VietNamNet Bridge – City authorities are planning several emergency response scenarios in case the main dam of the Dau Tieng Irrigation Reservoir in southwestern Tay Ninh Province collapsed or if the reservoir discharged too much water.

Hoa Binh Street in HCM City's Tan Phu District was flooded after prolonged heavy rain. Most low-lying areas in the city will be flooded if the main dam at the Dau Tieng Irrigation Reservoir in the southwestern province of Tay Ninh collapses.

Most low-lying areas in HCM City will be flooded if this scenario occurred, according to participants at a meeting held by the HCM City People's Committee on Wednesday.

The country's largest irrigation reservoir provides water for agriculture and industry as well as household use in Tay Ninh, Binh Duong and Long An provinces and HCM City as well. It also controls salt-water intrusion into the Sai Gon and Vam Co rivers.

The reservoir, which is located upstream of the Sai Gon River, is designed to release up to 2,800 cubic metres of flood water a second. However, the reservoir has released only 200-600cu.m of flood water a second over the past few years.

Tran Cong Ly, deputy head of the city's Steering Committee for Flood and Storm Prevention and Control and Rescue, said at the end of 2008 the reservoir released water at a speed of 400cu.m a second, flooding many areas in HCM City within two hours.

The city at that time asked the Ministry of Agriculture and Rural Development for assistance in controlling the discharge of water at the reservoir.

If the reservoir releases water at a speed of 2,800cu.m a second, about 26,000ha of land in 111 communes and wards in neighbouring Binh Duong Province and HCM City will be flooded, according to the ministry's Irrigation Department.

If the reservoir's main dam breaks, about 34,000ha of land in 125 communes and wards in Binh Duong Province and HCM City will be flooded, said the Irrigation Department.

Irrigation officials said that it was unlikely the reservoir dam would break, but warned that inclement weather or an earthquake could lead to collapse.

If a break occurred, the city's Cu Chi District would be 10.25 metres under water within three hours and 17 minutes, and the city's centre area would be 2.15 metres under water within 24 hours.

If such a break occurred with floods from upstream areas, Cu Chi District could be 12 metres under water within two hours and eight minutes, and the city's centre area 2.4 metres under water after 23 hours and 18 minutes, officials have projected.

Le Manh Ha, deputy chairman of the HCM City People's Committee, said the setting up of emergency-response scenarios would mitigate the damage caused to people and property.

Ha has asked the city's Steering Committee for Flood and Storm Prevention and Control and Rescue to set up detailed scenarios.

Various departments and city districts would then use these scenarios and base their plans to relocate residents to safe areas and deal with the consequences of flooding.

Built in 1981 and put into use in 1985, the reservoir's main dam is made from soil. It is 28 metres high, 1,100 metre long and eight metres wide.

The reservoir's secondary dam is 27 metres high, 27,000 metres long and five metres wide.

The reservoir's lowest water level is 17 metres and highest water level, 26.3 meters. When water reaches the highest level, the reservoir contains more than 2 billion cubic metres of water.

Source: VNS