Downstream Impacts of Lancang Dams in Hydrology, Fisheries And

Downstream Impacts of Lancang/ Upper Mekong Dams: An Overview

Pianporn Deetes International Rivers August 2014

• In the wet season, the Lancang dams run at normal operation levels for power generation and release extra water if the water level exceeds normal water level. • In the dry season, Xiaowan and Nuozhadu will generally release the water to downstream dams so that to ensure other dams can run at full capacity. • The total storage of six complete dams is 41 km3. And the total regulation storage is 22 km3

Dam Name Installed Dam Height Total Regulation Regulation Status Capacity (m) Storage storage Type (MW) (km3) (km3) Gongguoqiao 900 130 0.32 0.05 Seasonal Completed (2012) Xiaowan 4200 292 15 10 Yearly Completed (2010) Manwan 1550 126 0.92 0.26 Seasonal Completed (phase 1 in1995 and phase 2 in 2007) Dachaoshan 1350 118 0.94 0.36 Seasonal Completed (2003) Nuozhadu 5850 261.5 22.7 11.3 Yearly Completed (2012) Jinghong 1750 118 1.14 0.23 Seasonal Completed (2009) Ganlanba 155 60.5 Run-of- Planned river Hydrology Flow Lancang dams has increased dry season flows and reduces wet season flows: • At China border, the flow can increase as much as 100% in March due to the operation of Manwan, Daochaoshan Jinghong and Xiaowan dams (Chen and He, 2000) • On average, the Lower Lancang cascade increased the December–May discharge by 34 to155 % and decreased the discharge from July to September by 29–36 % at Chiang Saen station (Rasanen, 2012) • After the Manwan Dam was built, the average minimum flow yearly decreased around 25% at Chiang Saen (Zhong, 2007)

Rasanen (2012) Hydrology Water Level Monthly average water level data from Chiang Khong clearly showed the impacts of the first filling of Nuozhadu Dam.

Nuozhadu Phase Nuozhadu 1 and 2 Filling Phase 3 Filling 7.00

6.00

5.00 4.00 3.00

2.00 Water Level (m) Level Water 1.00

0.00

2011-1 2011-2 2011-3 2011-4 2011-5 2011-6 2011-7 2011-8 2011-9 2012-1 2012-2 2012-3 2012-4 2012-5 2012-6 2012-7 2012-8 2012-9 2013-1 2013-2 2013-3 2013-4 2013-5 2013-6 2013-7 2013-8 2013-9 2014-1 2014-2

2011-10 2011-11 2011-12 2012-10 2012-11 2012-12 2013-10 2013-11 2013-12

Year-Month Monthly water level

1996-2013 Average monthly water level Regulation capacity of the Lower Lancang Cascade is equal to Nuozhadu Dam reservoir capacity. We should expect similar changes happening near the end of dry season and the beginning of wet season every year, because the dams need to refill back to normal water levels after losing water to regulate other dams in the dry season. Delayed wet season and longer dry season is expected, esp in the dry year. Sedimentation

• Half of the sedimentation in Lower Mekong originates from the Lancang basin, which is about 80 million tons per year. • In the first ten years of Manwan Dam’s operation, the annual mean sediment trapped by the Manwan Dam was about 35% of total sedimentation transported from Lancang Basin to Lower Mekong. • Sedimentation at Chiang Saen has reduced by over 50% after Manwan Dam was built.

Estimation of Sediment trapped by the Manwan Dam (1993-2003)

20 Sediment (million tons) (million Sediment 10

0 1993 1994 1995 1996 1997 1998 1999 2000 2001 2002 2003 -- The reduction of sedimentation downstream not only can lead to riverbank erosion, but also reduces the nutrients carried in the flow and deposited in fertile flood plain areas, which in turn may decrease the biodiversity productivity. -- These impacts aren’t easily observed in a short term, but accumulate over the long-term. Sedimentation • Kummu (2007) estimated the theoretical trapping efficiency figures for each dam and the whole cascade of dams would theoretically trap 94% of the suspended sediment load coming from China

Xayaburi Dam Site 17 December 2013 Chiang Saen February 2014

Chiang Khan March 2014

Unusual Water Fluctuation: drastic impacts on ecosystems and livelihoods

Fish migration patterns and fisheries are affected impacts on dry-season riverbank agriculture (income, food security, etc.) No more Kai No one is taking responsibility... Key issues: - Upper Mekong dams built without consultation

- regional corporation with China has been challenging

- failure of MRC to be able to address the problems (needs political will to reform)

“Even though we don not build (dams), the Chinese will build (dams) anyway. ”

Xayaburi dam, July 2014

Thank you