Please elaborate on how rain harvesting is done?

Question

Rain Water Harvesting

Answer 1

Rain water harvesting is a very effective way to recharge the fast depleting groundwater resources. On one hand it reduces the tremendous pressure on the ground water resources and on the other, it plays a significant role in the water-cycle. Coming to the details of how rain water is harvested, I would lik to discuss here the most appripriate method which wil suit contemporary residential buildings:

Let all the rain water collected on top your roof to flow into a single or at most two or three outlet pipes.(Less outlets-more easy it is to harvest rain water). Arrange the pipes so that they can be combined into a single outlet finally.

Dig a circular or rectangular trench into the ground. You have top make your rainwaer filter in this trench. To make this filter, first fill the trench upto three feet depth with medium size (40mm) rocky material. Ensure that the material is free from other construction material like cement etc.. Lay the next layer(1 foot) with smaller stones (<20mm).

The next layer will be comprising of sand. This layer should be laid to a depth of two feet.

Above this layer, you can place thoroughly washed charcoal.

Considering an apartment complex comprises of 40 dwelling units, it will be necessary to dig a trench with 3 feet radius and 15 feet depth.

Answer 2

These days state govts in India are giving benefits and concessions for people who install this rain water harvesting system in their homes. Now that you know the method of doing it, do install it in your home.

       Save Water, Save Earth!!

Answer 3

Rain Harvesting is very easy as collecting stones. Just arrange a Bucket or Tank depends on the rain frequency and open there mouth to the sky.

Or Just see where the rain water is collecting and pouring haveily and put the bucket and tank there.

Maahi

Answer 4

A sufficient, clean drinking water supply is essential to life. Millions of people throughout the world still do not have access to this basic necessity. After decades of work by governments and organisations to bring potable water to the poorer people of the world, the situation is still dire. The reasons are many and varied but generally speaking, the poor of the world cannot afford the capital intensive and technically complex traditional water supply systems which are widely promoted by governments and agencies throughout the world. Rainwater harvesting (RWH) is an option that has been adopted in many areas of the world where conventional water supply systems have failed to meet people's needs. It is a technique that has been used since antiquity.

Examples of RWH systems can be found in all the great civilisations throughout history. In industrialised countries, sophisticated RWH systems have been developed with the aim of reducing water bills or to meet the needs of remote communities or individual households in arid regions. Traditionally, in Uganda and Sri Lanka, for example, rainwater is collected from trees, using banana leaves or stems as temporary gutters; up to 200 litres may be collected from a large tree in a single storm. Many individuals and groups have taken the initiative and developed a wide variety of RWH systems throughout the world.

It is worth distinguishing, between the various types of RWH practised throughout the world. RWH has come to mean the control or utilisation of rainwater close to the point rain reaches the earth. Its practice effectively divides into

Domestic RWH

RWH for agriculture, erosion control, flood control and aquifer replenishment.

It is worth bearing in mind that rainwater harvesting is not the definitive answer to household water problems. There is a complex set of inter-related circumstances that have to be considered when choosing the appropriate water source. These include cost, climate, hydrology, social and political elements, as well as technology, all play a role in the eventual choice of water supply scheme that is adopted for a given situation. RWH is only one possible choice, but one that is often overlooked by planners, engineers and builders.

The reason that RWH is rarely considered is often due to lack of information - both technical and otherwise. In many areas where RWH has been introduced as part of a wider drinking water supply programme, it was at first unpopular, simply because little was known about the technology by the beneficiaries. In most of these cases, the technology has quickly gained popularity as the user realises the benefits of a clean, reliable water source at the home. the town supply is unreliable or where local water sources dry up for a part of the year, but is also In many cases RWH has been introduced as part of an integrated water supply system, where often used as the sole water source for a community or household. It is a technology that is flexible and adaptable to a very wide variety of conditions, being used in the richest and the poorest societies on our planet, and in the wettest and the driest regions of the world.

Components of a domestic RWH system

DRWH systems vary in complexity, some of the traditional Sri Lankan systems are no more that a pot situated under a piece of cloth or plastic sheet tied at its corners to four poles. The cloth captures the water and diverts it through a hole in its centre into the pot. Some of the sophisticated systems manufactured in Germany incorporate clever computer management systems, submersible pumps, and links into the grey water and mains domestic plumbing systems. Somewhere between these two extremes we find the typical DRWH system used in a developing country scenario. Such a system will usually comprise a collection surface (a clean roof or ground area), a storage tank, and guttering to transport the water from the roof to the storage tank. Other peripheral equipment is sometimes incorporated, for example: first flush systems to divert the dirty water which contains roof debris after prolonged dry periods; filtration equipment and settling chambers to remove debris and contaminants before water enters the storage tank or cistern; handpumps for water extraction; water level indicators, etc.

Typical domestic RWH systems

Storage tanks and cisterns

The water storage tank usually represents the biggest capital investment element of a domestic RWH system. It therefore usually requires careful design - to provide optimal storage capacity while keeping the cost as low as possible. The catchment area is usually the existing rooftop or occasionally a cleaned area of ground, as seen in the courtyard collection systems in China, and guttering can often be obtained relatively cheaply, or can be manufactured locally.

There are an almost unlimited number of options for storing water. Common vessels used for very small-scale water storage in developing countries include such examples as plastic bowls and buckets, jerrycans, clay or ceramic jars, cement jars, old oil drums, empty food containers, etc. For storing larger quantities of water the system will usually require a tank or a cistern. For the purpose of this document we will classify the tank as an above-ground storage vessel and the cistern as a below-ground storage vessel. These can vary in size from a cubic metre or so (1000 litres) up to hundreds of cubic metres for large projects, but typically up to a maximum of 20 or 30 cubic metres for a domestic system. The choice of system will depend on a number of technical and economic considerations listed below.

- Space availability

- Options available locally

- Local traditions for water storage

- Cost of purchasing new tank

- Cost of materials and labour for construction

- Materials and skills available locally

- Ground conditions

- Style of RWH - whether the system will provide total or partial water supply

One of the main choices will be whether to use a tank or a cistern. Both tanks and cisterns have their advantages and disadvantages.

Much work has been carried out to develop the ideal domestic RWH tank. The case studies later in this document show a variety of tanks that have been built in different parts of the world.

Collection surfaces

For domestic rainwater harvesting the most common surface for collection is the roof of the dwelling. Many other surfaces can be, and are, used: courtyards, threshing areas, paved walking areas, plastic sheeting, trees, etc. In some cases, as in Gibraltar, large rock surfaces are used to collect water which is then stored in large tanks at the base of the rock slopes.

Most dwellings, however, have a roof. The style, construction and material of the roof affect its suitability as a collection surface for water. Typical materials for roofing include corrugated iron sheet, asbestos sheet; tiles (a wide variety is found), slate, and thatch (from a variety of organic materials). Most are suitable for collection of roofwater, but only certain types of grasses e.g. coconut and anahaw palm (Gould and Nissen Peterson, 1999), thatched tightly, provide a surface adequate for high quality water collection. The rapid move towards the use of corrugated iron sheets in many developing countries favours the promotion of RWH (despite the other negative attributes of this material).

Guttering



Guttering is used to transport rainwater from the roof to the storage vessel. Guttering comes in a wide variety of shapes and forms, ranging from the factory made PVC type to home made guttering using bamboo or folded metal sheet. In fact, the lack of standards in guttering shape and size makes it difficult for designers to develop standard solutions to, say, filtration and first flush devices. Guttering is usually fixed to the building just below the roof and catches the water as it falls from the roof.

Manufacture of low-cost gutters

Factory made gutters are usually expensive and beyond the reach of the poor of developing countries, if indeed available at all in the local marketplace. They are seldom used for very low-cost systems. The alternative is usually to manufacture gutters from materials that can be found cheaply in the locality. There are a number of techniques that have been developed to help meet this demand; one such technique is described below.

V- shaped gutters from galvanised steel sheet can be made simply by cutting and folding flat galvanised steel sheet. Such sheet is readily available in most market centres (otherwise corrugated iron sheet can be beaten flat) and can be worked with tools that are commonly found in a modestly equipped workshop. One simple technique is to clamp the cut sheet between two lengths of straight timber and then to fold the sheet along the edge of the wood. A strengthening edge can be added by folding the sheet through 90o and then completing the edge with a hammer on a hard flat surface. The better the grade of steel sheet that is used, the more durable and hard wearing the product. Fitting a downpipe to V-shaped guttering can be problematic and the V-shaped guttering will often be continued to the tank rather than changing to the customary circular pipe section downpipe. Methods for fixing gutters are shown in figure 5.

First flush systems

Debris, dirt, dust and droppings will collect on the roof of a building or other collection area. When the first rains arrive, this unwanted matter will be washed into the tank. This will cause contamination of the water and the quality will be reduced. Many RWH systems therefore incorporate a system for diverting this 'first flush' water so that it does not enter the tank.

The simpler ideas are based on a manually operated arrangement whereby the inlet pipe is moved away from the tank inlet and then replaced again once the initial first flush has been diverted. This method has obvious drawbacks in that there has to be a person present who will remember to move the pipe.

Other systems use tipping gutters to achieve the same purpose. The most common system (as shown in Figure 7a) uses a bucket which accepts the first flush and the weight of this water off-balances a tipping gutter which then diverts the water back into the tank.

The bucket then empties slowly through a small-bore pipe and automatically resets. The process will repeat itself from time to time if the rain continues to fall, which can be a problem where water is really at a premium. In this case a tap can be fitted to the bucket and will be operated manually. The quantity of water that is flushed is dependent on the force required to lift the guttering. This can be adjusted to suit the needs of the user.

Although the more sophisticated methods provide a much more elegant means of rejecting the first flush water, practitioners often recommend that very simple, easily maintained systems be used, as these are more likely to be repaired if failure occurs.

Filtration systems and settling tanks



Again, there are a wide variety of systems available for treating water before, during and after storage. The level of sophistication also varies, from extremely high-tech to very rudimentary. A German company, WISY, have developed an ingenious filter which fits into a vertical downpipe and acts as both filter and first-flush system. The filter, shown in Figure 8, cleverly takes in water through a very fine (~0.20mm) mesh while allowing silt and debris to continue down the pipe. The efficiency of the filter is over 90%. This filter is commonly used in European systems.

The simple trash rack has been used in some systems but this type of filter has a number of associated problems: firstly it only removes large debris; and secondly the rack can become clogged easily and requires regular cleaning.

The sand-charcoal-stone filter is often used for filtering rainwater entering a tank. This type of filter is only suitable, however, where the inflow is slow to moderate, and will soon overflow if the inflow exceeds the rate at which the water can percolate through the sand. Settling tanks and partitions can be used to remove silt and other suspended solids from the water. These are usually effective where used, but add significant additional cost if elaborate techniques are used. Many systems found in the field rely simply on a piece of cloth or fine mosquito mesh to act as the filter (and to prevent mosquitoes entering the tank).

Post storage filtration include such systems as the upflow sand filter or the twin compartment candle filters commonly found in LDC's. Many other systems exist and can be found in the appropriate water literature.

Sizing the system

Usually, the main calculation carried out by the designer when planning a domestic RWH system will be to size the water tank correctly to give adequate storage capacity. The storage requirement will be determined by a number of interrelated factors. They include:

local rainfall data and weather patterns

size of roof (or other) collection area

runoff coefficient (this varies between 0.5 and 0.9 depending on roof material and slope)

user numbers and consumption rates

The style of rainwater harvesting i.e. whether the system will provide total or partial supply (see the next section) will also play a part in determining the system components and their size.

There are a number of different methods used for sizing the tank. These methods vary in complexity and sophistication. Some are readily carried out by relatively inexperienced, first-time practitioners while others require computer software and trained engineers who understand how to use this software. The choice of method used to design system components will depend largely on the following factors:

- the size and sophistication of the system and its components

- the availability of the tools required for using a particular method (e.g. computers)

- the skill and education levels of the practitioner / designer

Answer 5

The simplest is just barrels connected to your gutter downspots. My friend has about 8 55 gal barrels that collects rainwater. He has a small portable pump he uses to pump out to his garden.

Answer 6

If u have a flat roof collect water by blocking any outlet for water and keeping a separate out let which will take water to Ur underground tank(if u have one or make one is about environment after all). This will ensure u will not require water from pipes for days.

Answer 7

Gaby and Kanya gave good answers.  Also check out www.rainwaterharvesting.org

Answer 8

pits, trenches n recharge wells may be used to store

Answer 9

first rain water is stored in dams or reservoirs ,and when time of harvesting they irrigate the fields with this rain water releasing water from reservoirs.

Answer 10

as the above person said is the elobration.

Answer 11

There are two main techniques of rain water harvestings.

Storage of rainwater on surface for future use.

Recharge to ground water.

The storage of rain water on surface is a traditional techniques and structures used were underground tanks, ponds, check dams, weirs etc. Recharge to ground water is a new concept of rain water harvesting and the structures generally used are :-

Pits :- Recharge pits are constructed for recharging the shallow aquifer. These are constructed 1 to 2 m, wide and to 3 m. deep which are back filled with boulders, gravels, coarse sand.

Trenches:- These are constructed when the permeable stream is available at shallow depth. Trench may be 0.5 to 1 m. wide, 1 to 1.5m. deep and 10 to 20 m. long depending up availability of water. These are back filled with filter. materials.

Dug wells:- Existing dug wells may be utilised as recharge structure and water should pass through filter media before putting into dug well.

Hand pumps :- The existing hand pumps may be used for recharging the shallow/deep aquifers, if the availability of water is limited. Water should pass through filter media before diverting it into hand pumps.

Recharge wells :- Recharge wells of 100 to 300 mm. diameter are generally constructed for recharging the deeper aquifers and water is passed through filter media to avoid choking of recharge wells.

Recharge Shafts :- For recharging the shallow aquifer which are located below clayey surface, recharge shafts of 0.5 to 3 m. diameter and 10 to 15 m. deep are constructed and back filled with boulders, gravels & coarse sand.

Lateral shafts with bore wells :- For recharging the upper as well as deeper aquifers lateral shafts of 1.5 to 2 m. wide & 10 to 30 m. long depending upon availability of water with one or two bore wells are constructed. The lateral shafts is back filled with boulders, gravels & coarse sand.

Spreading techniques :- When permeable strata starts from top then this technique is used. Spread the water in streams/Nalas by making check dams, nala bunds, cement plugs, gabion structures or a percolation pond may be constructed.

Answer 12

rain water harvesting is good one but the government appield  this system cannot reach the poor people so government announced the poor people when used (rwh) feed back come in future

Answer 13

no sour done for rain