Rainwater Harvesting System

Understanding Rainwater Harvesting

Before elaborating details of feasible installation, let we explain what is Rain Water harvesting. Conventionally we depend on natural water sources such as reservoirs, Rivers, Ground water (bore wells, Open wells) to satisfy our water needs. However nowadays everyone is well aware that these sources are not capable to satisfy our water needs throughout the year. Eventually we end up in paying huge cost and inconvenience due to Tanker water supply. This is because we generally do not pay much attention to one of the purest form of water, that is Rain Water. In every monsoon season huge amount of rainwater is getting wasted. Due to vast urbanization and cement concrete buildings and pavements this rain water cannot percolate in the ground and thus cannot re-charge the ground water sources resulting in drying of bore wells. This surface run off water gets drained down and finally proves to be useless. If we can trap and collect this huge water and naturally occurring water source then it can satisfy our water need very well and thus resulting in a huge savings which we may otherwise pay for water tanker supply. Rainwater harvesting systems in a simple term is to collect the rainwater from roof and from roads or ground pavements, treat this collected water and store it in to storage tanks or recharge in to bore well or open well.

Types of Rain water harvesting implementation strategies

Roof Top Rain Water Harvesting:

This is the most important method of rainwater harvesting because rainwater collected on the rooftop is less contaminated than the surface rainwater.

Roof top rain water harvesting system is comprises of following components

• Catchment Area: This is the area (in horizontal plane) which is exposed to the rain fall and thus this becomes the main component in this system. In simple terms the area of a roof or a terrace which is exposed to the rain fall is called as catchments area. Quantity of rain water harvested by such roof depends on the type of roof material as well as the shape of the roof. How to compute the quantity of rainwater, which can be collected by any roof, is explained in the section “Computationof rain water quantity”.
• Rainwater Conveyance System:Collected rainwater on the terrace area needs to be conveyed up to the rainwater filtration units. This conveyance system is depends on the type of roof present at the particular site. For a flat roof of a building, collected rainwater can be conveyed up to the filtration system with the help of a PVC (UV stabilized) pipes, AC or GI pipes. For a inclined roof or Industrial shed, for collection of rain water PVC (UV stabilized) rain water gutters or GI rain water gutters with intermediate withdrawal pipes can be used to convey the collected rain water up to the filtration units.
• Water Storage:Collected and treated rainwater can be stored in the existing storage tank (depending on the site condition) or new tank can be constructed as per the requirements. In rainwater storage very important aspect to keep in our mind is to maintain the hygienic condition of the storage tank. Regular cleaning and disinfections of the storage tank is essential. The capacity of the storage tank can be decided on the following factors.
• Filtration System:Space and funds available for the construction of a new tank .This is a very important factor to be considered while designing a storage tank. If it is intended to use the treated rainwater in the water scarcity period i.e.in the summer only. Then capacity of the storage tank to be built according to the summer water requirement for that particular site. However in that case stored rainwater should be disinfected regularly.
• Immediate use of the rainwater:: If the treated rainwater is intended to be reused in monsoon season. Then it is recommended to have storage capacity for three rainy days. Otherwise it can be recharged in to bore wells by connecting the main filtered water header to bore well casing piping.

Implementing Rainwater Harvesting Systems

For industries, residential complexes, and institutions aiming to implement a rainwater harvesting system, the following considerations are crucial:

• Site Assessment: Evaluating the total catchment area and potential water collection volume.
• Regulatory Compliance: Ensuring the system follows local water conservation policies and guidelines.
• System Design: Installing an efficient network of pipelines, filtration units, and storage tanks tailored to site requirements.
• Maintenance & Monitoring: Regularly cleaning filters, tanks, and pipes to prevent clogging and contamination.