Rainwater Harvesting

Rainwater Harvesting

Rainwater harvesting is a technique of collection and storage of rainwater into natural reservoirs or tanks, or the infiltration of surface water into subsurface aquifers (before it is lost as surface runoff). One method of rainwater harvesting is rooftop harvesting. With rooftop harvesting, most any surface — tiles, metal sheets, plastics, but not grass or palm leaf — can be used to intercept the flow of rainwater and provide a household with high-quality drinking water and year-round storage. Other uses include water for gardens, livestock, and irrigation, etc.

The reasons for using rainwater harvesting systems answer three questions:

What: Rainwater harvesting will improve water supply, food production, and ultimately 

Who: Water insecure households or individuals in rural areas will benefit the most from rainwater harvesting systems.

How: Since rainwater harvesting leads to water supply which leads to food security, this will greatly contribute to income generation.

-----------------------------------------------------------------------------------------------------------------------------------------

Advantages

Rainwater harvesting provides an independent water supply during regional water restrictions and in developed countries is often used to supplement the main supply. It provides water when there is a drought, can help mitigate flooding of low-lying areas, and reduces demand on wells which may enable ground water levels to be sustained. It also helps in the availability of potable water as rainwater is substantially free of salinity and other salts.

Quality

The concentration of contaminants is reduced significantly by diverting the initial flow of run-off water to waste.^[1]Improved water quality can also be obtained by using a floating draw-off mechanism (rather than from the base of the tank) and by using a series of tanks, with draw from the last in series. Pre-filtration is a common practice used in the industry to ensure that the water entering the tank is free of large sediment. Pre-filtration is important to keep the system healthy. One of the most effective pre-filtration units is the Wisy vortex filter.

System setup

Rainwater harvesting systems can be installed with minimal skills. The system should be sized to meet the water demand throughout the dry season since it must be big enough to support daily water consumption. Specifically, the rainfall capturing area such as a building roof must be large enough to maintain adequate flow. The water storage tank size should be large enough to contain the captured water. Rainwater Management Solutions is the largest rainwater harvesting company in North American for rainwater harvesting. There are rainwater harvesting company start-ups all over the country. The president of Rainwater Management Solutions is also the president of the America Rainwater Catchment System Association (ARCSA)and is currently working with multiple agencies to right codes and standards that can be adopted for the industry.

Rain water harvesting by freshwater flooded forests

New approachesRain water harvesting is possible by growing fresh water flooded forestswithout losing the income from the used /submerged land.The main purpose of the rain water harvesting is to utilize the locally available rain water to meet water requirements throughout the year without the need of huge capital expenditure. This would facilitate availability of uncontaminated water for domestic, industrial and irrigation needs.

Instead of using the roof for catchment, the RainSaucer, which looks like an upside down umbrella, collects rain straight from the sky. This decreases the potential for contamination and makes potable water for developing countries a potential application. Other applications of this free standing rainwater collection approach are sustainable gardening and small plot farming.

A Dutch invention called the Groasis Waterboxx is also useful for growing trees with harvested and stored dew and rainwater.

____________________________________________________________________________________________

History

Traditionally, storm water management using detention basins served a single purpose. However, optimized real-time control (OptiRTC) lets this infrastructure double as a source of rainwater harvesting without compromising the existing detention capacity. This has been used in theEPA headquarters to evacuate stored water prior to storm events, thus reducing wet weather flow while ensuring water availability for later reuse. This has the benefit of increasing water quality released and decreasing the volume of water released during combined sewer overflow events.

   

Earlier

Around the third century BC, the farming communities in Balochistan (now located in Pakistan, Afghanistan and Iran), and Kutch, India, used rainwater harvesting for irrigation.^[8] In ancient Tamil Nadu (India), rainwater harvesting was done by Chola kings. Rainwater from the Brihadeeswara temple (located in Balaganpathy Nagar, Thanjavur, India) was collected in Shivaganga tank.^[10] During the later Chola period, the Vīrānam tank was built (1011 to 1037 CE) in Cuddalore district of Tamil Nadu to store water for drinking and irrigation purposes. Vīrānam is a 16-kilometre (9.9 mi) long tank with a storage capacity of 1,465,000,000 cubic feet (41,500,000 m³).

Rainwater harvesting was done in the Indian states of Madhya Pradesh, Maharashtra, and Chhattisgarh in the olden days. Ratanpur, in the state of Chhattisgarh, had around 150 ponds. Most of the tanks or ponds were utilised in agriculture works.

Present India

• In the state of Tamil Nadu, rainwater harvesting was made compulsory for every building to avoid ground water depletion. It proved excellent results within five years, and every state took it as role model. Since its implementation, Chennai saw a 50 percent rise in water level in five years and the water quality significantly improved.
• In Rajasthan, rainwater harvesting has traditionally been practiced by the people of the Thar Desert. There are many ancient water harvesting systems in Rajasthan, which have now been revived  Water harvesting systems are widely used in other areas of Rajasthan as well, for example the chauka system from the Jaipur district
• At present, in Pune (in Maharashtra), rainwater harvesting is compulsory for any new society to be registered.
• An attempt has been made at Dept. of Chemical Engineering, IISc, Bangalore to harvest rainwater using upper surface of a solar still, which was used for water distillation

                                               

REFERENCES :

• WIKIPEDIA
• GOOGLE IMAGES 
• SLIDESHARE