11-02-2013, 12:41 PM
RAINWATER HARVESTING
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ABSTRACT
Rainwater harvesting is the accumulation and storage of rainwater for reuse before it reaches the aquifer. Uses include water for garden, water for livestock, water for irrigation, etc. In many places the water collected is just redirected to a deep pit with percolation. The harvested water can be used for drinking water, as well if the storage is a tank that can be accessed and cleaned when needed.
Rainwater harvesting provides an independent water supply during regional water is restrictions, and in developed countries is often used to supplement the mains supply. Rainwater harvesting systems are appealing as they are easy to understand, install and operate. They are effective in 'green droughts' as water is captured from rainfall where runoff is insufficient to flow into dam storages. The quality of captured rainwater is usually sufficient for most household needs, reducing the need for detergents because rainwater is soft. Financial benefits to the users include that rain is 'renewable' at acceptable volumes despite climate change forecasts, and rainwater harvesting systems generally have low running costs, providing water at the point of consumption.
Need for rainwater harvesting
Due to pollution of both groundwater and surface waters, and the overall increased demand for water resources due to population growth, many communities all over the world are approaching the limits of their traditional water resources. Therefore they have to turn to alternative or ‘new’ resources like rainwater harvesting. Rainwater harvesting has regained importance as a valuable alternative or supplementary water resource. Utilization of rainwater is now an option along with more ‘conventional’ water supply technologies, particularly in rural areas, but increasingly in urban areas as well. Rainwater harvesting has proven to be of great value for arid and semi-arid countries or regions, small coral and volcanic islands, and remote and scattered human settlements.
Rainwater harvesting has been used for ages and examples can be found in all the great civilizations throughout history. The technology can be very simple or complex depending on the specific local circumstances. Traditionally, in Uganda and in Sri Lanka rainwater is collected from trees, using banana leaves or stems as gutters; up to 200 liter may be collected from a large tree in a single rain storm. With the increasing availability of corrugated iron roofing in many developing countries, people often place a small container under their eaves to collect rainwater. One 20-litre container of clean water captured from the roof can save a walk of many kilometers to the nearest clean water source. Besides small containers, larger sub-surface and surface tanks are used for collecting larger amounts of rainwater.
Science of Rainwater Harvesting
In scientific terms, water harvesting refers to collection and storage of rainwater and also other activities aimed at harvesting surface and groundwater, prevention of losses through evaporation and seepage and all other hydrological studies and engineering inventions, aimed at conservation and efficient utilization of the limited water endowment of physiographic unit such as a watershed.
Rain is a primary source of water for all of us. There are two main techniques of rainwater harvesting: Storage of rainwater on surface for future use.
• Recharge to groundwater.
• Directly collected rainwater can be stored for direct use or can be recharged into the groundwater.
All the secondary sources of water like rivers, lakes and groundwater are entirely dependent on rain as a primary source.
Rainwater harvesting by Fresh Water Flooded Forest
Rain water harvesting is possible by growing fresh water flooded forests without 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.
Mission
RAIN aims to increase the access to water through developing capacity for the collection of rainwater, with a focus on regions where other means of water supply are not viable or available.
Each rainwater harvesting system consists of three basic components
• catchment or roof surface to collect rainwater
• To delivery system to transport the water from the roof to the storage reservoir (gutters and drainpipes)
• To storage reservoir or tank to store the water until it is used. The storage reservoir has an extraction device that- depending on the location of the tank- may be a tap, rope and bucket, or a pump.
Conclusion
It is no denying that sustaining and recharging the groundwater along with judicious use of the limited fresh water resources is the need of the hour. If sufficient measures are not taken up immediately, we will face a crisis which will be detrimental to the very survival of mankind. Efficient management of water resources and education about judicious utilization of water resources along with measures of harnessing, recharging and maintaining the quality of water and water bodies has to be taken up on war footing.