Introduction

As the population is rising and the climate is changing, the need for resources, like water, is rising. Although water is available in unlimited quantities in oceans and seas, this water is salty and not consumable. Therefore, the need for water conservation has given rise to the popularity of rainwater harvesting. The principle is to collect the water from rainfall for daily use rather than exploiting water resources further. Rainwater is a resource that is available to us but is not utilised to its fullest potential. Hence, the conclusion of rainwater harvesting or of adopting this means of water conservation is to counter water scarcity. 

What is Rainwater Harvesting?

Rainwater harvesting is a method of storing rainwater during rainfall, through certain procedures, for long-term uses. Moreover, rainwater harvesting also allows recharge of groundwater, as the groundwater levels are constantly getting depleted. The system for the collection of rainwater is artificially designed so as to collect and store water using man-made or natural catchment areas. 

Rooftop Rainwater Harvesting

In the case of rooftop rainwater harvesting, the rainwater is collected in catchment areas (watershed) present in rooftops, and then it is stored in the reservoirs. The catchment area can be built on roofs made of galvanised iron, reinforced cement concrete, or corrugated sheets. Usually, the roofs are sloping structures and the water gets collected around its edge, in channels. From these channels, the water needs to be transferred to a storage area, usually a tank/reservoir or a recharge structure, through conduits. 

The tank has a filter for the removal of suspended pollutants. This chamber or the filter unit uses fibre, gravel layers, and coarse sand as its filtering media. However, the first flush diverter is an important component of the system. It diverts the first rains, which usually contain more pollutants, from entering the storage unit. 

While for smaller households a 1000-2000 L tank can do a good job for greater purposes like irrigation, etc. the capacity needs to be a lot more. 

Moreover, other than for personal use rooftop rainwater harvesting also serves the purpose of recharging groundwater aquifers. The percolation of rainwater to recharge groundwater takes place using various structures like- bore wells, recharge trenches, recharge shafts, open wells, recharge pits, and so on. 

Advantages of Rainwater Harvesting System

• The additional water resource is available to the household without much cost. 
• The system advances means of water conservation and helps to reduce the rising demands for the resource.
• The strategy of rainwater harvesting not only adds to the quantity of depleting groundwater resources but also enhances its quality.
• The system setup is not that complex. It is quite easy for households to install as well as operate.
• A region that depends on rainwater harvesting becomes highly self-sufficient and self-reliant, in the face of a rising water crisis. 
• The collection of rainwater helps for irrigation purposes, especially in those regions which lack sufficient availability of water resources. 
• Rainwater Harvesting is also used to divert the collected water towards lakes and nearby ponds, whose water levels are decreasing.
• It stops the wastage of the potential of rainwater, as a resource. Rainfall usually leads to flooding, soil erosion, and wastage from run-off. Therefore, rainwater harvesting attempts to use rainwater in a way that is advantageous to humans and reduces a few of its negative aspects. 

Rainwater Harvesting in Irrigation

Rainwater harvesting system made for irrigation purposes has to effectively divert the water stored to the various landscapes. 

However, for a larger collection of rainwater, rooftop catchment areas might not necessarily serve the need. Therefore, for irrigation purposes, either natural catchment areas are to be used or special systems are to be made for such irrigation.

Rainwater is considered better for irrigation as it helps farmers to cut down on the water bills as well as rainwater is free from all sorts of chemicals which can yield better quality crops. 

Conclusion

The topic of rainwater harvesting has been explained and elaborated on. The essential question of what is rainwater harvesting has been answered. Moreover, one also has the scope to learn more about the popular rooftop rainwater harvesting system. The various advantages of implementing the rainwater harvesting strategy have been included, as well. The FAQs section attempts to address the most probable queries that might arise. The additional information in the FAQs section will enhance the understanding of the topic.