VietNamNet Bridge – The water monitoring results show that the underground water resources have been decreasing in many places. Meanwhile, the underground water has also got infected with ammonium and arsenic, which is a big threat to local residents who cannot access the national water supply system.
According to Dr Nguyen Thi Ha from the Center of Water Resource Monitoring and Forecasting under the Ministry of Natural Resources and the Environment (MONRE), in the Northern Delta, the water levels at some monitored places, including Mai Dich, Cau Giay in Hanoi, have decreased nearly to the allowed limits.
In some other areas of Hai Hau, Truc Ninh, Nam Dinh, Quynh Phu and Thai Binh, the decreased water levels are still within the safety line. However, scientists have warned that the aquifer has complicated hydrogeological conditions; therefore, it is necessary to apply necessary measures to prevent the saltwater intrusion caused by the water exploitation.
The monitoring results showed that in the dry season, 17 out of 32 water samples have manganese content higher than the allowed standards, four have the As content higher than the allowed level. The highest As content was 0.1500mg/l, or three times higher than the allowed level.
Meanwhile, in rainy season, 12 out of 30 samples were found as having the manganese content exceeding the allowed level, and 4 samples have As concentration higher than the allowed level. Especially, all the 18 samples have the NH4+ much higher than the allowed level.
In the southern delta, in some monitored places, the water levels have dropped deeply approaching to the allowed levels, especially in districts 1 and Binh Tan in HCM City.
Only the water quality in the Central Highlands remains relatively good which does not show signs of the underground water pollution. The concentration of microelements in the underground water can meet standards, except manganese. 13.4 percent of water samples in dry season and 4.35 percent of samples in rainy season have the manganese concentrations higher than the allowed standards.
Dr Nguyen Thi Ha stressed that it is necessary to give warnings about the salinity intrusion. The underground water being exploited is fresh water. However, the aquifers above and under the exploited one are salt water. The overexploitation may lead to the intrusion of the salt water into the fresh water aquifer.
To date, in Vietnam, there has been no thorough research work about the salinity intrusion into fresh water aquifers. However, scientists say it’s necessary to give warnings about the possibility of fresh water turning salt water.
Dr Tran Hong Con from the University of Natural Sciences under the Hanoi National University said that the decrease of the underground water and the pollution have been warned for a long time. However, all the measures applied so far still cannot help improve the situation, while the water quality is getting worse.
In principle, underground water can recover itself, but the natural water recovery would not be enough to satisfy the overly high demand. The water overexploitation may lead to the earth sinking, and badly affect the quality of underground water.
Experts have pointed out that in order to prevent the underground water from “reaching the bottom,” it is necessary to adjust the exploitation capacity. They have also called on to strictly control the drilling of wells for water. Meanwhile, there has been no regulation on the exploitation and the use of water from drilled wells.