4.Water Related Issues in the Asian River Basins
International Research Center for River Basin Environment University of Yamanashi
Specific characteristics of water problems in eight typical river basins in Asia are examined. The eight rivers are the Changjiang River in China, the Mekong River in Mainland Southeast-Asia, the Chao Phraya River in Thailand, the Brantas River in Java Island in Indonesia, the Syr Darya River in Central Asia, the Tigris-Euphrates River in the Middle East, the Yamuna River in India and the Saigon-Dong Nai River in Vietnam. Various kinds of water problems reflecting natural and social conditions in each region are discussed. Typical issues are shown as follows.
The Dongtinghu Lake areas along the Changjang River, which wer traditionally used for storing floodwater, have been increasingly used as farm and residence areas. No retarding ponds in the area were used for flood control even in the severe flood in 1998. Since then, clear provisions have been written in the Chinese law for flood defense to provide for appropriate usage of retarding ponds.
The Mekong River Commission is categorizing the water related problems in the Mekong River basin. Many efforts have been made to improve water use in the basin. Any development plan should be based on sufficient scientific knowledge. The Mekong Region is referred to as a “data rich, but information poor region”, due to gaps in information flow. The Mekong River Commission needs to address the challenges ahead in integrating and translating the generated knowledge and information.
The lower part of the Chao Pyraya basin consists of floodplain and has a high flood risk. Urbanization has increased the potential risk of damage.Integrated flood control combining both hard and soft countermeasures taken in the Bangkok Metropolitan area has been very effective, and it can be recommended to other urbanized areas in Asian monsoon regions.
In the Brantas River basin, the population and the GDP have increased and the goals of the master plans were achieved. However, the sedimentation caused by volcanic ash and increased utilization of the land surface due to increased human activity decreased the effective water storage of the reservoirs in the upper and middle reach of the river.Because of this, serious degradation of the riverbed downstream has occurred.
The Toktogul dam reservoir in the upper part of the Syr Darya River was constructed in the Soviet era for irrigation in the lower areas in summer using water stored during winter. After the collapse of the Soviet Union, the upper country occupied the dam reservoir, and it used and released much water for getting hydropower in winter. Uncontrolled water use in the upper country in the winter season caused flooding in winter and also caused water shortages in summer in the other lower countries. Moreover, soil salinity was observed in fields downstream.
The Euphrates River is different from the rivers in humid monsoon areas where water can be used at least during the rainy season. The water resources of the Euphrates River are mostly zero sum situations. Therefore, having a round table discussion among the river engineers of all the countries involved is thought to be important for integrated water management of the region.
According to the result of water quality measurement in the Yamna River, its quality is strongly affected by the direct urban wastewater drainage in the dry season. The result of water sampling at typical residential areas shows that pollutant load in the slum areas is lower than that in the other residential areas of the city.
Due to population increase, new problems have emerged in the Saigon-Dong Nai River basin. They are related to uncontrolled cage fishery in reservoirs, solid waste dumping in swampland, shrimp farming,the destruction of mangrove forests, deforestation due to coffee and sugar cane plantation and water pollution due to domestic and industrial effluents. Basin wide, scientific, integrated, river basin management is needed for sustainable development.