Groundwater table sinks 20-feet in some parts of northwest Bangladesh
Bangladesh-Australia joint research dispels concern over pumping irrigation water; identifies - low river flows, wetland loss and changes in rain patterns as key reasons
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For too long, Bangladeshi farmers have been blamed for overexploiting groundwater in growing dry season rice – Boro.
It was widely believed that 3,000 to 5,000 litres of water was required to grow one kilogram of rice and “overmining” of underground water for the purpose was responsible for the fast depletion in the groundwater table.
However, an international collaborative study has just found out that such a perception belied the real villains of groundwater depletion in Bangladesh, which are low flows in rivers, reductions in wetland areas, and declines in rainfall.
The research also debunked the myth of much water use and found out farmers in Bangladesh irrigate rice land most judiciously, using only 1,300 to 1,800 litres of water per kg of rice. With the expansion of water-saving technology such as AWD (alternate wetting and drying), farmers are reducing irrigation water consumption even further.
Still some parts of Bangladesh are showing marks of fast depletion in the groundwater table, particularly in the Barind Tract (north-western region).
Experts said the Teesta now dries up during winter, land grabbers feast on river foreshores and wetlands, and runoff water from high-intensity rains does not help much in recharging the groundwater tables in the northwest.
According to Barind Multipurpose Development Authority (BMDA) Executive Director Md Abdur Rashid, the groundwater table had sank by 20 feet since 1988 (from 39 feet to 59 feet) in many parts of Barind Tract.
The Bangladesh part of Barind Tract covers most of Dinajpur, Rangpur, Pabna, Rajshahi, Bogra, and Joypurhat, while the Indian part covers Uttar Dinajpur, Dakshin Dinajpur and most of Maldah districts in West Bengal.
For past 5 years, the Irrigation and Water Management (IWM) Division of the Bangladesh Rice Research Institute (BRRI) carried out coordinated studies in collaboration with the Commonwealth Scientific and Industrial Research Organization (CSIRO), Australia, and the University of Southern Queensland (USQ), Australia aiming to sustainably use groundwater in the northwest region of Bangladesh and develop technologies for low-cost rice production.
BRRI-CSIRO also conducted a few other research projects regarding judicial groundwater utilization with other research organizations of Bangladesh.
In the presence of Agriculture Minister Dr Muhammad Abdur Razzaque, a dissemination webinar was arranged recently where it was decided to hold a bigger workshop with all stakeholders to moot the issue of groundwater depletion and sustainable of agriculture.
Presenting some research findings, CSIRO Principal Research Scientist Dr Mohammed Mainuddin said if 20% water could be augmented from surface water sources, the depletion of the groundwater table in Rajshahi, Naogaon, and Chapainawabganj could be retained.
According to Dr Mainuddin, rice irrigation is not the prime reason for groundwater depletion. Rather, the drying up of rivers like the Teesta, silting up of waterbodies, wetlands and high-intensity short-duration rainfall patterns are contributing to the falling groundwater table.
It has been over a decade now that a deal over Bangladesh getting the right share of transboundary river Teesta fell through in 2011 due to an internal disagreement between the Indian central government and West Bengal state government.
According to the latest survey of the National River Conservation Commission of Bangladesh (NRCCB), there are over 65,000 grabbers who are feasting on river land and foreshores across the country.
Experts said if wetlands, rivers, open water bodies are not maintained properly, groundwater recharge is disrupted, and the underground water table sinks further.
“We need to focus on increasing recharge of groundwater,” said Dr Mainuddin.
The research also noticed less rainfall in recent years in some parts of Bangladesh than what they used to experience in the ‘80s and ‘90s. Experts said if too much rainfall occurs in a short spell, then runoff water does not help much in groundwater recharge.
Less intense rains throughout the monsoon better contribute in recharging groundwater.
In a separate presentation, BRRI Irrigation and Water Management Division Principal Scientific Officer Dr Md Maniruzzaman, showed an average availability of irrigation water in the range of 1296-1821 litres (for each kilogram of rice). A substantial part of this water returns to the aquifer, thereby recharging the groundwater.
Thanks to farmers growing dry season rice in Bangladesh, the country’s staple cereal production marked a threefold increase in last 30 years.
“This has been possible because of irrigated Boro rice,” he said.
According to Bangladesh Bureau of Statistics (BBS), irrigated-rice Boro now contributes 54% of the over 35 million tons of Bangladesh’s yearly rice output. Rainfed Aman and Aus contribute the remaining 46%.
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