1 The Red-Thai Bin river water system
The Red river basin originating from China territory and flowing into the South China Sea covers in total 169,000 km2. The part in Viet Nam occupies about 86,660 km2 including lands of the Hanoi capital and other 25 provinces in the North of Viet Nam with a population of 26 million persons and total agricultural lands of nearly 1.1 million hectares. Average annual rainfall is about 1900 mm in the part in Viet Nam (the basin average is 1500 mm a year approximately). Although large-scale multipurpose reservoirs such as Hoa Binh, Thac Ba and Tuyen Quang were built in the upper basin in Vietnam with total storage capacity around 15 billion m3 (active storage capacity of 9 billion m3), droughts have frequently happened in the dry seasons since 2005 because of climate change effects and irrational coordination in water release to the downstream. This caused difficulties to water users such as water supply, irrigation, navigation, power generation, environment protection and salinity prevention.
Conflicts among water uses, especially between agriculture, environment protection and power generation are more and more serious, in particular in dry seasons. Run-offs to downstream in the dry seasons of 2006 and 2007 have known a record reduction for last 100 years. Hundred thousands hectares of agricultural lands faced water shortage, navigation was interrupted, and water environment was seriously polluted resulting in mass fish death in Ha Nam province. At early 2006, water shortage interrupted domestic water supply to Phu Ly town and surroundings for a week causing inconveniences and difficulties to local people. Currently, two sub-basins of the Red river basin, i.e., Nhue-Day and Cau sub-basins are most hit by pollution in Vietnam because of water drying up as the primary reason (To Trung Nghia and Le Hung Nam, 2007). In the flood season, water conflicts between flood control and power generation and water storage for the downstream.
At present, the coordination for optimization of multipurpose multi-reservoir operation in the Red-Thai Binh river basin is not thoroughly studied due to inadequate methodologies, technologies and financial resources. Domestic researches had just dealt with reiteration to select regulation alternatives for the reservoirs but not addressed optimization of the system operation and of water uses which implies difficulties in negotiations on and compromises among water uses.
According to predictions on climate change published in 2007 by IPCC and UNDP, Vietnam is among the developing countries mostly hit by negative impacts of global climate changes, in particular of droughts, floods and sea level raising. Therefore, studies to assess water conflicts and current conditions of reservoir system operation as basis for introduction of optimization methodology for multipurpose multireservoirs are important in facilitating the proposal of rational operating rules for reservoir systems to meet the harmony of water uses and adapt to negative variations of climate changes in coming time.
In Vietnam, the water use optimization has been preliminarily studied and successfully applied in various researches and planning projects carried out by Institute of Water Resources Planning using GAMS technology (General Algebraic Modelling System) (To Trung nghia and Le Hung Nam, 2008; To Trung Nghia et al., 2006). Water use optimization is now emphasized in the world, notably the Decision Support System for Participatory and Integrated Planning with the multipurpose optimization software TwoLe developed by Politechnico di Milano (Italy). TwoLe is an advanced software with salient advantages and successfully introduced in recent practical applications (Soncini-Sessa et al., 2007a, Soncini-Sessa et al., 2007b). The combination of domestic and international advances, in particular the TwoLe of Politechnico di Milano is suitable to deal with water resources management and multipurpose multi-reservoir operation optimization in the Red-Thai Binh river basin in adapting to climate change.
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