The Vietnam National Mekong Committee conducted a Mekong Dam Study, the results of which were presented at the Greater Mekong Forum on Water, Food and Energy in Phnom Penh on Oct. 21, 2015. This is part one of their overview presentation.

1. Study of the Impacts of Mainstream Hydropower on the Mekong Delta
MDS Impact Assessment Framework, Approach, and Results Overview
Greater Mekong Forum on Water, Food and Energy
Phnom Penh, Cambodia
October 2015

2. Study of the Impacts of Mainstream Hydropower on the Mekong Delta
Outline
Project overview
Study area
Impact assessment
– Objectives
– Approach
Baseline data
Historical data
Research studies
Data issues
Impact assessment results overview

3. Study of the Impacts of Mainstream Hydropower on the Mekong Delta
Project objectives and study area
MDS Evaluation Area MDS Impact Assessment Area IAA Sub-divisions
To assess the overall impacts of the proposed LMB mainstream
hydropower cascade on the natural, social, and economic systems of
Cambodian and Vietnamese floodplains.

4. Study of the Impacts of Mainstream Hydropower on the Mekong Delta
Cambodian Floodplains Kratie to Phnom Penh (includes
the Great Lake - Tonle Sap System
(approx 5,690,683 hectares)
Cambodian Delta Phnom Penh to Vietnamese
Border (approx 930,811 hectares)
Vietnamese Delta Vietnamese border to East Sea
(approx 3,926,565 hectares)
The IAA covers approx 10.5 M hectares
Includes Ecozones 4, 5, and 6

5. Study of the Impacts of Mainstream Hydropower on the Mekong Delta
13 provinces in Viet Nam
– 128 Districts, 1,589 Communes
14 provinces in Cambodia
– 121 Districts, 1,057 Communes
The IAA includes 27 provinces

6. Study of the Impacts of Mainstream Hydropower on the Mekong Delta
Impact assessment was focused on areas that are
hydrologically connected to the Mekong River
mainstream
Flooded area duration map (7 days_10 cm)
Hydrological connection =
inundation potential
Flooding defined as:
– 10 cm inundation over 7 days
Using this definition the year 2000
flood would have inundated
approx. 40,955 km2 within the IAA
– About 40% is in the Vietnamese delta
(15,970 Km2)

7. Study of the Impacts of Mainstream Hydropower on the Mekong Delta
Drivers and receptors
Key drivers of change: Flow regime, sediment
loading, water quality,
longitudinal connectivity
(barrier effects)
Potential impacts on:
– Natural systems Biological habitats, biodiversity
– Social systems Livelihood
– Economic sectors Fisheries, Agriculture, Navigation

8. Study of the Impacts of Mainstream Hydropower on the Mekong Delta
Linkages between drivers and resources are complex, dynamic,
and multifaceted and include multiple feedback loops.

9. Study of the Impacts of Mainstream Hydropower on the Mekong Delta
Linkages between direct and indirect impacts are mediated by
multiple bio-physical and social factors.

10. Study of the Impacts of Mainstream Hydropower on the Mekong Delta
Net impacts will be influenced by the macro-level feedback loops
between institutional, natural, social, and economic systems.

11. Study of the Impacts of Mainstream Hydropower on the Mekong Delta
Evaluate and quantify (where permitted by data availability and
quality) direct and indirect impacts of:
– Changes in flow regime, sediment loading, and water quality on
– Extent of wetlands, biodiversity, fisheries, agriculture, navigation,
livelihood, and economic impacts
– Impacts to aquatic species due to barrier effects were also evaluated
Alternative operational strategies were considered (dry year-dry
season and dry year-wet season drawdowns)
Positive and negative and short- and long-term impacts
Impact assessment approach

12. Study of the Impacts of Mainstream Hydropower on the Mekong Delta
Impacts were cumulatively assessed across geographic areas:
– Cambodian floodplains
– The Great Lake – Tonle Sap System
– Vietnamese Delta
– Provinces and districts (livelihood, agriculture, and economic impacts
only)
Where relevant, impacts were cumulatively assessed across
sectors
Impact assessment approach
Sectors Fisheries Biodiversi
ty Agriculture Navigation Livelihood Economics
Fisheries X X X X
Biodiversity X X X
Agriculture X X X X
Navigation X X X
Livelihood X X X X
Economics X X X X X

13. Study of the Impacts of Mainstream Hydropower on the Mekong Delta
Extremely large study area with very complex ecosystem
characteristics
– influenced the resolution of the analyses
Lack of existing scientific tools/knowledgebase
– No suitable off-the-shelf tool were available to correlate changes in
sediment and nutrient loading to potential changes in biodiversity and
fisheries yields
Vietnamese Delta is highly altered
– influenced outcome of the agriculture and aquaculture impact
assessments
Data issues
– Influenced level of quantification of impacts
Impact assessment challenges

14. Study of the Impacts of Mainstream Hydropower on the Mekong Delta
Quantity
– Available collected at disparate locations, at different times, using varying
methodologies, for different purposes
Quality
– Lack of raw data, little or no information on analytical and QA/QC procedures
Accessibility
– Many different institutions collect data for different purposes
– hard copy v/s electronic
Period of record
– Varying data collection periods and frequency
– Some data is simply too old
Critical gaps
– Focused research studies to fill the gaps
Data issues

15. Study of the Impacts of Mainstream Hydropower on the Mekong Delta
Biodiversity
– Field Surveys within selected land cover types (5 sites, 3 seasons)
– Characterization of water management practices within selected
national parks and wetland reserves
– Wetlands map update
Fishery
– Habitat-based fish sampling surveys (39 sites, 6 sampling events)
– Fish yield sampling surveys
– Fisher surveys.
– Aquaculture production assessment
Livelihood
– Household surveys
– 2,520 households in Vietnam
– 720 households in Cambodia
Research studies

16. Study of the Impacts of Mainstream Hydropower on the Mekong Delta
Sediment
– Quantification of sediment loads under dry and wet weather conditions
– Data collected in Laos PDR, Cambodia and Vietnam
– Compare to the 2011 – 2013 DSMP data
Water Quality
– Nutrient transport associated with sediment transport
– Nutrient dynamics related to the transport and deposition/re-
suspension of sediments
Navigation
– Data on key navigation parameters is being collected through
questionnaire interviews at 14 sites in Vietnam and 5 sites in Cambodia
Research studies

17. Study of the Impacts of Mainstream Hydropower on the Mekong Delta
Hydro-meteorological conditions for the 1985–2013 period of
record
– includes extreme years (very wet [2000 and 2011] and very dry [ 1998])
and average years [represented by 2007])
– hydrologically representative of the conditions likely to occur in the LMB
in future
Salinity in the Delta (2007-2013)
Sediment transport, nutrient transport (2009-2013)
Environmental, social and economic conditions – 2011 to 2012
(supplemented by data collected during 2014)
Baseline conditions

18. Study of the Impacts of Mainstream Hydropower on the Mekong Delta
Scenario 1 – Mainstream hydropower cascade
Scenario 2 – Mainstream hydropower cascade plus tributary
dams
Scenario 3 – Mainstream hydropower cascade plus water
diversions
Hydropower development scenarios