Is ‘Water Machine’ Preventing More Flood Disasters in Bangladesh?
The study contradicts the idea that we should use less groundwater
Written by Rezwan at GlobalVoices.org: Being a riverine country, Bangladesh is prone to floods every year, and a large portion of the country goes under water during the monsoon season. The effects of the ongoing La Niña climate event have triggered excess monsoon rains in the South Asia region, which includes Bangladesh. In mid-2022, rapid floods inundated three districts of Bangladesh due to the record rainfall in the bordering Indian states of Meghalaya and Assam, affecting 4 million people.
A recent study in the journal Science by a group of researchers from the University College London, the University of Dhaka, and Bangladesh University of Engineering and Technology (BUET), and others shows that pumping groundwater to irrigate agricultural lands in Bangladesh can create the available subsurface storage for excess floodwater to be stored during the next monsoon. The research, aptly titled “The Bengal Water Machine,” reveals that millions of small farmers irrigate rice paddies during the dry season, pumping from the ground, lowering the groundwater level, which, under favorable conditions, amplifies groundwater replenishment during the subsequent monsoon and helps reduce flooding.
Science Magazine tweeted: “New in Science: Seasonal monsoon rainfall replenishes groundwater reserves in the Bengal basin of Bangladesh thanks to the region’s seemingly counterintuitive intensive dry-season irrigation practices.”
The research used millions of groundwater measurements between 1988 and 2018 from 465 sites across Bangladesh estimating how much groundwater was pumped by more than 16 million farmers using more than 1 million diesel and electric pumps. And the rate of depletion is not uniform — some groundwater was refilled during the monsoon season and some were not. However, this space allowed the replenishment of more than 20 trillion gallons of water over the last 30 years.
According to geoscientist and member of the study Mohammad Shamsudduha, farmers didn’t know about this so “no one really intended this to happen.”
Aditi Mukherji, Principal Researcher at the International Water Management Institute in India thinks that farmers in South Asia could see the dual benefits of increased food production and flood protection from more irrigation.
Farmers, especially the rice growers are usually blamed for overexploiting groundwater resources, however, research has indicated that other reasons such as low flows in rivers, reductions in wetland areas, and declines in rainfall play a role. To address overpumping concerns, the Bangladeshi government introduced restrictions on groundwater pumping and is pushing to replace 400,000 diesel-run pumps with solar pumps.
Readers in Bangladesh are also confused. On the Facebook Page Engineer’s Diary, Atikur Rahman Atik, a student comments on the study: “I have read so far everywhere on TV, newspapers that we need to reduce the use of underground water. The groundwater level is depleting fast. This article tells the opposite – to use groundwater more. So which one should we follow?”
Another user Ishrat Jahan replies to Atik: It should actually apply specifically to flood-affected areas. Overall, it is advisable to use groundwater less. Although I haven’t read the paper yet, this theory is completely absurd as one of the main causes of floods in Bangladesh — a dangerous one – is “flashflood”.
Another user Mohammad Asadullah comments: Due to the pumping of groundwater for irrigation during winter, our edible water tube wells run dry. Those who live in the village face much trouble.
Although the study shows the use of groundwater as favorable, it is not a good practice as rainfall is not at the same level in every Bangladeshi region and the replenishment of groundwater depends on that. When there is a case for it going into groundwater, it just moderates the flood; it doesn’t avert it. The research showed that, if not absorbed into groundwater stores, the excess water would have flooded the land and made its way to the Bay of Bengal eventually.
FEATURED VIDEO: Stagnant floodwater to underground water
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