Unplanned withdrawal of groundwater and adverse impacts of climate change pose dangerous threat to the lives and livelihood of about 60 million people in Bangladesh, state-run news agency BSS reported Monday, quoting leading water and environment experts.

Water table of groundwater is declining rapidly due to its excessive use for irrigation in agriculture sector, which causes salinity water intrusion, posing a serious thereat to the ecosystem and biodiversity of the southern part of the country, said Md Eftekharul Alam, Agriculture, Water and Environment Engineer of Bangladesh Agricultural Development Corporation (BADC).

He said in Bangladesh, 80 percent of irrigation water and 98 percent of drinking water is collected from underground sources without proper study and planning.

"The groundwater is the most valuable natural resource of the country. If this resource is polluted by saline water intrusion, it will destabilize the food security, the ecosystem and biodiversity of the southern part," he added.

"Over mining of groundwater of Dhaka city and Gazipur (a district beside the capital) regions have accelerated the speed of these intrusions. If depletion trend of groundwater of Dhaka city continues, it may be filled in by salt water and thus cause the city dwellers to migrate due to the shortage of fresh water," Alam said.

According to Dhaka Water Supply and Sewerage Authority (WASA), its total water production is 2,100 million liters per day for nearly 12.5 million Dhaka city dwellers, of which 87.72 percent is groundwater and 12.28 percent is surface water.

The WASA said groundwater table is declining by 2-3 meters in Dhaka city every year due to overuse.

However, Alam said sea water level is increasing due to the adverse impact of climate change, which is responsible for saline water intrusion in coastal districts of the country. Sea water is also accessing to soil in coastal areas easily as water level of groundwater is going down gradually, creating a negative impact on agriculture sector, he added.

Professor Umme Kulsum Navera of Department of Water Resources Engineering of Bangladesh University of Engineering and Technology (BUET) said lack of adequate flow of surface water and different human induced hazards in coastal areas have increased the intensity of salinity on soil, which has created a serious threat to the agriculture sector and ecology.

She said many countries including Australia have stopped the use of groundwater for irrigation to maintain ecological balance. "We should reduce dependency on groundwater for both drinking and irrigation to protect our ecology and agriculture sector from any kind of destruction."