India has 16 per cent of world’s population but only 4 per cent of its freshwater resources. This obviously has led to the present water crisis which will become worse in the coming years. 

The country is also the biggest user of groundwater resources in the world. India’s usage is almost 1/4th of the world’s ground water usage, surpassing that of USA and China combined. This has created a huge shortage of water; plummeting groundwater levels and increasing salt levels like Arsenic and others in them. There are estimates that 63 per cent of Indian districts are threatened with falling ground water levels and in some places like Punjab the groundwater levels have fallen by about 8-10 metres in the last 10 years. 

India’s expected water demand by 2025 is ~ 810 BCM (billion cubic meters). This includes all the water demand for agriculture, industry, household uses, etc. Agriculture is the biggest user of water with estimates of  75-80 per cent of total water usage by it.

India gets an average rainfall of about 3880 BCM.  Its total water demand is approximately 20 per cent of total rainfall.  This rainfall should theoretically satisfy all the country's needs.

However, the rainfall is unevenly distributed; does not always fall where it is needed; and with poor rainwater harvesting systems in place, most of the rainwater simply runs off into the oceans and in the process creates extensive soil erosion.  Thus water needs to be conserved, recycled, and used efficiently to satisfy the growing needs of a country of 1.4 billion population.             

Water vapor management system

Solar energy falling on earth evaporates water from the sea which forms clouds and falls as rain. Part of the water which has evaporated also becomes fog and condenses as dew.  Both these form a part of the water vapor system of the earth.

Water vapor is sufficient to nurture the earth. What is therefore needed are technologies for efficient water vapor management so that it can be used for all our needs. It should be noted that water vapor management is less energy intensive as compared to seawater desalination since solar energy has already evaporated the water. This water vapor management could either be in the form of rainwater collection; cloud seeding, or dew condensation.

Rainwater harvesting strategy

About 70 per cent of India’s agriculture is rainfed and since this sector uses the maximum amount of water it is necessary that proper rainwater harvesting should be developed in rural areas. Large-scale rainwater collection systems using dams that feed the canals have existed since last century. Their scales are huge and making new systems will entail massive costs.

The construction of small rainwater harvesting ponds, which are interconnected, could provide a possible economical solution in rural areas. These could be taluka-based systems where all the irrigation water could be provided by small ponds connected and possibly to river or canal sources.    

These small water storage bodies will act similarly to invertor-battery backup for electric supply. Artificial intelligence (AI) can be used for sizing and optimizing these ponds to provide a year-round water supply.   

Soil excavated during the construction of these ponds can be used for making bricks and in other aspects of the construction and agriculture industry. Naturally, the issue of ownership of these water bodies and the energy requirements to run them will have to be evaluated thoroughly. There is a need to set up a few experimental systems to validate this concept.

In urban areas, rainwater harvesting in every building will help the process. Already such systems exist in a few cities, but the scale is small, and they are few and far between. It should be made mandatory and incorporated as a part of building codes all over the country. The rainwater can be filtered and purified for various uses. Technologies already exist for doing so.

In our Institute we have developed a rainwater harvesting system with solar purification to provide clean drinking water for rural households.  We are now extending it to provide clean drinking water for rural schools. 

Cloud management

Since rain comes from the clouds, there is a need for a cloud management strategy. Solar energy has already evaporated water to form a cloud and hence there is a need to manage it for water production wherever it is needed. This is far better than desalination which requires a huge amount of energy to evaporate water.

Cloud management presently is done in a limited manner via cloud seeding but it is a dicey process since one is not sure where it will rain. I had the great honor of knowing and interacting in the US, during 1970s, with Vincent Schaefer, the father of cloud seeding. He had told me that the whole science of cloud seeding is very unpredictable and unfortunately, till today the situation has not improved.

We, therefore, dreamt of a scheme in the early 1980s about using specially designed kites to suck clouds and transport the vapor to the ground through a hollow pipe which would also act as kite “string”. The water vapor would be condensed by suitable means for water production. The scheme has remained a dream, but I guess with better materials and drone technology it should be possible to make a small prototype and test the idea. I am sure some young engineers may take up this challenge.

Clouds consist of charged water droplets. With varying magnetic fields of the earth, the cloud movement also changes, resulting in rains falling at unpredictable places. The total amount of cloud formation has remained the same since the solar energy is the same. But where they will rain can vary because of earth’s changing magnetic fields (EMF). A detailed understanding of cloud physics and EMF will help us in predicting climate changes and manage them for our benefit.

I am sure there can be many more creative schemes for cloud management, and they should be a challenge for young researchers and water technologists of this country to explore.

Dew condensation

Before the evaporated water goes very high to form a cloud it remains near the earth’s surface as dew. Most of it is found near the coastal areas but also exists in various proportions all over the land mass and is a function of atmospheric water vapor conditions. India’s mainland is endowed with a long coastline of over 5500 km. All the areas situated near this coastline can get clean drinking water through dew condensation.

We pioneered dew collection in early 1980s where we first developed the thermodynamic data for dew condensation for varying atmospheric conditions and then developed a scheme of large-scale dew collection for drinking water purposes for coastal areas.  The scheme envisaged bringing very cool (~ 6-70C) deep sea water to cool the water collection arrays on the shore for dew condensation and collection. 

The calculations based on our work show that the Indian coastline has the potential to produce ~ 40 per cent of India’s total drinking water demand.  Dew water is pure water and hence can be used directly for drinking. However, there is a need to develop economical and innovative dew harvest technologies.

Water is the most precious resource on this planet earth. We cannot survive more than three days without it. Thus there is a need to conserve and recycle it. That will also be the first step towards sustainability and will require innovative water technologies.

These water technologies should be based on the following water vapor management systems :

- Decentralized rainwater harvesting and its usage for various purposes.

- Development of innovative technologies for cloud management.

- Dew collection in coastal areas for drinking water production.

All these strategies combined can substantially alleviate the water crisis not only in India but in the rest of South Asia as well.

(The writer, an IIT and US-educated engineer,  a 2022 Padma Shri award winner, is the Director, of Nimbkar Agricultural Research Institute, Phaltan, Maharashtra. This article is extracted from the Institute lecture {video of lecture} that the author gave on 4 December 2023 at IIT Bombay on the occasion of the 3rd International Conference on Water Technologies)