Sand from Ganga riverbed must be used only to cultivate gangatva in other rivers, writes Devendra Swaroop Bhargava
Extensive mining of the Ganges riverbed is threatening to diminish the extraordinary self-purifying properties of Ganges water, referred to as gangatva, which destroys pathogens and maintains purity for long periods of time.
Instead of exploiting the mined resource for short-term economic gains, the sand should be the focus of further research to understand its properties better. One logical approach would be to conduct experiments using Ganges riverbed soil on the cultivation of the so-called gangatva in other rivers.
Of great religious significance to Hindus, the ganga-jal is believed to provide spiritual healing and salvation and is stored in every Hindu home for various religious rites, medicinal, and other daily uses. Unlike other river waters, ganga-jal can be stored in airtight containers for years without putrefying. During colonial times, the British Navy stored Ganga water in ships returning to England because it remained fresh throughout the voyage. Recognising its unique properties, the British, in reverence, named the river ‘The Ganges'.
Some scientific studies reveal that the Ganges acquires its gangatva from the soil bed containing a material that imparts disinfecting properties to the river water, which is heavily polluted in some sections.
In 1896, the British physician E Hankin established through experimental studies that cholera microbes (vibrio, a pathogen) died within a few hours in ganga-jal, but survived up to a few days in distilled water or in the Yamuna river water. Hankin concluded that ganga-jal lost its disinfecting property when boiled. It is inferred that a volatile material is responsible for imparting the disinfecting action in ganga-jal.
The Ganges soil bed is the source of the volatile material that provides the self-purifying property of the river. The 2,525-kilometer-long Ganges originates from Himalayan glacier water and snowmelt in northern India. In some parts of the year, the Ganges becomes almost dry after the famous holy town Hardwar, located 100 to 150 km downstream from its origin point.
After Hardwar, the river water is routed through the Ganga canal system that was constructed by British engineers for agricultural irrigation in the 19th century. The canal system at other downstream locations in the Ganga basin also removes most of the river water. Consequently, the Ganges after Hardwar does not carry snowmelt water from the Himalayan glacier; it carries only the continuously infiltering groundwater and tributary water that flows into the watercourse after Hardwar. Yet the gangatva remains intact in the Ganges despite the process of becoming ‘water-less' and ‘water-full' along its course. It is assumed that the volatile disinfecting material is provided by the soil in the entire course of the Ganges, because the river water after Hardwar contains mostly groundwater from the plains.
So what is the scientific explanation for the Ganges's ability to self-purifyIJ High dissolved oxygen levels and an unidentified volatile material that disinfects are two factors that account for the phenomena.
The river's extraordinarily high self-purifying abilities facilitate its ability to assimilate heavy pollution loads in a short time. Pathogens and coliforms do not survive in open waters in an open hostile environment. The Ganges' turbulent flow, high width-to-depth ratios, shallow swiftly flowing waters create an environment with extraordinarily high DO recovery rates that prevent anaerobic bacteria from growing.
The DO recovery rates in the Ganges with its coefficient of reaeration was of higher magnitude when compared to other rivers. Nowhere along its long course does the river become completely devoid of DO despite receiving heavy organic pollution in some stretches.
Also anaerobic bacteria through decomposition stabilise the organic material present in water in the absence of DO to produce methane, the foul-smelling gas manifesting staleness or putrefaction. Coliforms and pathogens are closer to anaerobes in terms of sensitivity to environmental hostility. The anaerobes causing putrefaction are thus unable to flourish and soon die in ganga-jal as do the pathogens. That finding explains why ganga-jal remains fresh even after long periods of airtight storage.
However, excavating Ganges sand, in effect, destroying large swathes of riverbed in Hardwar and other places along the Ganges, has drawn strong opposition from religious and environmental leaders. Sand from the Ganges is considered to be a good building material. Not surprising then that political support to powerful mining companies has enabled mining to continue unabated for the past decade.
Riverbed sand is in great demand for construction in India and abroad; however uncontrolled mining has made barren more than a million acres of agricultural land by lowering the water table, resulting in irrigation wells and pumps to go dry.
The impact of sand mining on water quality, ecology, and the economic foundations of many communities such as agriculture and fishing is taking a serious toll on the Ganges river basin. Yet, who can stop the waste of such a precious resource excavated from Ganga riverbedIJ Surely, the sand must be made off limits for mining and used only in limited quantities to explore its potential for cultivating gangatva in other rivers.
(The writer is an author of many research papers. He is a retired environmental professor at IIT Roorkee. This article has appeared in a longer version in WaterWorld — Water Environment Federation, USA)