Đang tải... (xem toàn văn)
It is a paper from FAO organization that related to forecast Flood and simulate River Basin in the Mekong basin. This paper addresses the topic of floods in this river and its tributaries. In the Mekong, the ratio between 10% low flows and 10% high flood discharge is approximately 50. Years with severe floods were 1961, 1966, 1971, 1978, 1984, 1991 and 1995. Despite the high discharges, it is not common for Mekong River floods to cause casualties. The principal problem from floods is damage to crops and infrastructure. In 1995, for example, severe floods caused substantial damage in the Vientiane Plain of Laos. During that monsoon, an area of approximately 40 000 ha was flooded resulting in a damage estimated at US21 million.
http://www.fao.org/DOCREP/004/AC146E/AC146E04.htm Technical Session III (Contd.) Flood forecasting and river modelling of the Mekong Basin Introduction The Mekong is ranked among the largest rivers of the world. The river drains an area of approximately 600 000 km 2 , covering parts of China, Myanmar, Thailand, Laos, Cambodia and Viet Nam (Figure 1). At Kratie, close to the upstream part of the Mekong Delta, the average annual discharge equals 437 billion m 3 /s, or an average discharge of around 14 000 m 3 /s. Downstream of Kratie, the river enters the extremely flat and low lying Mekong Delta. This paper addresses the topic of floods in this river and its tributaries. In the Mekong, the ratio between 10% low flows and 10% high flood discharge is approximately 50. Years with severe floods were 1961, 1966, 1971, 1978, 1984, 1991 and 1995. Despite the high discharges, it is not common for Mekong River floods to cause casualties. The principal problem from floods is damage to crops and infrastructure. In 1995, for example, severe floods caused substantial damage in the Vientiane Plain of Laos. During that monsoon, an area of approximately 40 000 ha was flooded resulting in a damage estimated at US$21 million. In view of the frequency of the floods, a good forecasting system is a necessity to improve the preparedness of the population to floods and to support evacuation plans. Since 1970 the Mekong Secretariat (now called the Mekong River Commission Secretariat, or MRCS) has operated a flood forecasting system for the Mekong River during the flood prone months from July to October. Over the past decades many dikes were built along the Mekong River, in particular along the borders with Thailand. Secondary effects of these dikes are the increase in downstream flood levels as a result of the reduction in flood plain storage, the faster propagation of floods along the river and impeded drainage of tributaries, causing local floods. However, there are also other factors contributing to a reduction of flood levels. In the Mekong Basin many reservoirs have been built or are under construction, which store water from the rainy season for use during the dry season, either for hydro-electric power production and/or for irrigation water supply. Incidentally, such reservoirs may have a negative impact on flood levels as a result of changing lag times between peaks or the delay in conveyance of water from the watersheds. Adri Verwey, River Modelling Specialist, WL/Delft Hydraulics, Netherlands FIGURE 1 Basin of Lower Mekong River [...]... develop the understanding of the flood mechanism of the Vientiane Plain This would also allow for a comparison of the floods occurring with and without the reservoir or the routing of other historic floods, such as the 1996 event; compare various options of controlled flooding of the Vientiane Plain and prioritize these in terms of various options of protecting parts of the flood plain, e.g construction of. .. Mekong River The level of protection against such floods, so far, is low Floods are a yearly returning threat to the farmers cultivating their crops in the vicinity of the Mekong River One of the most densely populated areas of the country is the Vientiane Plain, located North of the capital Vientiane, between the Nam Ngum I Reservoir (Figure 9) and the confluence of the Nam Ngum and Mekong Rivers The. .. monitoring of the Nile River Basin Introduction The Nile River is no doubt one of the great natural wonders of the world With an estimated length of over 6 800 km and a total area of about 3.2 million km2 it is the longest river in the world and one of the five largest in terms of size of its drainage area Yet, its annual runoff is more than modest as compared to other rivers in the world and the Nile River. .. building Flood control: example of Bangladesh Flood control in the flood plains of the Mekong Basin has already been applied on a substantial scale in Thailand The primary reason for flood control is the protection of agricultural production In larger river systems, with an often rather predictable time of arrival of the flood peak, the concept of controlled flooding has been introduced Controlled flooding... that almost all the runoff in the Nile Basin is generated on an area covering only 20% of the basin, while the remainder of its drainage area is in arid or semi-arid regions where the runoff is minimal or zero and where evaporation and seepage losses are large The major runoff contributing areas in the basin are located in the Ethiopian Highlands of the Blue Nile sub-catchment and in the Equatorial... in the Nile Basin, such as the D.R Congo for example, the Nile waters form only a small part of their total water resources Other Nilotic countries, as Rwanda, Uganda, Sudan and Egypt, are almost completely dependent on the Nile Basin for their water resources While all the water in Burundi and Rwanda and more than half of the water in Uganda is generated inside the countries' borders, most of the. .. locations The total package of modelling support, therefore, would include the following model components: • • • flood prediction model of the Vientiane Plain, for the study of the effects of flood propagation through the Plain as a result of the controlled and/ or uncontrolled upstream discharges, Mekong levels and the flood control works which could be constructed in the Plain The tools should preferably... evaluated the Mekong Hydrology Programme (MHP) seeking donor assistance for the execution of various projects The outcome was the recommendation to give priority to institutional strengthening of the Mekong Secretariat, both through capacity building and through the development of support software After the signing of the new agreement on continued co-operation on the Mekong in 1995 and the formation of MRC,... downstream of the Nam Ngum dam site with a catchment area of 5 212 km2; • additional local rainfall on the Vientiane Plain and the remaining part of the Lower Nam Ngum catchment, which has an area of 3 363 km2 of the total 16 963 km2 of the complete Nam Ngum catchment; and • high Mekong River levels, which impede drainage from the Vientiane Plain via the Nam Ngum River One of the factors that influenced the. .. per year In the text that follows more information is given about the importance of the Nile water for the basin countries as well as the description of several technical cooperation projects and activities executed within the FAO Nile Program which are addressing some of the many water resources and flood management issues in the Nile river basin The role of Nile water resources in the basin countries . Session III (Contd.) Flood forecasting and river modelling of the Mekong Basin Introduction The Mekong is ranked among the largest rivers of the world. The river drains an area of approximately. Thailand. Secondary effects of these dikes are the increase in downstream flood levels as a result of the reduction in flood plain storage, the faster propagation of floods along the river and. the banks of the Mekong River. The level of protection against such floods, so far, is low. Floods are a yearly returning threat to the farmers cultivating their crops in the vicinity of the