In Soc Trang, the worst hit province, more than 5,600ha were lost, according to the Southern Irrigation Science Research Institute.

The winter-spring crop a few months ago was similarly affected, with drought and saline water destroying 5,300ha in the country's rice granary.

Ponds for storing water to be used in agricultural production go dry in the suothern province of Kien Giang. Dorought has destroyed a large area of rice in the Mekong Delta

Speaking at a seminar held in Can Tho City on Monday, Tang Duc Thang, the institute's head, said seawater has entered deep into the delta since January.

"In some rivers, saline water has entered more than 60km from the mouth."

This year it has occurred a month earlier than usual and severely hit coastal provinces like Tien Giang, Ben Tre, Tra Vinh, and Soc Trang.

At the seminar, the Ministry of Agriculture and Rural Development said authorities in the delta have to take active steps to check the seawater intrusion and safeguard freshwater sources.

It also asked them to upgrade irrigation works and regularly update forecasts about water availability.

The delta provinces have to ensure that the area they have under rice is appropriate for existing conditions, it said.

Participants told the meeting that the southern region faced a severe water shortage in the dry season that just ended.

The water level in the Mekong's upstream is now 10-40 per cent lower than normal, they said.

Quach Van Nam, director of Soc Trang' Province's Department of Agriculture and Rural Development, said the region needs more money to upgrade irrigation canals to fight drought and seawater intrusion during the summer-autumn and autumn-winter crops.

The provinces also need money for forecasting water availability to effectively regulate irrigation systems, he said.

Thang listed the things that need to be done in future to fight drought and seawater intrusion — building the Cai Lon and Cai Be sluice gates to preserve freshwater in coastal areas, setting up electric pumping stations in the delta, and building sluice gates at river mouths where the salt content of water reaches four grammes per litre. The Government has approved a grant of VND282 billion (US$13.4 million) for the delta and south-central regions to buy seeds and fight drought and the intrusion of saline water.

The delta is expected to plant 700,000ha of rice for the autumn-winter crop between now and August.