rain water harvesting

Name: Genesia Rodrigues Subject: EVS Roll N.: 36

1


RAIN WATER

HARVESTING

Contents2


1.Introduction

2.Traditional Water Harvesting Methodsa. Percolation Pit Methodb.Bore Well With Settlement Tank Methodc. Open Well Methodd.Percolation Pit With Bore Well Method

3.What Is Rainwater Harvesting?

4.Components Of Rainwater Harvestinga. Catchmentsb.Coarsemeshc. Guttersd.Conduitse. First-Flushinf. Filter

5.Store Rainwater Or Use For Recharge

6.RWH- An Efficient Water Solution For Apartment

7.Why Harvest Rainwater?

8.Harvesting Rainwater Harnessing Life

9.Do’s And Don’t

3


INTRODUCTION

In the present scenario management and distribution of water has become centralized. People depend on government system, which has resulted in disruption of community participation in water management and collapse of traditional water harvesting system.

As the water crisis continues to become severe, there is a dire need of reform in water management system and revival of traditional systems. Scientific and technological studies needs to be carried out to assess present status so as to suggest suitable mitigative measures for the revival to traditional system/wisdom. Revival process should necessarily be backed by people's initiative and active public participation.

Living creatures of the universe are made of five basic elements, viz., Earth, Water, Fire, Air and Sky, Obviously, water is one of the most important elements and no creature can survive without it. Despite having a great regard for water, we seem to have failed to address this sector seriously. Human being could not save and conserve water and it sources, probably because of its availability in abundance. But this irresponsible attitude resulted in deterioration of water bodies with respect to quantity and quality both. Now, situation has arrived when even a single drop of water matters. However, "Better late than never", we have not realized the seriousness of this issue and initiated efforts to overcome those problems.

System of collection rainwater and conserving for future needs has traditionally been practiced in India. The traditional systems were time-tested wisdom of not only

4


appropriate technology of Rainwater Harvesting, but also water management systems, where conservation of water was the prime concern. Traditional water harvesting systems were Bawaries, step wells, jhiries, lakes, tanks etc. These were the water storage bodies to domestic and irrigation demands. People were themselves responsible for maintenance to water sources and optimal use of water that could fulfill their needs.

The term rainwater harvesting is being frequently used these days, however, the concept of water harvesting is not new for India. Water harvesting techniques had been evolved and developed centuries ago.

Ground water resource gets naturally recharged through percolation. But due to indiscriminate development and rapid urbainzation, exposed surface for soil has been reduced drastically with resultant reduction in percolation of rainwater, thereby depleting ground water resource. Rainwater harvesting is the process of augmenting the natural filtration of rainwater in to the underground formation by some artificial methods. "Conscious collection and storage of rainwater to cater to demands of water, for drinking, domestic purpose & irrigation is termed as Rainwater Harvesting."

An old technology is gaining popularity in a new way. Rain water harvesting is enjoying a renaissance of sorts in the world, but it traces its history to biblical times. Extensive rain water harvesting apparatus existed 4000 years ago in the Palestine and Greece. In ancient Rome, residences were built with individual cisterns and paved courtyards to capture rain water to augment water from city's aqueducts. As early as the third millennium BC, farming communities in Baluchistan and Kutch impounded rain water and used it for irrigation dams.

5


TRADITIONAL WATER HARVESTING METHODS

1. Percolation Pit Method

RECHARGE TRENCH METHOD

Similar to recharge pit but longitudinal in shape Size : 0.5 - 1 m wide 1 - 1.5 m depth. Length may vary from 1.0 - 5.0 km Filled with broken bricks /pebbles Suitable for sandy sub-soil area.

RECHARGE TRENCH WITH BORE METHOD

Along the recharge trench boreholes has to be drilled Borehole interval 10 -15 feet Suitable for clay area.

6


2. Bore Well With Settlement Tank Method

Roof top rain water may also be diverted to a borewell. Settlement / filter tank of required size has to be provided. Overflow water may be diverted to a percolation pit nearby. The rate of recharge through borewell is less effective than open wells. Defunctional borewells may also be used.

7


3. Open Well Method

Rainwater from the terrace is diverted to the existing open well using PVC pipes through a filter chamber. The minimum size of the filter chamber is 2" x 2" x 2" filled with broken bricks in the bottom and sand on the top. The chamber may be covered with RCC slab.

4. Percolation Pit With Bore Well Method

8


PERCOLATION PIT METHOD

Constructed in the open space at required intervals. Size " 1m x 1m x 1.5m (depth) Filled with broken bricks / pebbles Suitable for sandy sub - soil area One unit for 300 sq.ft area (approx.)

PERCOLATION PIT WITH BORE METHOD

A borehole to be drilled at the bottom of the percolation pit. Bore hole size : 150 - 300 mm dia with 10 –15M depth (approx.) Filled with broken bricks. Suitable for clay area.

9


WHAT IS RAIN WATER HARVESTING?

The Rainwater harvesting is the simple collection or storing of water through scientific techniques from the areas where the rain falls. It involves utilization of rain water for the domestic or the agricultural purpose. The method of rain water harvesting has been into practice since ancient times. Rainwater harvesting is the accumulating and storing, of rainwater. It is as far the best possible way to conserve water and awaken the society towards the importance of water. The method is simple and cost effective too. It is especially beneficial in the areas, which faces the scarcity of water.

People usually make complaints about the lack of water. During the monsoons lots of water goes waste into the gutters. And this is when Rain water Harvesting proves to be the most effective way to conserve water. We can collect the rain water into the tanks and prevent it from flowing into drains and being wasted. It is practiced on the large scale in the metropolitan cities. Rain water harvesting comprises of storage of water and water recharging through the technical process.

It has been used to provide drinking water, water for livestock, water for irrigation or to refill aquifers in a process called groundwater recharge. Rainwater collected from the roofs of houses, tents and local institutions, or from specially prepared areas of ground, can make an important contribution to drinking water. In some cases, rainwater may be the only available, or economical, water source. Rainwater systems are simple to construct from inexpensive local materials, and are potentially successful in most habitable locations. Roof rainwater can be of good quality and may not require treatment before consumption. Although some rooftop materials may produce rainwater that is harmful to human health, it can be useful in flushing toilets, washing clothes, watering the garden and washing cars; these uses alone halve the amount of water used by a typical home.

10

http://en.wikipedia.org/wiki/Groundwater_recharge

http://en.wikipedia.org/wiki/Aquifer

http://en.wikipedia.org/wiki/Irrigation

http://en.wikipedia.org/wiki/Livestock

http://en.wikipedia.org/wiki/Drinking_water


Household rainfall catchment systems are appropriate in areas with an average rainfall greater than 200 mm (7.9 in) per year, and no other accessible water sources (Skinner and Cotton, 1992).

RWH is most suitable where ...

groundwater is scarce

groundwater is contaminated

terrain is rugged or mountainous

seismic & flooding events are common

the aquifer is at risk of saltwater intrusion population density is low electricity & water prices are rising water is too hard or mineral laden consumers must restrict salt/chlorine intake where utility service is unreliable

... and where ... conservation is an objective

Practical Advantages of RWH

Availability not subject to outside utility control Not subject to pipelines interruption (seismic) Quality is controlled by the consumer Available even when power is interrupted Reduces run-off and erosion Available even when storms & disaster strike Available immediately for fire suppression Reduces mosquito breeding grounds (Dengue Fever) Thermal mass can naturally cool buildings Ideal for people on low sodium diets or with health

concerns (weakened immunity systems).

11


COMPONENTS OF A RAINWATER HARVESTING

SYSTEM

A rainwater harvesting system comprises components of various stages - transporting rainwater through pipes or drains, filtration, and storage in tanks for reuse or recharge. The common components of a rainwater harvesting system involved in these stages are illustrated here.

1. Catchments:

The catchment of a water harvesting system is the surface which directly receives the rainfall and provides water to the system. It can be a paved area like a terrace or courtyard of a building, or an unpaved area like a lawn or open ground. A roof made of reinforced cement concrete (RCC), galvanised iron or corrugated sheets can also be used for water harvesting. Rainwater harvesting can be harvested from the following surfaces.

Rooftops:

If buildings with impervious roofs are already in place, the catchment area is effectively available free of charge and they provide a supply at the point of

consumption.

Paved and unpaved areas:

That is, landscapes, open fields, parks, storm water drains, roads and pavements and other open areas can be effectively used to harvest the runoff. The main advantage in using ground

12


as collecting surface is that water can be collected from a larger area. This is particularly advantageous in areas of low rainfall.

Waterbodies:

The potential of lakes, tanks and ponds to store rainwater is immense. The harvested rainwater can not only be used to meet water requirements of the city, it also recharges groundwater aquifers.

Stormwater drains:

Most of the residential colonies have proper network of stormwater drains. If maintained neatly, these offer a simple and cost effective means for harvesting rainwater.

2. Coarse mesh:

At the roof to prevent the passage of debris.

3. Gutters:

Channels all around the edge of a sloping roof to collect and transport rainwater to the storage tank. Gutters can be semi-circular or rectangular and could be made using:

Locally available material such as plain galvanised iron sheet (20 to 22 gauge), folded to required shapes.

Semi-circular gutters of PVC material can be readily prepared by cutting those pipes into two equal semi-circular channels.

Bamboo or betel trunks cut vertically in half.

The size of the gutter should be according to the flow during the highest intensity rain. It is advisable to make them 10 to 15 per cent oversize.

Gutters need to be supported so they do not sag or fall off when loaded with water. The way in which gutters are fixed depends on the construction of the house; it is possible to fix iron or timber brackets into the walls, but for houses having wider

13


eaves, some method of attachment to the rafters is necessary.

4. Conduits:

Conduits are pipelines or drains that carry rainwater from the catchment or rooftop area to the harvesting system. Conduits can be of any material like polyvinyl chloride (PVC) or galvanized iron (GI), materials that are commonly available.

The following table gives an idea about the diameter of pipe required for draining out rainwater based on rainfall intensity and roof area.

Sizing of rainwater pipe for roof drainage

Diameter Of pipe (mm)

Average rate of rainfall in mm/h

50 75 100 125 150 200

50 13.4 8.9 6.6 5.3 4.4 3.3

65 24.1 16.0 12.0 9.6 8.0 6.0

75 40.8 27.0 20.4 16.3 13.6 10.2

100 85.4 57.0 42.7 34.2 28.5 21.3

125 - - 80.5 64.3 53.5 40.0

150 - - - - 83.6 62.7mm/ h - millimeters per hour; m - meters

5. First-flushing:

A first flush device is a valve that ensures that runoff from the first spell of rain is flushed out and does not enter the system. This needs to be done since the first spell of rain carries a relatively larger amount of pollutants from the air and catchment surface.

14


6. Filter

The filter is used to remove suspended pollutants from rainwater collected over roof. A filter unit is a chamber filled with filtering media such a fibre , coarse sand and gravel layers to remove debris and dirt from water before it enters the storage tank or recharge structure. Charcoal can be added for additional filtration.

(i) Charcoal water filterA simple charcoal filter can be made in a drum or an earthen pot. The filter is made of gravel, sand and charcoal, all of which are easily available.

(ii) Sand filtersSand filters have commonly available sand as filter media. Sand filters are easy and inexpensive to construct. These filters can be employed for treatment of water to effectively remove turbidity (suspended particles like silt and clay), colour and microorganisms.

In a simple sand filter that can be constructed domestically, the top layer comprises coarse sand followed by a 5-10 mm layer of gravel followed by another 5-25 cm layer of gravel and boulders.

(ii. a) Dewas FiltersMost residents in Dewas, Madhya Pradesh, have wells in their houses. Formerly, all that those wells would do was extract groundwater. But then, the district administration of

15


Dewas initiated a groundwater recharge scheme. The rooftop water was collected and allowed to pass through a filter system called the Dewas fillter, designed by Mohan Rao , district collecter of Dewas, and engineers of the rural engineering services. The water thus filtered is put into the service tubewell.

The filter consists of a polyvinyl chloride (PVC) pipe 140 mm in diameter and 1.2m long. There are three chambers. The first purification chamber has pebbles varying between 2-6 mm, the second chamber has slightly larger pebbles, between 6 and 12 mm and the third chamber has the largest - 12-20 mm pebbles. There is a mesh at the outflow side through which clean water flows out after passing through the three chambers. The cost of this filter unit is Rs 600.

Filter for large rooftops:When rainwater is harvested in a large rooftop area, the filtering system should accommodate the excess flow. A system is designed with three concentric circular chambers in which the outer chamber is filled with sand, the middle one with coarse aggregate and the inner-most layer with pebbles.

This way the area of filtration is increased for sand, in relation to coarse aggregate and pebbles. Rainwater reaches the centre core and is collected in the sump where it is treated with few tablets of chlorine and is made ready for consumption. This system was designed by Varun.

S Vishwanath, a Bangalore water harvesting expert, has developed a rainwater filter "VARUN". According to him, from a decently clean roof 'VARUN' can handle a 50 mm per hour intensity rainfall from a 50 square metre roof area. This means the product is relatively standardised. For new house builders we therefore can recommend the number of downpipes they have to optimise on and the number of filters they will need.

16


'VARUN' is made from a 90 litre High Density Poly Ethylene (HDPE) drum. The lid is turned over and holes are puched in it. This is the first sieve which keeps out large leaves, twigs etc. Rainwater coming out of the lid sieve then passes through three layers of sponge and a 150 mm thick layer of coarse sand. Presence of sponge makes the cleaning process very easy. Remove the first layer of sponge and soak /clean it in a bucket of water (which you then don't waste but use it for plants). The sand needs no cleaning at all. The basic cost of the filter is about Rs 2250/- .

(ii. b) Horizontal Roughing Filter And Slow Sand FilterThe introducton of horizontal roughing filter and slow sand filter (HRF/SSF) to treat surface water has made safe drinking water available in coastal pockets of Orissa. The major components of this filter are described below.

1) Filter channel : One square metre in cross-section and eight m in length, laid across the tank embankment, the filter channel consists of three uniform compartments, the first packed with broken bricks, the second with coarse sand, followed by fine sand in the third compartment. The HRF usually consists of filter material like gravel and coarse sand that successively decreases in size from 25 mm to 4 mm. The bulk of solids in the incoming water is separated by this coarse filter media or HRF. At every outlet and inlet point of the channel, fine graded mesh is implanted to prevent entry of finer materials into the sump. The length of a channel varies according to the nature of the site selected for the sump.

2) Sump: A storage provision to collect filtered water from the tank through the filter channel for storage and collection.

While HRF acts as a physical filter and is applied to retain solid matter, SSF is primarily a biological filter, used to kill microbes in the water. Both filter types are generally stable, making full

17


use of the natural purification process of harvested surface water and do not require any chemicals.

iii. Rain PC AcquaSure, a consortium of three specialist Netherlands-based companies, has developed a system for the conversion of rainwater to drinking water in the form of a Rainwater Purification Centre (RainPC).

RainPC is developed by scaling down the multi-staged water treatment method

(MST), which involves screening, flocculation sedimentation and filtration and incorporating existing technologies like upward flow fine filtration, absorption and ion exchange. Coming in a small compact 26 kg unit, the RainPC offers an affordable solution by converting rainwater into drinking water.

RainPC is made of ultra violet resistant poly-ethylene housing and cover, stainless steel rods and bolts, a nickel-brass valve and an adapter for maintaining constant volume. Xenotex-A and activated carbon catridges along with ultra membrane filtration or micro-membrane filtration modules incorporated in the RainPC has the capacity to deal with E-coli and the potential of meeting the Dutch as well as World Health Organisations (WHO) water regulation standards. The components can also be transported individually to be assembled at the site. Three product types are available based on their microbial contaminant removal capacity. This technology is ideally suited for virtually any situation and is a blessing particularly for those who have little or no access to regular safe drinking water.

WHETHER TO STORE RAINWATER OR USE IT

FOR RECHARGE

18


The decision whether to store or recharge water depends on the rainfall pattern and the potential to do so, in a particular region. The sub-surface geology also plays an important role in making this decision.

For example, Delhi, Rajasthan and Gujarat where the total annual rainfall occurs during 3 or 4 months, are examples of places where groundwater recharge is usually practiced. In places like Kerala, Mizoram, Tamil Nadu and Bangalore where rain falls throughout the year barring a few dry periods, one can depend on a small sized tank for storing rainwater, since the period between two spells of rain is short. Wherever sub-strata is impermeable recharging will not be feasible. Hence, it would be ideal to opt for storage.

19


In places where the groundwater is saline or not of potable standards, the alternate system could be that of storing rainwater.

Beyond generalisations, it is the requirement that governs the choice of water harvesting technique. For example, in Ahemadabad, which has limited number of rainy days as that of Delhi, traditional rainwater harvesting tanks, known as tankas, are used to store rainwater even today in residential areas, temples and hotels.

RAINWATER HARVESTING- AN EFFICIENT WATER

20


SOLUTION FOR APARTMENT

The demand for water is increasing day-by-day and government fails to supply water and meet the increasing demand. Rainwater harvesting is not a new concept or technique, it is practiced by our ancestors for irrigation and feeding cattle or livestock. Apartments are mushrooming all over our cities with the boom in the housing sector. By designing systems carefully and investing in sustainable technologies, apartments can provide supplementary water requirement. Apartment owners association can play vital role in setting up or installing rainwater harvesting in apartment.

Role of Apartment Owners Association

Apartment owners can put pressure to builder while constructing apartment to implement rainwater harvesting either for direst use or for recharging groundwater. Apartment owners can form an association for implementing rainwater harvesting system in the apartment. The cost can be divided equally by all owners. The cost of installing a rainwater harvesting is high but when comparing the amount saved on water bill for future, this cost is cheaper or nothing. There must be a separate pipeline for rainwater and for groundwater. Nowadays each apartment will have its own apartment owners association who play vital role in managing properties and

21


working for welfare of residents of apartment. An active apartment owners association can easily implement rainwater harvesting and your association can become role model for apartments in your neighborhood or in your city.

Rainwater Harvesting System

Rainwater harvesting system is collection of rainwater from the surface which directly receives rainfall. It can be a paved area like a terrace or courtyard of a building, or an unpaved area like a lawn or open ground. A channel or gutters are required to transfer rainwater collected from rooftops to storage tanks or recharge pit. One or more down-pipes are connected to gutters to transfer rainwater from rooftops or terrace. The size of the gutter should be according to the flow during the highest intensity rain.

When collecting rainwater it is very important to keep the water clean and safe. The first spell of rain carries a relatively larger amount of pollutants from the air and catchments surface. Without a first- flush system this will be washed off the roof and directly into your rainwater tanks causing the water to become dirty and possibly dangerous. The First- Flush Diverter is installed anywhere before the inlet of the water tank and the runoff from the first spell of rain is flushed out by using a first-flush before rainwater entering to the system or storage tank. There are several possible choices to selectively collect clean water for the storage tanks. The most common is the down-pipe flap. With this flap it is possible to direct the first flush of water flow through the down-pipe, while later rainfall is diverted into a storage tank. The filter is used to remove suspended pollutants from rainwater collected over roof. A filter unit is a chamber filled with filtering media such as fiber, coarse sand and gravel layers to remove debris and dirt from water before it enters the storage tank or recharge pit.

Working of Rainwater HarvestingRainwater harvesting system can be broadly classified as rooftop rainwater harvesting and artificial groundwater recharging.

22


Rooftop rainwater harvesting is quite popular since it is quite easy to collect rainwater falling on rooftops and terrace. In rooftop harvesting, the roof becomes the catchments, and the rainwater is collected from the roof of the house/building. It can either be stored in a tank or diverted to artificial recharge system. Rainwater from roof or trace is transported using PVC gutters. These gutters will be connected to filter using down-pipes. A filter unit is a chamber filled with filtering media to remove debris and dirt from water. Rainwater storage tanks collect all filtered rainwater and keep it for future use. The tank is placed on a small platform about 18 inches high and a tap is attached to it at the bottom. This makes it easy to collect water in a bucket.

23


WHY HARVEST RAINWATER?

It's a shame to let runoff go to waste when it can be used indoors and/or for irrigation. The benefits of rainwater harvesting can include:

Relief of strain on other water supply

Ability to build or farm in areas with no other water supply

Cleaner water

Increased independence and water security

Lower water supply cost

Reduced flood flows

Reduced topsoil loss

Improved plant growth

Greater sensitivity to and connection with natural cycles

24


HARVESTING RAINWATER

HARNESSING LIFE

A NOBLE GOAL -A COMMONESPONSIBILITY

Ground water exploitation is inevitable is Urban areas. But the groundwater potential is getting reduced due to urbanisation resulting in over exploitation. Hence, a strategy to implement the groundwater recharge, in a major way need to be launched with concerted efforts by various Governmental and Non-Governmental Agencies and Public at large to build up the water table and make the groundwater resource, a reliable and sustainable source for supplementing water supply needs of the urban dwellers.Recharge of groundwater through storm run off and roof top water collection, diversion and collection of run off into dry tanks, play grounds, parks and other vacant places are to be implemented by Special Village Panchayats/ Municipalities /Municipal Corporations and other Government Establishments with special efforts.The Special Village Panchayats /Municipalities/Municipal Corporations will help the citizens and builders to adopt suitable recharge method in one's own house or building through demonstration and offering subsidies for materials and incentives, if possible.

DO'S AND DON’TS

Harvested rainwater is used for direct usage or for recharging aquifers. It is most important to ensure that the rainwater

25


caught is free from pollutants. Following precautionary measures should be taken while harvesting rainwater: Roof or terraces uses for harvesting should be clean, free from dust, algal plants etc.

Roof should not be painted since most paints contain toxic substances and may peel off.

Do not store chemicals, rusting iron, manure or detergent on the roof.

Nesting of birds on the roof should be prevented.

Terraces should not be used for toilets either by human beings or by pets.

Provide gratings at mouth of each drainpipe on terraces to trap leaves debris and floating materials.

Provision of first rain separator should be made to flush off first rains.

Do not use polluted water to recharge ground water.

Ground water should only be recharged by rainwater.

Before recharging, suitable arrangements of filtering should be provided.

Filter media should be cleaned before every monsoon season.

During rainy season, the whole system (roof catchment, pipes, screens, first flush, filters, tanks) should be checked before and after each rain and preferably cleaned after every dry period exceeding a month.At the end of the dry season and just before the first shower of rain is anticipated, the storage tank should be scrubbed and flushed off all sediments and debris.

26


27

rain water harvesting

Documents

rain water harvesting

water sources

distribution of water

conservation of water

conserve water

water crisis

overflow water

concept of water harvesting