Steep fall of groundwater table blamed
About four lakh irrigation pumps out of over 16 lakh across the country go out of operation during the peak dry spell of March-April every year failing to draw the required quantity of water due to a sharp fall of groundwater level.
“Owing to a steep fall in ground water table, almost four lakh shallow tubewells (STWs) cannot lift the required volume of irrigation water during March-April period each year,” said Dr Eftekharul Alam, head of Minor Irrigation Information Services Unit (MIISU) of Bangladesh Agricultural Development Corporation (BADC).
Eftekhar headed a BADC team that recently completed the second groundwater zoning map of the country, and the first one in 2005.
Referring to the second map, he told The Daily Star yesterday the country’s “critical shallow tubewell” area increased by 17 percent between 2004 and 2010 from over 14 thousand square km to nearly 17 thousand square km.
Critical shallow tubewell refers to a groundwater level in the range of 9.8 to 11.3 metres below the surface from where STWs can’t draw required quantity of water for irrigating croplands.
Eftekhar also said the areas where STWs can’t lift water at all rose by 45 percent from 6,664 square km in 2004 to 9,638 square km in 2010.
Dry season irrigation is needed mainly to cultivate Boro rice that contributes 55 percent of the country’s annual food output. Groundwater is used for 80 percent of irrigation covering 5.22 million hectares of Boro land. Of the more than 16 lakh irrigation pumps in the country, around 14 lakh are STWs, mostly run by the farmers themselves. The rest are deep tubewells and low-lift pumps run by state agencies.
The MIISU chief said BADC had installed 3,466 observatory wells across the country, and prepared the groundwater zoning map 2011 analysing data received from the observatory wells throughout 2010.
“We’ve found that ground water table in the command areas of 462 observatory wells dipped below the mean sea water level during March-April period, thereby inviting southern salinity further inwards towards the north,” he said, and cautioned against over mining of groundwater.
Besides Dhaka, Eftekhar said, Gazipur, Mymensingh, Netrokona, Rajshahi, Naogaon, Chapainawabganj, Natore, Dinajpur and Rangpur regions experienced major fall in ground water table since 2004.
When her attention was drawn to this, Agriculture Minister Matia Chowdhury said, “We have been dragged into this situation because of emphasising too much irrigated rice cultivation in the country’s northern region in the past. We need to stop over mining of groundwater in the north.”
She went on, “We are going to shift our focus from the north to the south as far as growing irrigated rice is concerned. We will go for other less water consuming crops in the north, and develop saline-tolerant Boro rice varieties for producing those in the south.”
Matia also favoured giving more emphasis on rain-fed rice season Aman instead of depending too much on irrigated rice Boro.
But Dr MA Hamid Miah, who just retired as International Rice Research Institute’s (IRRI) Liaison Scientist in Bangladesh, sounded caution against any rush in shifting the focus from the north to the south for irrigated rice. “Lest we forget the natural disasters that often stalk the south during the harvesting season of Boro,” he said when contacted yesterday.
Hamid emphasised developing more effective saline- tolerant and short-duration rice varieties for dry season cultivation in the south.
Eftekhar suggested that the government stop sinking of more tubewells for drawing groundwater for irrigation purpose. He stressed digging canals, dredging rivers and excavating other water bodies to maximise use of surface water.
Courtesy of The Daily Star
