RAINWATER HARVESTING full report and ppt
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KSRM COLLEGE OF ENGINEERING
The paper outlines 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.
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.
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 rainwater harvesting?
In many regions of the world, clean drinking water is not always available and this is only possible with tremendous investment costs and expenditure. Rainwater is a free source and relatively clean and with proper treatment it can be even used as a potable water source. Rainwater harvesting saves high-quality drinking water sources and relieves the pressure on sewers and the environment by mitigating floods, soil erosions and replenishing groundwater levels. In addition, rainwater harvesting reduces the potable water consumption and consequently, the volume of generated wastewater.
Rainwater harvesting systems can be installed in both new and existing buildings and harvested rainwater used for different applications that do not require drinking water quality such as toilet flushing, garden watering, irrigation, cleaning and laundry washing. Harvested rainwater is also used in many parts of the world as a drinking water source. As rainwater is very soft there is also less consumption of washing and cleaning powder. With rainwater harvesting, the savings in potable water could amount up to 50% of the total household consumption.
Criteria for selection of rainwater harvesting technologies
Several factors should be considered when selecting rainwater harvesting systems for domestic use:
• type and size of catchment area
• local rainfall data and weather patterns
• family size
• length of the drought period
• alternative water sources
• cost of the rainwater harvesting system.
When rainwater harvesting is mainly considered for irrigation, several factors should be taken into consideration. These include:
• rainfall amounts, intensities, and evapo-transpiration rates
• soil infiltration rate, water holding capacity, fertility and depth of soil
• crop characteristics such as water requirement and length of growing period
. Components of a rooftop rainwater harvesting system
Although rainwater can be harvested from many surfaces, rooftop harvesting systems are most commonly used as the quality of harvested rainwater is usually clean following proper installation and maintenance. The effective roof area and the material used in constructing the roof largely influence the efficiency of collection and the water quality.
Rainwater harvesting systems generally consist of four basic elements:
(1) a collection (catchment) area
(2) a conveyance system consisting of pipes and gutters
(3) a storage facility, and
(4) a delivery system consisting of a tap or pump.
Fig. 2: A schematic diagram of a rooftop rainwater harvesting system.
(1) A collection or catchment system is generally a simple structure such as roofs and/or gutters that direct rainwater into the storage facility. Roofs are ideal as catchment areas as they easily collect large volumes of rainwater.
The amount and quality of rainwater collected from a catchment area depends upon the rain intensity, roof surface area, type of roofing material and the surrounding environment. Roofs should be constructed of chemically inert materials such as wood, plastic, aluminium, or fibreglass. Roofing materials that are well suited include slates, clay tiles and concrete tiles. Galvanised corrugated iron and thatched roofs made from palm leaves are also suitable. Generally, unpainted and uncoated surface areas are most suitable. If paint is used, it should be non-toxic (no lead-based paints).
(2) A conveyance system is required to transfer the rainwater from the roof catchment area to the storage system by connecting roof drains (drain pipes) and piping from the roof top to one or more downspouts that transport the rainwater
through a filter system to the storage tanks. Materials suitable for the pipework include polyethylene (PE), polypropylene (PP) or stainless steel.
Before water is stored in a storage tank or cistern, and prior to use, it should be filtered to remove particles and debris. The choice of the filtering system depends on the construction conditions. Low-maintenance filters with a good filter output and high water flow should be preferred. “First flush” systems which filter out the first rain and diverts it away from the storage tank should be also installed. This will remove the contaminants in rainwater which are highest in the first rain shower.
(3) Storage tank or cistern to store harvested rainwater for use when needed. Depending on the space available these tanks can be constructed above grade, partly underground, or below grade. They may be constructed as part of the building, or may be built as a separate unit located some distance away from the building. .
(4) Delivery system which delivers rainwater and it usually includes a small pump, a pressure tank and a tap, if delivery by means of simple gravity on site is not feasible.
Disinfection of the harvested rainwater, which includes filtration and/or ozone or UV disinfection, is necessary if rainwater is to be used as a potable water source.
Storage tanks or reservoirs
The storage reservoir is usually the most expensive part of the rainwater harvesting system such that a careful design and construction is needed. The reservoir must be constructed in such a way that it is durable and watertight and the collected water does not become contaminated.
Materials and design for the walls of sub-surface tanks or cisterns must be able to resist the soil and soil water pressures from outside when the tank is empty. Tree roots can also damage the structure below ground.
The size of the storage tank needed for a particular application is mainly determined by the amount of water available for storage (a function of roof size and local average rainfall), the amount of water likely to be used (a function of occupancy and use purpose) and the project and implimentationed length of time without rain (drought period).
First flush and filter screens
The first rain drains the dust, bird droppings, leaves, etc. which are found on the roof surface. To prevent these pollutants from entering the storage tank, the first rainwater containing the debris should be diverted or flushed. Automatic devices that prevent the first 20-25 litres of runoff from being collected in the storage tank are recommended.
Screens to retain larger debris such as leaves can be installed in the down-pipe or at the tank inlet. The same applies to the collection of rain runoff from a hard ground surface. In this case, simple gravel-sand filters can be installed at the entrance of the storage tank to filter the first rain.
Rainwater harvesting efficiency: The efficiency of rainwater harvesting depends on the materials used, design and construction, maintenance and the total amount of rainfall. A commonly used efficiency figure, runoff coefficient, which is the percentage of precipitation that appears as runoff, is 0.8.
For comparison, if cement tiles are used as a roofing material, the year-round roof runoff coefficient is about 75%, whereas clay tiles collect usually less than 50% depending on the harvesting technology. Plastic and metal sheets are best with an efficiency of 80-90%.
For effective operation of a rainwater harvesting system, a well designed and carefully constructed gutter system is also crucial. 90% or more of the rainwater collected on the roof will be drained to the storage tank if the gutter and down-pipe system is properly fitted and maintained. Common materials for gutters and down-pipes are metal and plastic, but also cement-based products, bamboo and wood can be used.
Benefits of rainwater harvesting
Rainwater harvesting in urban and rural areas offers several benefits including provision of supplemental water, increasing soil moisture levels for urban greenery, increasing the groundwater table via artificial recharge, mitigating urban flooding and improving the quality of groundwater. In homes and buildings, collected rainwater can be used for irrigation, toilet flushing and laundry. With proper filtration and treatment, harvested rainwater can also be used for showering, bathing, or drinking. The major benefits of rainwater harvesting are summarised below:
• rainwater is a relatively clean and free source of water
• rainwater harvesting provides a source of water at the point where it is needed
• it is owner-operated and managed
• it is socially acceptable and environmentally responsible
• it promotes self-sufficiency and conserves water resources
• rainwater is friendly to landscape plants and gardens
• it reduces stormwater runoff and non-point source pollution
. High Initial investment Costs - The main cost of a rainwater collection system generally occurs during the initial construction phase and no benefit is derived until the system is completed.
2. Regular Maintenance - Regular maintenance, cleaning and repair will be required for the operation of a successful rainwater collection system.
3. Vulnerable Water Quality - The quality of rainwater can be affected by air pollution, insects, and dirt or organic matter. The type and kind of construction materials used can also adversely affect water quality.
4. Water Supply is Climate Dependent - Droughts or long periods of time with little or no rain can cause serious problems with your supply of water.
5. Storage Capacity Limits Supply - The supply of water from a rainwater collection system is not only limited by the amount of rainfall but also by the size of the collection area and your storage facilities.
Effectiveness of technology
The feasibility of rainwater harvesting in a particular locality is highly dependent on the amount and intensity of rainfall. As rainfall is usually unevenly distributed throughout the year, rainwater harvesting can usually only serve as a supplementary source of household water. The viability of rainwater harvesting systems is also a function of the quantity and quality of water available from other sources, household size, per capita water requirements and available budget.
Accounts of serious illness linked to rainwater supplies are few, suggesting that rainwater harvesting technologies are effective sources of water supply. It would appear that the potential for slight contamination of roof runoff from occasional bird droppings does not represent a major health risk. Nevertheless, placing taps at about 10 cm above the base of the rainwater storage tanks allows any debris entering the tank to settle on the bottom, where it will not affect the quality of the stored water, provided it remains undisturbed.
Finally, effective water harvesting schemes require community participation which is enhanced by:
• sensitivity to people’s needs
• indigenous knowledge and local expertise
• full participation and consideration of gender issues, and
• taking consideration of prevailing farming systems as well as national policies and community by-laws.
Valid data on the economic efficiency of rainwater harvesting systems is not possible. Dependent on the regional conditions (water and wastewater prices, available subsidies), the amortization period may vary between 10 and 20 years. However, it should be taken into consideration that for the major investment (storage and pipe work) a period of use of several decades is expected.
The associated costs of a rainwater harvesting system are for installation, operation and maintenance. Of the costs for installation, the storage tank represents the largest investment which can vary between 30 and 45% of the total cost of the system dependent on system size. A pump, a pressure controller and fittings in addition to plumber’s labor represent other major costs of the investment.
Rainwater quality standards
The quality of rainwater used for domestic supply is of vital importance because, in most cases, it is used for drinking. Rainwater does not always meet drinking water standards especially with respect to bacteriological water quality. However, just because water quality does not meet some arbitrary national or international standards, it does not automatically mean that the water is harmful to drink.
Compared with most unprotected traditional water resources, drinking rainwater from well-maintained roof catchments is usually safe, even if it is untreated. The official policy of the Australian Government towards the question “Is rainwater safe to drink?” is as follows: “Providing the rainwater is clear, has little taste or smell and is from a well-maintained system, it is probably safe and unlikely to cause any illness for most users”. For immuno-compromised persons, however, it is recommended that rainwater is disinfected through boiling prior to consumption.
Drinking water from rainwater
In many countries of the world where water resources are not available at a sufficient quality fit for human consumption, rainwater acts as a substitute for drinking water and other domestic uses. In some remote islands around the globe, rainwater may even act as the major potable water source for their population.
The most important issue in collecting rainwater is keeping it free of dirt such as leaves, bird droppings and dead animals, and avoiding contamination with pollutants like heavy metals and dust.
Rainwater can be also treated for use as a potable water source. The use of slow sand filtration has proved to be a simple and effective treatment technology for the elimination of most of the organic and inorganic pollutants that may be present in rainwater, as well as producing a virtually pathogen-free water for drinking.
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An Introduction to Rainwater Harvesting.docx (Size: 41.31 KB / Downloads: 151)
Rainwater harvesting is a technology used for collecting and storing rainwater from rooftops, the land surface or rock catchments using simple techniques such as jars and pots as well as more complex techniques such as underground check dams. The techniques usually found in Asia and Africa arise from practices employed by ancient civilizations within these regions and still serve as a major source of drinking water supply in rural areas. Commonly used systems are constructed of three principal components; namely, the catchment area, the collection device, and the conveyance system.
A) Catchment Areas
• Rooftop catchments: In the most basic form of this technology, rainwater is collected in simple vessels at the edge of the roof. Variations on this basic approach include collection of rainwater in gutters which drain to the collection vessel through down-pipes constructed for this purpose, and/or the diversion of rainwater from the gutters to containers for settling particulates before being conveyed to the storage container for the domestic use. As the rooftop is the main catchment area, the amount and quality of rainwater collected depends on the area and type of roofing material. Reasonably pure rainwater can be collected from roofs constructed with galvanized corrugated iron, aluminium or asbestos cement sheets, tiles and slates, although thatched roofs tied with bamboo gutters and laid in proper slopes can produce almost the same amount of runoff less expensively (Gould, 1992). However, the bamboo roofs are least suitable because of possible health hazards. Similarly, roofs with metallic paint or other coatings are not recommended as they may impart tastes or colour to the collected water. Roof catchments should also be cleaned regularly to remove dust, leaves and bird droppings so as to maintain the quality of the product water (see figure 1).
• Land surface catchments: Rainwater harvesting using ground or land surface catchment areas is less complex way of collecting rainwater. It involves improving runoff capacity of the land surface through various techniques including collection of runoff with drain pipes and storage of collected water. Compared to rooftop catchment techniques, ground catchment techniques provide more opportunity for collecting water from a larger surface area. By retaining the flows (including flood flows) of small creeks and streams in small storage reservoirs (on surface or underground) created by low cost (e.g., earthen) dams, this technology can meet water demands during dry periods. There is a possibility of high rates of water loss due to infiltration into the ground, and, because of the often marginal quality of the water collected, this technique is mainly suitable for storing water for agricultural purposes. Various techniques available for increasing the runoff within ground catchment areas involve: i) clearing or altering vegetation cover, ii) increasing the land slope with artificial ground cover, and iii) reducing soil permeability by the soil compaction and application of chemicals (see figure 2).
• Clearing or altering vegetation cover: Clearing vegetation from the ground can increase surface runoff but also can induce more soil erosion. Use of dense vegetation cover such as grass is usually suggested as it helps to both maintain an high rate of runoff and minimize soil erosion.
• Increasing slope: Steeper slopes can allow rapid runoff of rainfall to the collector. However, the rate of runoff has to be controlled to minimise soil erosion from the catchment field. Use of plastic sheets, asphalt or tiles along with slope can further increase efficiency by reducing both evaporative losses and soil erosion. The use of flat sheets of galvanized iron with timber frames to prevent corrosion was recommended and constructed in the State of Victoria, Australia, about 65 years ago (Kenyon, 1929; cited in UNEP, 1982).
• Soil compaction by physical means: This involves smoothing and compacting of soil surface using equipment such as graders and rollers. To increase the surface runoff and minimize soil erosion rates, conservation bench terraces are constructed along a slope perpendicular to runoff flow. The bench terraces are separated by the sloping collectors and provision is made for distributing the runoff evenly across the field strips as sheet flow. Excess flows are routed to a lower collector and stored (UNEP, 1982).
• Soil compaction by chemical treatments: In addition to clearing, shaping and compacting a catchment area, chemical applications with such soil treatments as sodium can significantly reduce the soil permeability. Use of aqueous solutions of a silicone-water repellent is another technique for enhancing soil compaction technologies. Though soil permeability can be reduced through chemical treatments, soil compaction can induce greater rates of soil erosion and may be expensive. Use of sodium-based chemicals may increase the salt content in the collected water, which may not be suitable both for drinking and irrigation purposes.
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rian water harvesting.pptx (Size: 308.75 KB / Downloads: 176)
RAIN WATER HARVESTING
RWH is an outcome of awareness among
the people regarding the water scarcity.
Typical features of Rain Water Harvesting :-
Reutilization of waste water.
As RWH - neither energy-intensive nor
It can be a cost-effective alternative to
other water-accruing methods.
With the water table falling rapidly, & concrete surfaces and landfill dumps taking the place of water bodies, RWH is the most reliable solution for augmenting groundwater level to attain self-sufficiency
The main objectives of rain water harvesting are :-
Promote rain water harvestig by creating awareness among the people.
increasing the avaibility of ground water during periods of requirement.
preventing depletion of ground water reserviour in areas of over exploitation
Decreasing menace of flood on local and regional scale
reducing pressure on storm drains in urban areas
enhancing the quality of environment.
What is Rain Water Harvesting?
Rain water harvesting is simply collecting, storing and purifying the naturally soft and pure rainfall that falls upon your roof.
Rain water may be utilized for both potable and non- potabke requirements such as…
Drinking, cooking, bathing(potable water)
Landscape and Irrigation
Livestock and Animals
Necessity of Rain Water Harvesting
Water is one of the most important natural resource, it is the most basic need for all living beings as well as a very valuable national asset.
surface water source fail to meet the rising demands of water supply in ueban areas
water is being taken out from sub-surface water source on large scale, while on contamprary, input to it is not being matched up.
How To Harvest Rain Water?
The six basic components of a rain water harvesting system include:-
Catchment: Roof surface to collect rain.
Conveyance: Pipes from roof area to storagre.
Roof Washing: ‘First flush’ diverter to filter and remove contaminants.
Storage: Tanks where collected rain water is collected and stored.
Purification: Includes artificial filters, sand filters to remove suspended impurities
Distribution: System that delivers the rain water, usually including small pump and pressure tank.
Methods of rain water harvesting.
Roof Top Rain Water Harvesting System
Rooftop Rainwater Recharging
Following are the methods of recharging Ground Water Table:-
1. Well Recharging Method
2. Borewell Recharging Method:-
Other minor methods are:-
Farm Pit Method
Farm Trench Method
Costs and Economic Viability of Roof Water Harvesting System
Two types of systems:
Rooftop water harvesting
Rooftop rainwater recharging
Rooftop water harvesting costs:
Rs.50/m3 for 20-year life
Rs.25 for a 40-year life
RWHS won’t replace public systems in most physical and climatic conditions.
When Does RWHS Work?
Rain Water Harvesting– Advantages
1.Provides self-sufficiency to water supply
2.Reduces the cost for pumping of ground water
3.Provides high quality water, soft and low in minerals
4.Improves the quality of ground water through dilution when recharged
5.Reduces soil erosion & flooding in urban areas
6.The rooftop rain water harvesting is less expensive & easy to construct, operate and maintain
7. In desert, RWH only relief
8. In saline or coastal areas & Islands, rain water provides good quality water
Conservation of water.
since we cannot produce energy, but we can save it by preventing wastage.
In the same way we cannot produce water, but save it and protect our future
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What is rainwater harvesting-my article.doc (Size: 103.5 KB / Downloads: 54)
Water - H2O ,that means water contains one oxygen and two hydrogen atoms
Pure Drinking water, in adequate quantity and safe quality, is a basic requirement for life either for urban or rural people. According to Census 2001-around 22 per cent of households in India lack access to safe drinking water sources, like tap, hand pump and tube well
States of water
Water can be found in a
1. Liquid state
2. Solid state
4. Gaseous state (water vapor or steam).
5. Liquid crystal state.
Sources of water
1) Primary source of water - Rain is a primary source of water for us.
2) Secondary source of water -Rivers, lakes and groundwater are all secondary sources of water
Primary source of water is the ultimate source that feeds all these secondary sources and remains ignorant of its value. Hence it is necessary to understand the value of rain, and to make optimum use of the rainwater at the place where it falls.
Water management is an interdisciplinary field concerned with the management of water resources. Many national governments have departments which are in charge of water management, and regional governments often have smaller offices of their own to focus on this issue .
What is rainwater harvesting?
Every one might have studied the story of thirsty crow “a crow was very thirsty. Looked for water every where. Then saw a pot with a little water in it, could not reach the water. Then got an idea, picked up stone and dropped them into the pot one by one. Water came up then drank the water flew away happily” This water harvester of a crow could teach us. Let’s get on, like the crow. Fashion a drop by drop approach to meet our needs.
1) Recognize Rain is the source of all water
2) Recognize in India the monsoon is brief i.e. just 100 hours out of 8,760 hours in a year. But this is enough to meet our water needs, provide food security and eradicate rural poverty
3) The key component of water management is 'storage'
Rainwater harvesting, it means capturing rain where it falls or capturing the run off in our own village or town and using it. We can store it in tanks or we can use it to recharge groundwater. This is an age-old system our ancestor’s harvested rain just as naturally and now we all are forced to practice it. This is about making water all our business. This is about building our relationship with water with the environment.
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30-07-2012, 11:05 PM
You said the inportance of water in our country we have lot of prolems with water.... so we have to impliment these for each and every house so that water problem is avoided and usage of water also will be good.
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vry much helpful on preparation of my seminar and presentation.