Rain Water Harvesting

What is rain water harvesting?

Rain Water Harvesting or(RWH) is the collection and storage of rain, rather than allowing it to run off. Rainwater is collected from a roof-like surface and redirected to a tank, cistern, deep pit (well, shaft, or borehole), aquifer, or a reservoir with percolation. Dew and fog can also be collected with nets or other tools. Rainwater harvesting differs from stormwater harvesting as the runoff is collected from roofs, rather than creeks, drains, roads, or any other land surfaces. Its uses include watering gardens, livestock, irrigation, domestic use with proper treatment, and domestic heating. The harvested water can also be committed to longer-term storage or groundwater recharge.

Rainwater harvesting is one of the simplest and oldest methods of self-supply of water for households, and residential and household-scale projects, usually financed by the user. However, larger systems for schools, hospitals, and other facilities can run up costs only able to be financed by owners, organizations, and governmental units. Tamil Nadu was the first state to make rainwater harvesting compulsory for every building to avoid groundwater depletion. The project was launched in 2001 and has been implemented in all rural areas of Tamil Nadu. Posters all over Tamil Nadu including rural areas create awareness about harvesting rainwater. TN Govt site. It gave excellent results within five years, and slowly every state took it as a role model. Since its implementation, Chennai had a 50% rise in water level in five years and the water quality significantly improved.

What are the advantages of rainwater harvesting?

The advantages of rainwater harvesting are:

It is cost-effective
Conserves water
A source of water for landscape irrigation
It is a simple method and easy to practice
It reduces soil erosion and pollution of water bodies due to fertilizers and pesticides
What are the factors affecting the amount of rainwater harvested?

The factors affecting the amount of rainwater harvested are:

Catchment features
Quantum of runoff
The capacity of storage tanks

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What are the benefits of RWH( Rain Water Harvesting )?

Rainwater is very good for plants as it contains a lot of nutrients. It is slightly acidic, naturally, which helps in maintaining pH balance. It is believed that rain contains vitamin B12. It is true but rain does not inherently contain Vitamin B12.

Composition of Rainwater

The constituents of rainwater are built primarily by dissolved particulate materials from the upper troposphere and secondarily by dissolved gases. Rainwater compositions vary largely as per the geography of the place; the rain near coastal regions have salt content and CO2 as Bicarbonate anion (acidic pH). Even though rain absorbs gases and pollutants from the atmosphere, it gets pure as it reaches the earth’s surface.

Every rainwater harvesting system contains 5 basic components:

Catchment – A rooftop or a paved flooring surface or a landscaped area can be a catchment for the rainwater harvesting system. These are the areas where pouring rain is collected. Their surface area is calculated in square meters.
Gutters and Down take pipes – the components are used to transport water from catchment surface to storage tanks. Generally, PVC or FRP rooftop rain gutters are installed due to their anti-corrosive properties.
Filters and first flush devices – Rooftop or catchment surface filters are used to prevent grit, leaves, and dirt from entering the gutters or down take pipes. Additionally, a first flush device can be installed to divert the water from the first rain which accompanies great amount of pollutants, from entering the storage tank.
Storage tanks – The over-the-ground or underground concrete or plastic tanks for storing the collected rainwater.
Delivery systems – This includes piping systems that convey the stored rainwater to the point of end-use.

Advantages of Rainwater Harvesting

The benefits of rainwater harvesting system are listed below.

Less cost.
Helps in reducing the water bill.
Decreases the demand for water.
Reduces the need for imported water.
Promotes both water and energy conservation.
Improves the quality and quantity of groundwater.
Does not require a filtration system for landscape irrigation.
This technology is relatively simple, easy to install and operate.
It reduces soil erosion, stormwater runoff, flooding, and pollution of surface water with fertilizers, pesticides, metals and other sediments.
It is an excellent source of water for landscape irrigation with no chemicals and dissolved salts and free from all minerals.