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Hydrology and sediment initial baseline

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This presentation was delivered by Simon Tilleard at the Lancang – Mekong Environmental Study Workshop that took place at the 2016 Greater Mekong Forum on Water, Food and Energy.
The presentation documents the current condition and drivers of change for hydrology and sediment transport in the study section. It also provides information for biodiversity teams so that they can understand habitat availability.

Published in: Environment
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Hydrology and sediment initial baseline

  1. 1. Environmental study of the Lancang Mekong Development Plan (LMDP) for International Navigation Hydrology and sediment initial baseline
  2. 2. Purpose • Document the current condition and drivers of change for hydrology and sediment transport in the study section • Provide information for biodiversity teams so they can understand habitat availability Caveats • Desktop study based on literature review and data analysis • Findings needs to be expanded and confirmed through field visit/s Purpose of the study
  3. 3. Hydrology current status
  4. 4. Annual flood pulse
  5. 5. Importance of the Upper Mekong Dry season Wet season (MRC, 2005)
  6. 6. Sediment transport current status
  7. 7. Sediment supply • UPSTREAM CATCHMENTS – Main source of sediment supply (estimated as producing Suspended Sediment Yield of 700 t/km2/year (Walling, 2009) • TRIBUTARY CONFLUENCES – Could not be quantified – Qualitative assessment using satellite imagery shows seven tributaries likely to be supplying large amounts of sediment to the mainstream • BANK AND CHANNEL EROSION – Temporal-spatial analysis of satellite imagery shows that the river is not highly active therefore unlikely to be supply large sediment loads
  8. 8. Sediment supply – a stable river February 2008 February 2014
  9. 9. Sediment supply – a stable river April 2002 November 2015
  10. 10. Sediment transport capacity (Bravard and Goichot, 2014)
  11. 11. Sediment supply – sand April 2002 November 2015
  12. 12. Driver of change - Catchment land use
  13. 13. Change in catchment land use • 22% decrease in forest cover between 1960 to 2000 in Upper catchments, and similar decrease in catchments of tributaries entering study reach • No increase in flow over this period • Increasing sediment loads between the 1960s and early 2000sYear1961 Year2002 Year1961 Year1997 (Walling, 2008)
  14. 14. Driver of change - Upper Mekong reservoirs
  15. 15. Upstream dams – hydrology Study Findings Simulation of effects using modelling Rasanen et al, 2012 Amplitude of the annual flood pulse reduced Dry season flows increased Zhao et al, 2013 Increased flows in Jan, May and Jul Decreased flows in Oct and Nov May be climate factors Analysis of observed datasets Campbell 2007 Decreasing August flows at Chiang Saen Lu et al, 2014 Decreasing August flows at Chiang Saen More variable flows in the dry season Li and He, 2008 Decrease in dry season flows
  16. 16. Upstream dams – hydrology • Volume of flow during the dry season has significantly decreased in many years (1993, 1997-1999, 2004) at both Luang Prabang and Chiang Saen
  17. 17. Upstream dams – hydrology • Lowest monthly flow has significantly decreased in many years (1993, 1995, 1997- 1999, 2003-2007) at LB and CS
  18. 18. Upstream dams – hydrology • Our analysis based on 1950/60 to 2006/07 and observed change • New analysis using data up to 2014/15 shows that the later larger dams are having a more significant impact (baseline is changing further)
  19. 19. Upstream dams - sediment Chiang Saen Luang Prabang (Adamson, 2009)
  20. 20. Driver of change - urban development
  21. 21. Development – embankments 2013 2016
  22. 22. Development – urban areas
  23. 23. Driver of change - Climate change
  24. 24. Climate change 0 2,000 4,000 6,000 8,000 10,000 12,000 14,000 16,000 18,000 20,000 Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec Averagedailydischarge(m3/s) ChiangSen BL Chiangsen CC 0 2,000 4,000 6,000 8,000 10,000 12,000 14,000 16,000 18,000 20,000 Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec Averagedailydischarge(m3/s) Luang Prabang BL Luang Prabang C homPhanom BL homPhanom CC 25,000 30,000 35,000 40,000 45,000 50,000 lydischarge(m3/s) MukdahanBL MukdahanCC 25,000 30,000 35,000 40,000 45,000 50,000 lydischarge(m3/s) 0 2,000 4,000 6,000 8,000 10,000 12,000 14,000 16,000 18,000 20,000 Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec Averagedailydischarge(m3/s) ChiangSen BL Chiangsen CC 0 2,000 4,000 6,000 8,000 10,000 12,000 14,000 16,000 18,000 20,000 Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec Averagedailydischarge(m3/s) Luang Prabang BL Luang Prabang CC (ICEM, 2013)
  25. 25. Driver of change - Pak Beng hydropower
  26. 26. • Located on Mekong River 14km upstream of Pak Beng town • Concrete run-of-river gate dam • Installed capacity of 815 MW • Navigation lock for 500t capacity boats Pak Beng – project details
  27. 27. Pak Beng Dam – backwater extent
  28. 28. • Run-of-river so, once filled, should be negligible effect on downstream hydrology • Blocking of sediment behind dam wall leading to downstream sedimentation starvation • Changes in flow within the backwater extent Pak Beng – possible impacts
  29. 29. • Hydrology – Annual flood pulse – Importance of Upper Mekong catchment • Sediment transport – Importance of Upper Mekong catchments – Zone of deposition • A changing situation – Land use change – increasing sediment loads – Upper Mekong reservoirs – altering hydrology and sediment – Climate change – will alter hydrology – Lower Mekong reservoirs (Pak Beng) - TBC In conclusion
  30. 30. We are passionate about the protection and restoration of waterways, catchments and water resources. We strive to make a positive difference to the world we live in.

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