Saving Our Cities With Rainwater Harvesting : Sachin Agarwal, CMD – Maple Shelters 

In a land-locked city like Pune, the importance of water is inescapable. Even at a national and global level, climactic changes as well as other factors are causing water levels to decrease. Overpopulation has led to more and more acquisition of shallow lands for landfills, reducing the number of available water bodies. Deforestation has further compounded the scarcity of water, as this causes regional rainfall to become more unpredictable.

Though India is advantageously placed geographically, several regions are seriously affected by lack of usable water – a city like Pune is, in fact, a prime example of this phenomenon. In the years to come, the majority of the world’s population will be living in urban areas. Because of rapid real estate development in our cities, the highest demand for resources such as water is centered there. Moreover, with limited developable land, multi-story residential complexes are being built at a very fast rate.

The earth’s surface is 70% water; however, very little of this is drinkable or usable by humans. It is more than likely that we will soon reach a point when the amount of usable water present on the earth’s surface is not enough to meet all the needs of the growing population and the development taking place alongside. Water as a resource is needed in every activity, be it farming or construction of buildings. Rainwater harvesting is the only real solution available now, and is a practice that is catching on in urban as well as rural areas.

Rainwater harvesting involves collecting, filtering and storing rain water to be used for various residential and industrial purposes. The primary apparatus includes a down pipe and a first flush arrangement, a filter unit and a storage tank. Rainwater provides a clean, free source of potable water. Rainwater harvesting employed in residential properties, which usually involves trapping rainwater from roofs and guiding it into storage tanks or cisterns in the ground, can meet 50% of everyday household needs.

In fact, rainwater harvesting is not just a way to make maximum use of this natural resource, but also a way to do with minimum environmental impact. Naturally, it also results in significant cost savings on utilities bills.

The various benefits of harvesting rainwater in urban residential areas include:

Most water supply in urban areas comes from reservoirs, rivers and lakes. Urban water supply also involves putting up treatment plants, supply pipes as well as pumping stations. In most Indian cities, city planning authorities cannot match utilities with the pace of growth.

Water resources are impossibly stretched even in the most developed cities in the world, but the problem is worse in developing countries like India, which see a greater rate of population movement from rural areas to urban areas. Geologists and engineers are constantly struggling to find new sources of water. The demand for water for industrial uses has led to further depletion of ground water levels.

In Indian cities like Pune, there is relentless drilling for ground water, with shafts going deeper as the search for more water continues. In such a scenario, rainwater can significantly supplement a city’s water supply and reduce the pressure on conventional water supplies.

When rainwater is harvested in a housing complex, it can be used for various non-drinking purposes that require large volumes of water. For instance, rainwater can be used for functions such as household and vehicle cleaning, garden and green space maintenance and toilet flushing. This means greatly reduced utility bills, because rainwater can complement the conventional water supply system. This is equally applicable for industries that use up large quantities of water for various uses. Industries can make use of rainwater for the majority of their operations and therefore reducing pressure on ground water.

Rainwater harvesting can be used as an insurance for times when water supplies are compromised for any reason. This is important, because climate change has caused major disruptions in the weather patterns in many Indian cities. Rainwater can be collected and stored, and used during drought seasons to complement the stretched normal water supply. In cities like Pune and Mumbai, the dreaded bane of water shortage and rationing is significantly mitigated with rainwater harvesting, which also reduces the dependency on water reservoirs and dams.

When several residential buildings in a city use rain water harvesting systems, there is a significant decrease in surface run offs, floods, soil erosion and reduced pressure on the drainage system. Collecting rain water means less contamination of surface water from surface run off, when rainwater picks up pesticides and other harmful chemicals that ends up in rivers and lakes.

Collecting rainwater, especially in low-lying areas, reduces the possibility of floods. It can also protect the soil from erosion caused by peak storm runoffs. Rain water collection therefore also serves an environment conservation purpose by preventing contamination of other water sources and ensuring that less water is drawn from lakes and rivers.

Rainwater collection can be used to recharge ground water levels through various methods, and to improve the quality of ground water. This helps in improving urban greenery; in fact, this is the only reliable means of having green areas within urban areas without leeching off from existing water supplies. Within large residential projects, such water can be used for landscape irrigation.

Rainwater harvesting systems are easy to install and maintain. Since rainwater is pure, there is no need for the complex purifying systems that have to be employed to clean ground water. Rainwater collection systems are based on basic technology, and maintenance only involves occasional cleaning of the storage tanks and collection pipes to ensure that the rainwater collected is not contaminated.

In fact, rainwater harvesting can be achieved by anyone. Installation of gutters is the first step for any building without them, along with a filtration system to ensure that leaves or any other kind of debris do not find their way into the storage tank. Safety precautions include having locking lids or bars to prevent contamination of the stored water and the breeding of mosquitoes. Catchment areas in a city can include paved areas such as car parks, roads and paths, where water can be harvested for several non-drinking purposes.

The Indian government has laid out a number of plans concerning harvesting of rainwater and putting it to maximum use. A good example is the ongoing work done by Greater Vishakhapatnam Municipal Corporation (GVMC). The municipality is going to fine households that do not have the mandatory rainwater pits.

New apartment projects in several Indian states are now required to be engineered to have rainwater harvesting systems. In many areas, the government is also promoting rainwater harvesting as a means to address the scarcity of water for agriculture. As rainfall is getting visibly scantier, the government is planning to implement special measures and urge residential societies, educational institutions and similar buildings to optimize water saving and usage.

The increased areas of paving and roads is preventing the proper percolation of rainwater, ultimately affecting the water table and causing water bottlenecks in the outskirts. Installation of pits at regular intervals over urbanized localities is a good way to trap this water for better use.

The Centre for Science and Environment (CSE) is now promoting the maximum use of rainwater and its harvesting all across the country. It has launched various campaigns to educate people on India’s traditional water harvesting processes. The organization has gathered all NGOs working in this area under its wings, and is running consultancies to improve the conditions.

Rainwater harvesting should be the default code for sustainable households. Builders and architects are getting aware of and implementing the same in their designs. In many areas, buildings into which rainwater harvesting systems have not been integrated are being partially reconstructed to add this vital measure.