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11 Feb
Water Technology
By WAE Corp on "Water Technology"

Rainwater Harvesting: From Runoff to Recharge

Our planet is getting dehydrated due to incessant man-made maneuvers. The rainwater is the most viable freshwater source in the midst of the Global Water Crisis. Through Rainwater Harvesting, let’s divert the runoff and recharge our groundwater before it’s too late!

Full Article

Water, the majestic elixir of life! Water to the planet is what blood is to the humans. The ancient Indian scriptures chronicle the magnificence of water as it can neither be created nor destroyed. It only manifests itself into different forms and circulates around the planet depending on the climatic, geographic and biological factors.

The hydrological cycle, commonly known as ‘water cycle’ comprises the stages of water depicting its history as it flows in the water bodies, air, soils, plants and animals. It involves the total Earth system encompassing the atmosphere (the gaseous envelope), the hydrosphere (surface and surface water), lithosphere (soil and rocks) and the biosphere (plants and animals). In one of the three phases (solid, liquid and vapour) the water passes through these four parts of the earth system (Hydrology in ancient India). 

Water cycle

The water cycle begins with evaporation from the surface of the ocean. As moist air is lifted, it cools and water vapour form clouds through condensation. Moisture is transported around the globe through the air and returns to the surface as precipitation. Some of the water may evaporate back into the atmosphere and some water may penetrate the surface and become groundwater. The time taken by nature to revive its hydrological cycle is called ‘cycle capacity’. With rainfall and groundwater forming its fundamental parts, the hydrological cycle maintains terrestrial and aquatic equilibrium. This ecosystem equilibrium sustains all life forms. Any extremity would evidently put pressure on the natural balance of a healthy ecosystem.

Water Woes

Water scarcity exacerbated by climate change and human-induced disasters have put a lot of pressure on the water cycle. Population growth, climate change, pollution etc. are posing challenges to the hydrological sustenance.  By 2025, the total urban population is projected to double to more than five billion and 90% of this increase is expected to occur in developing countries. Agricultural intensification, water-intensive lifestyles, industrialization, urbanization are steering their way to the global water crisis. Indian economy that thrives largely on agriculture may face 6% loss in its GDP due to water scarcity.  The man-inflicted contamination and water pollution is reducing the hydration capacity of the existing water sources. Around 200,000 Indians die every year due to lack of access to clean water as per NITI Aayog report. It also alludes that 21 cities might run out of groundwater by 2020. The report, encapsulating data from 24 of India’s 29 states, says the crisis is ‘only going to get worse’ in the years ahead!

We need to avert ourselves from the drastic doom that these water extremities are coxswaining us to. Effective management of our existing water sources would engineer a sustainable system of water conservation. While the prevalent freshwater sources are limited and depleting, rainfall fills the streams, rivers, lakes and replenishes the groundwater. Therefore, the rainwater is the most viable freshwater source in the midst of water depletion and contamination.

Rain permeates beneath the ground and over some time becomes shallow stratum groundwater. The water then percolates deeper to form deep stratum groundwater over a long period of time. The occlusion of Earth’s crust with concrete and asphalt structures has reduced the area where rainwater can permeate underground thereby accelerating the surface water runoff.  In India, during monsoons, all the rain falls in about 200 hours and half of it in 30-40 hours. There goes the water down the drain! Ideally, for average rainfall of 1,000mm, approximately four million litres of rainwater can be collected in a year in an acre of land (4,047 m2), post-evaporation.

Rainwater Harvesting

From the standpoint of preserving our natural hydrological cycle, it is important to retain rainwater, channelize it towards human consumption and conserve the natural groundcover. Rainwater harvesting is, therefore, a viable alternative to large-scale water withdrawals and an environmentally sound solution to augment the freshwater sources.

It is basically a process to locally collect and store rainwater through different technologies to meet the future demands of human consumption. The art and science of rainwater harvesting synthesize the linkages between man and the ecosystem. It is an important aspect of land and water resource management for hydro-climatic balance, human wellbeing and ecosystem productivity.

Rainwater harvesting has been practised for more than 4000 years using traditional methods depending on the local conditions. This technology is suitable at places with significant rainfall and scarce good quality fresh surface water. The rainwater is the purest form of water and is acceptable for potable and non-potable purposes with little or no treatment. This technology not only supplements the other water sources but also provides a water supply buffer in the times of emergency or breakdown of public water supply systems. Because of India’s hydro-climatic extremes – Intense monsoons followed by prolonged droughts, storage of rainwater at appropriate sites becomes imperative.

The Rainwater (Harvesting and Storage) Bill, 2016 was introduced in the Lok Sabha “to provide for compulsory harvesting of rainwater in every Government, residential, commercial and institutional building to conserve water and ensure recharge of groundwater and for matters connected therewith.” In the light of the Bill, various states have begun formulating policies to make rainwater harvesting mandatory. Recently, National Green Tribunal slammed educational institutes in Delhi that had not yet installed rainwater harvesting systems.

The rainwater harvesting ought to be promoted as a mass movement initiated by the government. What is mandatory in the beginning would turn itself into a ‘practice’ among people. Eventually, this technology would be instrumental in achieving the goals of water security along with diminishing all water woes. So, let’s hydrate our planet by harvesting the downpour.



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