Maintaining Sediment Flows through Hydropower Dams in the Mekong River Basin
Publication: Journal of Water Resources Planning and Management
Volume 142, Issue 1
Abstract
The planning, design, and construction of hydropower dams are occurring at a rapid pace in the Mekong/Lancang River Basin in Southeast Asia. For years the river and its tributaries transported an average of 160 million metric tons of sediment per year to the South China Sea. Reservoirs are expected to trap significant fractions of this sediment, rendering much of it unavailable to transport nutrients and maintain the river’s geomorphic structure and ecological habitats. This paper introduces and applies a method for identifying and evaluating alternative dam siting, design, and operating (SDO) policy options that could help maintain more natural sediment regimes and for evaluating the effect of these sediment-management strategies on hydropower production. This paper focuses on the planned Lower Sesan 2 (LSS2) Dam in Cambodia. This dam would prevent a significant source of sediment from reaching critical Mekong ecosystems, such as Cambodia’s Tonle Sap Lake and the Mekong Delta in Vietnam. The concept of replacing LSS2 as planned with several smaller alternative dams with SDO modifications to enable reservoir sediment flushing is evaluated. These modifications could increase sediment discharge from this site by as much as three to four times compared to current plans but reduce short-term annual energy production by a third or more. Results demonstrate that most of the loss in energy production associated with SDO modifications (at least 94% in the cases considered) results from reduced reservoir size as opposed to modified reservoir operations. It is also found that, from an operational standpoint, sediment flushing is likely best conducted during the transition period between the dry and wet seasons.
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Acknowledgments
This work was funded in part by Cornell University’s David R. Atkinson Center for a Sustainable Future (ACSF). The authors wish to thank the MRC for providing data and advice throughout our studies, including reservoir and dam characteristics data (MRC 2012, 2014) and streamflow data (MRC 2011a). We extend our gratitude to Matt Kondolf and Zan Rubin for helpful discussions and sediment load predictions and to Tom Cochrane, Thanapon Piman, and Mauricio Arias for help in generating 3S basins maps (Fig. 1) and simulating 3S basins flows. We also thank the reviewers for their helpful comments on previous drafts of this manuscript.
References
Annandale, G. W. (2013). Quenching the thirst: Sustainable water supply and climate change, CreateSpace, North Charleston, SC.
Annandale, G. W., and Kaini, P. (2012). A climate resilient Mekong: Sediment pass-through at lower Se San 2, Golder Associates, Lakewood, CO.
Annandale, G. W., and Kaini, P. (2014). Lower Se San 2: Sediment management options, Golder Associates, Lakewood, CO.
Arias, M. E., et al. (2014). “Impacts of hydropower and climate change on drivers of ecological productivity of southeast Asia’s most important wetland.” Ecol. Modell., 272, 252–263.
Atkinson, E. (1996). “The feasibility of flushing sediment from reservoirs.” TDR Project R5839, Rep. OD 137, Oxfordshire, England.
Baird, I. G. (2009). Best practices in compensation and resettlement for large dams: The case of the planned Lower Sesan 2 hydropower project in northeastern Cambodia. Rivers Coalition in Cambodia, Phnom Penh, Cambodia, 138.
Baird, I. G., and Shoemaker, B. (2008). “Living aquatic resources and livelihoods.” People, livelihoods, and development in the Xekong River basin, I. G. Baird and B. Shoemaker, eds., White Lotus, Bangkok, Thailand, 203–246.
Baran, E. (2006). Fish migration triggers in the Lower Mekong basin and other tropical freshwater systems, Mekong River Commission, Vientiane, Lao PDR, 56.
Baran, E. (2010). Mekong fisheries and mainstream dams. Fisheries sections in: ICEM 2010. Mekong River Commission strategic environmental assessment of hydropower on the Mekong mainstream, International Centre for Environmental Management, Hanoi, Viet Nam, 145.
Baran, E., and Nasielski, J. (2011). Reservoir sediment flushing and fish resources, WorldFish Center, Phnom Penh, Cambodia.
Baran, E., Samadee, S., Jiau, T. S., and Cong, T. T. (2013). “Fish and fisheries in the Sekong, Sesan and Srepok basins (3S Rivers, Mekong Watershed), with special reference to the Sesan River, water and food challenge program in the Mekong, optimizing the management of a cascade of reservoirs at the catchment level.” WorldFish Center, Phnom Penh, Cambodia, 65.
Brandt, S. A., and Swenning, J. (1999). “Sedimentological and geomorphological effects of reservoir flushing: The Cachi reservoir, Costa Rica, 1996.” Geografiska Annaler, 81A(3), 391–407.
Bravard, J. P., Goichot, M., and Gaillot, S. (2013). “Geography of sand and gravel mining in the lower Mekong River: First survey and impact assessment.” EchoGeo., 26, 2–18.
Brune, G. M. (1953). “Trap efficiency of reservoirs.” Trans. AGU, 34(3), 407–418.
Buermann, Y., Du Preez, H. U., Steyn, G. J., Harmse, J. T., and Deacon, A. (1995). “Suspended silt concentrations in the lower Olifants River (Mpumalanga) and the impact of silt releases from the Phalaborwa Barrage on water quality and fish survival.” Koedoe, 38(2), 11–34.
Crosa, G., Castelli, E., Gentili, G., and Espa, P. (2010). “Effects of suspended sediments from reservoir flushing on fish and macroinvertebrates in an alpine stream.” Aquat. Sci., 72(1), 85–95.
Froese, R., and Pauly, D. (2014). “FishBase.” 〈www.fishbase.org〉 (Nov. 2014).
Fruchart, F. (2008). “Why and how to flush a reservoir without environmental impacts.” Proc., Regional Workshop on Discharge and Sediment Monitoring and Geomorphological Tools for the Lower-Mekong Basin, Mekong River Commission, Vientiane, Lao PDR, 33.
Fruchart, F., and Camenen, B. (2012). “Reservoir sedimentation: Different type of flushing—Friendly flushing, example of Genissiat Dam flushing.” Proc., Int. Symp. on Dams for a Changing World, International Commission on Large Dams, Paris, 6.
Gätke, P., et al. (2013). Fish passage opportunities for the Lower Sesan 2 dam in Cambodia—Lessons from South America, project report: Challenge program on water and food Mekong Project MK3, optimizing the management of a cascade of reservoirs at the catchment level, International Centre for Environmental Management (ICEM), Hanoi, Vietnam.
Grumbine, E. R., Dore, J., and Xu, J. (2012). “Mekong hydropower: Drivers of change and governance challenges.” Front. Ecol. Environ., 10(2), 91–98.
Halls, A. S. (2014). “The Lower Sesan 2 dam in the Sekong-Sesan-Srepok (3S) basin: Potential impacts on fish supply for consumption in Cambodia.”, International Union for the Conservation of Nature (IUCN), 104.
Halls, A. S., and Kshatriya, M. (2009). “Modelling the cumulative barrier and passage effects of mainstream hydropower dams on migratory fish populations in the Lower Mekong basin.” MRC Technical Paper No. 25, Mekong River Commission, Vientiane, 104.
Hesse, L. W., and Newcomb, B. A. (1982). “Effects of flushing spencer hydro on water quality, fish, and insect fauna in the Niobrara River, Nebraska.” North Am. J. Fish. Manage., 2(1), 45–52.
Hoanh, C. T., Jirayoot, K., Lacombe, G., and Srinetr, V. (2010). Impacts of climate change and development on Mekong flow regime, first assessment—2009, Mekong River Commission, Vientiane, Lao PDR.
Hortle, K. G. (2007). Consumption and the yield of fish and other aquatic animals from the lower Mekong basin, Mekong River Commission, Vientiane.
Junk, W. J., Bayley, P. B., and Sparks, R. E. (1989). “The flood pulse concept in river-floodplain systems.” Proc., Int. Large River Symp. (LARS), D. P. Dodge, ed., Vol. 106, Canadian Special Publication of Fisheries and Aquatic Sciences, 110–127.
Kantoush, S. A., Sumi, T., and Takemon, Y. (2011). “Lighten the load.” International water power and dam construction, 38–45.
Kibler, K. M., and Tullos, D. D. (2013). “Cumulative biophysical impact of small and large hydropower development in Nu River, China.” Water Resour. Res., 49, 3104–3118.
Koehnken, L. (2014). Discharge sediment monitoring project (DSMP) 2009–2013 summary and analysis of results, Mekong River Commission/Gesellschaft für Internationale Zusammenarbeit, Phnom Penh, Cambodia.
Kondolf, G. M., et al. (2014a). “Sustainable sediment management in reservoirs and regulated rivers: Experiences from five continents.” Earth’s Futures, 2, 256–280.
Kondolf, G. M., Rubin, Z. K., and Minear, J. T. (2014b). “Dams on the Mekong: Cumulative sediment starvation.” Water Resour. Res., 50, 5158–5169.
Kummu, M., Lu, X. X., Wang, J. J., and Varis, O. (2010). “Basin-wide sediment trapping efficiency of emerging reservoirs along the Mekong.” Geomorphology, 119(3–4), 181–197.
Kummu, M., Penny, D., Sarkkula, J., and Koponen, J. (2008). “Sediment—Curse or blessing for Tonle Sap Lake?” Ambio, 37(3), 158–163.
Kummu, M., and Varis, O. (2007). “Sediment-related impacts due to upstream reservoir trapping, the lower mekong River.” Geomorphol., 85(3-4), 275–293.
Lamberts, D. (2006). “The Tonle Sap Lake as a productive ecosystem.” Int. J. Water Resour. Dev., 22(3), 481–495.
Lamberts, D., and Koponen, J. (2008). “Flood pulse alterations and productivity of the Tonle Sap ecosystem: A model for impact assessment.” Ambio, 37(3), 178–184.
Lara, J. M., and Pemberton, E. L. (1963). “Initial unit weight of deposited sediments.” Proc., Federal Interagency Sedimentation Conf., Vol. 970, USDA-ARS Misc., 818–845.
Lauri, H., de Moel, H., Ward, P. J., Räsänen, T. A., Keskinen, M., and Kummu, M. (2012). “Future changes in Mekong River hydrology: Impact of climate change and reservoir operation on discharge.” Hydrol. Earth Syst. Sci., 16(12), 4603–4619.
Lu, X. X., and Siew, R. Y. (2006). “Water discharge and sediment flux changes over the past decades in the lower Mekong River: Possible impacts of the Chinese dams.” Hydrol. Earth Syst. Sci., 10(2), 181–195.
Mahmood, K. (1987). “Reservoir sedimentation: Impact, extent, mitigation.”, World Bank, Washington, DC.
Milliman, J. D., and Meade, R. H. (1983). “World-wide delivery of river sediment to the oceans.” J. Geol., 91(1), 1–21.
Morehead, M. D., Syvitski, J. P., Hutton, E. W. H., and Peckham, S. D. (2003). “Modeling the temporal variability in the flux of sediment from ungaged river basins.” Global Planet. Change, 39(1–2), 95–110.
Morris, G. L., and Fan, J. (1998). Reservoir sedimentation handbook, McGraw-Hill, New York.
MRC (Mekong River Commission). (2005). “Overview of the hydrology of the Mekong basin.” Vientiane, Lao, PDR, 73.
MRC (Mekong River Commission). (2009). “Preliminary design guidance for proposed mainstream dams in the lower Mekong basin.” Vientiane, Lao PDR, 38.
MRC (Mekong River Commission). (2010). “State of the basin report.” Vientiane, Lao PDR.
MRC (Mekong River Commission). (2011a). “Application of MRC modelling tools in the 3S basin.” Vientiane, Lao PDR.
MRC (Mekong River Commission). (2011b). “Basin development plan programme Phase 2: Assessment of basin-wide development scenarios.”, Vientiane, Lao PDR.
MRC (Mekong River Commission). (2012). “Hydropower project database.” Basin Development Plan Programme, Vientiane, Lao PDR.
MRC (Mekong River Commission). (2014). “Hydropower project database.” Basin Development Plan Programme, Vientiane, Lao PDR.
Newcombe, C. P., and Jensen, J. O. T. (1996). “Channel suspended sediment and fisheries: a synthesis for quantitative assessment of risk and impact.” North Am. J. Fish. Manag., 16 (4), 693–727.
Newcombe, C. P., and Macdonald, D. D. (1991). “Effects of suspended sediments on aquatic ecosystems.” North Am. J. Fish. Manage., 11(1), 72–82.
Nguyen, V. M., Nguyen, V. D., Nguyen, N. H., Kummu, M., Merz, B., and Apel, H. (2015). “Future sediment dynamics in the Mekong Delta floodplains: Impacts of hydropower development, climate change and sea level rise.” Global Planet. Change, 127, 22–33.
Palmieri, A., Shah, F., Annandale, G. W., and Dinar, A. (2003). “Reservoir conservation volume I: The RESCON approach, economic and engineering evaluation of alternative strategies for managing sedimentation in storage reservoirs. A contribution to promote conservation of water storage assets worldwide.” International Bank for Reconstruction and Development/World Bank, Washington, DC, 101.
PECC1 (Power Engineering Consulting Joint Stock Company). (2013). Sediment Rep. Prepared for Natural Heritage Institute (NHI), Hanoi City, Vietnam, 29.
Petts, G. E. (1984). Impounded rivers: Perspectives for ecological management, Wiley, Chichester.
Piman, T., Cochrane, T., Arias, M., Dat, N., and Vonnarart, O. (2015). “Managing hydropower under climate change in the Mekong tributaries.” Managing water resources under climate uncertainty: Examples from Asia, Europe, Latin America, and Australia, S. Shrestha, et al., eds., Springer, London, 223–248.
Piman, T., Cochrane, T., Arias, M., Green, A., and Dat, N. (2013a). “Assessment of flow changes from hydropower development and operations in Sekong, Sesan and Srepok rivers of the Mekong basin.” Water Resour. Plann. Manage., 723–732.
Piman, T., Lennaerts, T., and Southalack, P. (2013b). “Assessment of hydrological changes in the lower Mekong basin from basin-wide development scenarios.” Hydrol. Processes, 27(15), 2115–2125.
Räsänen, T. A., Joffre, O., Someth, P., Cong, T. T., Keskinen, M., and Kummu, M. (2015). “Model-based assessment of water, food and energy trade-offs in a cascade of multi-purpose reservoirs: Case study from transboundary Sesan River.” J. Water Resour. Plann. Manage., 05014007.
Sarkkula, J., Koponen, J., Lauri, H., and Virtanen, M. (2010). Mekong River Commission (MRC)/information and knowledge management program detailed modelling support (DMS) project: Origin, fate and impacts of the Mekong sediments, Mekong River Commission, Vientiane, Lao PDR, 53.
Shrestha, B., et al. (2013). “Impact of climate change on sediment yield in the Mekong River basin: A case study of the Nam Ou basin, Lao PDR.” Hydrol. Earth Syst. Sci., 17(1), 1–20.
Syvitski, J. P. M., et al. (2009). “Sinking deltas due to human activities.” Nat. Geosci., 2(10), 681–686.
Ta, K. T. O., Nguyen, V. L., Tateishio, M., Kobayashi, I., Tanabe, S., Saito, Y. (2002). “Holocene delta evolution and sediment discharge of the Mekong River, southern Vietnam.” Q. Sci. Rev., 21(16-17), 1807–1819.
Takamatsu, M., Kawasaki, A., Rogers, P. P., and Malakie, J. L. (2014). “Development of a land-use forecast tool for future water resources assessment: Case study for the Mekong River 3S sub-basins.” Sustainability Sci., 9(2), 157–172.
Ty, T. V., Sunada, K., and Ichikawa, Y. (2012). “Water resources management under future development and climate change impacts in the Upper Srepok River basin, Central Highlands of Vietnam.” Water Policy, 14(5), 725–745.
Walling, D. E. (2008). “The changing sediment load of the Mekong River.” Ambio, 37(3), 150–157.
Wang, J. J., Lu, X. X., and Kummu, M. (2011). “Sediment load estimates and variations in the lower Mekong River.” Riv. Res. Appl., 27(1), 33–46.
White, W. R. (2001). Evacuation of sediments from reservoirs, Thomas Telford, London.
Wild, T. B., and Loucks, D. P. (2012). SedSim model: A simulation model for the preliminary screening of sediment transport and management in river basins, version 3.0: Documentation and user’s manual, Dept. of Civil and Environmental Engineering, Cornell Univ., Ithaca, NY.
Wild, T. B., and Loucks, D. P. (2014). “Managing flow, sediment and hydropower regimes in the Sre Pok, Se San and Se Kong Rivers of the Mekong basin.” Water Resour. Res., 50(6), 5141–5157.
Wild, T. B., and Loucks, D. P. (2015a). “An approach to simulating sediment management in the mekong river basin.” Chapter 12, Sediment matters, P. Heininger and J. Cullman, eds., Springer, Heidelberg, 187–199.
Wild, T. B., and Loucks, D. P. (2015b). “Mitigating dam conflicts in the Mekong River basin.” Chapter 2, Conflict resolution in water resources and environmental management, K. W. Hipel, et al., eds., Springer, Heidelberg, 25–48.
Williams, G. P., and Wolman, M. G. (1984). Downstream effects of dams on alluvial rivers, USGS, Reston, VA, 83.
Ziv, G., Baran, E., Rodríguez-Iturbe, I., and Levin, S. A. (2012). “Trading-off fish biodiversity, food security and hydropower in the Mekong River basin.” Proc. Natl. Acad. Sci. USA, 109(15), 5609–5614.
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Journal of Water Resources Planning and Management
Volume 142 • Issue 1 • January 2016
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© 2015 American Society of Civil Engineers.
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Received: Dec 12, 2014
Accepted: Apr 22, 2015
Published online: Jul 9, 2015
Discussion open until: Dec 9, 2015
Published in print: Jan 1, 2016
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