenya,” Nile Water Science and Engineering Journal, Vol. 3, No. 2. 2010, pp. 64-78.
[17]	M. P. Tripathi, R. K. Panda and N. S. Raghuwanshi, “Development of Effective Management Plan for Critical Sub Watersheds using SWAT Model,” Hydrological Process., Vol. 19, No. 3, 2005, pp. 809-826.
[18]	M. Govender and C.S. Everson, “Modelling Streamflow from Two Small African Experimental Catchments Using SWAT Model,” Hyrological Process., Vol. 19, No. 3, 2005, pp. 683-692.
[19]	N. H. Bartes and P. Gicheru, “Soil Data Derived from SOTER for Studies of Carbon Stocks and Change in KENYA (Version 1.0),” Project Report 2004/01, ISRIC-World Soil Information, 2004.
[20]	F. Githui, F. Mutua and W. Bauwens, “Estimating Impacts of Land Cover Change on Runoff using the Soil water Assessment Tool (SWAT): Case study of Nzoia Catchment, Kenya,” Hydrological Sciences Journal, Vol. 54, No. 5, 2009, pp. 899-908. doi:10.1623/hysj.54.5.899
[21]	R. Jayakrishnan, R. Srinivasan, C. Santhi and J. G. Arnold, “Advances in the Application of the SWAT Model for Water Resources Management,” Hydrolocal Process, Vol. 19, No. 3, 2005, pp. 749-762.
[22]	D. N. Moriasi, J. G. Arnold, M. W. Van Liew, R. L. Binger, R. D Harmel and T. L. Veith, “Model Evaluation Guidelines for Systematic Quantification of Accuracy in Watershed Simulations,” Transactions of the American Society of Agricultural and Biological Engineers (ASABE), Vol. 50, No. 3, 2007, pp. 885-900.
[23]	B. Schmalz, F. Tavares and N. Fohrer, “Modelling 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