Paddy cultivation in many northwestern districts have long been facing greater difficulties for inadequate irrigation during the dry or Boro season due to the depletion of groundwater table, reveal some recent surveys.
This depletion of groundwater is actually linked to the extraction of excessive groundwater for nothing other than the growing irrigation demand for Boro rice fields, observed agriculture officials and farmers.
Additional director of Department of Agricultural Extension (DAE) in Rajshahi Region M Nurul Amin said some 16,433 deep tube-wells and
353, 767 shallow ones are in operation to provide irrigation to paddy cultivation in eight districts under his jurisdiction in the current Boro season.
Most of the 731,370 hectares of Boro acreage achieved in this season are irrigated with groundwater, he added.
“The number of tube-wells has already exceeded the sustainable limit. And we’re not allowing any new tube-wells since 2012,” he said.
Besides, we’re encouraging the farmers to go for alternative crops such as pulses and oil seeds that require less irrigation,” Nurul Amin added.
DAE Naogaon district deputy director SM Nuruzzaman said Boro acreage in his district had reduced by 1,300 hectares compared to that of the previous season due to the difficulties in pulling up the groundwater.
The DAE officials observed that the main reason for the difficulties is the excessive extraction of groundwater for the dry season irrigation.
According to records of Bangladesh Agricultural Development Corporation (BADC), groundwater extraction for irrigation through deep and shallow tube-wells stands at nearly 55 billion cubic metres (bcm) in recent years against the extraction of only 10-13 bcm surface water used in irrigation.
About a decade earlier, groundwater and surface water extraction for irrigation purpose stood at 40 bcm and 8 bcm respectively.
One of the major reasons for the saturation of aquifers in the Rajshahi, Naogaon and Chapainawabganj districts was that excessive number of deep tube-wells -- about 12,000 deep --has been drilled by the Barind Multipurpose Development Authority (BMDA), violating the provision of minimum distances between two deep tube-wells, claimed officials at the Minor Irrigation Division under BADC.
A distance of at least 2,800 metres should be maintained between two deep tube-wells, whereas BMDA kept only a 1,200-metre distance on average, complained the BADC officials.
The latest groundwater zoning maps formulated by BADC in 2004 and 2010 showed that groundwater level along the banks of the entire course of the Padma River (Rajshahi and Chapainawabganj districts) have sunk between two and three metres over the six years since 2004, whereas in Natore and Sirajganj the depletion was between one and two metres.
Shallow tube-wells over 23 thousand square kilometres in the country became inoperative for about two to four weeks between March and April, the peak of the irrigation activity, and deep tube-wells over six thousand kilometre area in the country became dysfunctional over the recent years, according BADC surveys updated till 2011.
Notably, a study on the recent trends of groundwater level in the Ganges-Brahmaputra-Meghna delta, published in 2009 in the international journal Hydrology and Earth System Sciences Discussions, states that the groundwater levels in western, northwestern, and northeastern areas are declining at a rate of 0.1 to 0.5 metres annually due to excessive irrigation in the dry season.
Though not visible, the changes taking place underground can be gauged easily by the growing difficulties faced by farmers while drawing the groundwater with the motor-driven tube-wells. In most of the northwestern districts, the farmers have been replacing the shallow-depth tube-wells with the deep ones.
Md Emdadul Haque Talukdar of Dhawapiction village in Bogra Sadar had to replace one shallow tube-well in his homestead with a deep tube-well and installed a submersible motor in the deep tube-well he used in the rice field back in 2011.
