The gradual decrease in the water level of the Padma River has intensified the groundwater depletion in the High Barind Tract, an arid region in the country鈥檚 north-western part known for its severe water scarcity.
This finding has been revealed in a study titled 鈥楽imulation of river aquifer dynamics and water scarcity in the left bank of River Ganges (Padma), Bangladesh鈥�. The study findings were published in the Netherlands-based journal 鈥楤iodiversity and conservation鈥� in January this year.
Professor Chowdhury Sarwar Jahan, a geology and mining professor at Rajshahi University, said that he along with his three colleagues investigated the simulation of groundwater flow characteristics and its dynamic exchanges with surface water for the period of 1980鈥�2020 in the left bank of Padma River.
He said that the study was conducted in an 85-kilometre area on the left bank of the River Ganges (Padma) starting from its entry point in Bangladesh in Chapai Nawabganj district to the Ishwardi upazila of Pabna district covering twelve upazilas of Chapainawabganj, Rajshahi and Pabna districts.
According to the study, the groundwater level in the Barind region鈥攁n area higher than the rest of the country in general, and with much less rainfall鈥攅xhibits a declining trend during the dry summer season. Before 2000, however, the groundwater level nearly recovered to its original state during the monsoon.
Since 2000, however, groundwater level in the region has been declining at an alarming rate, failing to return to previous level even during the monsoon.
Over the past four decades, groundwater level in the study area has dropped by 5.22 metres. The present total deficit between groundwater recharge and discharge in the region鈥檚 river basin area stands at 20,44,000 litres per year, according to the study.
鈥極ver exploitation in the upstream is a major cause of scarcity of groundwater,鈥� the study mentioned.
An analysis of the Bangladesh Water Development Board data from the past five years shows that during the dry season (January鈥揗ay), the water flow in the Padma River decreased from 2,093 cubic metres per second in 2019 to 1,076 cubic metres per second in 2024.
Before the opening of the Farakka Barrage, located 18km upstream of the India-Bangladesh border, the Padma River had a flow of 3,685 cubic metres per second in 1974.
Along with the reduced river flow, the yearly minimum water level has dropped from 4.59 metres in 2020 to 2.98 metres in 2024, while the yearly maximum water level has fallen from 13.47 metres in 2019 to 12.38 metres in 2024, according to the analysis.
鈥楾he declining value of groundwater level is higher in summer season than that of rainy season because of less amount of groundwater recharge and huge outflow of groundwater from aquifer system towards the river basin due to poor flow of river water as well as over-exploitation of groundwater for irrigation purpose in dry summer season鈥�, the study report explains.
The study predicts that over the next 40 years, the annual deficit between groundwater recharge by rain and discharge or outflow from aquifer systems will reach 8,17,60,000 litres, and the deficit would be even more aggravated if the flow of river water further declines while the withdrawal of groundwater for irrigation increases.
To ensure sustainability, the study suggests implementing coordinated water and land resource management strategies, including rainwater harvesting, creating mechanisms for directing captured rain into the ground, efficient irrigation techniques, crop diversification, soil management and regulated groundwater extraction.
A previous study conducted by the Institute of Water Modelling, a government agency, in 25 upazilas of Rajshahi, Naogaon and Chapainawabganj between 2018 and 2021 showed that the average groundwater level in the High Barind Tract dropped to 18 metres from 8 metres in the past three decades.
In some specific areas like Gomastapur upazila of Chapainawabganj, the average groundwater level dropped to as low as 46.87 metres in 2021 from 21 metres in 1990.
Meanwhile, cultivation of boro paddy, the country鈥檚 main staple crop, has decreased by 10,280 hectares in the Rajshahi agricultural region compared with the past year鈥檚 acreage due to severe water scarcity, according to the Department of Agricultural Extension officials.
Boro cultivation in the region largely depends on irrigation by extracting groundwater but, the farmers said, adequate water for irrigation cannot be extracted at places due to groundwater depletion.