Excessive use of groundwater poses threat to ecology

Excessive and unplanned use of groundwater for irrigation across the country poses a serious thereat to ecology severely affecting the agriculture sector, water and agriculture experts said Saturday. They said different parts of the country, particularly southern region, have already experienced adverse impact of the excessive use of groundwater. Agriculture, water and environmental engineer of Bangladesh Agricultural Development Corporation (BADC) Dr Md Eftekharul Alam told BSS that groundwater is being used for irrigation largely in an unplanned manner, which contribute to misuse of water keeping a huge negative impact on ecology and agriculture. Nearly 1.3 million tubewells mostly shallow are being used for irrigation through groundwater in crop production, he said adding the number of tubewells is move than requirement as 0.8 million tubewells are enough to meet demand of water for irrigation. Referring to his study, he said irrigation efficiency in the country through existing flooding method is at 34 per cent. Dr Iftekhar suggested increase of irrigation efficiency to ensure proper utilization of groundwater in agriculture sector to maintain ecological balance. Water distribution and marketing system should be improved for increasing irrigation efficiency to stop misuse of water, which will also cut production cost, he added. Groundwater level is declining gradually in different magnitudes across the country as irrigation still depends largely on groundwater, Dr Iftekhar said and added water table of many regions in the country including Gazipur, Mymensingh, Netrakona, Kishoreganj, Jessore and Khulna is going down at an alarming rate. He mentioned that water level of sadar upazila in the Gazipur district has declined to 66 feet in the last six years, 15 feet at Bhaluka in Mymensingh and on an average three feet at Jessore, Kushtia and Khulna region. The ecology, particularly in the southwestern region, will face an extreme impact as well as crop production, if the declining trend of water table continues. The BADC officials said in the last Rabi season, total irrigated area was 52,17,626 hectares, while groundwater covered 41,27,387 hectares which was 79.10 percent of total irrigated area. Surface water irrigation covered 10,90,239 hectares which was 20.90 percent of total irrigated area, according to a Minor Irrigation Survey Report (2009-10), they added. In a keynote presentation recently, Managing Director of Dhaka WASA Engr Taqsem A Khan said total water production of Dhaka Water Supply and Sewerage Authority (WASA) is 2100 million liters per day for nearly 12.5 million city dwellers, of which, 87.72 per cent is ground water while the rest 12.28 per cent is surface water. Referring to different environment impacts of groundwater use, he said groundwater table is declining 2-3 meters in Dhaka city per year due to its overuse. Prof Umme Kulsum Navera of Department of Water Resources Engineering of Bangladesh University of Engineering and Technology (BUET) said water table in major cities including Dhaka is declining fast due to inadequate recharge of groundwater. Many countries including Australia have stopped use of groundwater for irrigation to maintain ecological balance, she said adding, "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 soil and environment. Salinity in soil is increasing in southwestern region due to fall in groundwater level caused by its overuse," she added. Additional Director General of Water Development Board Engr Md A Wadud Bhuiyan said the government is giving priority to use of surface water for irrigation avoiding possible threat to ecology due to overuse of groundwater. Use of surface water in irrigation will protect farmland from salinity, he said adding, "We can increase availability of surface water by digging canals, river dredging and preserving rain water."