Estimation of Small Reservoir Sedimentation in Semi-Arid Southern Zimbabwe

Tavengwa Chitata, Francis Themba Mugabe, Japhet Joel Kashaigili

Department of Forest Mensuration and Management, Sokoine University of Agriculture, Morogoro, Tanzania.
Directorate of Research and Resource Mobilisation, Chinhoyi University of Technology, Chinhoyi, Zimbabwe.
Faculty of Natural Resources Management and Agriculture, Midlands State University, Gweru, Zimbabwe.

DOI: 10.4236/jwarp.2014.611096                

Abstract

Small surface reservoirs play an important role of providing ready and convenient source of water for various uses in semi-arid areas which are characterized by erratic and low rainfall. Lack of current data on reservoir capacity loss due to sedimentation is one of the challenges to the sustainable management of surface reservoirs. The study investigated the capacity loss due to sedimentation from 2000-2012, and estimated the trap efficiency of the Mutangi reservoir which is located in semi-arid Chivi, Southern of Zimbabwe. Hydrographic surveys, grab sampling and water depth-capacity methods were used to determine the capacity of the dam as of 2012. To compute capacity loss from 2000 to 2012, the 2000 and 2012 dam capacities were compared whilst the trap efficiency of the reservoir was determined using a set of empirical models that relates trap efficiency to the capacity-watershed area ratio and capacity-inflow ratio. The results show that Mutangi reservoir has a trap efficiency of 95% - 98% (av = 96.4%) and has lost 37% of its capacity due to sedimentation in 12 years (2000 and 2012). Rates of sedimentation were 8539 t·yr^-1, 9110 t·yr^-1 and 8265 t·yr^-1 for the hydrographic survey, grab sampling and water depth-capacity method respectively, and the little difference in these figures demonstrates that any method can be used to determine sedimentation rates. The area specific sediment yield (ASY) ranged from 14 - 15.5 t·ha^-1·yr^-1 (av = 14.956 t·ha^-1·yr^-1). At the current rate of sedimentation the projected dead level of the reservoir will be lost to sedimentation in 8 years while the useful life of the reservoir is estimated to be 30 years. Capacity loss due to sedimentation is further complicating the already strained water scarcity situation in semi-arid areas and management decisions should be made based on the current sedimentation rates estimated by different methods. These results imply that management practices that reduce erosion, hence sedimentation in these small reservoirs should be practiced in order to prolong their lifespan.

Keywords

Hydrographic Survey, Sedimentation, Semi-Arid Area, Small Reservoir, Water Resources

Conflicts of Interest

The authors declare no conflicts of interest.

References

[1]	Nyamudeza, P. (1998) Water and Fertility Management for Crop Production in Semi-Arid Zimbabwe. Unpublished PhD Thesis, University of Nottingham, Nottingham.
[2]	Andreini, M., Schuetz, T., Senzanje, A., Rodriguez, L., Andah, W., Cecchi, P., Boelee, E., Giesen, N., Kemp-Benedikt, E. and Liebe, J. (2009) Small Multi-Purpose Reservoir Ensemble Planning. Project Number 46, Small Multi-Purpose Reservoir Ensemble Planning CGIAR Challenge Program on Water and Food Project Report Series. www.waterandfood.org
[3]	Senzanje, A., Boelee, E. and Rusere, S. (2008) Multiple Use of Water and Water Productivity of Communal Small Dams in the Limpopo Basin, Zimbabwe. Irrigation and Drainage Systems, 22, 225-237. http://dx.doi.org/10.1007/s10795-008-9053-7
[4]	Zirebwa, J. and Twomlow, S. (2008) Historical Profile of Selected Small Dams in Communal Areas of Masvingo Province. Paper presented at the Engineering Technology for Increased Agricultural Productivity Conference, Harare, Zimbabwe, September 1999.
[5]	Dalu, T., Tambara, E.M., Clegg, B., Chari, L.D. and Nhiwatiwa, T. (2013) Modeling Sedimentation Rates of Malilangwe Reservoir in the South-Eastern Lowveld of Zimbabwe. Applied Water Science, 3, 133-144. http://dx.doi.org/10.1007/s13201-012-0067-9
[6]	Mavhima, G., Soropa, G., Makurira, H. and Dzvairo, W. (2011) Sedimention Impacts on Reservoir as a Result of Landuse on a Selected Catchment in Zimbabwe. International Journal of Engineering Science and Technology, 3, 6599-6608.
[7]	Ongwenyi, G.S., Kithiia, S.M. and Denga, F.O. (1993) An Overview of the Soil Erosion and Sedimentation Problem in Kenya. In: Hadley, R.F. and Muzuyama, T., Eds., Sedimentation Problems, Strategies for Monitoring, Prediction and Control, IAHS Publ. No 217, Wallingford, 216-221.
[8]	Le Roux, J.J., Morgenthal, T.L., Malherbe, J., Pretorius, D.J. and Sumner, P.D. (2008) Water Erosion Prediction at a National Scale for South Africa. Water SA, 34, 305-314.
[9]	Sharma, K.D. (1992) Runoff and Sediment Transport in an Arid Zone Drainage Basin. Ph.D. Thesis, Indian Institute of Technology, Bombay.
[10]	FAO (1987) Soil and Water Conservation in Semi-Arid Areas. Soil Bulletin, 17, 1-17.
[11]	Pilgrims, D.H., Chapman, T.C. and Doran, D.G. (1988) Problems of Rainfall-Runoff Modeling in Semi-Arid Regions. Hydrological Sciences Journal, 33, 379-400. http://dx.doi.org/10.1080/02626668809491261
[12]	Maskey, R.B., Binod, P., Sharma, S. and Joshi, M. (2003) Human Dimensions in Sustainable Land Use Management in Degraded Land Areas of Nepal. The Open Meeting of the Global Environmental Change Research Community, Montreal, 16-18 October 2003.
[13]	Ragab, R. and Prudhomme, C. (2002) SW—Soil and Water: Climate Change and Water Resources Management in Arid and Semi-Arid Regions: Prospective and Challenges for the 21st Century. Biosystems Engineering, 81, 3-34.
[14]	Carvalho, N.O., Júnior, N.P.F., Coutinho dos Santos, P.M. and Lima, J.E.F.W. (2000) Reservoir Sedimentation Assessment Guide. Brazilian Electricity Regulatory Agency-ANEEL Hydrological Studies and Information Department—SIH, Brasilia.
[15]	Soler-López, L.R. (2001) Sedimentation Survey of Lago Caonillas, Puerto Rico, February 2000. U.S. Geological Survey Water-Resources Investigation Report 01-4043, Caribbean Water Science Centre, 25p., 1pl.
[16]	Ristic, R., Ljujic, M., Despotovic, J., Aleksic, V., Radic, B., Nikic, Z., Milcanovic, V., Malusevic, I. and Radonjic, J. (2013) Reservoir Sedimentation and Hydrological Effects of Land Use Changes-Case Study of the Experimental Dicina River Watershed. Carpathian Journal of Earth and Environmental Sciences, 8, 91-98.
[17]	Chihombori, J., Nyoni, K. and Gamira, D. (2013) Causes and Rate of Reservoir Sedimentation Due to Changes in Catchment Management. A Case of Marah Dam in Masvingo Province of Zimbabwe. Greener Journal of Geology and Earth Sciences, 1, 7-12.
[18]	FAO (1999) Poverty Alleviation and food SECURITY in Asia: Land Resources. FAO Corporate Document Repository, Asia. http://www.fao.org/docrep/003/x6625e/x6625e00.htm.
[19]	Pitman, A.J., Narisma, G.T., Pielke Sr., R.A. and Holbrook, N.J. (2004) Impact of Land Cover Change on the Climate of Southwest Western Australia. Journal of Geophysical Research, 109, Article ID: d18109. http://dx.doi.org/10.1029/2003JD004347
[20]	Yusuf, Y.O. and Yusuf, F. (2013) An Assessment of the Rate of Siltation in Jibia Reservoir, Jibia, Katsina State. 7th International Conference on River Basin Management, RBM 2013, New Forest, 22-24 May 2013, Code 97100. WIT Transactions on Ecology and the Environment, 172, 189-200.
[21]	Butterworth, J.A., Schulze, R.E., Simmonds, L.P., Moriarty, P. and Mugabe, F. (1999) Hydrological Processes and Water Resources Management in a Dryland Environment IV: Long-Term Groundwater Level Fluctuations Due to Variations in Rainfall. Hydrology and Earth System Sciences, 3, 353-361. http://dx.doi.org/10.5194/hess-3-353-1999
[22]	Mugabe, F.T. (2005) Temporal and Spatial Variability of the Hydrology of Semi-Arid Zimbabwe and Implications on Surface Water Resources. Unpublished DPhil Thesis, Department of Soil, University of Zimbabwe, Harare.
[23]	Lovell, C. (2000) Productive Water Points in Dryland Areas: Guidelines on Integrated Planning for Rural Water Supply. ITDG Publishing, UK.
[24]	Scoones, I., Chibudu, C., Chikura, S., Jeranyama, P., Machaka, D., Machanya, W., Mavedzenge, B., Mombeshora, B., Mudhara, M., Murimbarimba, F. and Zirereza, B. (1996) Hazards and Opportunities, Farming Livelihoods in Dryland Africa: Lessons from Zimbabwe. Zed Books Ltd, London and New Jersey, in association with International Institute for Environment and Development, London.
[25]	Mugabe, F.T., Hodnett, M. and Senzanje, A. (2007) Effect of Temporal Rainfall Distribution and Soil Type on Soil Moisture and Runoff Generation in Semi-Arid Zimbabwe. Nordic Hydrology, 38, 249-263. http://dx.doi.org/10.2166/nh.2007.014
[26]	Muzuva, J. and Gotosa, J. (1999) Field Report on Geological and Soil Surveys of Mutangi micro-catchment, IES, UZ, Zimbabwe. IES publication, 26pp.
[27]	Campbell, B., du Toit, R. and Attwell, C. (1988) Relationship between the Environment and Basic Needs and Satisfaction in the Save Catchment. University of Zimbabwe, Harare, 119.
[28]	Brown, C.B. (1943) Discussion on Sedimentation in Reservoirs, by J. Witzig Q. Proceedings of the American Society of Civil Engineers, 69, 1493-1500.
[29]	Brune, G.M. (1953) Trap Efficiency of Reservoirs. Transactions, American Geophysical Union, 34, 407. http://dx.doi.org/10.1029/TR034i003p00407
[30]	Verstraeten, G. and Poesen, J. (2000) Estimating Trap Efficiency of Small Reservoirs and Ponds: Methods and Implications for the Assessment of Sediment Yield. Progress in Physical Geography, 24, 219-251. http://dx.doi.org/10.1177/030913330002400204
[31]	USDA (2003) National Range and Pasture Handbook, Management of Grazing Land. Natural Resources Conservation Services, Washington DC.
[32]	Gray, D.H. and Sotir, R.B. (1996) Biotechnical Soil Bioengineering Slope Stabilization: A Practical Guide for Erosion Control. John Wiley & Sons, New York.
[33]	Menashe, E. (1998) Vegetation and Erosion. A Literature Survey. Proceedings of the Native Plants Symposium, Oregon State University, Forestry Sciences Lab., Corvallis, 9-10 December 1998, 130-135.
[34]	Higgitt, D.L. and Lu, X.X. (2001) Sediment Delivery to the Three Gorges: 1. Catchment Controls. Geomorphology, 41, 143-156. http://dx.doi.org/10.1016/S0169-555X(01)00112-X
[35]	FAO (2002) Natural Resources Assessment. Irrigation Manual 2. FAO Southern Africa.
[36]	Lawrence, P. (1996) Guidelines on Field Measurement Procedures for Quantifying Catchment Sediment Yields. TDR Project R5836. Report OD/TN77. HR Wallingford Ltd, UK.
[37]	Kummu, M. and Varis, O. (2006) Sediment-Related Impacts Due to Upstream Reservoir Trapping, the Lower Mekong River. Geomorphology, 85, 275-293.
[38]	UNESCO and IRTCES (2011) Sediment Issues & Sediment Management in Large River Basins Interim Case Study Synthesis Report. International Sediment Initiative Technical Documents in Hydrology UNESCO Office in Beijing & IRTCES.
[39]	Barma, D. and Varley, I. (2012) Hydrological Modeling Practices for Estimating Low Flows-Guidelines. Australian Government National Water Commision, Turner.
[40]	WMO (2005) World Metrological Organisation No 898. Geneva.