Cities need multi-pronged efforts to conserve groundwater

The government of India recently informed the Parliament about high levels of toxic contamination of groundwater. Such pollutants from landfills and industries have been a matter of big worry. These along with pollution of groundwater caused by chemical fertilizers and pesticides have been flagged as major concerns already. Governments need a conclusive policy regime to take care of water woes in India

Groundwater depletion is a major concern the world is facing now. A scientific study published in 2014 found out that India is among the top five countries where groundwater depletion was the highest in the first decade of 21st century. The other countries are United States of America, Iran, Saudi Arabia, and China. This study further found that the rate of global groundwater depletionin the study period (2000-2009) is more than double in comparison to the period between 1960 and 2000. While the global groundwater depletion per year stayed at around 56 km³ (cubic kilometres) per year during 1960-2000, it rose to almost 113 km³ per year during 2000-2009. For India, this figure rose from 21.70 km³ to 43.14 km³. What is more important, about 15 percent of the globally abstracted groundwater was taken from non-renewable groundwater during
this period.
Another important scientific study by researchers from the University of California, analysing data from NASA’s GRACE satellite mission, published in 2015, found a decline in water reserves in 21 of the 37 largest aquifers of the world since 2003 threatening water availability in many regions. For more than two billion people across the world aquifers are the primary water source but the shocking reality is that key groundwater basins in all the inhabited continents are being drained. According to this study, the Ganges also faces a high rate of depleting groundwater caused by dense cities and extensive irrigation.

Cities and groundwater

In India, as per a recent report of the NITI Aayog, 21 cities, including the capital city, will run out of groundwater just in two years. It is estimated that about 50 per cent of urban drinking water is drawn from groundwater sources. The same report puts deaths due to drinking contaminated water at 2 lakh per year.
In this report the government said the groundwater in more than 50 per cent of districts of the country have been contaminated with nitrates exceeding permissible limits. This is not all. The government also has reported excessive levels of fluoride, iron, arsenic and heavy metals in groundwater. Just taking the example of India’s capital city should worry all of us. Delhi’s groundwater has been found with excessive levels of nitrate in eight of the eleven districts, excess fluoride in seven districts, excess lead in three districts and excess arsenic in two districts.
Even though the government finds groundwater in major parts of the country potable, the World Bank in 2012 had estimated that more than 60 percent of the country’s groundwater resources will be reaching critical condition in just about two decades. Some independent experts however say this level has already been reached.
According to the government, at the moment, excess of nitrate is found in groundwater in as many as 386 districts, fluoride in 335 districts, iron in 301 districts, salinity in 212 districts, arsenic in 153 districts, lead in 93 districts, chromium in 30 districts and cadmium in 24 districts. There could be presence of more than one, two or three contaminants in excess in groundwater of many districts.
It’s alarming.

Recharging surface water, tackling landfill menace

Cities of the country depend on groundwater reserves for almost half of their water supply, and unfortunately are also a major source of pollution of these resources.Urban areas are faced with a unique situation. While they block a lot of freshwater – falling on the land during monsoon through rainfall – from penetrating into the soil, they cause a lot of recharge of the groundwater with contaminants from leakages of wastewater drains and leaches from landfills and other dumping yards.
Researchers are of the opinion that despite the land sealing effect of several infrastructural projects that often tend to concretise the urban landscape preventing thereby natural recharge from precipitation, there could actually be an increase in groundwater recharge from leaking wastewater drains, water bodies converted into wastewater pools and leakages from poor on-site sanitation systems. According to the International Association of Hydrogeologists, urbanisation greatly modifies ‘groundwater cycle’ because the reduction consequent upon land impermeabilisation is more than compensated by water-mains leakage, waste water seepage, storm-water soak ways and excess garden irrigation; large sub-surface contaminant load from in-situ sanitation, sewer leakage, inadequate storage and handling of ‘community’ and industrial chemicals, and disposal of liquid effluents and solid wastes; and major discharge as a result of inflows to deep collector sewers and infrastructure drains.
Such modification, according to the association, is in continuous evolution, resulting in changes to the groundwater regime which can seriously reduce the resilience of urban infrastructure. The solution therefore for our cities is to go for green and blue infrastructure, as I have been arguing in this column regularly.
We need to let rainwater seep into soil through natural ecosystem-based conservation models in our cities, tighten our wastewater infrastructure and prevent it from leaking, convert all our landfills into sanitary landfill; and, most importantly, recycle, treat and reuse most of our resources, be it water or daily use materials. Above all, there is an urgent need for conservation and rejuvenation of existing wetlands and green spaces. Further, creation of new waterbodies and forests in urban geographies are essential to fight groundwater depletion and contamination.