rain water harvesting

Category: Education

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how can we and how much rain water can be saved...


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Water conservation Rain

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Contents : A brief introduction: Rain water harvesting: Brief introduction Urban model Collection of rain water(formula) : DRIP irrigation : Some successful stories:

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• Among all the different types of engineering Civil engineering is the most ancient one. Introduction: • Civil engineers have saved more lives than all the doctors in history — development of clean water and sanitation systems. So that now we can understand that future of our world is in our hands, so rain water harvesting is the best way to solve the world faced burning issue ie water scarcity.

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Water is the most important factor for the existence of life on earth. If we consider the past 20 years the population has increased from lakhs to crores and now in billions, so the water usage has also increased. Due to this the pure water resources are day by day decreasing . Now a days water scarcity is one of the burning issues, which can be solved by several ways. There are some ways like by constructing dams, barrages, reservoir, canals, large storage basins…But the above mentioned projects will costs high, time taking… but rain water harvesting process is will cost less and yield huge profits. There are several forms of water on the earth like oceans, rivers, lakes, ground water, rain… etc among them rain water is the ultimate source of fresh water which is being drained into seas unnecessarily . So by collecting rain water we can recharge ground water and can use it for several purposes. About water and it’s scarcity:

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Population, Water withdrawal, Water scarcity. but Fresh water resources

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Can’t we solve ? Yes…

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Rain Water Harvesting?. Rain Water Harvesting RWH- process of collecting, conveying & storing water from rainfall in an area – for beneficial use. RWH - yields huge amounts of water. For an average rainfall of 1,000mm, approximately four million liters of rainwater can be collected in a year in an acre of land (4,047 m2),.

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Urban model: . This method mainly insists on directly harvesting water from the roof tops. In Rooftop Rainwater Harvesting Systems rainwater from the house roof is collected in a storage vessel or tank for use during the periods of scarcity. Usually these systems are designed to support the drinking and cooking needs of the family at the doorstep. This system consists of: • Roof catchment • Gutters • Down pipe or first flush pipe • Filter unit • Storage tank • Collection pit

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The schematic diagram is as follows:

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Roof Catchment: The roof of the house is used as the catchment for collecting the rainwater. Roofs made of iron sheet, asbestos sheet, tiles or concrete can be utilized for harvesting the rainwater. But thatched roofs are not suitable as it gives some colour to water and also the water carries pieces of roof material (such as palm leaves).

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Downpipe: Down pipe is the pipe, which carries the rainwater from the gutters to the storage tank. Down pipe is joined with the gutters at one end, and the other end is connected to the filter unit. PVC or GI pipes of diameter 50 mm to 75 mm (2 inch to 3 inch) are commonly used for down-pipe. Gutters: Gutters are channels fixed to the edges of roof all around to collect and transport the rainwater from the roof to the storage tank.. Locally available material such as plain galvanized iron sheet can be easily folded to required shapes to prepare semi-circular and rectangular gutters. Semi-circular gutters of PVC material can be readily prepared by cutting the PVC pipes into two equal semi-circular channels. Bamboo poles can also be used.

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First Flush Pipe: Dirt and dust collect on the roofs during non-rainy periods. When the first rains arrive, this unwanted material will be washed into the storage tank. This causes contamination of water collected in the storage tank and such water is unfit for drinking and cooking purposes. Therefore, a first flush system is incorporated to dispose off the water from ‘first rain’ so that it does not enter the tank. There are two such simple systems. One is based on a simple manually operated arrangement, where by, 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, a 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 first flush pipe, the valve is closed to allow the water to enter the down pipe and reach the storage tank.

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Filter Unit: The filter unit is a container filled with filter media such as coarse sand, charcoal, coconut fiber, pebbles and gravels to remove the garbage and dirt from water that enters the tank. The container is provided with a perforated bottom to allow the passage of water. The filter unit is placed over the storage tank. Commonly used filters are of two types. One is a ferrous - cement filter unit, which is comparatively heavy and the other is made of either aluminum or plastic bucket. Another simple way of filtering the debris and dust particles that came from the roof along with rainwater is to use a fine cloth as filter media. The cloth, in 2 or 3 layers, can be tied to the top of a bucket or vessel with perforations at the bottom.

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Storage Tank: Storage tank is used to store the water that is collected form the Roof tops. Common vessels used for small scale water storage are plastic cans, buckets, jerry cans, old oil drums etc. For storing larger quantities of water the system will usually require a bigger tank with sufficient strength and durability. There are unlimited number of options for the construction of these tanks with respect to the shape (cylindrical, rectangular and square), the size (Capacity from 1,000 lt. to 15,000 lt. or even higher) and the material of construction (brickwork, stonework, cement bricks, Ferro cement, plain cement concrete and reinforced cement concrete). For domestic water needs, taking the economy and durability of tanks into consideration, Ferro cement tanks of cylindrical shape in capacities ranging between 4,000 lt. and 15,000 lt. are most suitable. Plain cement concrete and reinforced cement concrete are used for tank capacities usually more than 50,000 lt. Brick, stone, cement brick may be used for capacities ranging between 15,000 lt. to 50,000 lt.

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The Ferro cement tanks are usually constructed above ground level because of the following advantages : a) ease in finding structural problems/leaks, b) easy to maintain and clean and c) easy to draw water. The storage tank is provided with a cover on the top to avoid the contamination of water from external sources. The cover will be in dome shape having a raise of about 20-30 cm. in the middle. The dome is provided with two circular openings, one for manhole and another for accommodating the filter. A lid covers the manhole avoiding exposure of stored water to the outside environment. The storage tank is provided with pipe fixtures at appropriate places to draw the water, to clean the tank and to dispose of the excess water. They are named tap or outlet, drainpipe and over flow pipe respectively. PVC or GI pipes of diameter 20 mm to 25 mm (¾ inch to 1 inch) are generally used for this purpose. Collection Pit: A small pit is dug in the ground, beneath the tap of the storage tank and constructed in brick masonry to make a chamber, so that a vessel could be conveniently placed beneath the tap for collecting water from the storage tank. A small hole is left at the bottom of the chamber, to allow the excess water to drain-out without stagnation. Size of collection pit shall be 60 cm x 60 cm x 60 cm.

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Collection of rainwater : The quantity of rainwater that can be harvested from a roof area of 1000 sq. ft for 100 mm of average annual rainfall and with a surface run off coefficient of 0.6 would be : 0.1 x 100 x 0.6 x 0.9295 = 5.577 m³ or 5570 litres / annum. 100 mm of rain falling on 1 hectare of land means 1 million liters of water. Even if 50 % of this water is collected, it can provide 15 liters of water/day to 91 persons for a whole year.

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Hero Honda Motors (Gurgaon): Total roof-top area = 11080 sq. m annual rainfall in mm = 577.8 Total rainwater available from rainfall = 5441 meter cubic The water requirements for potable and non potable purposes are met by four bore wells located in the factory premises. The rainwater is collected through a series of collection chambers and interconnecting pipes and is diverted to 6 different recharge wells of size 3m x 2m x 3m located in the factory premise. The recharge wells are provided with recharge bore wells of 8 inch diameter and 40m depth. the recharge wells are filled with three layers of pebbles ranging from 10 mm to 100 mm which ensures efficient filtration. This plan was completed by the end of February, 2004 and the results are quite good as the ground water level has increased to 60 feet below ground level. Also, the quality of water has improved a lot. Cost incurred in this project = 12 lakhs. Success Stories

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BPCL Housing Complex (Noida): Total roof-top surface area = 13910 sq. m Average annual rainfall in mm = 792.4 Total volume of rainwater harvested = 4446 meter cubic. Water requirement is met by one bore well and is supplemented by municipal supply. Roof-top rain water is collected in collection chambers and diverted to recharge wells through interconnecting pipe-lines. Recharge wells are of the size 3m x 2m x 2m and provided with recharge bore of 16 m depth and 150 mm diameter. Filtering materials used are boulders, pebbles and coarse sand. Surface run off generated from the paved area and roads is harvested through two recharge trenches of size 3m x 0.6m x 0.9m constructed along the road side. These trenches are also provided with recharge bores of same dimension as mentioned above. This plan was completed by end of year 2002 and the ground water level has increased to 56 feet below ground level. cost incurred in this project = 4.5 lakhs.

simple irrigation system which bring life to barren land: : 

simple irrigation system which bring life to barren land: Raindrops are like liquid gold to farmers in the poorest countries of the world. Yet when the rains do come - and in many places they come increasing or with decreasing frequency - most of that precious moisture is washed away, unused. Land is so dehydrated that they are unable to grow enough produce even to sustain their families, There are two simple effective irrigation systems to combat this issue. So instead of dusty fields, there are life-giving gardens with hearty fruit and vegetables.

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Even if rainfall is low or erratic, the drip irrigation system enables farmers to nourish and grow the crops they need. This is how it works: * * A large, water harvesting tank in the village catches the rain and stores it. * A farmer fills a 20-litre drip bucket and places it one metre above the ground on poles. * The drip bucket is attached to a long hose, punctured with small holes every twelve inches, that criss -crosses the crop field. * Simple gravity provides enough pressure to force the water through the hose. * Water drips through the holes in the hose, directly onto the roots of the plants. * 100-200 plants can be grown using just one drip bucket system Drip irrigation Drip irrigation is sometimes called trickle irrigation and involves dripping water onto the soil at very low rates (2-20 liters/hour) from a system of small diameter plastic pipes fitted with outlets called emitters or drippers * Water is applied close to plants so that only part of the soil in which the roots grow is wetted, unlike surface and sprinkler irrigation, which involves wetting the whole soil profile. With drip irrigation water, applications are more frequent (usually every 1-3 days) than with other methods and this provides a very favourable high moisture level in the soil in which plants can flourish.

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. Suitable crops Drip irrigation is most suitable for row crops (vegetables, soft fruit), tree and vine crops where one or more emitters can be provided for each plant. Generally only high value crops are considered because of the high capital costs of installing a drip system. Suitable soils Drip irrigation is suitable for most soils. On clay soils water must be applied slowly to avoid surface water ponding and runoff. On sandy soils higher emitter discharge rates will be needed to ensure adequate lateral wetting of the soil. Suitable irrigation water One of the main problems with drip irrigation is blockage of the emitters. All emitters have very small waterways ranging from 0.2-2.0 mm in diameter and these can become blocked if the water is not clean. Thus it is essential for irrigation water to be free of sediments. If this is not so then filtration of the irrigation water will be needed.

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In the case of large fields we need a pressure regulator to supply the water to the plants.

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conclusion: The one and only advantage of this type of process is we can save the water, but we know that water has infinite advantages. Thus we can stop the water wars which are occurring in the streets by this process which is neither energy intensive nor labour intensive.

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