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Here is a term paper on ‘Rainwater Harvesting’. Find paragraphs, long and short term papers on ‘Rainwater Harvesting’ especially written for school and college students.
Term Paper on Rainwater Harvesting
Term Paper Contents:
- Term Paper on the Introduction to Rainwater Harvesting
- Term Paper on Rooftop Rainwater Harvesting
- Term Paper on Rooftop Rainwater Harvest-Cum-Groundwater Recharge Structure
- Term Paper on Rainwater Harvest as a Practice
- Term Paper on Watershed-Linked Rainwater Management
- Term Paper on the Remote-Sensing Technique in Mapping of Watersheds
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Term Paper # 1. Introduction to Rainwater Harvesting:
The rainwater is the first form of water on the land area in the Hydrological Cycle or Water Cycle. The Hydrologic Cycle or Water Cycle starts with the evaporation of the ocean or sea water. As the moisture-laden vapours in the air rises, cooling takes place and the water vapors condense to form rain-bearing clouds.
The moisture-laden clouds are transported over large terrestrial regions until the moisture returns to the Earth’s surface as rainfall. Out of this rainwater that reaches the land, a part of it evaporates back into the atmosphere. A significant part of the rainwater percolates into the subsurface and become groundwater.
A part of the groundwater seeps into the oceans, rivers and streams, and a part merges back into the atmosphere by transpiration. A part of the rainwater flows as surface is runoff and gets emptied into lakes, rivers and streams, and eventually flows in to the oceans, from where the hydrological or water cycle repeats.
The Hydrological or Water Cycle can be described in nine major processes that form a continuum of the water movement. The pathways of these movements or the cycle include its passage from gaseous form in the atmosphere, through the Earth’s hydrosphere like oceans, glaciers and lakes, and simultaneous moving or seeping through the soil and rock to the subsurface. The water is returned to the atmosphere by repetition of the above processes.
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A notable characteristic of the hydrologic cycle is that it has no beginning and it has no end.
The hydrological or water cycle can be studied from any of the following nine processes round and round:
(i) Evaporation,
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(ii) Condensation,
(iii) Precipitation,
(iv) Interception,
(v) Infiltration,
(vi) Percolation,
(vii) Transpiration,
(viii) Runoff, and
(ix) Storage.
The rainwater is the least polluted and softest of all the water sources, since rainwater does not contain any salts or contaminants or pathogenic substances when it falls on a clean surface or storage system. Therefore, the rainwater is the least expensive potable water when collected the moment it is precipitated. Rainwater Harvesting is a practice in which the pure rainwater is harnessed as and when it reaches the land in a clean state, stored for a certain length of period and used for consumption with or without appropriate treatments.
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Rainwater collection for a later use is not new to India, because, from time immemorial, the rainwater is collected as surface runoff and stored in johad (in Rajasthan), ponds, lakes and reservoirs, and put to use for consumption by a small local population and for irrigation.
A part of the surface runoff percolates beneath the surface without any efforts on the part of humans and gets accumulated in the groundwater system. Though some people think that the practice of rainwater harvesting is thought to be of recent age, many researchers believe that in reality it seems to be much older as it used to be practised even during the Vedic times in India.
The water-stress necessitates rainwater harvesting by individuals and community levels. The easiest and least expensive method of rainwater harvesting on a large scale for a small community use as that of a village or a small group of villages is the practice of collecting the surface runoff in ground-level tanks, reservoirs and bund structures. This practice does not involve installation of any particular structure except bund or barrier to impound the water in the tank or reservoir, and therefore, it is least expensive.
This practice would involve only periodic de-silting and dredging operations for the tanks and reservoirs, so that larger quantities of water can be collected and impounded, and larger communities of population can use the water thus collected. Except periodic costs towards labour for the de-silting and dredging operations, this method does not involve recurring expenditure. The water impounded can be used for agriculture and human consumption, though certain quantity is lost due to the evaporation and some quantity percolates to the groundwater system.
Term Paper # 2. Rooftop Rainwater Harvesting:
The rainwater harvesting by a family or a small group of families in the urban residential complexes, such as apartments or clusters of group housing, would involve a different approach. Rainwater is collected from the house rooftop where it first falls and diverted to the tanks or sumps or storage system built exclusively for the purpose of water storage.
Water is drawn from the storage tanks for day-to-day consumption. This approach would involve installation of cisterns or storage tanks and proper pumping and plumbing facility. This practice is called as Rooftop Rainwater Harvesting.
Let us consider that a house has a rooftop catchment area of 100 square metres. If we assume that the average annual rainfall of the area is 80 centimetres, the total rainfall that would be received by this rooftop area will be 80,000 litres (= rooftop area multiplied by the average annual rainfall). If a deduction of 25 percent towards splash effect from the roof, spill over and other wastages is considered, the total water that can be collected works out to 60,000 litres.
Assuming that the per capita consumption of water per day by an Indian family consisting of five members is about 200 litres, the 60,000 litres of water thus collected from the rooftop of the house will last for 300 days. By minimizing the wastages such as spill over, and increasing the rooftop area the rainwater collected can be as high as 75,000 litres, which would be sufficient almost for the whole year.
The rainfall in India is spread over a four-month- long monsoon season. Hence, adequate replenishment during that four-month period is possible. If it were presumed that at the end of the monsoon season the total collection and storage of water from rooftop is 75,000 litres, this stored water would thus be available throughout the next dry season. This, in brief, is all about domestic rooftop rainwater harvest setup and concept.
Rooftop rainwater collection or harvest has the following advantages:
i. Collection of rainwater directly from the rooftop is preferred to the collection from surface runoff since the contamination will be absent in the case of collection from the rooftop.
ii. The time and cost involved in the transportation of water for day-to-day can be avoided in the case of rooftop method of rainwater harvest.
iii. It would not be necessary to wait in anticipation of the piped water supply provided by the water supply authorities.
iv. With a one-time expenditure at the time of construction of the rooftop rainwater harvesting facility, the advantages that accrue are tremendous and multiple.
v. Collection of potable water from the pure rainwater source.
vi. Since rainwater is free from dissolved salts and mineral contents, its storage in tank as well as transport through pipes do not cause scaling or corrosion or deposition on the system.
vii. Participation by individuals at grass-root level in soil conservation by preventing soil erosion due to floods, flood mitigation in urban areas and groundwater conservation.
The rooftop rainwater harvest system consists of the following four aspects:
1. Catchment or Rooftop area for collection of the rainwater the moment it is precipitated.
2. Storage tank with provision of input piping from the catchment/rooftop.
3. Treatment of water during storage.
4. Pump and piping system to the residence for distribution.
1. Catchment or Rooftop:
Rainwater can be captured from any constructed structure that has a roof, including a small residence. The structures which have large roof surfaces have advantage in that they can catch more volume of water and divert it to the storage system. It is preferred that the roof has a gentle slope on either one side or both sides.
In modern type construction it is customary to provide for terrace with parapet walls, in which case plastering of the floor of the terrace needs be provided with a gentle slope of about 5 degrees. The rainwater shall be collected on the down-slope side and directed into the drainpipes, which in turn, empty the water in the sump or other storage system.
The catchment area of roof surface has to be clean, since clean water contact surface averts contamination of water. Or, the catchment area surface needs to be washed at the onset of rainy season. Screens or sieves have to be provided at the mouth of the drainpipe that drains the rainwater into the storage system, as well as the inlet point at which the rainwater enters the storage tank from the drainpipe. These screens and sieves have to be cleaned periodically to clear dirt, silt, fine sand and other sediments that are likely to choke the entry of the rainwater into the drainage pipe and the storage tank.
2. Storage Tank:
A storage tank or cistern of 60,000 to 75,000 litre capacity may be provided for collection of the rainwater from the rooftop. This is the expensive part of the domestic rooftop rainwater harvest system. Provision for a 60 to 75 cubic-metre storage tank or a cistern can to be made within the house site at the time of planning the house. Polyethylene or ferro-cement storage tanks shall suit the purpose.
Several numbers of cistern or storage tank may be interconnected in a cascading or any other appropriate manner in such a way that the input-output process is suitably manipulated to fill all tanks. Rainwater does not contain dissolved salts and minerals. Hence, tank, pipes and fittings do not get scaling or undergo corrosion or deposition on the system.
3. Treatment of Water:
The water that is collected in the rainwater harvest storage tanks is retained for a certain period of time before it is used for drinking or cooking purposes. It is likely that during this storage period its quality might be affected due to the contact of external infectants such as bacteria and micro-organisms.
Therefore, a few basic treatments would be required if it is to be used for direct oral consumption and for cooking purposes. For all the other activities, such as washing of cloths, use in toilets and for personal hygiene, only suspended particles and fine sediments need to be isolated from the stored water.
The use of screens and sieves at a few places before the rainwater gets accumulated in the storage tank or sump acts as a coarse filtration process in the beginning. Filtration to upgrade the water to potable level by removal of the suspended particulate matters such as clay and silt, colloidal and precipitated matters and micro-organisms can be achieved by the use of filters or by granular media filters using materials like sand, crushed anthracite, coal or granular activated carbon. Activated charcoal filters the water by adsorption, as chemical and heavy metal impurities are attracted to the surface of the charcoal and attached to it.
The treatment for the stored water has to be conducted to disinfect the water and ensure that consumption of the stored water does not cause water-borne diseases. The disinfection of the water can be defined as the elimination of pathogens that are responsible for the water-borne diseases. Disinfection at the domestic level stored rainwater can be effectively carried out by simple methods like boiling, chlorination and ultra-violet irradiation.
Boiling of the water for about five minutes ensures elimination of most of the pathogens and micro-organisms. Chlorination is a popular and easily performable disinfection process on the stored water. Use of free chlorine or calcium hypochlorite or bleaching power is some of the simple forms of chlorination method adopted for water disinfection.
If the bleaching powder is used for disinfection, the frequency of disinfection by its use needs to be increased because of its unstable nature of the chlorine-content on storage for long time. The ultra-violet (UV) irradiations of the stored water in the 240 to 280 nanometer (nm) kills the bacteria most effectively. A few companies in India manufacture the UV irradiation-based water purifiers and their use ensures total elimination of bacteria and micro-organisms.
4. Pump and Piping System:
These two components are of peripheral nature, but integral part of the rooftop rainwater water system and they can suit the size of the system or the number of the families that would use the facility. Continuous innovations in the techniques and improvement of the plumbing materials, patterns in simple but effective plumbing and use of less expensive materials are happening in the rooftop rainwater harvest installations.
Term Paper # 3. Rooftop Rainwater Harvest-Cum-Groundwater Recharge Structure:
In the ‘integrated rooftop rainwater harvest-cum- groundwater recharge system’, a storage tank (Rainwater Harvest Tank) is provided to collect the rainwater. The rainwater in excess after filling up the storage tank spills over to the adjacent sump for more harvest and storage. From the sump, the excess water overflows into the groundwater system through the Recharge Pit.
The excess spill over water infiltrates through the sub-strata and reaches the groundwater system and get stored there. This structure facilitates collection and storage of pure rainwater for direct oral consumption as well as to recharge the groundwater to raise the groundwater table in and around the living area.
If several such structures were built in close-by houses and apartments in urban areas, it would also facilitate substantial percolation of rainwater to the groundwater aquifers to raise the water table on a regional scale. They would also help in averting soil erosion, groundwater contamination through urban pollutants and hazards of urban floods.
If installed in large numbers in the coastal cities, a cluster of several installations would recharge the coastal aquifers through the groundwater recharge part of the integrated system, even as the rainwater collected in the storage tank part can be drawn daily for use. As a result of this recharging of the coastal aquifers, the ingression of seawater in to the aquifer would be arrested and the aquifer would remain saturated with fresh water.
The authorities would do well if they mount campaigns on the integrated rooftop rainwater harvest-cum-groundwater recharge system. The authorities should impress upon the citizens on the twin benefit of self-reliance for their drinking water needs and contributing to the cause of improving the health of the coastal aquifers, which have been over-exploited in the recent past resulting in seawater ingression into them.
The stress on clean water in the coastal cities such Chennai, Visakhapatnam, Nellore, Ongole, Ernakulam and Mangalore can be relieved to a great extent by this way, simultaneously paving way to recharge the aquifers that are situated nearby these cities. This is the way to involve common man at grass root level in the participation of the movement on rainwater harvest and groundwater recharge at one stroke.
Term Paper # 4. Rainwater Harvest as a Practice:
In India there are many success stories in terms of rainwater harvesting in many States. Several State government organisations, NGOs and private entrepreneurs are currently active in helping out the prospective individuals and organisations which are keen to have rainwater harvesting system in their premises.
Since cisterns, water pumps and plumbing materials are available in plenty all over India, those interested in installation of the rooftop water harvesting plants within their residential premises can give their own innovative designs to this technology with the assistance of the skilled workers like plumbers, duly taking into account the size of their plots and the rooftop area of their building.
Civil engineers, builders and building contractors can bring innovations to the design of rooftop rainwater harvesting structures to suit the needs of the individual plot of the house, depending upon the shape and size of the residential building plots. Rooftop rainwater harvesting is a micro-level water resource management adopted at a grass-root level by the common man.
Encouraging more and more common people in the country to resort to rooftop rainwater harvesting practice would mean creation of awareness in the common man on the value of the water resource, which is becoming more precious and scarcer day by day, as well as involving the common man in the movement of the water conservation.
There is an onus on the entrepreneurs and the engineers in the matter concerning the commodities of rooftop rainwater harvesting, as they need to find out ways to continually improvise the existing accessories of the technology so as to bring down their costs to make them affordable to the common man.
That might be an easy and practical way to popularise the rooftop rainwater harvest technology and lure the masses into adopting it. Rainwater harvesting is a social movement to conserve water as it is received as rain, and augment the water resource by stocking the rainwater which would otherwise go waste.
The urban development authorities have to make rainwater harvesting structures mandatory for independent houses and group houses of appropriate size, including the apartments. It would substantially reduce the stress faced by the municipalities and water supply authorities due to water supply that they have to provide to the houses and apartments.
If entrepreneurship in the sector of rainwater collection, storage, processing and distribution in the Indian urban centres is encouraged and nurtured by those in the authority, it can tackle two problems, namely the unemployment of the qualified youth on one hand and the water supply on the other.
Rooftop rainwater harvesting and the integrated rainwater harvest-cum-groundwater recharge system not only help conserve water resource that would otherwise go waste, but also augments the recoverable natural water in its purest form for the use of a large human community.
The country’s water policy should make it mandatory on the part of those who propose to build new residential buildings, be it a single house or group housing or a multi-storeyed apartment, to make provision for the rooftop rainwater harvest system in their proposed building.
Though a few States in India have issued notification on this matter, when it comes to implementation the rules are broken with impunity. This can be achieved only if the ministries and organizations dealing with Urban Planning, Municipal Corporation, Housing and Water Work department function in an orchestrated manner.
What is important is strict adherence to the rules concerning rainwater harvest- cum-groundwater recharge structure by the prospective builders to actually provide for the rooftop rainwater harvesting facility in their buildings needs to be ensured by those in the authority in letter and spirit. That would the one way by which the government would involve the common man at the grass root level in the movement of water conservation and water resource management.
Until and unless this is not done, the citizens of the country would continue to feel that the water supply is the sole responsibility of the government, without they themselves directly participating in the social responsibility and mass movement of conserving the country’s water resource and using the precious water wealth with prudence and judiciousness.
Term Paper # 5. Watershed-Linked Rainwater Management:
Watershed is a terrain or an area comprising a natural drainage system made up of streams and tributaries which join and drain at a particular point in the downstream side. Watershed is a mappable unit of a terrain in which the runoff waters essentially flow through the streams channels and drains through a particular location within the drainage basin.
The mappability may be on any appropriate or convenient or given scale. Watershed may be visualized as an area draining the rainwater into a stream. The term watershed might appear to offer the same connotation as that of catchment area of a reservoir or a drainage basin, but it has a major difference from the latter in that several watersheds constitute a drainage basin.
Watersheds are small units of terrain, which can be ably administered by the water management authorities with ease in terms of gauging, monitoring and distribution of the water resource available or accrue during rainy seasons in the streams that drain the terrain units, by means of effective management for irrigation of arable lands and a source for potable water.
Therefore, planning for effective water conservation and water resource management of a large area or terrain containing a drainage basin shall start with planning at the watershed level. Watersheds being rain-fed, the water conservation and management of water resources in the watersheds would mean that the rainwater received during a rainy season in the smaller terrains is effectively administered for a variety of human activities.
In the case of massive surface runoffs at the time of active monsoon or heavy rains, the rainwater may skip a number of streams in a watershed, as it would follow the available natural slopes on ground to create floods in one or more watersheds.
In the case of the watershed-linked water conservation and management, the rainwater is made to saturate the dry parched stretches of land situated within the watershed area, which is the main objective of the watershed development concept. The water that drains in the lower order streams is frequently impounded in tanks and bonded reservoirs for the purpose of irrigation and rural water supply, as well to facilitate replenishment of the groundwater resource.
In 1993, the WHO (World Health Organization) had recommended that the watersheds should be protected from human activities. This is due to the fact that the micro-level water pollution begins with fouling of water mostly at watershed level. It is because the quality of water over large areas depends on the cleanliness maintained in the watersheds, and the cleanliness, in turn, is hinged to the human activities.
This would include isolation of the watershed and control of polluting activities such as dumping of solid waste, bio-wastes, hazardous wastes, mining, quarrying, use of fertilizers and pesticides in the area, and the restricting all sorts of anthropogenic pollution activities.
These facts underline the necessity to delineate the watersheds in appropriate areas in terms of area in square-kilometres, in the entire country. That would help in mapping them in great detail using various technologies, linking them together, and eventually bring out the compiled maps of the major water sheds and in turn the drainage basins.
The availability of these maps of watersheds and drainage basins would facilitate arriving at appropriate decisions by the concerned authorities in the government at various levels with regard to locating the sites for reservoirs and tanks by construction of dam or bund across the streams that carry the rainwater in a watershed. Most importantly, the watershed administration of the governments can decide on diverting excess water from a part of a watershed to the water-deficient areas of the same watershed, or to other nearby parched watershed.
Term Paper # 6. Remote-Sensing Technique in the Mapping of the Watersheds:
India is a global force in the fields of satellite launch, satellite imagery generation and multi-thematic interpretation of the satellite imagery data, a technique which is otherwise known as Remote-Sensing. The Indian Remote-sensing Satellite (IRS) imagery are world class in terms of spatial and spectral resolutions.
The IRS imagery are currently in use in a host of advanced scientific applications such as agriculture, forestry, geology, environment study, urban planning, laying of telecommunication network, seismic and landslide studies, Ocean Colour Monitoring for the purposes of fishery, water resource identification and the mapping of watersheds.
The remote-sensing technology using satellite imagery is the empirical means to delineate and map the watersheds in most speedy, precise, scientific and modern means which can stand scrutiny and verification, anytime and from any part of the globe. Therefore, organized delineation of the watersheds of any appropriate area in terms of its size and location, and suggestion for proper measures for the management of the watersheds thus delineated, should form one of the thrust areas in the scientific research. A processed satellite imagery of an identified watershed and the watershed map interpreted from the same imagery.
Some of the organizations that carry out remote-sensing have already generated a huge wealth of data pertaining to the watersheds in India. These data are accessible only in bits and pieces for isolated locations of the country. Generation of these data almost lack a uniform and systematic approach.
The data on watersheds have to be made available to any work group of planners and policy makers on contiguous basis in terms of drainage basin or river basin, in order that the reasons for the root causes for dry conditions and poor surface runoff can be pointedly understood. This is necessary for implementing appropriate and meaningful management practices for the water resource development from the watershed levels.
In the absence of data on continuous watersheds, the planning and implementation would go totally haywire and the purpose for which the watershed management exercise was undertaken would not yield the desired results. The huge scientific data generated by several organizations for many watersheds tend to be repetitive, lacking uniformity or contradict in scientific contents.
The aspects that are conspicuously lacking in most of these studies are the empirical field validation of the imagery-interpreted data, meaningful synthesis of the watersheds in terms of effective management, and authoritative information on meteorology, geomorphology and geologic structures like faults that are likely to have a bearing on the seismicity too.
All these information of fundamental nature on each watershed are expected from the remote sensing scientists to facilitate the Governments of the Indian Union and the States to arrive at a comprehensive policy on water conservation, resource augmentation and management.