'Excess groundwater use threat to agriculture'

Excessive and unplanned use of groundwater for irrigation across the country poses a serious thereat to the ecology, severely affecting the agriculture sector, said water and agriculture experts yesterday.
They said different parts of the country, particularly the southern region, already experienced an adverse impact of the excessive use of groundwater.
Agriculture, water and environmental engineer of Bangladesh Agricultural Development Corporation (BADC) Dr Md Eftekharul Alam spoke to the news agency recently.
He said groundwater is being used for irrigation largely in an unplanned manner, contributing to its misuse and causing an immense negative impact on ecology and agriculture.
Nearly 13 lakh tube wells, mostly shallow, are being used to draw groundwater for irrigation. But eight lakh tube wells are enough to meet the demand, he said.
Dr Eftekhar said excessive numbers and the short distance between each tube well and other machineries used to lift groundwater pushed down the water level rapidly.
Referring to a study of his, Dr Eftekhar said irrigation using the existing flooding method is 34 percent efficient.
He suggested increasing efficiency to ensure proper utilisation of groundwater in the agriculture sector to maintain the ecological balance.
Water distribution and marketing system should be improved to prevent misuse, which will also cut production costs, he added.
Groundwater level is gradually declining in different magnitudes across the country as irrigation still depends largely on groundwater, Dr Iftekhar said.
Water tables of many regions including Gazipur, Mymensingh, Netrakona, Kishoreganj, Jessore and Khulna are going down at an alarming rate, he added.
He mentioned that water level of sadar upazila in Gazipur district declined by 66 feet in the last six years, 15 feet at Bhaluka in Mymensingh and on an average three feet at Jessore, Kushtia and Khulna regions.
The country's ecology and crop production, particularly in the southwestern region, will face an extreme impact if the declining trend continues, he added.
BADC officials said, according to a Minor Irrigation Survey Report (2009-10), groundwater covered 41,27,387 hectares in the last Rabi season, 79.10 percent of the total irrigated area measuring 52,17,626 hectares.
Meanwhile, surface water irrigation covered 10,90,239 hectares, 20.90 percent of the total irrigated area, they added.
Engineer Taqsem A Khan, managing director of Dhaka Water Supply and Sewerage Authority (Wasa), recently gave a keynote presentation on Dhaka Wasa's production for nearly 12.5 million city dwellers.
He said of the 2,100 million litres of water prepared per day, 87.72 percent comes from underground while the rest from the surface.
Referring to different environmental impacts of groundwater use, he said groundwater table in Dhaka city is declining by two to three metres per year due to overuse.
This decline is due to the inadequate recharging of groundwater, said Prof Umme Kulsum Navera of Department of Water Resources Engineering of Bangladesh University of Engineering and Technology (Buet).
Many countries including Australia stopped using groundwater for irrigation to maintain the ecological balance, she said.
“We should reduce dependency on groundwater for both drinking and irrigation to protect our ecology and agriculture sector from any kind of destruction.
“Overuse of groundwater has various negative impacts on the soil and the environment. Salinity in soil is also increasing in southwestern region due to the fall in groundwater level caused by its overuse,” she added.
Additional Director General of Water Development Board Engineer Md A Wadud Bhuiyan said the government is prioritising use of surface water for irrigation to avoid the possible ecological threats resulting from overuse of groundwater.
Use of surface water in irrigation will protect farmland from salinity, he said. “We can increase the availability of surface water by digging canals, dredging rivers and preserving rain water,” he said.