BNU Ecological effects & Hydropower dams & Transboundary river 11 th International River International Riversymposium and Environmental Flows Conference, Brisbane, Australia 3 rd, September, 2008 Hongjuan ZHAI (Zhai H.J.) School of Environment, Beijing Normal University, China Email: zhaichina@hotmail.com
Recent work National Key Basic Research Development Program of China (973)- Ecosystem changes in Longitudinal Range-Gorge Region (LRGR) and transboundary eco-security in southwest China (No. 2003CB415104) Fiver famous academies in China have been working on this program since 2003. Hydropower cascade construction International highways construction
LRGR
Lancang-Mekong Distribution of hydrological stations River Basin China Yunjinghong Length: 4880km Annual mean discharge is 4750 10 8 m 3 Chiang Saen Yunjinghong station-the last national hydrological station before Lancang River flows out of China; Chiang Saen station-the first hydrological station on the mainstream of the Lower Mekong River.
Main results Flow Water level Sediment
Flow (He et al., 2006) The tributaries between the Yunjinghong station and the border of China and Laos generate 15.44% (113.7 10 8 m 3 ) of the total annual average flow of Lancang watershed. China Lancang-Mekong river Yunjinghong station Since this portion of the runoff is below Jinghong Dam, is not affected by the construction or operation of the Lancang Cascade. Mouth Burma Laos Chiang Saen Station Thailand National boundaries
Flow Simulated monthly runofff changes under the regulation of Lancang Cascade (He et al., 2006) Runoff change (%) 120 100 80 60 40 20 0-20 -40 Jun. Jul. Aug. Sep. Oct. Nov. Dec. Jan. Feb. Mar. Apr. May. The runoff change due to the operation of the Manwan and Dachaoshan dams is not significant. As the completion of Xiaowan Dam, the operation of Lancang Cascade will have significant effects on flow distributions, especially on dry seasons. Month Affected by Manwan and Dachaoshan dams Affected by Manwan, Jinghong, Dachaoshan and Xiaowan dams
Water level Intra-annual allocations of monthly water level (H) (Li et al., 2006) 10 1987-1992 1993-1996 8 1997-2003 (a) Yunjinghong 9 8 7 6 1987-1992 1993-1996 1997-2003 (b) Chiang Saen H/m 6 4 H/m 5 4 3 2 2 0 0 Jan. Feb. Mar. Apr. May. Ju Jul. n. Aug. Sep. Oct. Nov. Dec. Jan. Feb. Mar. Apr. May. Ju Jul. n. Aug. Sep. Oct. Nov. Dec. 1 Month Month Main causes: Flow from upstream (China); High local inflow between the two hydrological stations.
Sediment Theoretical trapping efficiencies for individual dams of Lancang Cascade 1 0.9 0.8 0.7 0.6 0.5 68.0% 59.2% 76.0% 89.0% 82.6%81.7% 61.0% 91.9% 67.5% 62.2% 92.2% 62.7% 0.4 0.3 0.2 0.1 0 Liutongjiang Jiabi Wunonglong Tuoba Huangdeng Tiemenkan Gongguoqiao Xiaowan Manwan Dachaoshan Nuozhadu Jinghong TE(%) Reserviors
Sediment Monthly mean sediment concentration at the two stations (Fu et al., 2006) Chiang Saen station 2.0 Dachaoshan Dam was closed. Sediment concentration (kg/m 3 ) 1.0 0 0 1.5 3.0 1987 1989 1991 1993 1995 1997 1999 2001 2003 4.5 Yunjinghong station
Sediment Regression scatters points of the sediment concentration at the two stations (Fu et al., 2006) Maximum mean monthly sediment concentration 2.5 0.10 Mean annual sediment concentration 0.8 Minimum mean monthly sediment concentration Chiang Saen (kg/m 3 ) 2.0 1.5 1.0 0.5 Chiang Saen (kg/m 3 ) 0.08 0.06 0.04 0.02 Chiang Saen (kg/m 3 ) 0.6 0.4 0.2 Yunjinghong 0 1 2 3 4 Yunjinghong 5 0 0.05 0.10 0.15 0.20 Yunjinghong 0 0.5 1.0 1.5 2.0 Yunjinghong 0.8km-the sediment concentration restored to 89% of the saturation (Qian, et al, 1987; 1983). 314km: Dachaoshan Dam-Yunjinghong station; 662km: Dachaoshan Dam-Chiang Saen station. Main Drivers: 1 Manwan Dam; 2 Dachaoshan Dam; 3 Land use change in northern Laos. Downstream erosion
Main transboundary problems The ecological effects of Manwan Dam and Dachaoshan Dam are not significant on downstream countries. However, significant problems will be rushed after the operation of Xiaowan Dam and Nuozhadu Dam. The main effects will occur in the Laos and the northern Thailand. Flow--- ---Changes of intra-annual annual flow distribution patterns; Sediment--- ---Downstream erosion between Yunjinghong and Chiang Sean stations.
Main water use China Hydropower (Mainstream); Navigation (Mainstream). Burma The effects of dam constructions on water use in Burma is limited. LRGR Laos Navigation (mainstream); Hydropower (tributary). Cambodia Assure the water balance of Tonle Sap Lake; Agricultural irrigation. Thailand Agricultural irrigation. Vietnam Prevention of encroachment of sea water in dry season; Agricultural irrigation; Water pollution control; Flood control.
Regulation system Find main transboundary security problems Flow decrease Water pollution Sediment decrease Barrier Main driving forces Analyze problems Characteristics Negative effects Positive effects Distribution patterns Solve problems International cooperation Policy and law construction Ecological compensation Monitoring platform
For more information: http://www.lancang-mekong.org/ zhaichina@hotmail.com hongjuanzhai@hotmail.com