Is the ‘water machine of Bengal’ preventing more flood disasters in Bangladesh?

Farmers irrigate their land pumping groundwater in Bangladesh. Image via Flickr by Ranak Martin/International Maize and Wheat Improvement Center (CIMMYT). CC BY-NC-SA 2.0.

Farmers irrigate their land by pumping groundwater in Bangladesh. Image via Flickr by Ranak Martin/International Maize and Wheat Improvement Center (CIMMYT). CC BY-NC-SA 2.0.

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 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 favourable conditions, amplifies groundwater replenishment during the subsequent monsoon and helps reduce flooding.

Science Magazine tweeted:

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:

এতদিন টিভি, পত্রিকা সবজায়গায় পড়লাম ভূগর্ভস্থ পানির ব্যবহার কমানোর জন্য। পানির লেয়ার নীচে চলে যাচ্ছে।
এখন এই আর্টিকেল দেখাচ্ছে ভূগর্ভস্থ পানি বেশী করে ব্যবহারের জন্য। তাহলে কোনটা আমরা মেনে চলব?

I have read sofar 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:

এটা আসলে বন্যা কবলিত এলাকা গুলোর জন্য সাময়িকভাবে প্রযোজ্য হবে। সামগ্রিক ভাবে ভূগর্ভস্থ পানি কম ব্যবহার করাই যুক্তিযুক্ত। যদিও এখনো পেপার টা পড়িনি, তবুও বাংলাদেশে বন্যার অন্যতম প্রধান যে কারণ গুলো আছে এবং সবচেয়ে বড় খতিকর বন্যা “ফ্ল্যাশফ্লাড” সেটার জন্য এই থিওরি একেবারে ই অযৌক্তিক।

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:

শীতকালে সেচের কাজে পানি ব্যবহারের ফলে সাধারন টিউবওয়েলে পানি থাকে না। আমরা গ্রামের মানুষ মুসিবতে পড়ে যাই।

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 favourable, 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.

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