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

Transcription

1 Technical Review of Pak Beng Hydropower Project Water Quality, Aquatic Ecology and Fisheries The 2 nd Regional Stakeholder Forum The Pak Beng Hydropower Project 5 th May 2017 Vientiane, Lao PDR 1

2 Outline of the Presentation 1. 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

3 Water Quality and Aquatic Ecology

4 Water quality class of the upper LMB Protection of aquatic life Human health in terms of human health acceptability A: High Quality ; B: Good Quality; C: Moderate Quality PBHPP Only general statements made about water quality current water quality monitoring carried out by PBHPP considered inadequate for impact assessment

5 Water quality issues 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 during inundation Eutrophication and algal growth [Thermal stratification] Water quality issues to be managed by good practice

6 Aquatic Ecology PBHPP 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

7 Modified Flows and Aquatic Ecology 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

8 Conclusions 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.

9 Alignment with PDG 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

10 Recommendations Programme for integrated monitoring of water quality, flows and habitats and aquatic ecology, coupled with indepth 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

11 Fisheries and Fish Passage

12 Fisheries in the Mekong Basin Pak Beng dam area in Zone 1 Pak Beng 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

13 PBHPP Fisheries assessment 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 inadequate to make any assessment missed species, size groups and wrong classification Rithron resident Main channel resident Main channel spawner Floodplain spawner Generalist Floodplain resident Estuarine Resident Anadromous Catadromous Marine Non native

14 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

15 Main Findings Fish Passage 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

16 Main Findings Fish Passage River flow Upstream Water levels Downstream Water levels BIOLOGY HYDROLOGY Migration Flows HYDRAULICS Depth Velocity Turbulence Discharge Roughness Fish Passage Options Cost & Benefit Analysis Proper decision

17 Main Findings Fish Passage Flow & migration 1 Year Recurrence Flow = 5,000 m 3 /s (smallest peak every year) 24,000 Main Fish Migration Season 18,000 Potential spillway operation during flow peaks: June November 12,000 6,000 0 Spillway operational over 5771 m 3 /s (powerhouse max. flow) Mean flow J F M A M J J A S O N D Chiang Sean (upstream of Pak Beng) Peak flows Spillway Spillway Operation - unknown M

18 Main Findings Fish Passage Flow & migration Practical flow range for upstream fish passage 1,887 m 3 /s to 5,000 m 3 /s (1 Year Recurrence Flow = smallest peak every year) 5 m (PBHPP) Dam 9 m 5,000m 3 /s 2 m (PBHPP) M

19 Main Findings Fish Passage Proposed Fishpass Entrance end section High flow, 5,000 m3/s 9 m entrance underwater 2 m (PBHPP) 310 m 312 m 308 m Low flow, 1,887 m 3 /s entrance perched 310 m 312 m 308 m 17 m

20 Main Findings Fish Passage Proposed Fishpass Entrance by PBHPP Proposed Fishpass Attraction zone of migratory fish Fishway underwater at high flows Electric fence Turbines Attraction zone high flows Spillway

21 Main Findings Fish Passage Proposed Upstream Fishpass recommendations General 1. Requires functional compatibility with Xayaburi 2. Review design options (function first, then cost benefit) Specific 1. Abandon electric fence (does not work in large rivers) 2. Relocate main entrance to powerhouse (turbines) 3. Add entrances at all turbines (collection gallery) same as Xayaburi 4. Cut channel from fishpass to deep channel of river (for large fish) 5. Scale physical modelling in hydraulics laboratory

22 Main Findings Fish Passage Proposed Upstream Fishpass recommendations Specific 6. Flow proposed: 14.4 m 3 /s (< 1% of min. flow) required: m 3 /s (10% of flow) 7. Increase tailwater range (channel height) to 9 m 8. Change slope from 1:54 (too steep, turbulent for fish) to 1:100 to 1:200 (standard for bypass channels) 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)

23 Main Findings Fish Passage Proposed Upstream Fishpass recommendations Do Physical modelling Review fishpass options. Use 187 m 3 /s to 500 m 3 /s. If bypass channel, use a 1:100 to 1:200 gradient. Cut deep channel or Shape thalweg to lead to main fishpass entrance Add collection gallery to direct migratory fish to the fishpass Remove electric fish barrier Multiple exits, if dam used at multiple levels. Add fish passage function to fish lock

24 Main Findings Fish Passage Downstream Fish Passage 1. Through the reservoir 2. Turbines 3. Spillway (Fishpass and navigation lock negligible downstream passage)

25 Main Findings Fish Passage Downstream Fish Passage 1. Through the reservoir Drifting eggs and larvae Reservoir Dam

26 Main Findings Fish Passage Downstream Fish Passage 1. Through the reservoir Mitigation: manage reservoir water levels and velocities

27 Main Findings Fish Passage Downstream Fish Passage 2. Turbines Impacts i.) Blade strike ii.) Pressure impacts iii.) Shear Mitigation Screens for larger fish Deep turbines- CFD Turbine design

28 Main Findings Fish Passage Downstream Fish Passage 3. Spillway Overshot better than undershot Recommend PBHPP change spillway gates to overshot; or Operate fully lifted

29 Downstream Fishpass recommendations Fish screen for medium and large fish to the fishpass 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) Change undershot gates to overshot design, if gates used partially open. Assess reservoir manage egg and larval drift, with hydraulic modelling

30 Main Findings Fish Passage Pak Beng and Xayaburi Strategic Scenarios Scenario 1. Re design Pak Beng fishpass Scenario 2. Wait for monitoring results of Xayaburi fish passage Hold funds Address only FEEG recommendations that are not costly Address all FEEG recommendations Monitoring of Xayaburi fish passage Fish passage ineffective Likelihood: Very High Fish passage effective Likelihood: High Xayaburi fish passage effective Use findings to enhance Pak Beng Design Use funds for fish passage at Pak Beng Xayaburi fish passage ineffective Use funds for offsets (e.g. multiple small fishways)

31 Fish Passage and Fisheries Ecology Assessment 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

32 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.

33 Alignment with PDG 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

34 Recommendations (1) 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

35 Recommendations (2) 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

36 Thank you! 36