JWARP  Vol.5 No.12 , December 2013
Assessment of Sedimentation Impacts on Small Dams—A Case of Small Reservoirs in the Lotsane Catchment
ABSTRACT

Sedimentation is a major problem for agricultural dams in Botswana, as it reduces the storage capacity and life span of the reservoirs. The process of sedimentation starts from day one of the impounding of water in any given reservoir. Even though a provision is made for every reservoir during planning for a certain storage capacity, specifically for sediment deposition, called dead storage, a major portion of the sediment gets deposited for many years of the reservoir’s life in areas other than the dead storage, and this trend cannot be reversed at easy cost. This study is aimed at the analysis of prevailing sedimentation processes in the nearby dozens of dams found in the Lotsane catchment located within the Limpopo Basin of Botswana, and focuses on assessment of annual sedimentation rate. A spatial analysis and modelling study was conducted based on the Revised Universal Soil Loss Equation and GIS to determine sediment yield and degree of impact of each reservoir for a given landscape, rainfall and catchment heterogeneity. Field observations and soil sampling were carried out in order to determine the factors that lead to reservoir sedimentation. Spatial data on the dams in Lotsane catchment were also collected from Ministry of Agriculture, which were used for ground-truthing, GIS-based calculations and model validation. The average sediment rate and sediment delivery ratio were found to be 1.74 t/ha/year and 81%, respectively. These are useful parameters to estimate service life of the dams and plan remedial measures related to sedimentation problems.


Cite this paper
B. Alemaw, M. Majauale and T. Simalenga, "Assessment of Sedimentation Impacts on Small Dams—A Case of Small Reservoirs in the Lotsane Catchment," Journal of Water Resource and Protection, Vol. 5 No. 12, 2013, pp. 1127-1131. doi: 10.4236/jwarp.2013.512118.
References
[1]   R. Lal, “Soil Erosion by Wind and Water: Problems and Prospects,” In: R. Lal, Ed., Soil Erosion Research Methods, 2nd Edition, Soil and Water Conservation Society, St. Lucie Press, 1994, p. 19.

[2]   K. G. Renard, G. R. Foster, G. A. Weesies, D. K. McCool and D. C. Yoder, “Predicting Soil Erosion by Water: A Guide to Conservation Planning with the Revised Universal Soil Loss Equation (RUSLE),” Agriculture Handbook No. 703, 1997, USDA-ARS.

[3]   E. Z. Nyakatawa, K. C. Reddy and J. L. Lemunyon, “Predicting Soil Erosion in Conservation Tillage Cotton Production Systems Using the Revised Universal Soil Loss Equation,” Soil Till Research, Vol. 57, No. 4, 2001, pp. 213-224.
http://dx.doi.org/10.1016/S0167-1987(00)00178-1

[4]   W. H. Wischmeier and D. D. Smith, “Predicting Rainfall Erosion Losses,” Agriculture Handbook, No. 537, 1978, USDA Science and Education Administration.

[5]   G. Fu, S. Chen and K. D. McCool, “Modeling the Impacts of No-Till Practice on Soil Erosion and Sediment Yield Using RUSLE, SEDD and ArcView GIS,” Soil Tillage Research, Vol. 85, No. 1-2, 2006, pp. 38-49.
http://dx.doi.org/10.1016/j.still.2004.11.009

[6]   E. H. Erdogan, G. Erpul and I. Bayramin, “Use of USLE/ GIS Methodology for Predicting Soil Loss in a Semiarid Agricultural Environment,” Environmental Monitoring and Assessment, Vol. 131, No. 1-3, 2007, pp. 153-161.
http://dx.doi.org/10.1007/s10661-006-9464-6

[7]   L. A. Lewis, G. Verstraeten and H. Zhu, “RUSLE Applied in a GIS Framework: Calculating the LS Factor and Deriving Homogeneous Patches for Estimating Soil Loss,” International Journal of Geographical Information Science, Vol. 19, No. 7, 2005, pp. 809-829.
http://dx.doi.org/10.1080/13658810500105705

[8]   B. F. Alemaw, J. Jiyane and T. E. Simalenga, “Resilience of Small Reservoirs and Water Development in the Limpopo Basin: The Human and Climate Change Dimension,” Proceedings of the 3rd International Forum on Water and Food, 14-17 November 2011.

[9]   A. C. Brunner, “Soil Erosion Modeling at Small Reservoir Scale by WaTEM/SEDEM,” Small Reservoirs Tool Kit. 2012. www.smallreservoirs.org

[10]   K. Van Oost, G. Govers and P. J. J. Desmet, “Evaluating the Effects of Changes in Landscape Structure on Soil Erosion by Water and Tillage,” Landscape Ecology, Vol. 15, No. 6, 2000, pp. 579-591.
http://dx.doi.org/10.1023/A:1008198215674

[11]   A. Van Rompaey, G. Verstraeten, K. Van Oost, G. Govers and J. Poesen, “Modelling Mean Annual Sediment Yield Using a Distributed Approach,” Earth Surface Processes and Landforms, Vol. 26, No. 11, 2001, pp. 1221-1236. http://dx.doi.org/10.1002/esp.275

[12]   G. R. Foster, D. K. McCool, K. G. Renard and W. G. Moldcrnhauer, “Conversion of the Universal Soil Less Equation to SI Metric Units,” Journal of Soil and Water Conservation, Vol. 3, 1981, pp. 355-359.

[13]   W. H. Wischmeier, C. B. Johnson and B. V. Cross, “A Soil Erodibility Nomograph for Farmland and Construction Sites,” Journal of Soil and Water Conservation, Vol. 26, 1971, pp. 189-193.

[14]   A. Lufafa, M. M. Tenywa, M. Isabirye, M. J. G. Majaliwa and P. L. Woomer, “Prediction of Soil Erosion in a Lake Victoria Basin Catchment Using a GIS-Based Universal Soil Loss Model,” Agricultural Systems, Vol. 73, 2003, pp. 1-12.

[15]   J. R. Williams and H. D. Berndt, “Sediment Yield Computed with Universal Equation,” Journal of Hydraulic Division, ASCE, Vol. 98, 1972, pp. 2087-2098.

[16]   A. C. Brunner, “Bathymetric Survey by Depth-Sonar and Lake Sediment Coring by Beaker Sampler to Identify Sediment Budgets and Siltation Rates of Small Reservoirs,” Small Reservoirs Tool Kit, 2012.
www.smallreservoirs.org

 
 
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