This study analyzed influence of land cover changes and climatic variability from 1973 to 2000 on discharge regime of Njoro River Catchment in Kenya. Analysis focused on hydro-meteorological data of 1977-1984 (Period I) and 1992-2000 (Period II), which are the periods found with available data and Landsat imageries for the same periods. Results show a downward trend of annual discharge that corresponded to increased deforestation. Forest area decreased by 25% while open fields combined with grasslands increased by 58% between the two periods. Discharge in Period I was 36% (0.23 m3/s or 82 mm/a) higher than Period II whereas increase of annual temperature (0.75℃) between the two periods was significant (P < 0.05) but decrease in rainfall (24.87 mm/a) was not significant with effect of 25% deforestation. Statistical analysis of both four rainy and four dry years in the two periods showed that: 1) mean monthly discharge in Period I was not different (P < 0.05) and variability in decreases was higher (z-score: 4.60 > 3.98) in rainy years compared to dry years, and 2) mean discharge in Period II was different (P < 0.05) and variability in decreases was higher again in rainy years than dry years (z-score: 4.78 > 4.77). Influence of climatic variability alone accounted for 25% (0.06 m3/s) on reduction of discharge while human activity mainly deforestation accounted for 75% (0.17 m3/s) on reduction of discharge in Period II. This implies that land cover changes were largely responsible for decrease in discharge and therefore, intervention measures of restoring forest cover are recommended for Njoro River Catchment.
Cite this paper
Mwetu, K. K. (2019). Influence of Land Cover Changes and Climatic Variability on Discharge Regime of Njoro River Catchment in Kenya. Open Access Library Journal, 6, e5461. doi: http://dx.doi.org/10.4236/oalib.1105461.
Marcos, H.C., Aurelie, B. and Jeffrey, A.C. (2003) Effects of Large-Scale Changes in Land Cover on the Discharge of the Tocantins River, Southeastern Amazonia. Journal of Hydrology, 283, 206-217. https://doi.org/10.1016/S0022-1694(03)00267-1
Dyhr-Nielsen, M. (1986) Hydrologic Effects of Deforestation in the Chao Phraya Basin in Thailand. International Symposium on Tropical Forest Hydrology and Application, Chiang Mai, 11-14 June 1986, 16.
Li, L.J., et al. (2007) Assessing the Impact of Climate Variability and Human Activities on Streamflow from the Wuding River Basin in China. Hydrological Processes, 21, 3485-3491. https://doi.org/10.1002/hyp.6485
Mutie, S.M., Mati, B., Home, P., Gadain, H. and Gathenya, J. (2006) Evaluating Land Use Change Effects on River Flow Using USGS Geospatial Stream Flow Model in Mara River Basin, Kenya. Proceedings of the 2nd Workshop of the EARSeL SIG on Land Use and Land Cover, Bonn, 28-30 September 2006, 141-148.
Mustafa, Y.M., Amin, M.S.M., Lee, T.S. and Shariff, A.R.M. (2005) Evaluation of Land Development Impact on a Tropical Watershed Hydrology Using Remote Sensing and GIS. Journal of Spatial Hydrology, 5, 16-30.
Mutua, B.M. and Gichaba, C.M. (2006) Effect of Land Use Change on Hydrological Regime in a Rural Catchment: A Case of River Njoro Catchment, Kenya. SOPHYWA, BOKU Vienna, Vienna.
Yillia, P.T., Kreuzinger, N. and Mathooko, J.M. (2008) The Effects of In-Stream Activities on the Njoro River, Kenya. Part II: Macro-Water Quality. Physics and Chemistry of the Earth, 33, 729-737. https://doi.org/10.1016/j.pce.2008.06.040
Baldyga, T.J. (2005) Assessing Land Cover Change Impacts in Kenya’s River Njoro Watershed Using Remote Sensing and Hydrologic Modelling. MSc Thesis, University of Wyoming, Laramie.
Mathooko, J.M. (2001) Disturbance of a Kenyan Rift Valley Stream by the Daily Activities of Local People and Their Livestock. Hydrobiologia, 458, 131-139. https://doi.org/10.1023/A:1013160918203
Kundu, P.M. (2007) Application of Remote Sensing and GIS Techniques to Evaluate the Impact of Land Use and Land Cover Change on Stream Flows: The Case for River Njoro Catchment in Eastern Mau-Kenya. PhD Thesis, Egerton University, Njoro.
Maingi, J.K. and Marsh, S.E. (2001) Assessment of Environmental Impacts of River Basin Development on the Riverine Forests of Eastern Kenya Using Multi-Temporal Satellite Data. International Journal of Remote Sensing, 22, 2701-2729. https://doi.org/10.1080/01431160010031298
Mohamed, A.M. (2006) Catchment Degradation and Impacts on the Hydrology of River Systems in Kenya. WWF, Eastern African Regional Programme Office Report.
Dawes, W.R., Gilfedder, M., Walker, G.R. and Evan, W.R. (2004) Biophysical Modelling of Catchment-Scale Surface Water and Groundwater Response to Land-Use Change. Mathematics and Computers in Simulation, 64, 3-12. https://doi.org/10.1016/S0378-4754(03)00116-2
Milly, P.C.D. and Dunne, K.A. (2002) Macro-Scale Water Fluxes 2. Water and Energy Supply Control of Their Inter-Annual Variability. Water Resources Research, 38, 1206. https://doi.org/10.1029/2001WR000760
Andrew, T.H and Carol, A.W. (2000) Deforestation in Mwanza District, Malawi, from 1981 to 1992, as Determined from Landsat MSS Imagery. Applied Geography, 20, 155-175. https://doi.org/10.1016/S0143-6228(00)00002-3
Jon, E.S., Graeme, L. and Brian, S.H. (2006) Impacts of Land Cover on Stream Hydrology in the West Georgia Piedmont, USA. Journal of Environmental Quality, 35, 2123-2131. https://doi.org/10.2134/jeq2006.0113
Hirsch, R.M., Walker, J.F., Day, J.C. and Kallio, R. (1990) The Influence of Man on Hydrologic Systems. In: Wolman, M.G. and Riggs, H.C., Eds., Surface Water Hydrology, Geological Society of America, Boulder, 329-359. https://doi.org/10.1130/DNAG-GNA-O1.329
Paul, M.L. and Meyer, J.L. (2001) Streams in the Urban Landscape. Annual Review of Ecology and Systematic, 32, 333-365. https://doi.org/10.1146/annurev.ecolsys.32.081501.114040
Congalton, R.G. and Green, K. (1999) Assessing the Accuracy of Remotely Sensed Data: Principles and Practices. Lewis Publishers, Boca Raton, 137. https://doi.org/10.1201/9781420048568
Mainuri, Z.G. (2005) Land Use Effects on the Spatial Distribution of Soil Aggregate Stability within the River Njoro Watershed, Kenya. MSc. Thesis, Egerton University, Njoro.
Mariara, J.K. and Karanja, F.K. (2007) The Economic Impact of Climate Change on Kenyan Crop Agriculture: A Ricardian Approach. Global and Planetary Change, 57, 319-330. https://doi.org/10.1016/j.gloplacha.2007.01.002
Ma, X., et al. (2009) Response of Hydrological Processes to Land-Cover and Climate Changes in Kejie Watershed, South-West China. Hydrological Processes, 23, 1179-1191.
Cheng, G.W. (1991) An Approach to the Relationship between Runoff Characters and Forest in the Basin of Sichuan. Journal of Soil and Water Conservation, 5, 48-52.
Liu, C.M. and Zhong, J.X. (1978) A Preliminary Study to Relationship between Forest and Annual Runoff in Loess Plateau. Acta Geographica Sinica, 33, 112-116.
Van Lill, W.S., Kruger, F.J. and Van Wyk, D.B. (1980) The Effects of Afforestation with Eucalyptus grandis Hill EX Maiden and Pinus patula Schlecht. Journal of Hydrology, 48, 107-118. https://doi.org/10.1016/0022-1694(80)90069-4
Sandstroem, K. (1995) Forests and Water-Friends of Foes: Hydrological Implication of Deforestation and Land Degradation in Semi-Arid Tanzania. Department Theme Research, University of Link?ping, Link?ping.
Chen, Y.N., Takeuchi, K., Xu, C., Chen, Y.P. and Xu, Z.X. (2006) Regional Climate Change and Its Effects on River Runoff in the Tarim Basin, China. Hydrological Processes, 20, 2207-2216. https://doi.org/10.1002/hyp.6200
Costa, M.H. and Foley, J.A. (1997) The Water Balance of the Amazon Basin: Dependence on Vegetation Cover and Canopy Conductance. Journal of Geophysical Research: Atmospheres 102, 23973-23989. https://doi.org/10.1029/97JD01865