FISHERIES IMPACT ASSESSMENT

Transcription

1 FISHERIES IMPACT ASSESSMENT

2 2 Key strategic question To what extent can mainstream dams alter fish biodiversity, fish migration patterns and fish catches in the Mekong aquatic systems? Outline 1- Baseline situation (reminder) Main features Future trends without LMB mainstream dams 2- Impact assessment (future trends with LMB mainstream dams) Methodology Preliminary findings Generic findings Findings by zone

3 Baseline 3

4 4 Black fishes: migrate between floodplains and ponds White fishes: migrate between floodplains and remote tributaries Grey fishes: migrate between floodplains and local tributaries

5 5 Nam Chi Even in absence of mainstream dams a number of sub-basins will be blocked to migrations Nam Mun Dams existing Dams under construction BDP definite future scenario

6 6

7 7 Relative sustainability (no unit, level 100 in year 2000) Capture fish production is expected to decline in the future even in the absence of mainstream dams

8 8 Aquaculture will plateau soon in Vietnam, within 15 years in Thailand, and will remain low in Laos and Cambodia

9 Summary 9 The Mekong River has the second highest fish biodiversity in the world Mekong fisheries produce million tonnes each year; this represents 7 to 22% of the world s freshwater fisheries Capture fish production is huge and not yet declining, but will not increase in the future The migratory fish resource at risk from mainstream dam development ranges between 0.7 and 1.6 million tonnes per year LMB countries consume the most freshwater fish in the world Freshwater fish supply is critical for food security in the basin, particularly in Cambodia. Aquaculture cannot replace capture fish production

10 Impact assessment METHODOLOGY 10 Gongguoqiao Xiaowan Manwan Dachaoshan Jinghong Nuozhadu Ganlanba Mengsong Pak Beng Luang Prabang Upstream cluster Xayaburi Pak Lay Sanakham Pak Chom Middle cluster Ban Koum Latsua Downstream cluster Don Sahong Stung Treng Sambor ICEM MRC SEA of mainstream hydropower Impacts Assessment Workshop May 2010 Present dams Planned dams

11 Fraction of the river network blocked by dams 11 Methodology Heart of the migratory system = downstream floodplains Km 2 of watershed upstream not accessible to migrations upstream of a given dam Use of BDP2 development scenarios Assessment of cumulative surface area of watershed obstructed by dams

12 Number of dams:

13 Wetlands, floodplains and fish productivity 13 Floodplains Wetlands (= floodplains + rice fields + permanent water bodies + aquaculture + swamps)

14 14 Methodology LMB wetlands = 184,900 km 2 LMB floodplains = 50,152 km 2 Rice fields = floodplain rice fields (high fish productivity) + rainfed rice fields (RRF, lower fish productivity) Floodplain productivity: low=50kg/ha/year, average= 119± 25 kg/ha/year, high=200 kg/ha/year

15 Fish production of dam reservoirs 15 Methodology Review of reservoir production figures in the Mekong and in Asia Analysis of the best predictor of reservoir fish production area Calculation of i) surface area of each mainstream reservoir ii) average and cumulated surface area of reservoirs in tributaries

16 Proportion of white and black fish basinwide 16 Methodology Method 1: mainstream catch monitoring (MRC ) Method 2: surveying experts Method 3: catch statistics in Cambodia Method 4: update integrating black fish production in non-floodplain rice fields

17 Long-distance migrants and fish production 17 Methodology i) Use assessment of dominant species in catches basinwide (Halls and Kshatriya in press) ii) Use all migration maps from MFD2003 iii) Combine all ecological information in FishBase and MFD 2003 migration patterns and contribution to catches of 43 long-distance migrants representing 30% of the total catch

18 Impact assessment 18 I. PRELIMINARY FINDINGS

19 2015: Dry season Q: %; wet season WL: - 50 to 60 cm Hydrological changes (i) 2030 no MD: Dry season Q: %; wet season WL: - 0 to 50 cm 2030, 6 MD: Dry season Q: %; wet season WL: -50 to 70 cm , 9 MD: Dry season Q: % 2030, 11 MD: Dry season Q: %; wet season WL: -50 to 70 cm 2015: Dry season Q: +32%; wet season WL: - 30 cm 2030, no MD: Dry season Q: +31%; wet season WL: - 40 cm 2030, 6 MD: Dry season Q: +32%; wet season WL: - 50 cm 2030, 9 MD: Dry season Q: +33% 2030, 11 MD: Dry season Q: +33%; wet season WL: - 50 cm 2015: Dry season Q: %; wet season WL: - 30 cm, Floodplains: -251,000 ha 2030 no MD: Dry season Q: %; wet season WL: -20 to 60cm 2030, 6 MD: Dry season Q: %; wet season WL: -20 cm 2030, 9 MD: Dry season Q: % 2030, 11 MD: Dry season Q: %; wet season WL: -20 to 60 cm, Floodplains: -309,000 ha

20 Hydrological changes (ii) 20 Floodplain before the dam Dry season water level Losses in floodplains should be computed as the surface area that will not be flooded any more in the wet season plus the surface area that will be permanently flooded in the dry season. Floodplain after the dam Wet season water level Area not flooded any more in the wet season New area permanently flooded in the dry season Areas characterized by loss of flood pulse = loss of productivity

21 Hydrological changes (iii) 21 Hydrological changes detailed by BDP2 are seasonal; these changes are minimal compared to daily variability in downstream water levels following peak operation. Problem already experienced with the Yali Falls dam in Vietnam. This daily variability is expected to have major effects on fish resources and on the environment in general and cannot be ignored in future analyses. Louang Prabang Seasonal variation from baseline (cm) in nearest hydrological monitoring site Wet season: 68 Dry season: +149 Xayaburi Wet season: 68 Dry season: +149 Pak Lay Wet season: 68 Dry season: +149 Pakchom Wet season: 53 Dry season: +145 Latsua Wet season: 47 Dry season: +51 Stung Treng Wet season: 47 Dry season: +51 Sambor Wet season: 61 Dry season: +85 Daily variation in the reservoir (cm) Mode of operation 200 Peak load h/day 0 NA Peak load 8 10 hours/day 200 Continuous 200 Peak load >16 hours/day 200 Continuous small NA

22 Proportion of white and black fish basinwide 22 between 35% and 70% of the fish production basinwide is made of long-distance migratory species vulnerable to mainstream dam development 70% the current level of knowledge does not allow a lower uncertainty range. 35%

23 Fish production of dam reservoirs 23 for mainstream dams, the surface area alone is the best single predictor of reservoir productivity productivity ranges between 20 kg/ha/year and 200 kg/ha/year largely unpredictable nature of reservoir fish production

24 Impact assessment 24 II. GENERIC FINDINGS

25 Fraction of the river network blocked by dams 25 In 2000, 20.6% of the Lower Mekong Basin was already barred by 16 dams In 2015, 23.6% of the LMB will be barred to fish migrations due to 47 dams on tributaries In 2030: if no mainstream dams are built, 37.3% of the LMB will be inaccessible to long distance migrant fish because of 77 dams on tributaries if mainstream dam development is limited to the 6 dams of the upstream cluster, then 68.7% of the basin will be barred if 9 mainstream dams are built (but none in Cambodia) then 78.8% of the basin will not be accessible to long distance migrant fish. if 11 mainstream dams are constructed, then 81.3% of the watershed will be obstructed and fish migrating from floodplains fish will not be able to migrate further than Kratie (Sambor dam)

26 100,000 Km 2 of watershed upstream of the dam 200, , , , , ,000 Stung Treng Sambor Latsua Don Sahong Ban Kum Pakchom Pakbeng Luangprabang Xayabuly Paklay Sanakham 26 Luang Prabang Pak Beng Xayaburi Pak Lay Sanakham Pak Chom Ban Koum Latsua Don Sahong Stung Treng Sambor

27 Fraction of the mainstream turned into a reservoir 27 Calculated after dams heights and a digital terrain model Upstream cluster Middle cluster Downstream cluster Dam Reservoir length (km) Pak Beng 180 Luang Prabang 150 Xayaburi 100 Pak Lay 110 Xanakham 90 Pak Chom 85 Ban Koum 155 Lat Sua 10 Don Sahong 5 Stung Treng 45 Sambor 90 Total length of reservoirs (km) River length (km) % of mainstream turned into a reservoir Total

28 Fraction of the mainstream turned into a reservoir 28 If 11 reservoirs are built, 55% of the mainstream in the LMB will be turned into a dam reservoir. If 6 dams are built between Chiang Saen and Vientiane, then 90% of the Mekong mainstream between these two points will be turned into a reservoir ecosystem. If Cambodian dams are not built but 9 other mainstream dams are, then 48% of the mainstream in the LMB would be turned into a reservoir. Stung Treng + Sambor reservoirs = 1/3 of Tonle Sap surface area

29 Fish production of dam reservoirs 29 Predict fisheries production in reservoirs Range of productivity based on previous cases (20 to 200 kg/ha/year) Most important characteristic is surface area (less important is depth)

30 30 Combination of surface areas of reservoirs created by mainstream dams (150,000 ha) and fish productivity of reservoirs (20 to 200 kg/ha/year depending on reservoir characteristics): the highest fish production to be expected from reservoir fisheries in mainstream dams amounts to 30,000 tonnes basinwide. in fact the most likely production represents about 10,000 tonnes.

31 Long-distance migrants and fish production white fish species, 30% of the catch of the fish catch basinwide: 95% of them (= 28.5% of the catch basinwide) migrate through Khone Falls; 2/3 undertake a migration between Khone Falls and upstream >27 species Vientiane >28 species >15 species Mun/Chi >41 species Khone Falls 3S >25 species Kratie >43 species >28% of total catch

32 Impact assessment 32 III. FINDINGS BY ZONE

33 Upstream cluster 33 The migration barrier effect would apply to 40 sub-basins Hydrologically, the area is dominated by the influence of Chinese dams A drop in the recruitment of local species is expected even in absence of mainstream dams. The contribution of these upstream species to the fish biodiversity of the basin is very important (in particular Balitoridae) 90% of the river in this section will be converted to reservoirs if 6 mainstream dams are built

34 Upstream cluster species are specifically at risk, including the Giant Mekong catfish (at risk of extinction if dams completed) The risk of fish production losses in case the 6 upstream mainstream dams are built amounts to 130, ,000 tonnes. Reservoir fish production would range between 2,000 and 20,000 tonnes of fish, the most likely estimate being around 7,000 tonnes

35 Middle cluster 35 The migration barrier effect would apply to = 80 sub-basins The Latsua dam would have much more negative impact on fish migrations than the Ban Kum dam because it would block access to the Mun/Chi system (70,000 km2). The Latsua dam would have the same impact than the Pak Mun dam on Mundependent fish species, plus additional impact on species migrating up the mainstream. Mekong River THAILAND Mun River Ban Kum Pak Mun Border LAOS Latsua Ban Koum Latsua

36 Middle cluster 36 The Ban Koum and Latsua mainstream dams would result in some 78% of the Basin being blocked to migrating fish These dams would create 147 km 2 of reservoir, i.e. 23% of the mainstream between Pakse and Vientiane would be turned into a reservoir. These reservoirs can be expected to produce between 300 and 3,000 tonnes of reservoir fish, the most likely estimate being 330 tonnes The risk of capture fish production losses in case the 2 mainstream dams of the middle cluster are built amounts to 210, ,000 tonnes

37 Downstream cluster 37 The migration barrier effect would apply to = 86 sub-basins, including the Sekong-Sesan-Srepok system (second largest in Mekong) Overall, these dams would be those blocking most migration routes and thus would have the biggest impact on fish resources.

38 Downstream cluster 38 The risk of fish production losses in case the 2 mainstream dams of the downstream cluster are built amounts to 220, ,000 tonnes The loss of floodplains inherent to these dams corresponds to 3,000 to 12,000 tonnes of fish only The Stung Treng and Sambor mainstream dams would create 950 km2 of reservoir. This area can be expected to produce between 2000 and 19,000 tonnes of reservoir fish, the most likely estimate being 8,000 tonnes

39 39 IV. CONCLUSIONS

40 40 The 11 dams, if built as planned, would result in a loss of fish production ranging between 700,000 and 1.4 million tonnes In the same conditions, the recent BDP2 report on fisheries impact predicts a loss of 600,000 tonnes The most conservative estimate common to all studies and reports is a loss of 600,000 tonnes of annual fish production in case of hydropower development. This corresponds to the whole freshwater fish production in West Africa (15 countries) Reservoir fisheries from mainstream dams will not compensate for losses in capture fisheries, since they will produce at most 30,000 tonnes per year

41 41 If all 11 dams are built, then 55% of the Lower Mekong mainstream will be turned into a reservoir The planned dams will not be uniformly damaging to fisheries, certain dams having more impact than others: Latsua blocking the large Mun/Chi system Stung Treng/Don Sahong blocking Khone Falls Sambor largest dam blocking 78.8% of the Mekong system

42 42 Several additional aspects relating to fisheries remain to be addressed: Impact of sediment retention on water and fish production Effect of changes in species composition on nutritional value Effect of changes in species composition on market value of fisheries products Effect of changes in fish and fisheries on socio-economics of various social groups The present study is an initial attempt to assess the impact of investments worth USD 18,847 million on a resource worth USD 2,100 3,800 million. The magnitude of possible impacts calls for major investment in view of assessing in detail the impacts of hydropower development on food security and livelihoods in the Mekong Basin.

43 Thank you!