Technical Review of Pak Beng Hydropower Project –Water ......1 The nd2 Regional Stakeholder Forum The Pak Beng Hydropower Project 5th May 2017 Vientiane, Lao PDR Technical Review

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The 2nd Regional Stakeholder ForumThe Pak Beng Hydropower Project5th May 2017 Vientiane, Lao PDR

Technical Review of Pak Beng Hydropower Project – Water Quality, Aquatic Ecology and Fisheries

Outline of the Presentation1. Water quality and aquatic ecology

• Main Review Findings• Conclusions• Alignment with PDG• Recommendations

2. Fisheries and fish passage• Main Review Findings• Conclusions• Alignment with PDG• Recommendations

Water Quality and Aquatic Ecology

Water quality class of the upper LMBHuman health in terms of human health acceptabilityProtection of aquatic life

A: High Quality ; B: Good Quality; C: Moderate Quality

PBHPPOnly general statements made about water qualitycurrent water quality monitoring carried out by PBHPPconsidered inadequate for impact assessment

• Increased sediment due to excavation, earth moving, construction of roads, deforestation, etc.

• Increased organic pollution from worker camps and human population expansion.

• Accidental spillages during construction.• Changes in sediment dynamics during operation• Decomposition of vegetation duringinundation

• Eutrophication and algal growth• [Thermal stratification]

Water quality issues to be managed by good practice

Water quality issues

• Aquatic ecological surveys in dry (January 2011) and rainy seasons (July 2011) at 6 locations in project area.

• Sampling restricted to basic plankton net trawling (59 µm mesh), Eckmann grabs for benthic invertebrates

• PBHPP conclusion: poor benthic macroinvertebrate diversity

Overall sampling frame and description of biota highly superficial and limited number of samples precludes any definitive assessment of the current baseline status.

No analysis of value of habitats that will be lost, or potential impacts on wider LMB ecosystem

Aquatic Ecology PBHPP

• Transboundary flow impacts appear to be related to BDP2, 6‐cascade dam scenario (MRC 2010) and not specifically Pak Beng

• Flood events during early wet season largely eliminated.

• Loss of dry season low flows.

Transboundary effects, especially the impacts in the productive floodplain reaches of Laos, Cambodia and the Delta have not been explored

Modified Flows and Aquatic Ecology

• Baseline assessment of water quality and aquatic ecology in the PBHPP EIA and EMMP is limited.

• No modelling of likely impacts on aquatic habitats, and thus aquatic biota. Including in downstream reaches.

• Water quality issues during the construction period can be largely managed through good practice.

• Water quality during operation managed through vegetation management in reservoir.

• EIA and EMMP deficient in description of aquatic habitats including geomorphology and hydraulics of the channel likely to be affected, the habitats and their ecological significance.

• Potential large scale disruption of ecosystem services.

Conclusions

• Documents provided only partial alignment with PDG

Addressing Water Quality problems seems acceptable but needs more attention to monitoring

Addressing potential flow alteration and impact on ecology less clear

Potential loss of habitat not been effectively addressed.

No specific provisions to avoid, minimise or mitigate against the loss of critically endangered or endangered species, or to monitor these impacts

Alignment with PDG

• Programme for integrated monitoring of water quality, flows and habitats and aquatic ecology, coupled with in‐depth studies into the fisheries of the region need to be designed and implemented.

• Full EIA, based on in‐depth studies, needed before any decisions on impacts can be made – currently PNPCA is scoping analysis

• Relationships between impact of PBHPP and other dams requires full assessment

• Assessment of long‐distance transboundary impacts of modified flows and sediments on change in habitat, productivity and aquatic ecology required

Recommendations

Fisheries and Fish Passage

Fisheries in the Mekong Basin

Pak Beng Pak Beng dam area in Zone 1

Fisheries have high ecological and

socio‐economic importance

200+ species; 30+ of high

commercial importance

Higher number of endemic species

Several critically endangered &

endangered species (IUCN red list)

Catch in zone 1 = 40‐60,000 tonnes

Rithron resident

Main channel resident

Main channel spawner

Floodplain spawner

Generalist

Floodplain resident

Estuarine Resident

Anadromous

Catadromous

Marine

Non‐native

• Fisheries surveys based on two sampling periods at 6 locations in the project area

• Sampling by 50‐m beach seine plus market surveys

• PBHPP Conclusion: species composition and abundance already low

• FEEG conclusion: fisheries surveys inadequateto make any assessment –missed species, size groups and wrong classification

PBHPP Fisheries assessment

Justification for fish passage facilities

Many species migrate through Zone 1 including Mekong

giant catfish

Large number of individuals and high biomass of fish

Range of species and sizes of individuals

Migration in all seasons

includes surface, mid‐water and bottom dwelling fishes

Upstream and downstream migration need addressing

Two components to fish passage:

1. Attraction (fish need to find the entrance)‐ Proportion of flow‐ Upstream limit of migration ‐ Discrete of flow for fish to locate

2. Passage (fish need to swim through channel safely)‐ Fish behavior‐ Swimming ability

Main Findings ‐ Fish Passage

River flow‐ Upstream Water levels ‐ Downstream Water levels

Migration Flows

HYDRAULICS

Cost & Benefit Analysis

HYDROLOGYBIOLOGY

Fish Passage Options


DepthVelocityTurbulenceDischargeRoughness

Proper decision

Flow & migration

J F M A M J J A

M

S O N D

24,000

6,000

12,000

18,000

0

Main Fish Migration Season

Mean flow

Peak flows

Chiang Sean (upstream of Pak Beng)

1 Year Recurrence Flow = 5,000 m3/s(smallest peak every year)

Spillway

Spillway Operation- unknown


Spillway operational over 5771 m3/s (powerhouse max. flow)

Potential spillway operation during flow peaks: June – November

Dam

M

Flow & migration• Practical flow range for upstream fish passage• 1,887 m3/s to 5,000 m3/s (1 Year Recurrence Flow = smallest peak every year)

5 m (PBHPP)

9 m5,000m3/s

2 m (PBHPP)


Proposed Fishpass Entrance – end section

308 m

310 m312 m

Low flow, 1,887 m3/s‐ entrance perched

17 m

308 m

310 m312 m

High flow, 5,000 m3/s‐ entrance underwater

9 m

2 m (PBHPP)


Proposed Fishpass Entrance by PBHPP

Fishway underwater at high flows

Turbines

Spillway

Attraction zone of migratory fish

Attraction zone ‐high flows

ProposedFishpass

Electric fence


Proposed Upstream Fishpass recommendations

1. Abandon electric fence (does not work in large rivers)

3. Add entrances at all turbines (collection gallery)– same as Xayaburi

1. Requires functional compatibility with Xayaburi

2. Review design options (function first, then cost‐benefit)

General

Specific

2. Relocate main entrance to powerhouse (turbines)

4. Cut channel from fishpass to deep channel of river (for large fish)

5. Scale physical modelling in hydraulics laboratory


Proposed Upstream Fishpass recommendations

6. Flow ‐ proposed: 14.4 m3/s (< 1% of min. flow) required: 187‐500 m3/s (10% of flow)

8. Change slope from 1:54 (too steep, turbulent for fish) to 1:100 to 1:200 (standard for bypass channels)

Specific

9. Do hydraulic design of fishpass (only a concrete channel shown)

10. Do hydraulic design of exit (probably need 5, not 2 exits, if dam used at multiple levels)

7. Increase tailwater range (channel height) to 9 m



Add collection gallery to direct migratory fish to the fishpass

Remove electric fish barrier

Multiple exits, if dam used at multiple levels.

• Review fishpass options.• Use 187 m3/s to 500 m3/s. • If bypass channel, use a 1:100

to 1:200 gradient.

Do Physical modelling

Cut deep channel or Shape thalweg to lead to main fishpass entrance

• Proposed Upstream Fishpass recommendations

Add fish passage function to fish lock

Downstream Fish Passage

1. Through the reservoir

2. Turbines

3. Spillway

(Fishpass and navigation lock negligible downstream passage)


Drifting eggs and larvae

DamReservoir

1. Through the reservoirDownstream Fish Passage


1. Through the reservoir


Mitigation: manage reservoir water levels and velocities



2. Turbines

i.) Blade strikeii.) Pressure impacts iii.) Shear

Mitigation

Screens for larger fishDeep turbines- CFDTurbine design

Impacts


Downstream Fish Passage3. Spillway

Overshot better than undershot

• Recommend PBHPP change spillway gates to overshot; or

• Operate fully lifted


Downstream Fishpass recommendations

Fish screen for medium and large fish to the fishpass

Change undershot gates to overshot design, if gates used partially open.

Assess reservoir – manage egg and larval drift, with hydraulic modelling

Turbines: Do computer modelling (CFD) to assess impacts of shear and pressure. Assess blade strike of small fish that pass through the fish screen. If required, modify turbine blades and redesign turbines (deep turbines)

Pak Beng and Xayaburi Strategic Scenarios

Use funds for offsets

(e.g. multiple small fishways)

Use funds for fish passage at

Pak Beng

Fish passage effective

Monitoring of Xayaburi fish passage

Hold funds

Fish passage ineffective

Likelihood:Very High

Likelihood: High

Scenario 1. Re‐design Pak Beng fishpass

Address only FEEG recommendations that are not costly

Xayaburi fish passage ineffective

Use findings to enhance Pak Beng

Design

Address all FEEG recommendations

Xayaburi fish passage effective

Scenario 2.Wait for monitoring results of Xayaburi fish passage


Fish Passage and Fisheries EcologyAssessment of other mitigation measures proposed by PBHPP

Proposed measures weak and only relate to management of fish production in reservoir

No measures to compensate for lost wild fish production, especially for rural poor who will not be able to take up fish farming

No indication is given what fisheries personnel provided to support fisheries and aquaculture development

Stocking measures are not considered adequate because of impoundment hydrology and impacts of stocking exotic/invasive species

Fish Passage and Fisheries Ecology

Monitoring

Insufficient information on monitoring before, during & after construction

Does not address downstream passage success and survival through turbines

Underfunded

Many issues not covered, especially social and economic impacts and livelihoods analyses.

• Documents provided only partial alignment with PDG Fish passage facilities highly superficial Planning and design of the fishways not fully integrated into

the dam design and relationship to downstream dams has not be explored

Weaknesses in the ecological appraisal of the fisheries around PBHPP related to effectiveness of fish passage facilities for the diversity of species

No information on the hydrological and hydraulic conditions in and around the dam site and proposed fish passage facilities

Information on monitoring and evaluation superficial and needs full specification

Alignment with PDG

1. Recommendations regarding fish passage design:

Full review of upstream/downstream passage options,

including cost and benefit analysis

Workshop with Developer’s Design Team to further

evaluate the design and risks, and develop solutions

Recommendations (1)

2. Full fish ecology and fisheries impact assessment required: To fill gaps about fish ecology and fisheries and loss of

biodiversity in relation to dam operation

Transboundary fisheries impact assessment required

3. Programme for fish management and monitoring required:

Social and economic livelihoods impact analysis

Develop detailed monitoring and mitigation programme,

especially to mitigate or compensate for loss of fisheries

Develop sustainable fishery management system

Recommendations (2)

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Thank you!