For people living in coastal areas rivers and lakes are not ubiquitously available. They thus depend on groundwater for their needs, which leads to probabilities of saline water ingression. Groundwater close to the coast can be easily laden with salt, especially when the equilibrium between coastal aquifers and sea water is disturbed.
N.C. Mondal, V.P. Singh, V.S. Singh and V.K. Saxena in their paper titled ‘Determining the interaction between groundwater and saline water through groundwater major ions chemistry’ (2010) analyze that salt water ingression due to this mixing can occur due to a variety of pathways, and the degree to which this interaction can occur depends upon topography, sub-surface hydraulic properties, temporal variation in precipitation, local groundwater flow patterns, tidal and estuarine activity, sea level rise, low filtration, and excessive withdrawal.
They also opine that sea water can also reach inland aquifers through extraordinary events such as natural hazards i.e, through tsunamis and hurricanes. Apart from contaminating the groundwater, saline water ingression also affects the fertility of the soil, stunting agricultural production and ecosystems.
In a separate paper by V.K. Saxena, N.C. Mondal and V.S. Singh, titled ‘Identification of sea-water ingress using strontium and boron in Krishna Delta’ (2003) talk about the decrease in the fertility in the soil in the Krishna river delta in erstwhile Andhra Pradesh due to rapid sea water ingression.
Although known for high agricultural yields, over 70 per cent of the population in the Krishna river delta depend on groundwater for their water needs, and employ hand pumps, dug wells and dug-cum-bore wells for this purpose. Increasing salinity of groundwater over decades is turning most of the fertile land into wasteland and it is reported that there has also been a decrease in the cultivation rate.
The authors cite the chief causes for saline water ingression in the region as (i) increasing urbanization, (ii) an increasing number of bore wells, dug wells and hand pumps put to use. They note the chief cause for saline water ingression in the area as the pumping out of excessive groundwater through hand pumps, dug wells and dug-cum-bore wells.
India’s sea boundary is about 7500 km in length, stretching from the Rann of Kutch in Gujarat to the Sunderbans in West Bengal. The continental shelf in the western coast is much narrower than the eastern coast, and is littered with backwaters and mud flats, while the eastern coast is composed mainly of river deltas and estuaries. In India, according to data from the Central Ground Water Board (CGWB), saline water can lie over an aquifer, freshwater can lie over saline water, or an alternatively arranged sequence of freshwater and saline water aquifers can occur (CGWB, 2017).
Two areas in India face the most acute problem with saline water ingression, namely, Minjur, Tamil Nadu and the Chorwad-Porbandar belt in the Saurashtra coast (Ground Water Quality Features of the Country, CGWB, 2017).
Saline banks descending inland are present in an 8 to 10 km stretch in Odisha in its Subarnrekha, Salandi and Brahamani regions. The Pondicherry region also reports marked saline water ingression, eastwards from the Neyveli lignite mines (CGWB, 2008).
Conserving India’s Groundwater
S.C. Dhiman and D.S. Thambi in their paper titled ‘Groundwater management in Coastal Areas’ (2010) suggest several measures for the management of aquifers in India –
In the event of severe groundwater problem, an alternative water source or a suitable remedial measure must be found.
Restrictions must be placed on groundwater withdrawal in these areas to prevent over-exploitation of groundwater sources.
Awareness must be created among the masses about groundwater quality in these areas.
A policy document, like the Model Groundwater Regulation Bill, must be instituted for equitable distribution of the resource.
Threatened aquifers require the establishment of a buffer zone along the coast.
The Coastal Regulation Act must include proper provisions for saline water ingression.
As groundwater accounts for about 85 per cent of rural drinking water, and bore well irrigation increased by 60 per cent between 1960-61 to 2006-07 (CGWB, 2017), the Indian government has increasingly felt the need for management of groundwater resources. This is especially pertinent in a country largely with seasonal rainfall where agriculture meets its water requirements mostly with groundwater.
With these considerations in mind, the government under the Central Ground Water Board instituted the National Project on Aquifer Mapping in the 12th and 13th Five Year Plan under the Ministry of Water Resources.
This undertakes documentation of aquifers combined with mapping, management and implementation of its goals. The project is meant to pave the way for a participatory groundwater management programme that is based on comprehensive coordination at all levels such as between government institutions, research institutes, civil society and local level operatives garnering raw data.
The government has also instituted the Indian National Committee on Groundwater (INCGW) for research on groundwater resources (CGWB, 2017). Although it is not known how far reaching the participatory programme will be in practice, these represent a tilt in policy towards proper enumeration and management of groundwater resources in India, that could eventually steer the policy infrastructure towards management of saline water ingress in India, that acts to reduce soil fertility in certain regions, thus hampering agricultural productivity.
However, groundwater resources are not fully documented in India and its management is quite nascent. The Ministry of Water Resources drafted the Model Bill for Conservation, Protection and Regulation of Groundwater in 2016with the purpose of moving groundwater away from the Easements Act as private property to groundwater held by government as a public trust (Vishwanath, 2016).
Part of its stipulations include the notification of certain areas for the management of groundwater to be undertaken by State governments, with a clause that withdrawal from aquifers shall not disturb the natural equilibrium of water in these aquifers. This could establish limits on the otherwise excess extraction that frequently causes sea water to rush into aquifers, thus increasing saline water ingression.