What do we do to control uncertain floods and running water? We build dams. However, to build dams, we need supporting geographical structures such as hills or valleys to hold water. This is why dams don’t exist in Bangladesh, as it is a flatland country lying a few meters above sea level. Interestingly, millions of Bangladeshi farmers have discovered their own conventional but logical system to control floods taking advantage of the country’s climate. The system is named “The Bengal Water Machine.”
Image Credits: Pixabay
Decoding The Bengal Water Machine
Bangladesh acts as a delta, where the River Ganges and Brahmaputra empty their water into the Bay of Bengal, they leave behind the sediments they are carrying with them. The sediments turn into one of the most fertile soils, such as alluvial soil, that supports vegetation and crop production.
Bangladesh’s climate relies on the annual monsoon, which is significant for agriculture. But heavy rains can cause floods. However, its warm climate allows farmers to grow crops, especially rice, for which they pump groundwater. This creates space in the ground so rainwater can accumulate in the wet season.
“Imagine the soil as a sponge that soaks water. Now, imagine a place that gets lots of rain, and the soil (aka sponge) remains wet more or less throughout the year. Then, new rain falls, and the soil/sponge is so soaked that it cannot contain any more water and that excess water, then causes floods,” said Aditi Mukherji, a researcher at International Water Management Institute, India.
“Now imagine that before rains arrive, someone wrings the sponge dry. That’s what millions of farmers are doing when they pump groundwater from the aquifers before the onset of rains.”
The study authors wanted to know whether continuous pumping was depleting the groundwater. They analysed data from 465 government-controlled stations that monitor Bangladesh’s irrigation systems. They found that in many regions of the nation, the water wasn’t depleting. This was due to alluvial soil deposits that can soak water into the ground, and farmers can use it for irrigation.
Image Credits: Pixabay
How is it vital for the Asian subcontinent or the world?
Groundwater is one of the widely used resources when it comes to agriculture. Many developing countries in the Asian subcontinent, where monsoons are plentiful, including India, rely on it for crop production. However, the uniqueness of the machine is that it maintains the groundwater level and doesn’t lead to over-extraction, added Mukherji.
Heavy rainfalls and the nature of alluvial soil play a crucial role in maintaining the groundwater cycle that is usually not seen in arid and semi-arid areas where the rains are low. But Bangladesh is blessed with unique geography that has helped it to become self-reliant in terms of food production. This is a significant milestone achieved by a small country having one of the highest population densities.
Researchers think that storing water underground has its own advantage as water is less vulnerable to evaporation. Farmers can pump water from the ground instead of relying on water shuttles.
What factors can affect the Bengal Water Machine?
According to Mukherji, the machine can work properly in areas having humid or sub-humid climates. However, a warm climate can affect monsoons and change their direction where they deliver rain. And this is what researchers need to look into.
Besides, the Bengal Water Machine faces other challenges too. In 2019, the Bangladeshi government made changes to its agriculture policies and put limitations on the usage of pumps in the fields to curb overpumping issues which made groundwater pumping more inaccessible. Also, balancing the machine means not using groundwater excessively. And this is happening in the west of Bangladesh which is low in rainfall compared to east Bangladesh. Hence, the frequency of floods in the eastern zone is higher than in the west. Moreover, the researchers also noticed this and found less groundwater depletion in the west than in the east.
“Intensive use of groundwater in the dry season can reduce flood intensity. However, there are limits to recharge – limits dictated by surface geology and the amount of rainfall. So, if groundwater use is more than potential for recharge, the region will experience a drawdown in groundwater levels,” said Mukherji.
What can help control uncertainties associated with the machine?
Groundwater irrigation is important to ensure food security and must be a discussable topic at a global level. Initiatives must be taken at the ground and national levels to solve irrigation and agriculture-related problems. Better and sustained groundwater monitoring and the use of precautionary principles such as the promotion of efficient irrigation through proper policies and incentives can help minimise the negative impacts associated with the Bengal Water Machine, Mukherji concluded.
The study was published in the journal Science.
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