RAINWATER HARVESTING

Rainwater harvesting is the process of collecting, filtering and storing water from roof tops, paved and unpaved areas for multiple uses. The harvested water can also be used for potable purposes after testing and treatment. The surplus water after usage can be used for recharging ground water aquifer through artificial recharge techniques. This can also result in improving the quality of the ground water e.g. lower fluoride content in ground water. Rainwater harvesting mechanisms are designed after assessing the site conditions such as incident rainfall, subsurface strata and their storage characteristics, infiltration test and by building suitable structures to collect and store rainwater.

Rainwater harvesting system provides a source of soft, high quality water, reduce dependence on wells and other sources, and, in many contexts, are cost effective. Rainwater harvesting system can range in size from a simple PVC tank  to a contractor designed and built sump – costing thousand of rupees. Rainwater system are inherently simple in form. Harvesting rainwater is not only water conserving, it is also energy saving since the energy input required to operate a centralized water system can be bypassed.

A range of filters for different filtration rates have also been designed using different filter media.

Benefit

• To harness good quality water resource now being wasted
• To prevent groundwater depletion
• To augment the expensive piped water supply
• To save expenditure on water
• To prevent soil erosion and urban flooding
• Inexpensive and simple technology
• Aids ecological conservation

Rainwater Harvesting in Different type of Buildings :

Normally,debris, dirt and dust get deposited on the roof during non-rainy periods.When the first rains arrive, this unwanted material will be washed into the storage tank. This may cause contamination of water collected in the storage tank thereby rendering it unfit for drinking and cooking purposes. Therefore, a first flush system can be incorporated in the Roof top Rainwater Harvesting Systems (RRHS) to dispose of the first flush so that it does not enter the tank. There are two such simple systems. One is based on a simple manually operated arrangement whereby, the down pipe is moved away from the tank inlet and replaced again once the first flush water has been disposed. In another simple and semi automatic system, separate vertical pipe is fixed to the down pipe with a valve provided below the T junction. After the first rain is washed out through the first flush pipe the valve is closed to allow the water to enter the down pipe and reach the storage tank.

Rainwater Harvesting Basic Components

Rainwater systems come in all shapes and sizes, from simple catchment system under a downspout to large above and/or underground cisterns with complex filtration systems that can store thousands of gallons of water. Most rainwater collection systems are comprised of the following basic components:

Catchment surface - rooftop or other raised solid surface. The best catchment systems have hard, smooth surfaces such as metal roofs or concrete areas. The amount of water harvested depends on the quantity of rainfall, and the size of the surface and the slope of the catchment area.

Gutters and downspouts - also known as distribution systems that channel the water from the catchment area to a holding container such as a barrel, cistern, planted area, etc.

Leaf screens - a screen that removes or catches debris.

Roof washers - a device that diverts the "first flush" of rain before it enters the storage tank. Most rainwater suppliers recommend that the "first flush" of water is diverted to an outside area of the storage system, since the catchment surface may accumulate bird droppings, debris and other pollution.

Storage tanks - In general, the storage tank is the most expensive component of a rainwater harvesting system. There are numerous types and styles of storage tanks available. Storage can be above-ground or underground. Storage containers can be made from galvanized steel, wood, concrete, clay, plastic, fiberglass, polyethylene, masonry, etc. Examples of above-ground storage include; cisterns, barrels, tanks, garbage cans, above ground swimming pools, etc. Storage tank prices vary based on different variables such as size, material and complexity. To inhibit the growth of algae, storage tanks should be opaque and preferably placed away from direct sunlight. The tanks should also be placed close to the areas of use and supply line to reduce the distance over which the water is delivered. Also consider placing the storage at an elevated area to take advantage of gravity flow. The tank should always be placed on a stable and level area to prevent it from leaning and possibly collapsing.

Delivery systems - gravity-fed or pumped to the landscape or other end use areas.

Purification/treatment system - needed for potable systems to make the water safe for human consumption. Please check with your local health department for information on filtration systems and certification requirements.