VNMC Mekong Dam Study: Fisheries Impact Assessment
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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 presentation overviews their Fisheries Impact Assessment.
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VNMC Mekong Dam Study: Fisheries Impact Assessment
- 1. Study of the Impacts of Mainstream Hydropower on the Mekong Delta Greater Mekong Forum on Water, Food and Energy: Phnom Penh, Cambodia, 21 October 2015 Fisheries Impact Assessment INSERT PHOTOS HERE INSERT PHOTOS HERE
- 2. Study of the Impacts of Mainstream Hydropower on the Mekong River Outline • Background • Assessment Objectives • Indicators • Impact Assessment Strategy – Historical data – Research study – Data issues (limitations and challenges) • Results – Scenario 1 – 11 mainstream dams
- 3. Study of the Impacts of Mainstream Hydropower on the Mekong River Fisheries of the lower Mekong Basin Total first-sale value is US$7.0 billion per year • Per capita consumption average is about 46 kg/person/year 200+ species; 30+ of high commercial importance More than 50% of total fish catch in the lower Mekong basin (about 1.3 million tonnes worth US$2.5 billion) dependent on migratory fish Fish migrate all seasons of year
- 4. Study of the Impacts of Mainstream Hydropower on the Mekong River Links between fisheries and hydrological cycle regimes 0 200 400 600 800 1000 1200 01-May 29-May 26-Jun 24-Jul 21-Aug 18-Sep 16-Oct 13-Nov 11-Dec 08-Jan 05-Feb 05-Mar 02-Apr 30-Apr Waterdischarge(m3/s) Day-month High flow nursing and feeding in the floodplain Minimum flow refuge in dry season habitat (deep pool) Medium flow moving from mainstream to tributary Extreme flow spawning in the floodplain Medium flow migrating from floodplain to mainstream for dry season refuge
- 5. Study of the Impacts of Mainstream Hydropower on the Mekong River White fish: undertake long distance migrations, in particularly between lower floodplains and the Mekong mainstream and its major tributaries. Characteristics of the main fish groups Grey fish: ecologically intermediate between other groups - fishes that spend dry season in floodplain ponds, and do not undertake long distance migrations. Black fish: Floodplain resident fish, with limited lateral migrations from the river onto floodplains and no longitudinal migrations.
- 6. Study of the Impacts of Mainstream Hydropower on the Mekong River 0 500 1,000 1,500 2,000 2,500 1995 1996 1997 1998 1999 2000 2001 2002 2003 2004 2005 2006 2007 2008 2009 2010 2011 2012 2013 Production(tons) Aquacultureproduction(tx1000) Fish Shrimp Otheraquatic species Fisheries and aquaculture - status and trends 0 20,000 40,000 60,000 80,000 100,000 120,000 140,000 160,000 180,000 200,000 2000 2001 2002 2003 2004 2005 2006 2007 2008 2009 2011 Inlandproduction(tons) Cà Mau Bạc Liêu Sóc Trăng Hậu Giang Cần Thơ Kiên Giang An Giang Đồng Tháp Vĩnh Long Trà Vinh Bến Tre Tiền Giang Long An Inland capture Aquaculture Declining inland capture fisheries : Possible cause - disconnection of floodplain for rice – see later Growing aquaculture sector – based on intensification
- 7. Study of the Impacts of Mainstream Hydropower on the Mekong River Overview – cause effect of dams on fisheries Mainstream Hydropower Projects Changes in River Flows, Sediment Transport, and Water Quality Changes in Fish Habitat Quality, Quantity, & Productivity Obstructions in Fish Migration Routes & Habitat Connectivity Fish Abundance and Community Composition Yield and Consumption Social & Economic Impacts Other exogenous factors
- 8. Study of the Impacts of Mainstream Hydropower on the Mekong River Overview - questions Review designed to answer the following key questions: • How will changes in water flow regime, water quality, and connectivity of the Mekong River affect the species composition of catch and size of high economic value fish species? • What fish species will be affected significantly and how? • How much will capture and aquaculture fisheries production change and where? Assessment Scenario 1: 11 mainstream dams
- 9. Study of the Impacts of Mainstream Hydropower on the Mekong River Fisheries Impact Assessment Methodology
- 10. Study of the Impacts of Mainstream Hydropower on the Mekong River Assessment Indicators – linked to fish guilds Indicator Unit Comments Impact on capture fisheries Loss of fish catch yield tonnes, % Relate to hydrological and sediment variables and barrier effect.Loss of OAAs yield tonnes, % Loss of yield of economically important fish species tonnes Relate changes in exploitation patterns to hydrological change Species at risk species Determine number of species at risk Impact on aquaculture Change in extent of aquaculture area per species group ha Relate change in aquaculture production patterns to hydrological change and saline intrusion Change in production per aquaculture species group tonnes
- 11. Study of the Impacts of Mainstream Hydropower on the Mekong River Primary impact assessment –fisheries and OAAs Assessment methodologies • Alteration of habitat availability impacts • Hydrology/flow modification impacts on fish productivity • Sediment/nutrient loss on fisheries yield • Disruption to longitudinal connectivity (barrier and reservoir) impacts on fish migration and production • Changes in fish catch biodiversity • Impact of changes in water flow regime and water quality on aquaculture • Baseline fisheries and OAA yield based on Hortle 2007 consumption study
- 12. Study of the Impacts of Mainstream Hydropower on the Mekong River Impact assessment –fisheries data sources • Dai Fishery Monitoring Programme (DFMP), Tonle Sap, Cambodia (1994–2013); • Lee trap and Gill net Monitoring Programme Lao PDR (1994-2013) – outside impact assessment area • Vietnam fisher catch database-2005-Feb 2013 –good spatial and temporal coverage of catch composition and CPUE • GSO/MARD fish and aquaculture production data – 1990-2013 - • DoF fisheries and aquaculture production maps – prediction for future production areas • Fish Abundance and Diversity Monitoring Programme (FADMP) at up to 40 sites across the LMB (2003–2013) - provides spatial and temporal catch composition and CPUE per habitat and gear • Fish Larvae Density Monitoring Programme (FLDMP), Cambodia and Viet Nam (1999–2013) provides temporal fluctuations in catch composition and CPUE . • MDS fisheries surveys (2014) - provides catch composition and CPUE per habitat and gear.
- 13. Study of the Impacts of Mainstream Hydropower on the Mekong River Data Issues • Much of the available data – are fragmented and of varying quality and completeness – original purpose of data was not for focused impact assessment analyses. – Fish and fishery production vary substantially between years in response to varying climatic and hydrological conditions and not collected by standardised methods • GSO (VN) and FiD (Cam) known to underestimate fisheries harvest and lack cross validation. • Data generated by the MDS RIA2 study intended for use in impact assessment, but are collected over less than one year • Data constraining factors may influence robustness of the impact analyses and the interpretation of the tangible outputs
- 14. Study of the Impacts of Mainstream Hydropower on the Mekong River Fisheries Impact Assessment Alteration of habitat availability impacts • Areas of different habitats in impact area determined. • Fisheries productivity of different habitat types determined from literature and RIA2 study • Changes in wetted areas of different habitat types under scenario 1 determined using MDS hydrology model output. • Change in fisheries productivity calculated
- 15. Study of the Impacts of Mainstream Hydropower on the Mekong River Fisheries Impact Assessment Alteration of habitat impacts Yield-per-unit area (kg ha-1 yr-1) Guild Proportions Habitat category OAA Blackfish Whitefish Greyfish River-floodplain 250 0.11 0.39 0.43 0.18 Rainfed wetlands 100 0.11 0.95 0.00 0.05 Large water bodies outside flood zone 200 0.11 0.40 0.00 0.60 Inland capture fishery yield estimates for each major aquatic habitat category (Based on Halls 2014 and Hortle & Bamrungrach 2013
- 16. Study of the Impacts of Mainstream Hydropower on the Mekong River Fisheries Impact Assessment Flow modification impacts • Models of fish production versus hydrological variable developed for • VN freshwater provinces • Cambodian floodplain area • Dai fishery • Shifts in fisheries productivity due to changes in hydrological patterns predicted y = 47575x - 15010 R² = 0.5366 0 20000 40000 60000 80000 100000 120000 0 0.5 1 1.5 2 2.5 1995 1996 1997 1998 1999 2000 2001 2002 2003 2004 2005 2006 2007 2008 2009 2010 2011 2012 2013 2014 Capturefishyield(t) Meanannualwaterlevel(m) mean annual Delta fishery Tonle Sap
- 17. Study of the Impacts of Mainstream Hydropower on the Mekong River Fisheries Impact Assessment Flow modification impacts • SC1: No detectable change in flow level = no loss of fish production • Possible impact of onset and offset and duration of flood pulse on fisheries with other scenarios • Problem with external factors disrupting flow fisheries relationship, e.g. rice production 0 0.5 1 1.5 2 2.5 3 3.5 4 4.5 01/12/2006 31/12/2006 30/01/2007 01/03/2007 31/03/2007 30/04/2007 30/05/2007 29/06/2007 29/07/2007 28/08/2007 27/09/2007 27/10/2007 26/11/2007 Averagedailywaterlevel(m) Tan Chau_SC0 Tan Chau_SC1 0 1 2 3 4 5 6 7 8 9 10 01/12/2006 31/12/2006 30/01/2007 01/03/2007 31/03/2007 30/04/2007 30/05/2007 29/06/2007 29/07/2007 28/08/2007 27/09/2007 27/10/2007 26/11/2007 Averagedailywaterlevel(m) Prek Kdam_SC0 Prek Kdam_SC1
- 18. Study of the Impacts of Mainstream Hydropower on the Mekong River Fisheries Impact Assessment Alteration of habitat impacts Distribution of fisheries production (capture and culture) in the Mekong delta in Viet Nam 0 100000 200000 300000 400000 500000 600000 700000 800000 900000 1000000 Area(ha) SC0 SC1 Vietnam Delta 0 100000 200000 300000 400000 500000 600000 700000 800000 Area(ha) SC0 SC1 Cambodian floodplain 0 100000 200000 300000 400000 500000 600000 700000 800000 Area(ha) SC0 SC1 Tonle Sap 1206 t loss of fish production 56 t loss of fish production 2572 t loss of fish production
- 19. Study of the Impacts of Mainstream Hydropower on the Mekong River Fisheries Impact Assessment Assess potential impact of reduced sediment loading of fisheries yield on capture fisheries yield. • Tabulate potential changes in extent of fisheries yield per zone for each hydropower development scenario. • Evaluate potential impact of reduced sediment loading of fisheries yield
- 20. Study of the Impacts of Mainstream Hydropower on the Mekong River Fisheries Impact Assessment - - sediment Predicted loss of sediment and associated nutrients at Kratie and Tân Châu + Châu Đốc Scenario Total sediment (million tons/ per year) Kratie Tân Châu + Châu Đốc Baseline 54.6 32.1 Scenario 1 (11 dams) 22.4 13.9 Nutrient (remaining) Total nutrient (1000 tons/ per year) Kratie Tân Châu + Châu Đốc P Baseline 19.1 11.6 Scenario 1 (11 dams) 10.1 6.3 N Baseline 48.7 29.6 Scenario 1 (11 dams) 13.8 8.6
- 21. Study of the Impacts of Mainstream Hydropower on the Mekong River Estimated loss in bioavailable phosphorus and equivalent loss in fish (adjusted for double accounting for loss of white fish by barrier effect) and OAA yield in the Mekong Delta and Cambodian floodplain bioavailable P (t x 1000) bioavailable P (t x 1000) Yield (t) Yield (t) loss in aquatic production t Loss in aquatic production t Capture fisheries Kratie Tân Châu + Châu Đốc Cambodia floodplain and Tonle Sap Viet Nam Delta Cambodia floodplain and Tonle Sap Viet Nam Delta Baseline level (t x 1000/yr 19.1 11.6 481,537 692,118 Scenario 1 (11 dams) 10.1 6.3 [378,662] [585,120] 63931 64905 Fisheries Impact Assessment - sediment OAAs Baseline level (t x 1000/yr 19.1 11.6 105,467 160,705 Scenario 1 (11 dams) 10.1 6.3 82.935 135,861 22532 24844
- 22. Study of the Impacts of Mainstream Hydropower on the Mekong River Fisheries Impact Assessment Impact of loss of connectivity in Mekong by mainstream dams on fisheries Dam creates barrier • Interrupts migratory pathways – mitigate with fish passage facilities • Disruption of downstream passage – adults, eggs and larval stages • Reduction in species diversity and abundance Problems due to: • Loss of species migrating to spawning habitats • Impoundment floods spawning and nursery areas • Disruption of downstream flows • Limited passage over dams, especially for larval stages • Reduced flow through reservoirs -Impoundment acts as egg and larval sink • Passage through turbines
- 23. Study of the Impacts of Mainstream Hydropower on the Mekong River Fisheries Impact Assessment Impact of loss of connectivity in Mekong by mainstream dams on fisheries (Following procedures of Halls 2014) • Estimate loss of yield of whitefish caused by loss of migration potential caused by barrier • Fish species allocated to guilds • Estimate proportion of catch of white-long distance migrators, white –short distance migrators • Based on fisheries monitoring of catches – RIA2, MRC and national surveys • Change in fish production • ΔY = loss of white fish production • No account for replacement by grey + short distance whitefish
- 24. Study of the Impacts of Mainstream Hydropower on the Mekong River Fisheries Impact Assessment Disruption to longitudinal connectivity Contribution of fish species guilds to catches 40.02 17.44 10.27 17.08 13.06 2.10 whitefish grey fish black fish marine/estuarine exotics OAAs Vietnam Cambodia 40 % whitefish [33 species] in Vietnam highly vulnerable/at risk based on RIA2 study 37.20 33.40 28.90 0.20 whitefish grey fish black fish marine/estuarine
- 25. Study of the Impacts of Mainstream Hydropower on the Mekong River Fisheries Impact Assessment Disruption to longitudinal connectivity Fish production (t) SC0 -VN SC0-Cam SC1 -VN SC1-Cam Δ -VN Δ-Cam White fish loss Consumption (Hortle 2007) 692,118 481,537 415,271 303,368 - 276,847 - 178,169
- 26. Study of the Impacts of Mainstream Hydropower on the Mekong River Fisheries Impact Assessment Impact of changes in water flow regime and water quality on aquaculture. • Changes in water level for average, wet, and dry years determined from MDS model. • GIS modelling to determine extent of aquaculture production for key species and how it relates to flooding cycle. • GIS modelling of change in aquaculture production area caused by change in flood regime
- 27. Study of the Impacts of Mainstream Hydropower on the Mekong River Impact on aquaculture Distribution of aquaculture production areas) in the Mekong delta in Viet Nam Shrimp culture Extensive pond and flood forest areas Pangasius culture Intensive pond and cage production
- 28. Study of the Impacts of Mainstream Hydropower on the Mekong River Impact on aquaculture 0 500 1000 1500 2000 2500 1995 1996 1997 1998 1999 2000 2001 2002 2003 2004 2005 2006 2007 2008 2009 2010 2011 2012 2013 Totalaquacultureproductionbyprovince (tx000) Cà Mau Bạc Liêu Sóc Trăng Hậu Giang Cần Thơ Kiên Giang An Giang Đồng Tháp Vĩnh Long Trà Vinh Bến Tre Tiền Giang Long An 0 500 1,000 1,500 2,000 2,500 1995 1996 1997 1998 1999 2000 2001 2002 2003 2004 2005 2006 2007 2008 2009 2010 2011 2012 2013 Production(tons) Aquacultureproduction(tx1000) Fish Shrimp Otheraquatic species Pangasius - pond Pangasius - cage Shrimp - pond Province Species group
- 29. Study of the Impacts of Mainstream Hydropower on the Mekong River Impact on aquaculture • Changes in extent of aquaculture production of Pangasius negligible although expansion to coastal provinces may be affected by saline intrusion. • Negligible loss of mangrove area for shrimp culture under scenario 1 • May be indirect effects of ‘trash’ fish used for aquaculture feeds
- 30. Study of the Impacts of Mainstream Hydropower on the Mekong River Fisheries Impact Assessment – losses SC1 Indicator/Sub-indicator Vietnam Cambodia Baseline Fisheries yield1 (t) 692,118 481,537 Baseline OAA yield1 (t) 160,705 105,467 Loss of fish due to reduced habitat flooding (t) 721 1,650 Loss of OAAs due to reduced habitat flooding (t) 227 473 Loss due barrier effects of dams (t) [primarily white fish] 276,847 178,169 Loss of fish due to reduction in sediment loading and nutrients 63,931 64,605 Loss of OAAs due to reduction in sediment loading and nutrients 24,844 22,532 Cumulative loss of fish adjusting for whitefish loss due to barrier effects (t) 341,499 244,425 Cumulative loss of OAAs (t) 25,701 23,004 Total loss of capture fishery and OAA yield 366,570 267,428
- 31. Study of the Impacts of Mainstream Hydropower on the Mekong River Questions? Prepared by: Fisheries Team Leader: Prof. Ian Cowx Director, Hull International Fisheries Institute