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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
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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
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
Study of the Impacts of Mainstream Hydropower on the Mekong River
Links between fisheries and hydrological cycle regimes
0
200
400
600
800
1000
12000
1-M
ay
29
-May
26
-Ju
n
24
-Ju
l
21
-Au
g
18
-Se
p
16
-Oct
13
-No
v
11
-De
c
08
-Jan
05
-Fe
b
05
-Mar
02
-Ap
r
30
-Ap
r
Wat
er
dis
char
ge (
m3/s
)
Day-month
High flow nursing and feedingin 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
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.
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
20
11
2012
2013
Pro
du
ctio
n (
ton
s)
Aqu
acu
lture
pro
du
ctio
n
(t x
10
00) Fish
Shrimp
Other aquatic 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
Inla
nd p
roducti
on (
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
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
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
Study of the Impacts of Mainstream Hydropower on the Mekong River
Fisheries Impact Assessment Methodology
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
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
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.
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
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
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
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
19
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00
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Cap
ture
fis
h y
ield
(t)
Mea
n a
nn
ual
wat
er le
vel (
m)
mean annual
Delta fishery
Tonle Sap
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
01/1
2/2
006
31/1
2/2
006
30/0
1/2
007
01/0
3/2
007
31/0
3/2
007
30/0
4/2
007
30/0
5/2
007
29/0
6/2
007
29/0
7/2
007
28/0
8/2
007
27/0
9/2
007
27/1
0/2
007
26/1
1/2
007
Avera
ge d
aily
wate
r le
vel (
m)
Tan Chau_SC0
Tan Chau_SC1
0
1
2
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8
9
10
01/1
2/2
006
31/1
2/2
006
30/0
1/2
007
01/0
3/2
007
31/0
3/2
007
30/0
4/2
007
30/0
5/2
007
29/0
6/2
007
29/0
7/2
007
28/0
8/2
007
27/0
9/2
007
27/1
0/2
007
26/1
1/2
007
Avera
ge d
aily
wate
r le
vel (
m)
Prek Kdam_SC0
Prek Kdam_SC1
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
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Are
a (h
a)
SC0 SC1
Vietnam Delta
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100000
200000
300000
400000
500000
600000
700000
800000
Are
a (h
a)
SC0 SC1
Cambodian floodplain
0
100000
200000
300000
400000
500000
600000
700000
800000
Are
a (h
a)
SC0 SC1
Tonle Sap
1206 t loss of fish production
56 t loss of fish production
2572 t loss of fish production
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
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
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
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
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
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
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
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
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
Study of the Impacts of Mainstream Hydropower on the Mekong River
Impact on aquaculture
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Tota
l aqu
acul
ture
pro
duct
ion
by p
rovi
nce
(t x
000)
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
Pro
duct
ion (
tons)
Aquacu
lture
pro
duct
ion (t
x 1
000) Fish
Shrimp
Other aquatic species
Pangasius - pond
Pangasius - cage
Shrimp - pond
Province
Species group
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
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
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