Abstract
The downstream impact of dams is a complex problem in watershed management. In the upper Mekong River watershed and its main channel, dam construct ion projects were started in the 1950s to meet increasing demands for energy and food production. Dams called the Mekong Cascade were completed on the Mekong River in China, the Manwan Dam in 1996 and the Dachaoshan Dam in 2003. We evaluated the impact of the Manwan Dam and its related watershed development on seasonal water discharge and suspended sediment transportation using hydrologica l simulations of target years 1991 (before dam construction) and 2002 (after dam completion). Our study area was the main channel of the Mekong River in northern Thailand extending about 100 km downstream from the intersection of Myanmar, Thailand and Laos. We used the MIKE SHE and MIKE11 (Enterprise) models to calculate seasonal changes of water discharge and sediment transport at five points 15- 35-km apart in this interval. Sediment load was calculated from a regression equation between sediment load and water discharge, using suspended sediment concentrations in monthly river water samp les taken between November 2007 and November 2008. Finally we estimated annual sediment load alo ng the study reach using from both of simulated ann ual hydrograph and the regression equation. Our simulat ions showed that after construction of the dam, the re was a moderate decrease in peak discharge volume and during the rainy season in August and September and a corresponding increase in the subsequent mont hs. Accordingly, sediment transportation budgets we re increased in months after the rainy season. The sus pended sediment transportation in Chiang Sean was increased from 21.13 to 27.90 (M ton/year) in our m odel condition.
Highlights
The Mekong River is the largest international river in East Asia, with a watershed area of 795,000 km2 and a main channel 4800 km long
We evaluated the impact of the Manwan Dam and its related watershed development on seasonal water discharge and suspended sediment transportation using hydrological simulations of target years 1991 and 2002
The period of decreasing flow was delayed from September to October in the 1991 hydrograph, which we attribute to a prolonged rainy season that year
Summary
The Mekong River (called the Lancang River in China) is the largest international river in East Asia, with a watershed area of 795,000 km and a main channel 4800 km long. Its watershed includes parts of six countries: China, Myanmar, Laos, Viet Nam, Thailand and Cambodia. Within this watershed, traditional social and industrial activities have long been conducted in harmony with the ecological services associated with the Mekong River (Hudson-Rodd and Shaw, 2003; Ringler and Cai, 2006). Six more dams are under construction or in the planning stage These dams are the first constructions in history to have blocked the Mekong River (Hu et al, 2009; Zhai et al, 2010). The social impacts and the effects on watershed ecosystems downstream of these dams as transboundary environmental issues has brought international attention (Bai et al, 2009; Cui et al, 2007; Tilt et al, 2009; Wei et al, 2007; Webby et al, 2007)
Sign-in/Register to view highlights & summary Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call