rain water harvesting project

RAIN WATER HARVESTING 2016-17

INTRODUCTION

INTRODUCTION TO RAIN WATER HARVESTING

Rainwater Harvesting is the accumulation and deposition of rainwater for reuse on-site, rather than allowing it to run off. Rainwater can be collected from rivers or roofs, and in many places the water collected is redirected to a deep pit (well, shaft, or borehole), a reservoir with percolation, or collected from dew or fog with nets or other tools. Its uses include water for gardens, livestock, irrigation, domestic use with proper treatment, and indoor heating for houses etc. The harvested water can also be used

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as drinking water, longer-term storage and for other purposes such as groundwater recharge. 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 appropriate technology of Rainwater Harvesting, but also water management systems, where conservation of water was the prime concern. Traditional water harvesting systems were Beware, step wells, hires, 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 fulfil their needs



What is Rain Water Harvesting ?

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 urbanization, 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."

Why Harvest Rainwater ?

This is perhaps one of the most frequently asked questions, as to why one should harvest rainwater. There are many reasons but following are some of the important ones.

To arrest ground water decline and augment ground water table To beneficiate water quality in aquifers To conserve surface water runoff during monsoon To reduce soil erosion To inculcate a culture of water conservation

It is highly likely that there will come a point where mains water supply will no longer be able to meet the needs of our growing population. This almost inevitable situation will have an environmental and financial impact on the infrastructure used by the water companies, which will be passed onto their customers. This is why more and more people are capturing their own rainwater, a price



they can afford and at the same time minimise their impact on the environment.Quality & Quantity of Harvested Rainwater :-

Quality Of Harvested Rainwater :- Rainwater that is captured and stored correctly is a safe, economical and sustainable source of quality water. Rainwater is as safe as any source of water, provided certain safety precautions are taken as part of water capture, storage and distribution. In fact some say that rainwater is safer than water supplied through mains or reticulated water systems. Our mains water is typically stored in dams, treated with chemicals such as chlorine to kill of bacteria and make it safe, and then pumped through a network of pipes throughout the community.

Council & Health Department Recommendations :- Many Local Councils, State Health Departments and Industry Associations have either have developed, or are in the process of developing guidelines for use of rainwater harvesting systems. These guidelines have been developed to help optimise water quality. Key aspects of many of these guidelines are:

(i) Incorporating Gutter Mesh Systems – To help ensure gutters do not become blocked with leaves and debris to prevent mosquito breeding habitats.

(ii) Fitting Rain Heads at Gutter Downpipes – To separate leaves and debris from the flow of water to keep mosquitoes out of pipe systems to the tank (especially in “wet” systems).

(iii) Preventing the First Flush of Rainwater from entering the Tank – To reduce the amount of roof pollutants.



(iv) Insect Proofing all Tank Openings (inlets and overflow outlets) – To prevent mosquitoes breeding.

Regular Tank Maintenance of the tank, catchment system, roof and gutters, inlets to ensure a safe supply of water. Desludging may be enquired every 2-3 years, and whilst regular disinfection should not be necessary, can be undertaken if preferred.

Rain Water Characteristics :- The cleanest water is always that which falls freely from the sky. The natural water cycle is very efficient in screening out contaminants that are normally found in ground water and other sources. Rainwater does not come in contact with the soil, and so it does not contain contaminants such as harmful bacteria, dissolved salts, minerals or heavy metals. Rainwater is healthy and is soft water so, among other things, you will use less soap.

Quantity Of Harvested Rainwater :-

1. Reservoir Capacity : As an example let us consider a roof of 120 m² in an area with mean annual rainfall of 450 mm. We assume that less than 100% of the calculated amount of water will be collected. This is due to unavoidable small leakages in the gutter downpipe system, or rainfalls which are too light to produce sufficient runoff, or a possible overflow of gutters in the case of an extreme downpour. For this reason we can generally assume that only 90% of the rainwater can be collected.



2. Roof Finish : Not all materials used for roofing finishes are equally good but the most commonly used material, metal sheeting (corrugated galvanized iron and aluminium sheets) is very suitable for rainwater catchment likewise, brick tiles of all variations, and also thatch can be used, but these are less efficient.

3. Roof Type & Catchment : The shape of any given catchment area has a considerable influence on the catchment possibilities. Therefore different types of roofs provide different catchment possibilities of the most common roof types, the single pitch roof is the most appropriate for rainwater harvesting, since the entire roof area can be drained into a single gutter on the lower side and one or two downpipes can be provided depending on the area. A more difficult roof for rainwater catchment is the tent roof. It requires a gutter on each side and at least two downpipes on opposite corners. If a tent roof is large enough, it could be drained into four tanks located at each corner of the house. The main problem is always the corner. A 90° angle in the gutter should be avoided. It is extremely difficult to adjust gutters in such a way that water really flows easily downwards. It seldom works well when downpours occur, and it is the heavy downpours that should be caught. The hip roof is not very efficient either, since it also needs gutters all around the building. Flat roofs can be used for catchment if they are furnished with an edge, keeping the water on the slab until it has drained through the gutter or downpipe.

Rain Fall Region In India : - The climate of India comprises a wide range of weather conditions across a vast geographic scale and varied topography, making generalisations difficult. Based on the Koppen


https://en.wikipedia.org/wiki/K%C3%B6ppen_climate_classification


system, India hosts six major climatic subtypes, ranging from arid desert in the west, alpine tundra and glaciers in the north, and humid tropical regions supporting rainforests in the southwest and the island territories. Many regions have starkly different microclimates. The nation has four seasons: Winter (January and February), Summer (March, April and May), a Monsoon (rainy) season (June to September), and a Post-monsoon period (October to December).

Measurement Of Rain Water :- It's that simple. Most standard rain gauges have a wide funnel leading into the cylinder and are calibrated so that one-tenth of an inch of rain measures one inch when it collects inside. The funnel is 10 times the cross-sectional area of the tube. Rainfall as low as .01 inches can be measured with this instrument.


https://en.wikipedia.org/wiki/Monsoon

https://en.wikipedia.org/wiki/Microclimate

https://en.wikipedia.org/wiki/India

https://en.wikipedia.org/wiki/K%C3%B6ppen_climate_classification


Process of Rain Water Harvesting :- Broadly there are two ways of Harvesting Rainwater :

Surface runoff harvesting. Roof top rainwater harvesting.

(i) Surface Runoff Harvesting :- In urban area rainwater flows away as surface runoff. This runoff could be caught and used for recharging aquifers by adopting appropriate methods.

(ii) Roof top Rainwater Harvesting :- It is a system of catching rainwater where it falls. 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. This method is less expensive and very effective and if implemented properly helps in augmenting the ground water level of the area.



Components of the Roof Top Rainwater Harvesting System :- The illustrative design of the basic components of roof top rainwater harvesting system is given in the following typical schematic diagram

The system mainly constitutes of following components:

Catchments Transportation First flush Filter

The surface that receives rainfall directly is the catchment of rainwater harvesting system. It may be terrace, courtyard, or paved or unpaved open ground. The terrace may be flat RCC/stone roof or sloping roof. Therefore the catchment is the area, which actually contributes rainwater to the harvesting system.

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.



Gutters & Down take Pipes :- Rainwater from rooftop should be carried through down take water pipes or drains to storage/harvesting system. Water pipes should be UV resistant (ISI HDPE/PVC pipes) of required capacity. Water from sloping roofs could be caught through gutters and down take pipe. At terraces, mouth of the each drain should have wire mesh to restrict floating material.

First Flush :- First flush is a device used to flush off the water received in first shower. The first shower of rains needs to be flushed-off to avoid contaminating storable/rechargeable water by the probable contaminants of the atmosphere and the catchment roof. It will also help in cleaning of silt and other material deposited on roof during dry seasons Provisions of first rain separator should be made at outlet of each drainpipe.



Filter :- There is always some scepticism regarding Roof Top Rainwater Harvesting since doubts are raised that rainwater may contaminate groundwater. There is remote possibility of this fear coming true if proper filter mechanism is not adopted. Secondly all care must be taken to see that underground sewer drains are not punctured and no leakage is taking place in close vicinity. Filters are used for treatment of water to effectively remove turbidity, colour and microorganisms. After first flushing of rainfall, water should pass through filters. There are different types of filters in practice, but basic function is to purify water.

Types of Filter :

(a) Sand Gravel Filter :-

These are commonly used filters, constructed by brick masonry and filleted by pebbles, gravel, and sand as shown in the figure. Each layer should be separated by wire mesh.



(b) Charcoal Filter :-

Charcoal filter can be made in-situ or in a drum. Pebbles, gravel, sand and charcoal as shown in the figure should fill the drum or chamber. Each layer should be separated by wire mesh. Thin layer of charcoal is used to absorb odour if any.

(c) PVC – Pipe Filter :- This filter can be made by PVC pipe of 1 to 1.20 m length; Diameter of pipe depends on the area of roof. Six inches dia. pipe is enough for a 1500 Sq. Ft. roof and 8 inches dia. pipe should be used for roofs more than 1500 Sq. Ft. Pipe is divided into three compartments by wire mesh. Each component should be filled with gravel and sand alternatively as shown in the figure. A layer of charcoal could also be inserted between two layers. Both ends of filter should have reduced of required size to connect inlet and outlet. This filter could be placed horizontally or vertically in the system.



(d) Sponge Filter :-

It is a simple filter made from PVC drum having a layer of sponge in the middle of drum. It is the easiest and cheapest form filter, suitable for residential units.

Ideal Uses of Rain Water Harvesting :

(i) Storage for Garden / External Use :- Plants grow better in rainwater, which has a balanced pH and is free of chemicals such as chlorine. With the onset of water restrictions, hose-pipe bans and drought orders it makes perfect sense to collect roof water for later use. No doubt you will have experienced just how little a traditional water butt actually stores, meaning that it can only take a few dry days, and the supply has gone. Save money, a standard hosepipe can deliver up to 500 litres per hour, it is very easy to forget just how expensive it can be to use water in the garden. It's not until the end of the summer when the bill arrives, when you will find out just how much it costs. This cleaner water is less likely to carry-over disease, therefore reducing the risk to plants and fish.



(ii) Recharging Ground Water Aquifers :- Ground water aquifers can be recharged by various kinds of structures to ensure percolation of rainwater in the ground instead of draining away from the surface. Commonly used recharging methods are:-

Recharging of bore wells Recharging of dug wells Recharge pits Recharge Trenches Soak ways or Recharge Shafts Percolation Tanks

(a) Recharging of bore wells :- Rainwater collected from rooftop of the building is diverted through drainpipes to settlement or filtration tank. After settlement filtered water is diverted to bore wells to recharge deep aquifers. Abandoned bore wells can also be used for recharge. Optimum capacity of settlement tank/filtration tank can be designed on the basis of area of catchment, intensity of rainfall and recharge rate as discussed in design parameters. While recharging, entry of floating matter and silt should be restricted because it may clog the recharge structure. "First one or two shower should be flushed out through rain separator to avoid contamination. This is very important, and all care should be taken to ensure that this has been done."



(b) Recharging of dug wells :- Dug well can be used as recharge structure. Rainwater from the rooftop is diverted to dug wells after passing it through filtration bed. Cleaning and desalting of dug well should be done regularly to enhance the recharge rate. The filtration method suggested for bore well recharging could be used.

(c) Recharge Pits :- Recharge pits are small pits of any shape rectangular, square or circular, constructed with brick or stone masonry wall with weep hole at regular intervals. To of pit can be covered with perforated covers. Bottom of pit should be filled with filter media. The capacity of the pit can be designed on the basis of catchment area, rainfall intensity and recharge rate of soil. Usually the dimensions of the pit may be of 1 to 2 m width and 2 to 3 m deep depending on the depth of pervious strata. These pits are suitable for recharging of shallow aquifers, and small houses.



(d) Recharge Trenches :- Recharge trench in provided where upper impervious layer of soil is shallow. It is a trench excavated on the ground and refilled with porous media like pebbles, boulder or brickbats. It is usually made for harvesting the surface runoff. Bore wells can also be provided inside the trench as recharge shafts to enhance percolation. The length of the trench is decided as per the amount of runoff expected. This method is suitable for small houses, playgrounds, parks and roadside drains. The recharge trench can be of size 0.50 to 1.0 m wide and 1.0 to 1.5 m deep

(e) Soak ways or Recharge Shafts :- Soak away or recharge shafts are provided where upper layer of soil is alluvial or less pervious. These are bored hole of 30 cm dia. up to 10 to 15 m deep, depending on depth of pervious layer.Bore should be lined with slotted/perforated PVC/MS pipe to prevent collapse of the vertical sides. At the top of soak away required size sump is constructed to retain runoff before the filters through soak away. Sump should be filled with filter media.



(f) Percolation Tanks :- Percolation tanks are artificially created surface water bodies, submerging a land area with adequate permeability to facilitate sufficient percolation to recharge the ground water. These can be built in big campuses where land is available and topography is suitable. Surface run-off and roof top water can be diverted to this tank. Water accumulating in the tank percolates in the solid to augment the ground water. The stored water can be used directly for gardening and raw use. Percolation tanks should be built in gardens, open spaces and roadside green belts of urban area.

Advantages & Dis-advantages of Rain water Harvesting

֍ Advantages :

1. Easy to Maintain: Utilizing the rainwater harvesting system provides certain advantages to the community. First of all, harvesting rainwater allows us to better utilize an energy resource. It is important to do so since drinking water is not easily renewable and it helps in reducing wastage. Systems for the collection of rainwater are based on simple technology.

2. Reducing Water Bills: Water collected in the rainwater harvesting system can be put to use for several non-drinking functions as well.



For many families and small businesses, this leads to a large reduction in their utilities bill. On an industrial scale, harvesting rainwater can provide the needed amounts of water for many operations to take place smoothly without having to deplete the nearby water sources. It also lessens the burden of soil erosion in a number of areas, allowing the land to thrive once again.

3. Suitable for Irrigation: As such, there is little requirement for building new infrastructure for the rainwater harvesting system. Most rooftops act as a workable catchments area, which can be linked to the harvesting system. This also lessens the impact on the environment by reducing use of fuel based machines.

4. Reduces Demand on Ground Water: With increase in population, the demand for water is also continuously increasing. The end result is that many residential colonies and industries are extracting ground water to fulfil their daily demands. This has led to depletion of ground water which has gone to significant low level in some areas where there is huge water scarcity.

֍ Dis-advantages :

1. Unpredictable Rainfall: Rainfall is hard to predict and sometimes little or no rainfall can limit the supply of rainwater. It is not advisable to depend on rainwater alone for all your water needs in areas where there is limited rainfall.

2. Initial High Cost: Depending on the system’s size and technology level, a rainwater harvesting system may cost anywhere between $200 to $2000 and benefit from it cannot be derived until it is ready for use. Like solar panels, the cost can be recovered in 10-15 years which again depends on the amount of rainfall and sophistication of the system.

3.Regular Maintenance: Rainwater harvesting systems require regular maintenance as they may get prone to rodents, mosquitoes,



algae growth, insects and lizards. They can become as breeding grounds for many animals if they are not properly maintained.

4. Storage Limits: The collection and storage facilities may alsoimpose some kind of restrictions as to how much rainwater you canuse. During the heavy downpour, the collection systems may not beable to hold all rainwater which ends in going to drains and rivers.

Do's and Don’t Harvested rainwater is used for direct usage or for recharging aquifers. It is most important to ensure that the rainwater 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.

Major Rain Water Harvesting Project In Karnataka :-

Municipal water supply in most Indian cities is unreliable. Many villages in India do not have potable water supply. Hence Rainwater Harvesting (RWH) has been proposed as an ideal sustainable solution. The Karnataka State Council for Science and Technology (KSCST) has undertaken steps to promote, implement and create awareness on sustainable water harvesting and groundwater recharge concepts. Among the three projects initiated by the council, ‘Rainwater harvesting in rural Karnataka’ funded by Rural Development and Panchayat Raj Department (RDPR), Government of Karnataka is probably the largest rainwater harvesting project in the world.



PROJECT ON RAIN WATER HARVESTING

Plan & Design :-

Location : # 34 , 2nd Stage , Raja Ram Mohan Roy Street Bengaluru – 563130 ,, Karnataka

ESTIMATION & COSTING OF THE PROJECT :-Estimation :

SL No

Particulars Of Items Nos Length Breadth

Depth

Quantity

1Earth work in

Excavation Grating Cover



1st Layer 1 1.5 1.5 1.5 3.375m3 2nd Layer 1 1.5 1.5 1.5 3.375m3 3rd Layer 1 1.5 1.5 3 6.75m3 Total = 13.5m3

2 Concrete Rings 22 0.3 0.03 6 1.188 Catchment area 1 30 38 - 1140 P V C Pipes 6 - - 6 36

Abstract Estimation :

SL No

Particular Of Items

Quantity Unit Rate Per

Amount (INR)

1Earth Work Excavation 13.5 m3 150 m3 2025

2 Concrete Rings 22 m3 750 m3 165003 P V C Pipes 40 M 1600 m 640004 Elbow Joints 8 Nos 170 Nos 13605 Collar Joints 5 Nos 170 Nos 850

6Labour Cost With Transport Lump sum 70300

155035

Add 5% For Contingencies = 7751.75

Add 7% For Work Charged

Establishment = 10852.45

Total - 173639.2

Water Storage Capacity Chart :

No of Tank Length In Mt’s

Breadth in Mt’s

Liquide Depth In Mt’s

Liquid Capacity Provided

1 1.5 1.5 1.5 3.375



1 1.5 1.5 1.5 3.3751 1.5 1.5 3 6.75

Total = 13.5

Resul ts & Discussion :-

The environmental characterization indicated that the best scenario in both urban models is the distributed-over-roof tank (D3, C3), which provided a reduction in impacts compared to the worst scenario of up to 73% in diffuse models and even higher in compact ones, 92% in the most dramatic case.

The lower impacts are related to the better distribution of tank weight on the building, reducing the reinforcement requirements, and enabling energy savings. The storage subsystem and the materials stage contributed most significantly to the impacts in both urban models. In the compact density model, the underground-tank scenario (C1) presented the largest impacts in most categories due to its higher energy consumption. Additionally, more favourable environmental results were observed in compact densities than in diffuse ones for the Global Warming Potential category along with higher water efficiencies.

Conclusions :-

The implementation of one particular RWH scenario over another is not irrelevant in drought-stress environments. Selecting the most favourable scenario in the development of newly constructed residential areas provides significant savings in CO2 emissions in comparison with retrofit strategies.



Therefore, urban planning should consider the design of RWH infrastructures using environmental criteria in addition to economic, social, and technological factors, adjusting the design to the potential uses for which the rainwater is intended.

References :-References Web Sites :

www.google.co.in www.scholar.google.co.in www.wikipedia.org www.sustainable.com www.mppcb.nic.in www. akvopedia.org www.sswm.info Water Recourses Engineering (Civil)


http://www.sswm.info/

http://www.mppcb.nic.in/

http://www.sustainable.com/

http://www.wikipedia.org/

http://www.scholar.google.co.in/

http://www.google.co.in/

rain water harvesting project

Environment