Rainwater Harvesting in India

Table of Contents

• What is Rainwater Harvesting
• Importance of Rainwater Harvesting
• Benefits of Rainwater Harvesting
• Rainwater Harvesting Methods
  • Ground Water Recharge
  • Surface Runoff Harvesting
• Types of Rainwater Harvesting
  • Rooftop Rainwater Harvesting
  • Contour Bunds
  • Gabion Structure
  • Percolation Tanks
  • Check Dams
  • Dugwell Recharge
• Limitations of Rainwater Harvesting
• Future Potential of Rainwater Harvesting in India

What is Rainwater Harvesting

Rainwater harvesting is the method of collection and storage of rainwater in a tank over the surface or under the surface, prior to it being wasted as runoff. This saved water can then be used at the time of need. This approach is ancient and has been practised in India for ages. Water is crucial for the development of humans, agriculture, cattle and various other aspects. However, with time, several regions face water scarcity, which demands the adoption of different approaches to preserve water.

Rainwater harvesting is one of the most widely used approaches to ensure sufficient water supply when required for different purposes such as irrigation, laundry and others. In recent years, it has gained popularity due to the economic and environmental benefits it offers. The groundwater levels are decreasing, and the frequent fluctuation in climate conditions force the use of this approach to preserve water and mitigate the hostile effects of water scarcity.

Importance of Rainwater Harvesting

Rainwater harvesting is important as it is highly needed to mitigate the water scarcity crisis. It helps overcome the water inadequacy to meet the requirement. It is useful in preserving the declining groundwater level and helps enhance water availability in specific regions. The water can later be used for different purposes, promoting sustainable development.

Rainwater harvesting helps increase the water level in the subsoil, which has been declining in urban areas because of the paving of the open areas. It is helpful in improving the water quality through dilution and increasing the productivity in agriculture.

Benefits of Rainwater Harvesting

• Water Conservation
• Increased Water Availability
• Reduced Soil Erosion
• Sustainable Irrigation
• Cost Savings and Community Engagement

Water Conservation: Rainwater harvesting helps reduce water runoff, as the water is collected in tanks or reservoirs. This ensures water conservation, which can be used for various required activities.

Increased Water Availability: when the rainwater is harvested and stored, it can be used according to the need without relying on other water sources.

Reduced Soil Erosion: When the rainwater is harvested, it helps stop soil erosion by reducing water runoff.

Sustainable Irrigation: Stored water collected from rainwater harvesting can be used for irrigation, thus offering a sustainable irrigation method with a steady supply of water.

Cost Savings and Community Engagement: Rainwater harvesting offers a cost-effective method to access high-quality water, allowing farmers to take advantage of it and use it responsibly for agricultural purposes. This also promotes community engagement as the farmers can create a single reservoir from where all farmers can use water for irrigation.

Rainwater Harvesting Methods

Ground Water Recharge

This is one of the rainwater harvesting models, where water from the surface moves downward to the groundwater. Groundwater recharge, being a hydrologic process, allows water to reach an aquifer. This aquifer acts as a distribution system where the surplus water can be used to recharge the groundwater level using artificial methods.

Surface Runoff Harvesting

In this rainwater harvesting system, the rainwater flows away as runoff from the surface and is stored. The flow of the water from various streams is diverted towards the tank or reservoir present underground or at the surface. This collected water is then used for agriculture, cattle farming, or domestic work. This harvesting method is most useful in urban settings.

Types of Rainwater Harvesting

There are different types of rainwater harvesting, which are as follows:

• Rooftop rainwater harvesting
• Contour Bunds
• Gabion Structure
• Percolation Tanks
• Check Dams
• Dugwell Recharge

Rooftop Rainwater Harvesting

In this type of rainwater harvesting, the water is collected from the rooftop of a house or any infrastructure. The water is collected through pipes or gutter directly connected to the reservoir. This water is then used later for different purposes.

Contour Bunds

This type effectively conserves soil moisture during long-duration watersheds. In low rainfall areas, these are well suited as the farmers can easily hold the runoff by creating bunds along the contour with equal elevation. Adequate spacing between buds prevents water from reaching speeds that can erode the land.

Gabion Structure

This is a form of check dam constructed at around 0.5 m height over a stream less than 10 m wide. The bund here is created using steel wires and boulders locally available by farmers, which are then anchored at the stream's banks. The excess water overflows the dam, and the remaining water is stored as a recharge source. The slit deposits over time and vegetation growth make the bund impermeable, assisting in greater water retention.

Percolation Tanks

These tanks are created on the water body to recharge the groundwater. It allows water to infiltrate the ground and replenish the groundwater. These are formed at a significant height from where the water can run down to cultivable lands or wells for the majority of the benefits of the farmlands.

Check Dams

Also known as nala bunds or cement plugs, these are constructed on the gentle slope of a small stream. With a height usually less than 2 m, allowing excess water to overflow, it is made to recharge the stored water quickly. Shallow trenches are created to form low-cost check dams. A series of these dams are constructed in the stream to gain maximum water recharge using clay-filled cement bags.

Dugwell Recharge

These are the wells that already exist and are used as recharge structures after proper cleaning and desilting. The water is guided to the structure using pipes from the desilting chamber. This structure helps farmers easily gain access to water when required. However, periodic chlorination is required to control bacteriological contaminations.

Limitations of Rainwater Harvesting

• Limited storage
• Frequent maintenance
• High initial cost
• Infrastructure issues

Limited storage: The storage facility is usually limited, which restricts the amount of water collected.

Frequent maintenance: The storage units, tanks, or reservoirs are susceptible to algae growth, insects, and lizards, which means regular maintenance is necessary.

High initial cost: The initial cost is high and varies based on the storage size, location, and technology.

Infrastructure issues: Different materials are used in different rainwater harvesting systems, and thus, some roofs or walls are prone to chemical seepage, dirt, and insects.

Future Potential of Rainwater Harvesting in India

Some of the reasons rainwater harvesting in India is gaining importance are:

• Water Shortage: With the increasing population, demand for water is only increasing. A sustainable water source is required for agriculture; thus, rainwater harvesting becomes an easy solution. The water is collected and used for different purposes, reducing the dependence on municipal water supplies.
• Cost Saving: The lack of sufficient water for everyone’s use has resulted in increasing water costs in several areas. Collecting rainwater allows farmers to reduce expenses associated with municipal water supply and use collected water for agriculture.
• Water Security: Lack of access to clean water is a common issue faced by several people, and thus, rainwater harvesting provides a sustainable and more accessible answer to water security. It offers a dependable water source for communities, households and farming needs.
• Climate Change: Water availability is affected due to changes in climatic conditions. From changing rainfall patterns to droughts, rainwater harvesting allows farmers to tackle these changes through a reliable water source, thus maintaining their farms.