Massive deposit of silt in most of the rivers is the main cause as farmers can not use water from dying rivers, according to water and agriculture experts and environmentalists.

Farmers now use groundwater to meet about 56 per cent of their needs for irrigation, which was only 11 percent in 1978, according to data available from the Department of Agricultural Extension (DEA).

The districts are Jhenidah, Kushtia, Meherpur, Chuadanga, Magura, Jessore, Satkhira, Bagerhat, Narail and Khulna.

The trend is increasing as at least 15 rivers in the region have silted up.

DEA officials in Kushtia told this correspondent that the groundwater level has fallen by 3 to 4 feet last several years in the region.

This is damaging the soil structure, which will have disastrous affect on the ecology if not checked right now.

Damaged soil structure will make the area vulnerable to earthquake, according to environmentalists. Besides its effect on the greenery, fishery and crops, this will increase arsenic contamination of groundwater, they said.

Arsenic-free water is found deep into the soil. If the water level continues to fall, arsenic-free water will be beyond the reach of tubewells, they said.

According to the DEA, about 1161690 acres now under cultivation in the ten districts need irrigation for Aus, Aman and Boro crops. In many areas, farmers have to depend mainly on groundwater also during the wet season.

Seeing the prospect of use of surface water, the GK (Ganges Kabadak) project, the biggest irrigation project in the country, was launched in 1965 to irrigate five 5 lakh hectares in the ten districts. The project was designed depending on the mighty Padma and its 15 tributaries.

But water levels of Padma and its tributaries over the years has now made the project virtually useless. In last 15 years, the command area under the GK project was been reduced to 28 per cent. Only about 70, 000 hectares of land can be irrigated now under the project, sources said.

The rest lands under the project's command area using groundwater, extracted by pump.

According to DEA source, at least 17061 pumps are being used now for irrigation in the region. Of these 2742 are deeps tube wells, 11232 power pumps and 3087 hand tubewells, which irrigate about 158392 acres.

These pumps extracted over 33,000 crore cubic feet of groundwater last year, according to DAE.

The number of irrigation pumps are increasing every year. Only 6922 pumps were used in 1997.