hydrology and sediment initial baseline
TRANSCRIPT
Environmental study of the Lancang Mekong Development Plan (LMDP) for International Navigation Hydrology and sediment initial baseline
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
Hydrology current status
Annual flood pulse
Importance of the Upper Mekong
Dry season
Wet season
(MRC, 2005)
Sediment transport current status
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
Sediment supply – a stable river
February 2008
February 2014
Sediment supply – a stable river
April 2002
November 2015
Sediment transport capacity
(Bravard and Goichot, 2014)
Sediment supply – sandApril 2002
November 2015
Driver of change - Catchment land use
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 2000sYe
ar 1
961
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200
2
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196
1
Year
199
7(Walling, 2008)
Driver of change -Upper Mekong reservoirs
Upstream dams – hydrology
Study FindingsSimulation of effects using modellingRasanen et al, 2012
Amplitude of the annual flood pulse reducedDry season flows increased
Zhao et al, 2013
Increased flows in Jan, May and JulDecreased flows in Oct and NovMay be climate factors
Analysis of observed datasetsCampbell 2007 Decreasing August flows at Chiang SaenLu 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
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
Upstream dams – hydrology
• Lowest monthly flow has significantly decreased in many years (1993, 1995, 1997-1999, 2003-2007) at LB and CS
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)
Upstream dams - sediment
Chiang Saen Luang Prabang
(Adamson, 2009)
Driver of change - urban development
Development – embankments
2013 2016
Development – urban areas
Driver of change - Climate change
Climate change
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Nakhom Phanom BL
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Mukdahan BL Mukdahan CC
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(ICEM, 2013)
Driver of change - Pak Beng hydropower
• 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
Pak Beng Dam – backwater extent
• 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
• 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
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.