Coastal belt witnesses rapid salinity intrusion
Reveals BADC study
Coastal parts of the country witnessed rapid salinity intrusion within one year, according to a recent study of Bangladesh Agricultural Development Corporation (BADC).
"Salinity concentration in groundwater in Barguna, Pirojpur,
Bagerhat, Satkhira and Khulna districts has increased two deci siemens (DS) per metre in one year," BADC Agriculture, Water and Environmental Engineer Dr Md Eftekharul Alam told the news agency.
Salinity concentration in the southern districts was 12 DS per metre in 2011 while 14 DS per metre in 2012, he said adding, "Increase of two DS per metre salinity concentration within one year is alarming to our ecology."
Eftekhar said BADC conducted the study in southern region to assess the state of invisible underground saline water intrusion.
Under the study, 182 salinity observation wells were installed in the coastal region and data of those wells showed increase of two DS metre salinity concentration at 110 feet depth in the region, he added.
The study revealed that saline water is advancing towards the north at two district depths at about 110 feet and 650 feet from the ground level.
Eight percent irrigation water and ninety-eight percent drinking water are collected from underground source and it is abstracted without proper planning, Eftekhar added.
He said abnormal increase of salinity concentration in the groundwater of southern region exposed serious thereat to ecosystem and biodiversity that will destabilise the food security of the country.
He said if groundwater is polluted by saline water intrusion, it will destabilise the food security and ecosystem and biodiversity of about 12 percent southern area of the country where about 60 million people live.
Country's groundwater is now in unbalanced condition due to more abstraction than its total annual recharge, Efthekhar said adding groundwater levels in different parts of the country are going down below the mean sea level due to excessive and unplanned use of groundwater.
BADC sources said in some areas it is about 174 feet and thus most of the suction mode irrigation pump cannot lift water in dry season. Besides, this vacuum is being filled in by saline sea from the Bay of Bengal through underground aquifers, they added.
Concentration of salinity in the groundwater of southern part is found maximum at a depth of 110 feet from ground level, they said adding maximum salt concentration at a depth of 110 feet is provably due to less discharge in the international rivers and excessive withdrawal of groundwater by tubewells.
Efthekhar said 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 13 lakh tubewells mostly shallow are being used for irrigation through groundwater in crop production, he said adding the number of tubewells is excess than requirement as eight lakh tubewells are enough to meet demand of water for irrigation.
Dr Eftekhar said the excessive number and short distance installation of tubewells as well as other machinated equipment for lifting water pushed down the water table rapidly.
Prof Umme Kulsum Navera of Department of Water Resources Engineering of Bangladesh University of Engineering and Technology (Buet) said the unplanned shrimp cultivation requiring saline waters in the coastline deteriorated the state of environment in the region.
Salinity intrusion is engulfing the coastal region rapidly due to less discharge of rivers in coastal region, Navera said adding flow of the river Gorai should be increased to keep water levels of other rivers normal, which will help resist influx of saline water from Bay of Bengal.
Groundwater level in almost all parts of the country is declining fast from mean sea level due to its overuse and less discharge of rivers, Eftekhar said adding rapid decline in aquifer level is inviting saline water which increases concentration of salinity in groundwater.
The water and environment experts feared that the country will witness a catastrophe, if declining of groundwater level continues.
Many countries already reduced dependency of groundwater for both drinking and irrigation purposes, said Navera supplementing Eftekhar.
"We should ensure availability of surface water through canal digging programme and capital dredging in all major rivers aiming to reduce dependency of groundwater," Eftekhar said adding preserving rainwater and increasing irrigation efficiency would also cut dependency on groundwater.
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