Sixteen million smallholder farmers in Bangladesh led the pumping of groundwater, resulting in a massive storage capture of underground reservoirs that rivals the storage capacity of the world’s largest dams.
According to a study published in Science, groundwater-fed irrigation transformed much of Bangladesh’s single-crop, rain-watered floodplains into highly productive double-cropping lands. Some areas even transformed into triple-cropping lands, making Bangladesh the world’s fourth-highest producer of rice.
Ninety percent of rainfall in Bangladesh occurs during the May to October wet season, while the rest of the year falls under the dry season. Due to the droughts that hit the country between 1992 and 1994, there was a rapid increase in groundwater use.
Researchers involved in the study explain that the pumping up of water during the dry season reduces groundwater levels. These levels are then restored by leaching from ponds, rivers, and lakes during the monsoon months. Researchers have dubbed the process of capturing surface water to lead to the recovery of groundwater levels and help limit flooding as “The Bengal Water Machine”.
Mohammad Shamsudduha, the corresponding author of the study affiliated with University College, London, says, “The Bengal Water Machine is a nature-based solution, requiring a comparatively minimal intervention — i.e. shallow irrigation wells that are less than 100 meters below ground level — relative to dams, to increase seasonal capture of freshwater that would otherwise drain to the Bay of Bengal.”
The researchers analyzed one million weekly groundwater-level observations from 465 wells across Bangladesh, taken between 1988 and 2018. According to the study, over the past 40 years, the monsoon rainfall has recharged 75 to 90 cubic kilometers of water in Bangladesh. This volume is equivalent to twice the reservoir capacity of the Three Gorges Dam in China.
The phenomenon has allowed farmers to transform the economy and food security in Bangladesh, as well as improve the country’s resilience to climate change.
“In order to benefit from the operation of the Bengal Water Machine, we recommend identifying the potential areas where further freshwater capture is possible under current and projected changes in monsoon rainfall and irrigation demand. Continuous monitoring of groundwater levels and abstraction can ensure the sustainability of the Bengal Water Machine,” Shamsudduha stated.
The study has also been noted to have implications for future estimation of groundwater recharge and use in the agriculture sector of the production of food grain in the densely-populated country of Bangladesh.
Furthermore, researchers have also noted that a wider replication of the study findings may also be possible in Vietnam’s Mekong delta and the delta of China’s Huang He river. Both areas are susceptible to the effects of climate change.