An international team of researchers has advised against the application of the ‘Ganges Water Machine’ concept as a one-size-fits-all approach to manage the water resources of the Ganges River Basin (GRB).
The concept of Ganges Water Machine (GWM) relies on the assumption that the Ganges river runs through a high-yielding, homogeneous porous aquifer that can be used to store transient flood waters during the monsoon and as a perpetual source of water for withdrawal throughout the rest of the year.
In an article published in the journal ACS ES&T Water, the researchers noted that a basin-wide, in-depth study of groundwater-Ganges river water interactions is required, before any policy augmentation.
Recently, there has been much interest in how to manage the water resources of the GRB, currently supporting over 500 million people. This also includes cleaning up the Ganges river, regarded as one of the most polluted mega-rivers of the world.
Historically, the transboundary Ganges river and its tributaries, flowing through India, Nepal, and Bangladesh, have become extensively polluted and disrupted, mostly because of river engineering and increased discharge of industrial and urban waste, the researchers said.
Compounding the problem, in the past few decades, intense groundwater abstraction from the GRB aquifers has led to unprecedented groundwater level depletion in some locations, they noted.
“Some recent studies in the Ganges delta areas of Bangladesh argued that the “Water Machine” concept is favourable and works efficiently in the study area,” said Abhijit Mukherjee, Professor at the Indian Institute of Technology Kharagpur (IIT KGP).
“Consequently, water managers and agencies across the world have started to re-visit the ‘Ganges Water Machine’ concept,” Mukherjee, co-author of the article, told PTI.
The GWM scenario imagines the subsurface aquifer of the GRB as a roughly homogeneous sandbox, with discernible natural, seasonal groundwater fluctuations as a response to dry and wet seasons.
From this hypothetical GRB aquifer, groundwater can be abstracted at an enhanced rate to substantially decrease the dry season groundwater level.
Subsequently, the wet season rainfall water should infiltrate to replenish the GRB aquifer to the wet season groundwater level, the GRB subsurface thus working like a transient repository of the groundwater.
However, the researchers said this theoretical concept has several drawbacks.
The Ganges basin aquifers are already severely over-stressed, and enhanced abstraction would only hasten their demise, they said.
These aquifers are extremely heterogeneous and have complex and spatially variable river-groundwater interactions, therefore, annual monsoon flooding on the main river channels may not replenish the areas of the aquifer where groundwater is most needed, according to the researchers.
Also, recent studies have shown that increasing summer groundwater abstraction across the aquifer could lead to a further reduction in Ganges flow, thereby concentrating the river pollutant load, and endangering groundwater storage increasing the risk of drought and food security for millions of people, they said.
“There are still many aspects of this unique water system that we do not understand, and the past mistakes should serve as a warning not to undertake large-scale changes and hydrological engineering without careful consideration,” Mukherjee said.
“Hence, we advise against the application of the Ganges Water Machine concept in a “one-size-fits-all” approach. A basin-wide, in-depth study of groundwater-Ganges river water interactions is required, before any further policy augmentation,” he added.
Other co-authors of the article are from Oak Ridge National Laboratory, NASA Goddard Space Flight Center, both in the US, King Abdullah University of Science and Technology, Saudi Arabia, Jadavpur University, Kolkata, Manav Rachna International Institute of Research and Studies, Haryana and British Geological Survey, UK.
