The reservoir at Son La plant, Vietnam's largest hydro power project, began to receive water on Saturday as the plant is scheduled to start running at the end of this year.
Prime Minister Nguyen Tan Dung said the event was really important as it marked the beginning of a new power source that can boost the country's development, and that of the northwest region in particular.
Putting the first unit of the 2,400-megawatt plant on line in December, or two years earlier than previously planned, would mean a great deal for the economy and prove that Vietnamese people are capable of building large power projects, Dung said in a statement published on the government's website.
Construction of the US$2.3-billion project in the northern province of Son La is scheduled to be completed in 2012. The reservoir has the capacity to store 9.26 billion cubic meters of water.
Power demand in Vietnam is set to rise 18 percent this year on the back of an economic recovery.
The lack of water in reservoirs because of drought conditions will translate into a loss of nearly 1 billion kilowatt-hours of electricity at hydro power plants, the government said in a statement in April.