Yesterday, 22 March, the world including India celebrated World Water Day 2018, the theme of which was Nature for Water. Its aim is to generate awareness of the fact that nature-based solutions should be explored to meet water challenges of the 21st century.

Nature-based solutions cover a wide range of approaches and technologies which use natural process to address a variety of environmental, social and economic challenges in sustainable ways.

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Such solutions relevant in the field of water management are water resources management, river protection, wastewater treatment, pollution prevention, etc.

The sustainable development goals (to be achieved by 2030) on water and sanitation, aim to echo the above concept by stressing on protection and restoration of water-related ecosystems, including mountains, forests, wetlands, rivers, aquifers and lakes.

They also target improvement of water quality by reducing pollution, minimising release of hazardous chemicals, and reducing the proportion of untreated waste water substantially by increasing recycling and safe reuse globally.

The 21st century challenges in the water sector, inter alia, centre around water availability and its access. Over the world, about 2.1 billion people are without access to safe water.

In India, over 76 million people lack access to safe water, the population living in peri-urban areas, etc. The available water is not always safe and is contaminated.

To augment the safe water availability, not only should the water be of potable quality, but the sources of supply have to be enhanced. Unlike conventional water supply through piped water, use of drinking water ponds in some rural coastal areas, or developing integrated tanks including revival of surface water ponds are examples of natural measures for augmenting the sources.

Further, the rainwater harvesting tool would help in this direction, being a natural process of augmenting safe water availability.

Many states/cities have mandated these measures. This option also helps in recharging of ground water resources.

The water can also be collected on rooftops by residents and stored in private tanks to be used for various purposes such as toilet flushing, gardening etc.

Second, waste water in a circular economy is a resource and if recycled and treated, augments water availability. Globally, 10 per cent waste water is treated. In India, capacity to treat waste water is about 37 per cent.

Treating waste water on site rather than using conventional methods through sewage treatment plants is one example of nature-based solutions being tried in many cities.

Further, wetland ecosystem helps treatment of waste water in a natural way. Wetlands have important ecological functions such as maintaining ground water table and preventing excessive soil erosion.

They also capture run off and clean water. For instance, the East Kolkata Wetland, a Ramsar site since 2002, acts as a kidney to Kolkata for its wastewater treatment, and has 254 sewage-fed fisheries, garbage farming fields, and agricultural land.

And it also produces 11,000 metric tonnes of fish annually and helps fish farmers save Rs 60 million annually through the reduced need for fish feed.

Third, river rejuvenation and cleaning the river are potential areas where nature-based solutions can be very effective.

Today Indian rivers are under threat due to flow alteration, water extraction, degradation of flood plains and drainage basins, over-exploitation of fish and of course, climate change.

Further, there is not enough vegetation on land; when land is covered by rain forest, precipitation gathers in the soil and feeds the streams and rivers.

There is a need to treat the river as a ‘living entity’, thereby focusing on its health and life. To meet these challenges, the environmental flow in a river should be ensured, which will enhance the biodiversity in the river ecosystem.

Unfortunately, there is no comprehensive policy today on the subject. Many rivers dry up in India during the post monsoon season. In some cases, the river water does not even travel to the sea.

The drying up of rivers has high linkage with ground water depletion and drying up of riverside tanks/ponds.

Tree plantation on the river side augments river flow. The forests have beneficial impact on control of soil erosion, control of floods, improvement of water quality and increase in base flow in a river.

Fourth, water pollution occurs when there is physical, chemical or biological change to quality of water bodies – rivers, lakes, oceans, etc – that has harmful effects on any living things that use or live in it.

Such pollution is caused by untreated sewage, waste from domestic households, industrial and agricultural activities. Like surface water, the groundwater and especially underground acquifers are also contaminated.

Such contamination results due to excessive drawal of ground water, resulting in inland salinity, presence of fluoride materials in both igneous and sedimentary rocks, existence of arsenic and its compounds, etc.

The nature-based solutions to minimise pollution include various measures such as denitrification, use of septic tanks, having wet lands, etc.

For example, dentrification is an ecological process that converts nitrates into nitrogen gas, and prevents leaching of nitrate into soil to contaminate ground water.

It avoids over-fertilization as a result of fertilizer run off which increases the nitrogen content of water and causes excess growth of algae, etc. Septic tanks treat sewage by separating solids from liquids, relying on biological processes to degrade the solids into liquids.

Wetlands also serve as a buffer zone to filter rain run-off and help remove pollutants from water.

In addition to conventional water solutions, nature-based solutions to India’s water problems should be undertaken for more comprehensively addressing the 21st century’s water woes.

The writer is a Distinguished Fellow and Senior Director, Natural Resources and Climate, TERI, New Delhi and a former Secretary, Ministry of Water Resources, Govt. of India.