Water sources for energy development decline in quality, quantity

According to the 2011-2015 national report on the environment, Vietnam has average rainfall of 1,900-2,000 mm a year. It has 2,360 rivers which are 10 kilometers or more in length, including 109 main rivers.

The total annual surface water volume in Vietnam is 830-840 billion cubic meters, mostly in large river valleys, including Hong-Thai Binh, Bang Giang-Ky Cung, Ma, Ca, Vu Gia-Thu Bon, Ba, Dong Nai and Mekong.

However, 63% of Vietnam’s surface water (520 billion cubic meters) originates outside Vietnam and only 310 billion cubic meters are from Vietnam. 

According to MONRE (Ministry of Natural Resources and the Environment), although Vietnam has 1.5 times more than the average volume of water per capita in the world, it can only exploit a much smaller volume than normal compared to the availability. 

Any country with exploited water volume of less than 4,000 cubic meters a year would be listed as a country with water shortage, said IWRA (International Water Resources Association).

According to ADB (the Asian Development Bank), Vietnam is among the world’s top 10 and the region’s top 3 countries which have the lowest water resource security indexes. There is a shortage of clean water for several months of the year.

The total rainfall volume in Vietnam is high, but the rainfall varies among localities. 

The rainfall is high in Bach Ma area of Thua Thien – Hue province (8,000 mm a year), while it is very low in Phan Rang of Ninh Thuan and Phan Ri of Binh Thuan province (400-700 mm).

There are only two seasons – dry and rainy – in the Mekong River Delta. In dry season which lasts seven months, the rainfall just accounts for 10%, while 90% of rainfall comes in the 5-month long rainy season.

Mekong is the largest river system in Vietnam with 57% of the nation’s total water volume, which is 54 times higher than the water volume in the country’s northeast. 

The water capacity in flood season may reach 40,000 cubic meters per second, while it is just 2,500 cubic meters per second in the dry season.

The Institute of Meteorology and Hydrology has warned that drought has seriously threatened the Mekong Delta and the Central Highlands, and rising sea water levels have also posed additional threats to the quality of water resources.

About 82% of surface water is used for irrigation in agricultural production, 11% for aquaculture, 5% for industrial production and 3% for people’s daily use.