1.1. Definition Of Rainwater Harvesting

CHAPTER 1 INTRODUCTION 1.1.

Definition of rainwater harvesting: Rainwater Harvesting is a simple technique of catching and holding rainwater where

its falls. Either, we can store it in tanks or we can use it to recharge groundwater depending upon the situation. Water is essential for the environment, food security and sustainable development. Water forms the lifeline of any society. Availability of drinking water and provision of sanitation facilities are the basic minimum requirements for healthy living. Water supply and sanitation, being the two most important urban services, have wide ranging impact on human health, quality of life, environment and productivity. In most urban areas, the population is increasing rapidly and the issue of supplying adequate water to meet societal needs and to ensure equity in access to water is one of the most urgent and significant challenges faced by the policy-makers. Rainwater harvesting, in its broadest sense, is a technology used for collecting and storing rainwater for human use from rooftops, land surfaces or rock catchments using simple techniques such as jars and pots as well as engineered techniques. Rainwater harvesting has been practiced for more than 4,000 years, owing to the temporal and spatial variability of rainfall.

1.2.

Need for rainwater harvesting:

• To overcome the inadequacy of surface water to meet our demands. •

To arrest decline in ground water levels.

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To enhance availability of ground water at specific place and time and utilize rain water for sustainable development.

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To increase infiltration of rain water in the subsoil this has decreased drastically in urban areas due to paving of open area.

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To improve ground water quality by dilution.

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To increase agriculture production.

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To improve ecology of the area by increase in vegetation cover etc. 1  

 

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Water shortage is one of the reasons to implement rainwater harvesting. It is explained below:

a) Fresh water today is a scarce resource and it is being felt over the world. b) The reality of water crisis cannot be ignored. India has been notorious of being poor in management of water resources. The demand of water is already outstripping the supply. Majority of the population in cities today are ground water dependent. c) Shortage of water for industrial and domestic use and even for drinking purpose is a cause of concern throughout the world especially in developing and under developed countries. d) More than 2000 million people who live under conditions of high water stress by the year 2015. e) Ground water table is falling at alarming rate. f) Extraction of ground water is being done unplanned and uncontrolled resulting in hydrological imbalance and rise in energy requirements for pumping.

1.2.1. Studies carried out globally: Today due to rising population & economical growth rate, demands for the surface water is increasing exponentially. Rainwater harvesting is seems to be a perfect replacement for surface & ground water as later is concerned with the rising cost as well as ecological problems. Thus, rainwater harvesting is a cost effective and relatively lesser complex way of managing our limited resources ensuring sustained long-term supply of water to the community. In order to fight with the water scarcity, many countries started harvesting rain. Major players are Germany (Biggest harvesting system in Germany is at Frankfurt Airport, collecting water from roofs of the new terminal which has an large catchment area of 26,800 m2), Singapore (as average annual rainfall of Singapore is 2400 mm, which is very high and best suited for rainwater harvesting application), Tokyo (as RWH system reserves water which can be utilized for emergency water demands for seismic disaster), etc.      

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Figure 1. Showing water scarcity places  

1.2.2. Studies carried out in India today: Only 2.5 per cent of the entire world’s water is fresh, which is fit for human consumption, agriculture and industry. In several parts of the world, however, water is being used at a much faster rate than can be refilled by rainfall. In 2025, the per capita water availability in India will be reduced to 1500 cubic meters from 5000 in 1950. The United Nations warns that this shortage of freshwater could be the most serious obstacle to producing enough food for a growing world population, reducing poverty and protecting the environment. Hence the water scarcity is going to be a critical problem if it is not treated now in its peanut stage. Contrasting figures of water scarcity in world between two timeline (1999 & 2025) are shown in the fig. 2 & fig 3. Some of the major city where rainwater harvesting has already implemented is Delhi (Centre for Science and Environment's (CSE) designs sixteen model projects in Delhi to setup rainwater harvesting structures in different colonies and institutions), Bangalore (Rainwater harvesting at EscortsMahle-Goetze, Designed by S Vishwanath, Rainwater club, Indore (Indore Municipal Corporation (IMC) has announced a rebate of 6 per cent on property tax for those who have implemented the rainwater harvesting work in their house/bungalow/building). 3    

1.2.3. Studies carried out in Hyderabad: The twin reservoirs (Osmansagar and Himayatsagar) yield 45 millions of gallons per day, but a shortfall of 20 millions of gallons per day is expected from these sources. What it means is a deficit of 40 millions of gallons per day for the city, which is struggling to manage with the present supply of 340 millions of gallons per day. For instance the level in Osmansagar this year stood at 1761.340 feet against 1772.450 last year. In Himayatsagar, the water level is 1732.450 (1747.640 last year), Singur 1690.387(1703.495 last year). For all 4    

these reasons and to reduce water shortage, rainwater harvesting should be made mandatory at all places.

1.3. Advantages of Rainwater Harvesting: 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. The overall cost of their installation and operation is much lesser than that of water purifying or pumping systems. Maintenance requires little time and energy. The result is the collection of water that can be used in substantial ways even without purification. 2. Reducing water bills: Water collected in the rainwater harvesting system can be put to use for several nondrinking 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. In fact, it can also be stored in cisterns for use during times when water supplies are at an all time low. 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 catchment area, which can be linked to the harvesting system. This also lessens the impact on the environment by reducing use of fuel based machines. Rainwater is free from many chemicals found in ground water, making it suitable for irrigation and watering gardens. In fact, storing large reservoirs of harvested water is a great idea for areas where forest fires and bush fires are common during summer months.

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4. Reduces demand on ground water: With increase in population, the demand colonies and industries are extracting ground water to fulfill 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. 5. Reduces Floods and Soil Erosion: During rainy season, rainwater is collected in large storage tanks which also help in reducing floods in some low lying areas. Apart from this, it also helps in reducing soil erosion and contamination of surface water with pesticides and fertilizers from rainwater runoff which results in cleaner lakes and ponds. 6. Can be Used for Several Non-drinking Purposes: Rainwater when collected can be used for several non-drinking functions including flushing toilets, washing clothes, watering the garden, washing cars etc. It is unnecessary to use pure drinking water if all we need to use it for some other purpose rather than drinking.

1.4. Disadvantages of Rainwater Harvesting: 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. Rainwater harvesting is suitable in those areas that receive plenty of 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.

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4. Certain Roof Types may Seep Chemicals or Animal Droppings: Certain types of roofs may seep chemicals, insects, dirt or animals droppings that can harm plants if it is used for watering the plants. 5. Storage Limits: The collection and storage facilities may also impose some kind of restrictions as to how much rainwater you can use. During the heavy downpour, the collection systems may not be able to hold all rainwater which ends in going to to drains and rivers. Rainwater harvesting is a system that is gaining speed over time. Areas that experience high amounts of rainfall will benefit the most from the system and will be able to distribute water to dry lands with ease. However, the beneficial environmental impact of the system is what drives it further as of now.

1.5.

Study area:

RAINWATER HARVESTING AT MAGADHA VILLAGE: As a part of our project, the importance of rainwater harvesting at Magadha village, we clearly came to know the all the advantages which we can draw out by implementing this small but highly efficient technique. Thus to increase the potential, benefits of this system and draw maximum advantages from it, we need to have large rooftop areas which will be going to act as catchment areas. More the catchment areas more will be the surface runoff and thus more will be the amount of harvested water. It is essential for storing water and using it during summer. The rainwater harvesting system could serve for many uses like reusing the water for gardening, flushes etc. and also to increase the ground water levels. As of now there is no shortage of water but foreseeing the future bad effects of ground water levels depletion, it is better to have rainwater harvesting system. The site shows favorable conditions for a rainwater harvesting systems as all the catchment areas are rectangular and it is easy to collect water from these roof tops. The slopes are also towards favorable sites for the construction of storage tank and recharge structures. Hence Magadha village is considered as the part of project. 7    

Magadha village is located at 78.33E longitude and 17.38N latitude in Rangareddy district of Telangana state. The areal extent of the study area is 20 acres. Total existing built up area is 37760.148 sq.m. The climate in the study area is semi-arid with an average annual rainfall of 668.05mm, monsoon rainfall is 450mm and non-monsoon rainfall is 130.30mm. The minimum and maximum temperatures range from 12 °C in winter and 43 °C in summer respectively. Daily mean relative humidity is 51%. The highest wind speed is 136km/hr.

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CHAPTER 2 LITERATURE REVIEW 2.1. Components of rainwater harvesting system: A rainwater harvesting system comprises of components for - transporting rainwater through pipes or drains, filtration, and tanks for storage of harvested water. The common components of a rainwater harvesting system are: 2.1.1. Catchments: The surface which directly receives the rainfall and provides water to the system is called catchment area. 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), galvanized iron or corrugated sheets can also be used for water harvesting.

Figure 5. Catchment 2.1.1.1. Catchment Area Features:

The nature of the catchment distinguishes rainwater collection from other kind of

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harvesting. Four types of catchment areas have been considered namely; roof, rainwater platforms,

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watershed management and hill slopes. Catchments used to collect rainwater are frequently artificial or else ground surfaces, which

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have been specifically prepared and demarcated. Rainwater may be collected from any kind of roof – tiles, metal, palm leaf, grass thatch.

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Lead flashing roof or roof painted with lead-based paint or asbestos roof is generally

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regarded as unsuitable. A well-thatched roof has been said not to be presenting much hazard to the collected water.

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These have been covered with plastic sheets in some areas in Manipur. Catchment area consisting of rooftop /the plot area or the complex area from where the rainwater runoff is proposed to be collected has to be maintained so as to ensure that the resultant rainwater runoff is not contaminated. At times paints, grease, oil etc. are often left on the roof or in the courtyards. These can result in contamination of the rainwater runoff. Therefore, the households have to ensure that they keep the catchment area clean at all

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times especially during the rainfall season.

2.1.1.2. Catchment Surface: The catchment area of a water harvesting system is the surface, which receives rainfall directly and contributes the 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. Temporary structures like sloping sheds can also act as catchments. In Botswana, house compounds and threshing floors are surfaced with clay / cow dung plaster and used effectively as rainwater catchments. Rainwater harvested from catchment surfaces along the ground, because of the increased risk of contamination, should only be used for non-potable uses such as lawn watering. For in house uses, rooftop harvested rainwater is safer for drinking purposes than the runoff harvested water.

2.1.2. Coarse Mesh: It prevents the passage of debris, provided in the roof.

Figure 6. Coarse mesh 10    

2.1.3. 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 galvanized iron sheet (20 to 22 gauge), folded to required shapes.

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

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Bamboo or betel trunks cut vertically in half.

2.1.4. Conduits: Conduits are pipelines or drains that carry rainwater from the catchment or rooftop area to the harvesting system. Commonly available conduits are made up of material like polyvinyl chloride (PVC) or galvanized iron (GI). 2.1.5. First-flushing: A first flush device is a valve which ensures flushing out of first spell of rain away from the storage tank that carries a relatively larger amount of pollutants from the air and catchment surface.

Figure 7: Showing function of a first flush system

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2.1.6. Filters: The filter is used to remove suspended pollutants from rainwater collected from rooftop water. The Various types of filters generally used for commercial purpose are Charcoal water filter, Sand filters, Horizontal roughing filter and slow sand filter. 2.1.6.1. Charcoal water filter: A 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.

 

Figure 8. Charcoal water filter 2.1.6.2. Sand filter: Sand 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), color 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.

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Figure 9. Sand filter 2.1.6.3. Dewas filter: Most 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 dewas initiated a groundwater recharge scheme. The rooftop water was collected and allowed to pass through a filter system called the dewas filter 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. 2.1.7. Storage facility: There are various options available for the construction of these tanks with respect to the shape, size, material of construction and the position of tank and they are: 2.1.7.1. Shape: Cylindrical, square and rectangular.

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2.1.7.2. Material of construction: Reinforced cement concrete (RCC), masonry, Ferro cement etc. 2.1.7.3. Position of tank: Depending on land space availability these tanks could be constructed above ground, partly underground or fully underground. Some maintenance measures like disinfection and cleaning are required to ensure the quality of water stored in the container. If harvested water is decided to recharge the underground aquifer/reservoir, then some of the structures mentioned below are used. 2.1.8. Recharge structures:

Rainwater Harvested can also be used for charging the groundwater aquifers through suitable structures like dug wells, bore wells, recharge trenches and recharge pits. Various recharge structures are possible - some which promote the percolation of water through soil strata at shallower depth (e.g., recharge trenches, permeable pavements) whereas others conduct water to greater depths from where it joins the groundwater (e.g. recharge wells). At many locations, existing structures like wells, pits and tanks can be modified as recharge structures, eliminating the need to construct any fresh structures. Some of the few commonly used recharging methods are recharging of dug wells and abandoned tube wells, Settlement tank, Recharging of service tube wells, Recharge pits, Soak ways /Percolation pit , Recharge troughs, Recharge trenches, Modified injection well.

Figure 10. Typical water harvesting structure

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2.2. Features of Rainwater Harvesting: •

Reduces urban flooding.

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Ease in constructing system in less time.

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Economically cheaper in construction compared to other sources, i.e. dams, diversion, etc.

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Rainwater harvesting is the ideal situation for those areas where there is inadequate groundwater supply or surface resources.

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Helps in utilizing the primary source of water and prevent the runoff from going into sewer or storm drains, thereby reducing the load on treatment plants.

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Recharging water into the aquifers which help in improving the quality of existing groundwater through dilution.

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Artificial rainwater harvesting structures can be used for harvesting the rainwater. These artificial recharge structure address the following: a) To enhance the sustainable yield in areas where over development has depleted the aquifer. b) To utilize the rainfall runoff this is going to the sewer or storm water drain. c) Conservation and storage of excess surface water for further requirements. d) Due to rapid urbanization infiltration of rainwater into the subsoil has decreased drastically and recharge of groundwater has diminishes. e) To arrest seawater ingress. f) To improve vegetation cover and reduce flood hazard. g) To improve the quality of existing ground water through dilution h) To reduce power consumption. i) To raise water levels in wells and bore wells that are frying up. j) To remove bacteriological and other impurities from sewage and waste water so that water is suitable for reuse.

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2.3. Rainwater harvesting techniques:

Figure 11. Classification of rainwater harvesting techniques.    

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2.4. Methods for rainwater harvesting: Broadly there are two ways of harvesting rainwater: i) Surface runoff harvesting ii) Roof top rainwater harvesting 2.4.1. 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. Recharging ground water aquifers are: 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: a) Recharging of bore wells b) Recharging of dug wells c) Recharge pits d) Recharge trenches e) Soak ways or recharge shafts f) Percolation tanks 2.4.1.1. 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. 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.

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Figure 12: Representing filtration tank 2.4.1.2. 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. A schematic diagram of recharging into dug well is indicated.

Figure 13. Recharge through dug wells

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2.4.1.3. Recharge pits: Recharge pits are small pits of any shape rectangular, square or circular, contracted with brick or stone masonry wall with weep hole at regular intervals. Top 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.

Figure14. Typical recharge pit 2.4.1.4. 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,

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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.

Figure15. Recharge trench 2.4.1.5. 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.

 

Figure 16. Recharge shaft 20    

2.4.1.6. 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.

Figure 17. Percolation tank 2.4.2. Roof top water harvesting: Rooftop Rain Water Harvesting is a technique through which rain water is captured from roof catchments & stored in reservoirs. Harvested rain water can be stored in storage tanks to meet the household needs or sub-surface ground water reservoir by adopting artificial recharge techniques. Main Objective is to make water available for future use. Capturing and storing rain water for use is particularly important in dry land, hilly, urban and coastal areas. In alluvial areas energy saving for 1m rise in ground water level is around 0.40 kilo watt per hour. 21    

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In urban areas:

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Identify potential zones in overexploited areas, & design & implement suitable, sitespecific roof water & surface water harvesting structures to raise the groundwater table.

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Promulgate roof and surface water harvesting techniques through Community Rainwater Harvesting methods.

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Sustain existing water supply schemes by artificial recharge.

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Introduce water-harvesting structures on unpolluted storm water drains, open areas, parks & playgrounds.

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Use stagnant water for recharge purposes in relatively low-lying areas, store floodwater in appropriate locations, & construct suitable recharge structures in water logging areas.

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Introduce site-specific artificial recharge structures on wide roads, which become waterways during heavy downpour in the monsoon season.

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Design projects for Recycling and Reuse of wastewater.

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Construct site-specific artificial recharge structures, like Percolation pits, Dug cum Bore wells, Mini Artificial Aquifer System, Trench cum Percolation Pits, Percolation Ponds, Recharge wells.

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Develop mass awareness programs.

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Make roof water harvesting a people’s movement.

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Commence and sustain training programs for executives of Government and Non Government Organizations, and strengthen ongoing awareness projects.

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Figure 18. Rooftop rainwater harvesting 2.4.2.1. Need for Roof Top Rainwater harvesting: •

To meet the ever increasing demand for water

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To reduce the runoff which chokes storm drains

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To avoid flooding of roads

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To augment the ground water storage and controlν decline of water levels

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To reduce ground water pollution

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To improve the quality of ground water

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To reduce the soil erosion

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To supplement domestic water requirement duringν summer, drought etc.

2.4.2.2. Design Criteria of Recharge Structures: •

The runoff should be assessed accurately for designing the recharge structure and may be assessed by following formula.

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Runoff = Catchment area * Runoff Coefficient * Rainfall

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Runoff coefficient plays an important role in assessing the runoff availability and it depends upon catchment characteristics. General values are tabulated below which may be utilized for assessing the runoff availability. Table 1 showing type of catchment and runoff coefficient: Type of catchment

Runoff coefficient

Roof top

0.70-0.90

Paved area

0.50-0.85

Bare ground

0.10-0.20

Green area

0.05-0.10

2.4.2.3. Roof top rainwater harvesting through recharge pit: •

In alluvial areas where permeable rocks are exposed on the land surface or at very shallow depth, rooftop rain water harvesting can be done through recharge pits.

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The technique is suitable for buildings having a roof area of 100 sq.m and is constructed for recharging the shallow aquifers.

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Recharge pits may be of any shape and size and are generally constructed 1 to 2 m wide and 2 to 3 m deep which are back filled with boulders (5-20cm), gravels (510mm) and coarse sand (1.5-2mm) in graded form. Boulders at the bottom, gravels in between the coarse sand at the top so that the silt content that will come with runoff will be deposited. Rooftop rainwater harvesting through recharge pit the top of the coarse sand layer and can easily be removed. For smaller roof area, pit may be filled with broken bricks/cobbles.

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A mesh should be provided at the roof so that leaves or any other solid waste/debris is prevented from entering the pit and a desalting/collection chamber may also be provided at the ground to arrest the flow of finer particles to the recharge pit.

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The top layer of sand should be cleaned periodically to maintain the recharge rate.

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By-pass arrangement is provided before the collection chamber to reject the first showers.

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Figure 19. Showing roof top rainwater harvesting through recharge pit 2.4.2.4. Roof top rainwater harvesting through recharge trench: •

Recharge trenches are suitable for buildings having roof area of 200-300 sq.m and where permeable strata are available at shallow depths.

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Trench may be 0.5 to 1 m wide, 1 to 1.5 m deep and 10 to 20 m long depending upon availability of water to be charged.

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A mesh should be provided at the roof so that leaves or any other solid waste/debris is prevented from entering the pit and a desalting/collection chamber may also be provided at the ground to arrest the flow of finer particles to the recharge.

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By-pass arrangement is provided before the collection chamber to reject the first showers. Boulders at the bottom, gravels in between the coarse sand at the top so that the silt content that will come with runoff will be deposited on the top of sand layer and can easily be removed.

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These are back filled with boulders (5-20cm), gravels (5-10mm) and coarse sand (1.52 mm) in graded form.

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Figure 20. Showing roof top rainwater harvesting through recharge trench 2.4.2.5. Roof top rainwater harvesting through existing tube wells: •

In areas where the shallow aquifers have dried up and existing tube wells are tapping deeper aquifer, rooftop rain water harvesting through existing tube well can be adopted to recharge the deeper aquifers.

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PVC pipes of 10cm diameter are connected to roof drains to collect rainwater. The first roof runoff is let off through the bottom of drain pipe. After closing the bottom pipe, the rainwater of subsequent rain showers is taken through a online PVC filter.

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The filter is provided with a reducer of 6.25 cm on both the sides.

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The filter is 1-1.2 m in length and is made of PVC pipe. Its diameter should vary depending on the area of roof, 15 cm if roof area is less than 150 sq.m and 20 cm if the roof area is more.

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Figure 21. Showing roof top rainwater harvesting through existing tube well 2.4.2.6. Roof top rainwater harvesting through trench with recharge wells: •

In the areas where the surface soil is impervious and large quantities of roof water or surface runoff is available within a very short period of heavy rainfall, the use of trench/pits is made to store the water in a filter media and subsequently recharge to ground water through specially constructed recharge wells.

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Recharge well of 100-300 diameter is constructed to a depth of at least 3 to 5 m below the water level.

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A later trench of 1.5 to 3 m width and 10 to 30 m length, depending upon the availability of water is constructed with recharge well in the centre.

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If the aquifer is available at greater depth say more than 20m, a shallow shaft of 2 to 5 m diameter and 3-5 m deep may be constructed depending upon availability of runoff.

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2.5. Hydro-meteorological analysis: 2.5.1. Factors affecting runoff: Apart from rainfall characteristics such as intensity, duration and distribution, there are a number of site (or catchment) specific factors which have a direct bearing on the occurrence and volume of runoff. i. Soil type: •

The infiltration capacity is among others dependent on the porosity of a soil which determines the water storage capacity and affects the resistance of water to flow into deeper layers.

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Porosity differs from one soil type to the other. The highest infiltration capacities are observed in loose, sandy soils while heavy clay or loamy soils have considerable smaller infiltration capacities.

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Figure 22 illustrates the difference in infiltration capacities measured in different soil types.

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The infiltration capacity depends furthermore on the moisture content prevailing in a soil at the onset of a rainstorm.

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The initial high capacity decreases with time (provided the rain does not stop) until it reaches a constant value as the soil profile becomes saturated.

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This however, is only valid when the soil surface remains undisturbed.

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Figure 22. Showing infiltration capacity curves for different soil types It is well known that the average size of raindrops increases with the intensity of a rainstorm. In a high intensity storm the kinetic energy of raindrops is considerable when hitting the soil surface. This causes a breakdown of the soil aggregate as well as soil dispersion with the consequence of driving fine soil particles into the upper soil pores. This results in clogging of the pores, formation of a thin but dense and compacted layer at the surface which highly reduces the infiltration capacity. This effect, often referred to as capping, crusting or sealing, explains why in arid and semi-arid areas where rainstorms with high intensities are frequent, considerable quantities of surface runoff are observed even when the rainfall duration is short and the rainfall depth is comparatively small. Soils with a high clay or loam content (e.g. Loess soils with about 20% clay) are the most sensitive for forming a cap with subsequently lower infiltration capacities. On coarse, sandy soils the capping effect is comparatively small.

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ii. Vegetation: •

The amount of rain lost to interception storage on the foliage depends on the kind of vegetation and its growth stage. Values of interception are between 1 and 4 mm. A cereal crop, for example, has a smaller storage capacity than a dense grass cover.

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More significant is the effect the vegetation has on the infiltration capacity of the soil. A dense vegetation cover shields the soil from the raindrop impact and reduces the crusting effect as described earlier.

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In addition, the root system as well as organic matter in the soil increase the soil porosity thus allowing more water to infiltrate. Vegetation also retards the surface flow particularly on gentle slopes, giving the water more time to infiltrate and to evaporate.

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In conclusion, an area densely covered with vegetation, yields less runoff than bare ground.

iii. Slope and catchment size: •

Investigations on experimental runoff plots have shown that steep slope plots yield more runoff than those with gentle slopes.

•

In addition, it was observed that the quantity of runoff decreased with increasing slope length.

•

This is mainly due to lower flow velocities and subsequently a longer time of concentration (defined as the time needed for a drop of water to reach the outlet of a catchment from the most remote location in the catchment). This means that the water is exposed for a longer duration to infiltration and evaporation before it reaches the measuring point. The same applies when catchment areas of different sizes are compared.

•

The runoff efficiency (volume of runoff per unit of area) increases with the decreasing size of the catchment i.e. the larger the size of the catchment the larger the time of concentration and the smaller the runoff efficiency.

30    

Figure 23. Showing runoff efficiency as a function of catchment size

It should however be noted that the diagram in Figure 25 has been derived from

investigations in the Negev desert and not be considered as generally applicable to others regions. The purpose of this diagram is to demonstrate the general trend between runoff and catchment size. 2.5.2. Rainfall characteristics: •

Precipitation results largely from convective cloud mechanisms producing storms typically of short duration, relatively high intensity and limited areal extent.

•

Rainfall intensity is defined as the ratio of the total amount of rain falling during a given period to the duration of the period. It is expressed in depth units per time, usually as mm/hour.

•

The statistical characteristics of high-intensity, short duration, convective rainfall are essentially independent of locations within a region and are similar in many parts of the world. Analysis of short-term rainfall data suggests that there is a reasonably stable relationship governing the intensity characteristics of this type of rainfall.

31    

•

Studies carried out suggest that, on average, around 50 percent of all rain occurs at intensities in excess of 20 mm/hour and 20-30 percent occurs at intensities in excess of 40 mm/hour.

2.5.3. Variability of annual rainfall: •

Water harvesting planning and management in arid and semi-arid zones present difficulties which are due less to the limited amount of rainfall than to the inherent degree of variability associated with it.

•

In temperate climates, the standard deviation of annual rainfall is about 10-20 percent and in 13 years out of 20, annual amounts are between 75 and 125 percent of the mean.

•

In arid and semi-arid climates the ratio of maximum to minimum annual amounts is much greater and the annual rainfall distribution becomes increasingly skewed with increasing aridity. With mean annual rainfalls of 200-300 mm the rainfall in 19 years out of 20 typically ranges from 40 to 200 percent of the mean and for 100 mm/year, 30 to 350 percent of the mean. At more arid locations it is not uncommon to experience several consecutive years with no rainfall.

•

Design rainfall is defined as the total amount of rain during the cropping season at which or above which the catchment area will provide sufficient runoff to satisfy the crop water requirements. If the actual rainfall in the cropping season is below the design rainfall, there will be moisture stress in the plants; if the actual rainfall exceeds the design rainfall, there will be surplus runoff which may result in damage to the structures.

•

The design rainfall is usually assigned to a certain probability of occurrence or exceedance. If, for example, the design rainfall with a 67 percent probability of exceedance is selected, this means that on average this value will be reached or exceeded in two years out of three and therefore the crop water requirements would also be met in two years out of three.

•

The design rainfall is determined by means of a statistical probability analysis.

32    

2.5.4. Surface runoff process: •

When rain falls, the first drops of water are intercepted by the leaves and stems of the vegetation. This is usually referred to as interception storage.

Figure 24. Showing relationship between rainfall, infiltration and runoff

•

As the rain continues, water reaching the ground surface infiltrates into the soil until it reaches a stage where the rate of rainfall (intensity) exceeds the infiltration capacity of the soil. Thereafter, surface puddles, ditches, and other depressions are filled (depression storage), after which runoff is generated.

•

The infiltration capacity of the soil depends on its texture and structure, as well as on the antecedent soil moisture content (previous rainfall or dry season). The initial capacity (of a dry soil) is high but, as the storm continues, it decreases until it reaches a steady value termed as final infiltration rate. 33  

 

•

The process of runoff generation continues as long as the rainfall intensity exceeds the actual infiltration capacity of the soil but it stops as soon as the rate of rainfall drops below the actual rate of infiltration. .

34    

CHAPTER 3 CASE STUDY OF A RAIN WATER HARVESTING SITE 3.1. JNTUH: A case study of rain water harvesting structure at Jawaharlal Nehru Technological University, Hyderabad was referred. A detailed study was done on the site and the methodology adopted there. Roof top rainwater harvesting was adopted for girl’s hostel building. The images of the structure are as follows:

Figure 25. Demonstrating rainwater harvesting structure in JNTUH

35    

3.1.1. Introduction: Rooftop rainwater collection is one of the solutions for solving or reducing the problem of water availability, where there is inadequate groundwater supply and surface sources are either lacking or insignificant quality. Average annual rainfall in the campus of Jawaharlal Nehru Technological University, Hyderabad is 821 mm with unutilized noncommitted surplus monsoon runoff. Ground water levels are being monitored since 2008 and found to be 25 to 30m below ground level deep in pre-monsoon period and 16 to 19m below ground level in post-monsoon which indicates the ample scope for artificial recharge of rainwater. Present study deals with the geomatic approach by employing GIS, GPS and Remote Sensing techniques for identifying sites for construction of rooftop rainwater harvesting structures in the study area by preparing various spatial maps. There are 10 recharge structures,3 piezometers and 13 recharge shafts. To meet the deficit water requirement in the campus through artificial recharge and re-use of ground water, three recharge structures each with a capacity of 1,00,000 liters and one reuse structure with a capacity of 2,00,000 liters have been identified using Geomatics and remaining six recharge structures each with a capacity of 50,000 liters have been identified.

Figure 26. Showing recharge shaft at JNTUH 36    

The total water requirement to the entire campus is to the entire campus is to the tune of 1687 m^3/day. To meet the entire water requirement, the Hyderabad Metro Water supply and Sewerage Board supplies water to the tune 1000m^3/day. The remaining 687m^3/day water requirement is being met through the ten bore wells in the campus. However, during the summer period, the bore wells yield and Hyderabad Metro Water Supply and Sewerage Board Supply reduce considerably, and this deficit is met by purchasing water through tanker supply. In this context, it is proposed to meet the above deficit in demand through artificial recharge. The specific objective of the present study is to identify the sites and assessing the site conditions for constructing rainwater harvesting structures using Geomatics. In the fig 27 there is a layer called geomembrane of thickness 300 microns and below the geomembrane layer there are coarse gravel, fine gravel etc.

Figure 27. Showing recharge pit at JNTUH 3.1.2. Study Area: The area selected for present study is the campus of Jawaharlal Nehru Technological University, Hyderabad located in the capital city of Hyderabad, Telangana, India which lies between latitudes 17029’23.5” to 17029’50.3” North and longitudes 78023’22.9” to 78023’41.3” East. The areal extent of the study area is 89.19 Acres. Total existing built-up 37    

area within the campus is 53,822.24 m^2. The topography of the area is highly undulating, sloppy and well drained. 3.1.3. Methodology: Methodology adopted for the present study consists of several steps. For the preparation of digital elevation model (DEM), collection of source data like latitude, longitude and elevation data of the study area is essential. It was done using hand held GPS. In present study, MAGELLAN explorist XL hand held GPS is used. In the present study, 3DAnalyst tool has been used in Arc GIS 3D-Analyst in an Arc GIS extension that provides advanced tools for three dimensional visualization, analysis and surface generation. Thematic maps such as road network, drainage, contour, vegetation and built up area maps were prepared using Remote sensing, GIS and GPS technologies. These thematic were integrated in GIS environment for the identification of suitable locations and capacity for constructing of rooftop rainwater harvesting structures in the study area. Contours of present study area are generated with 2m contour interval with the help of latitude, longitude and elevation values using 3D Analyst tool in GIS environment. Highest and lowest values observed in the study area are found to be 559 and 593m. Table 2 describing rainwater harvesting structure at JNTUH: S. No.

Description of structure

Location

1.

Rooftop rainwater harvesting

Near PG Boys (Manjeera)

with a capacity of 2, 00,000

hostel.

liters and use. 2.

Rooftop rainwater collection

1. Near Civil Engg. Building

with a capacity of 1, 00,000

2.Near UGC-ASC Building

liters along with recharge

3.Near girls Hostel

shafts.

To meet the deficit water requirement in the campus through artificial recharge and re-use of ground water, three recharge structures each with a capacity of 1, 00,000 liters and 38    

one reuse structure with a capacity of 2, 00,000 liters have been identified. Three measuring bore wells were dug for a depth of 30m near the recharge structures for impact assessment studies. Water levels measured in the three bore wells on weekly basis were found to be 86, 85, 32 feet in the month of April, 2013 and the corresponding water levels have been improved to 60, 62, 11 feet respectively in the month of August 2013. Total water recharged in the campus through construction of rooftop rainwater harvesting structures is 14, 00,000.

39    

CHAPTER 4 DATA COLLECTION 4.1. Rainfall data of Gandipet: Rainfall data is the recorded data of rainfall in mm and its intensity in mm/hr. The data are measured by using a rain gauge. For the design of a rain water harvesting system, this rainfall data is required. This is required to calculate the capacity of storage tank of the system and a suitable recharge structure. Approximately 10 years data is needed for the design of the rainwater harvesting system. So the essential data was collected. It is shown here under. 4.1.1. Rainfall data for 14 years: Magadha village is located at 78.33E longitude and 17.38N latitude in Rangareddy district of Telangana state. It has a tropical climate and receives high rainfall during Southwest monsoon (June-September) and retreating Northeast monsoon (DecemberJanuary). Average annual rainfall ranges between 120-200mm. The average monthly rainfall data are being taken from Ground WATER Department. The nearest rain gauge for the Magadha village is situated at Moinabad. Thus monthly rainfall data of this place was collected and is given below in the table 3. Table 3 showing monthly rainfall data: Month

June

July

Aug

Sep

Oct

Nov

Dec

Jan

Feb

Mar

Apr

May

2001

167.6 72.10 306.0 133.0 33.00 0.00

1.2

0.00 0.00

0.00

21.0

0.00

2002

122.2 44.00 117.5 145.1 153.2 0.00 0.00 0.00 0.00

0.00

0.00

26.4

2003

49.20 67.00 267.4 28.00 134.0 0.00 0.00 0.00 0.00

12.4

8.20

0.00

2004

60.20 259.8 288.1 106.2 89.00 0.00 0.00 10.2 0.00

9.00

12.0

52.0

2005

22.00 265.2 42.00 127.4 90.00 0.00 0.00 0.00 0.00

17.0

56.8

20.0

2006

5.00

19.0

56.0

36.0

Year

360.0 115.0 200.0 285.0 0.00 0.00 0.00 0.00 40  

 

2007

76.00 57.00 135.0 102.8 14.00 19.0 0.00 0.00 0.00

2008

195.0 23.00 128.0 170.0

2009

46.00

79.2

2010

101.8

46.0

35.4

12.0

3.00

8.00 0.00 0.00 56.0 141.0 5.00

40.0

259.6 208.0

3.00

35.0 0.00 0.00 0.00

0.00

45.0

5.20

196.4

52.00 38.0 5.00 9.20 0.00

0.00

0.00

15.0

2011

142.2 260.2 222.0 241.0 80.40 40.0 22.8 0.00 19.2

0.00

12.4

5.00

2012

32.8

74.6

147.6

94.2

32.40 0.00 0.00 0.00 0.00

0.00

4.00

0.00

2013

116.8 160.0

68.4

60.8

73.20 23.6 0.00 0.00 14.6

0.00

7.60

23.4

2014

143.8

58.20 47.80 70.91 20.1 0.00 0.00 10.3

0.00

0.00

2.51

73.8

90.4

Table 4 showing annual rainfall data: Year

Rainfall (mm)

2001

733.9

2002

608.4

2003

566.2

2004

886.5

2005

640.4

2006

1076

2007

451.2

2008

768

2009

712

2010

553.8

2011

1045.2

2012

385.6

2013

548.4

2014

427.21

Average rainfall from above data=668.05mm=0.66m

41    

0.00

4.2. Runoff Coefficient Data: Runoff coefficient values were collected from the CPWD manual. Table 5 showing runoff coefficient values: 1. ROOF CATCHMENT

CO-EFFICIENT

a) Tiles

0.8-0.9

b) Corrugated metal sheets

0.7-0.9

2. GROUND SURFACE COVERING

CO-EFFICIENT

a) Untreated ground catchments

-

•

Soil on slope less than 10%

0.0-0.3

•

Rocky material catchment

0.2-0.5

•

Business area

•

Down town

0.7-0.95

•

Neighborhood

0.5-0.7

-

b) Residential complexes in urban areas

-

•

Single family

0.3-0.5

•

Multiunit’s , detached

0.4-0.6

•

Multiunit’s , attached

0.6-0.75

c) Residential complexes in suburban areas

0.5-0.7

d) Industrial

-

•

Light

0.5-0.7

•

Heavy

0.6-0.9

e) Parks , cemeteries

0.1-0.25

f)Play grounds

0.2-0.35

g)Railroad yard

0.2-0.35

h)Unimproved land areas

0.1-0.3

i)Asphetic or concrete pavement

0.7-0.95

j)Brick pavement

0.7-0.85

k)Lawns, sandy soil having slopes

-

42    

GROUND SURFACE COVERING

CO-EFFICIENT

•

Flat 2%

0.05-0.1

•

Average 2 to 7%

0.1-0.15

The ratio of rainfall in mm to runoff in mm is called runoff coefficient. This runoff coefficient is required to calculate the capacity of the storage tank. Hence the value was collected. The value of runoff coefficient for Magadha village ranges from 0.4 to 0.6 as villas are multiunit’s detached.

4.3. Surveying: 4.3.1. Introduction: Survey is concerned in knowing what (objects) is where (space) and when (time) using a field based or an object based concept of “reality of real world”. In other words, surveying is the process of determining the earthen features and transferring its relative position on to the paper. Surveying principles can be applied in a variety of ways to accomplish the aim of position finding. The preferred survey method for both two and three dimensional position finding has changed through the years in response to the advances in technology. We can say that Total Station is the ultimate in survey instruments. It can measure angles and distances horizontally and vertically. The Total Station has a built in calculator that performs trigonometric calculations as well as an electronic notebook used for storing data. It can also interface with a computer for data transfer. The latest methodology with Total Station instrument had emerged as a very reliable and efficient technology for meeting most of the needs of investigation surveys related to irrigation projects. Instrument of choice for the modern surveyor integrates an electronic digital theodolite, an electronic distance measuring instrument and a computer in to single unit. The resulting hybrid instrument is called a ‘Total Station’ A total station automatically measures 43    

and displays distance and direction data (both horizontal and vertical angles) and results to its computer. Hence the total station instrument is a combination of a. Distance measuring instrument (EDM) b. Angle measuring instrument (Theodolite) c. A simple micro processor 4.3.2. Components of total stations:

Figure 28. Showing components of total station 44    

4.3.3. Functions of total station: a)

It simultaneously measures the angle, distance and record with the help of EDM,

theodolite and microprocessor respectively. Recording facility saves lot of time and Creates facility to store the data for long time. b) Correcting distances with the following factors instantaneously: i) Prism constant: It is the distance between the center of prism rod on vertical axis and the plane of reflection of laser beam on the cuboidal prism. Most of the prisms having prism constant from 10mm to 13mms and depends on the manufacturer. ii) Atmospheric and temperature constant: The atmospheric pressure and temperature at the instrument and at the place of prism may not be same when the survey is at hill ranges. In case, both are fed to total station before shooting the point, it will automatically correct forth coming distances with the help of pre programmer fed to microprocessor. Similarly, correction required due to curvature of earth and refraction. c) Computing the point elevation: With the help of the trigonometrical equations and data collected through EDM, Total Station can find elevation of any point (in the same vertical plane) like towers, pillars, building heights etc., d) Computing the coordinates at every point: Total Station can generate Northing, Easting and elevation of every point where the prism reflector is placed with reference to the known point coordinates and datum. e) Remote Elevation Measurement (REM): The prism reflector is set directly below the place to be measured and by measuring the prism height, the height of the target can be found out. This makes us easy to determine the height of electrical power lines, suspension bridge cables and other large items used in construction. f) Remote Distance Measurement (RDM): Horizontal distance, slope distance, difference in height and percentage of slope between the reference point and the observations point are measured. In a particular traverse, a missing line measurement cans also the made with this function.

45    

g) It has the Data transfer facility from the total station instrument to the computer software (compatible) and vice versa. The point whose coordinates are known but the location at field is not known, and then this stakeout technology in Total Station will be useful to identify the point location at field. This will help the irrigation Engineers to set a curve in canal alignment within reasonable time. By way of traditional procedure it takes longer time. h) Conversion of units: With the help of microprocessor, the units can be changed (from MKS to FPS or from EPS to MKS) without much effort. i) Resection: when the coordinates of occupied point is not known and occasionally there are two points whose coordinates are available nearby, then Total Station can give coordinates of such occupied point. j) Area calculations: Starting with known coordinates in a closed traverse, Total Station has the option to give the area instantaneously with a press of button using trignometrical functions/formulae fed to microprocessor. k) Sequential point numbers are allocated for each prism point and also the station point and an identified code for each measurement can be entered up to 16/24 alphanumeric characters. 4.3.4. Accuracy and range of total station: Angular accuracy of Total Station =0.5 sec to 7 sec (for the recent instrument models) Otherwise it is 1 to 20 sec. Linear accuracy of Total Station varies from 1mm to 10mm per kms. Range of total station with Single Prism is up to 2.50 kms Two Prisms – up to 5 to 7 kms Three prisms – up to 10 to 12 kms Even the least short-range Total Stations generally exceed the abilities of optical survey instruments. The angular accuracy matches that of the distance measuring, so that radial, lateral, and vertical errors are similar. Typical configurations are shown in the table below. 46    

Anyone considering the acquisition of a Total Station will need to balance these factors, along with other features mentioned.

4.4. Contour Data: Contours are the curves of same elevations. This data is required to determine the location of artificial recharge structure by finding the downward slopes from contour map. Hence the data was collected and shown here under. Contour values were calculated from total stations survey at Magadha village. ST1

+00001000.000

+00001000.000

+00000100.000  

P1

ST2

+00001078.644

+00000933.190

+00000102.512

P1

ST3

+00001069.383

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P1

ST4

+00001069.383

+00000941.643

+00000101.967

P1

ST5

+00001054.252

+00000955.771

+00000101.258

P1

ST6

+00001040.835

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P1

ST7

+00001031.748

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P1

ST8

+00001021.743

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P1

ST9

+00001014.377

+00000993.895

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P1

ST10

+00001007.599

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P1

ST11

+00001002.633

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P1

ST12

+00001010.674

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P1

ST13

+00001019.900

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P1

ST14

+00001027.843

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P1

ST15

+00001032.887

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P1

ST16

+00001039.438

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P1

ST17

+00001050.265

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P1

ST18

+00001066.148

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P1

ST19

+00001072.778

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P1

ST20

+00001098.174

+00001102.573

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P1

ST21

+00001003.887

+00001004.976

+00000099.924

P1

47    

ST22

+00000982.518

+00001017.690

+00000099.700

P1

ST23

+00000968.754

+00001030.939

+00000099.431

P1

ST24

+00000952.007

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+00000099.224

P1

ST25

+00000928.569

+00001069.067

+00000098.965

P1

ST26

+00000915.512

+00001087.135

+00000098.619

P1

ST27

+00000915.694

+00001087.343

+00000098.606

P1

ST28

+00000905.342

+00001095.254

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P1

ST29

+00000905.160

+00001099.258

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P1

ST30

+00000921.059

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P1

ST31

+00000933.201

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P1

ST32

+00000947.606

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+00000099.201

P1

ST33

+00000970.449

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P1

ST34

+00000967.615

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P1

ST35

+00000967.049

+00001163.984

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P1

ST36

+00000967.070

+00001163.955

+00000100.003

P1

ST37

+00000980.53

+00001178.102

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P1

ST38

+00000893.736

+00001087.294

+00000098.399

P1

ST39

+00000881.314

+00001074.239

+00000097.964

P1

ST40

+00000865.655

+00001057.831

+00000097.451

P1

ST41

+00000858.007

+00001049.974

+00000097.294

P1

ST42

+00000846.993

+00001038.158

+00000097.285

P1

ST43

+00000863.969

+00001051.847

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P1

ST44

+00000868.343

+00001041.734

+00000097.491

P1

ST45

+00000877.519

+00001033.538

+00000097.662

P1

ST46

+00000889.160

+00001022.557

+00000097.867

P1

ST47

+00000861.337

+00001053.528

+00000097.443

P1

ST48

+00000846.456

+00001067.533

+00000097.284

P1

ST49

+00000831.402

+00001081.971

+00000096.989

P1

ST50

+00000824.665

+00001088.116

+00000096.869

P1

ST51

+00000807.301

+00001104.506

+00000096.700

P1

48    

ST52

+00000789.649

+00001120.902

+00000096.624

P1

ST53

+00000766.090

+00001142.236

+00000096.215

P1

ST54

+00000941.732

+00001122.669

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P1

ST55

+00000942.636

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+00000099.268

P1

ST56

+00000946.541

+00001102.546

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P1

ST57

+00000951.269

+00001082.408

+00000099.580

P1

ST58

+00000957.262

+00001056.598

+00000099.721

P1

ST59

+00000963.380

+00001032.163

+00000099.958

P1

ST60

+00000971.679

+00000998.179

+00000100.377

P1

ST61

+00000989.035

+00000989.035

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P1

ST62

+00000989.576

+00001131.265

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P1

ST63

+00000996.057

+00001105.447

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P1

ST64

+00001001.749

+00001082.636

+00000100.577

P1

ST65

+00001008.209

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P1

ST66

+00001014.729

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P1

ST67

+00001019.329

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P1

ST68

+00001021.672

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P1

ST69

+00001026.094

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P1

ST70

+00000965.040

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P1

ST71

+00000954.317

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P1

ST72

+00000960.542

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P1

ST73

+00000956.181

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P1

ST74

+00000960.040

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P1

ST75

+00000982.525

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+00000099.687

P1

ST76

+00000953.498

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P1

ST77

+00000947.158

+00001208.255

+00000098.843

P1

ST78

+00000941.783

+00001229.970

+00000098.680

P1

ST79

+00000934.616

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P1

ST80

+00000950.261

+00001176.895

+00000099.095

P1

ST81

+00000931.597

+00001172.548

+00000098.807

P1

49    

ST82

+00000917.005

+00001168.738

+00000098.642

P1

ST83

+00000913.224

+00001167.548

+00000098.581

P1

ST84

+00000907.869

+00001166.335

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P1

ST84

+00000888.702

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P1

ST85

+00000876.473

+00001158.211

+00000097.903

P1

ST86

+00000871.705

+00001156.935

+00000097.797

P1

ST87

+00000867.441

+00001156.026

+00000097.691

P1

ST88

+00000845.058

+00001151.128

+00000097.208

P1

ST89

+00000829.374

+00001147.028

+00000096.921

P1

ST90

+00000914.948

+00001172.902

+00000098.494

P1

ST91

+00000920.743

+00001195.188

+00000098.227

P1

ST92

+00000924.912

+00001210.747

+00000098.059

P1

ST93

+00000929.411

+00001227.922

+00000097.950

P1

ST94

+00000935.855

+00001252.685

+00000097.697

P1

ST95

+00000943.453

+00001281.004

+00000097.320

P1

ST96

+00000945.040

+00001285.423

+00000097.311

P1

ST97

+00000870.943

+00001161.422

+00000097.688

P1

ST98

+00000863.105

+00001193.147

+00000097.284

P1

ST99

+00000865.113

+00001222.360

+00000096.954

P1

ST100

+00000844.285

+00001267.088

+00000096.602

P1

ST101

+00000846.886

+00001278.781

+00000096.705

P1

ST102

+00000862.418

+00001285.563

+00000097.086

P1

ST103

+00000875.038

+00001291.755

+00000097.246

P1

ST104

+00000884.190

+00001295.988

+00000097.384

P1

ST105

+00000896.738

+00001301.410

+00000097.542

P1

ST106

+00000910.213

+00001345.328

+00000097.976

P1

 

50    

4.5. Direct shear test: In many engineering problems such as design of foundation, retaining walls, slab bridges, pipes, sheet piling, the value of the angle of internal friction and cohesion of the soil involved are required for the design. Direct shear test is done to find the shear stress of the soil. By using this shear stress and normal stress values, the values of cohesion coefficient (C) and angle of friction (Ф) can be determined. These values are used in the design calculations when earth pressure of soil is taken into consideration. Hence they were determined by performing direct shear test on soil of Magadha village.

Figure 29. Direct shear test apparatus

51    

4.5.1. Apparatus required: a) Direct shear box apparatus b) Loading frame (motor attached). c) Dial gauge. d) Proving ring. e) Tamper. f) Straight edge. g) Balance to weigh up to 200 mg. h) Aluminum container. i) Spatula. 4.5.2. Procedure: 1. Place the lower half on the shear box on a level base. 2. Place proper gripper plate with its grooves facing up & perpendicular to direction of motion. 3. Place the top half of the shear box over the bottom half. 4. Connect the top half to the lower half by means of two locking pins, which are removable. 5. Pour sand inside the box over bottom gripper plate & level to about 1.5 to 2cm depth. 6. Place the top gripper plate with grooves facing the sample. 7. Place the loading cap, steel ball etc.and seat the set up on the loading unit.

52    

1.4

Shear stress Shear stress (kg/sq.cm)

1.3

1.2

1.1

0.5

1.0

1.5

Normal stress (kg/sq.cm)

Figure 30. Direct shear test graph (normal stress Vs shear stress) C=0 Ф=43.6 Table 6 showing direct shear values: S.No

Normal stress (kg/cm^2)

1. 2. 3.

0.5 1 1.5

Max .reading on proving ring dial gauge 130 170 240

4.6. Bulk density by core cutter method: 4.6.1. Apparatus: •

Core cutter

•

Steel rammer

•

Steel dolly 53  

 

Maximum shear force (T)

Shear stress (kg/cm^2)

34.76 44.5 62.8

1.107 1.233 1.374

•

Balance

•

Steel rule

•

Pick-axe

•

Straight edge

•

Drying oven

4.6.2. Procedure: 1. Measure the height and internal and internal diameter of the core cutter. 2. Weigh the clean core cutter (W1). 3. Clean and level the place where density is to be determined. 4. Press the cutter into the soil to its full depth with the help of steel rammer. 5. Remove the soil around the cutter. 6. Remove the cutter. 7. Trim the top and bottom surfaces of the sample carefully. 8. Clean the outside surface of the cutter. 9. Weigh the cutter with the sample and take representative sample in the containers to determine the moisture content.

4.7. Specific gravity of soil particles using Pycnometer: 4.7.1. Apparatus: •

Pycnometer

•

Drying oven

•

Balance

•

Distilled water

•

Glass rod

•

Pipette 54  

 

•

4.75mm I.S.Sieve

•

Distilled water

Figure 31. Pycnometer 4.7.2. Procedure: 1. Weigh a clean dry pycnometer with the cap accurate to 0.01g (W1) 2. Place oven dry soil passing 4.75 mm I.S.Sieve into the pycnometer and weigh it (W2). Soil taken will fill up one-third of the bottle. 3. Fill the pycnometer to half its height with distilled water and mix it thoroughly with glass rod. Replace the screw top after applying grease to the screw top and fill the pycnometer, flush with hole in the conical cap. Dry the pycnometer from outside, and weigh it (W3). 4. Remove the contents, wash the pycnometer, pour distilled water flush with the hole of the conical cap and weigh it (W4). 5. Repeat steps 2 and 3 for two more times to arrive at an average value. Gs = {(W2 – W1) x Gt } / {(W4 – W1) – (W3 – W2)}  

55    

CHAPTER 5 METHODOLOGY 5.1. Hydrological analysis: On the basis of experimental evidence, Mr. H. Darcy, a French scientist enunciated in 1865, a law governing the rate of flow (i.e. the discharge) through the soils. According to him, this discharge was directly proportional to head loss (H) and the area of cross-section (A) of the soil, and inversely proportional to the length of the soil sample (L). In other words,  

Q α (H/L) x A

 

Q = Runoff, H/L represents the head loss or hydraulic gradient (I), K is the co-efficient of permeability Hence, finally, Q = K. I. A.  

Similarly, based on the above principle, water harvesting potential of the catchment area was calculated. The total amount of water that is received from rainfall over an area is called the rainwater legacy of that area. And the amount that can be effectively harvested is called the water harvesting potential. The formula for calculation for harvesting potential or volume of water received or runoff produced or harvesting capacity is given as:Harvesting potential or Volume of water Received (m^3) = Area of Catchment (m^2) X Amount of rainfall (mm) X Runoff coefficient  

56    

Runoff coefficient for any catchment is the ratio of the volume of water that runs off a surface to the volume of rainfall that falls on the surface. Runoff coefficient accounts for losses due to spillage, leakage, infiltration, catchment surface wetting and evaporation, which will all contribute to reducing the amount of runoff. Runoff coefficient varies from 0.5 to 1.0. In present problem statement, runoff coefficient is equal to 1 as the rooftop area is totally impervious. Eco-Climatic condition (i.e. Rainfall quantity & Rainfall pattern) and the catchment characteristics are considered to be most important factors affecting rainwater Potential. Given below the table showing the value of runoff coefficient with respect to types of surface areas:Table 7 showing value of runoff coefficient (k): S.No

Types of area

1.

Urban areas

0.55

Rolling land 5%-10% slope 0.65

2.

Single family

0.3

0.3

0.3

Flat land 0-5 % slope

Hilly land 10%-30% slope -

residence 3.

Cultivated Areas

0.5

0.6

0.72

4.

Pastures

0.30

0.36

0.42

5.

Wooden land or

0.3

0.35

0.50

forested areas  

5.2. Methods for storage of harvested rainwater in tank:  Finally, we need to store the water which is obtained from the rooftop areas of the

different buildings. The volume of tank which stores the harvested water will be directly proportional to the total volume of water harvested. Technically, there are two types of methods for distributing the harvested rainwater: •

Rationing method (RM)

•

Rapid depletion method (RDM)

57    

The detail calculation is carried out to get the valuable steps. Later on, these crucial steps are again applied and number of days for consumption of stored water is calculated by using both of these methods. 5.2.1. Rationing Method (RM): The Rationing method (RM) distributes stored rainwater to target public in such a way that the rainwater tank is able to service water requirement to maximum period of time. This can be done by limiting the amount of use of water demand per person. Suppose in this method, the amount of water supplied to member is limited which is equal to say, 100 lt/day per capita water demand. •

Population of Magadha village = 320

•

Then, Total amount of water consumption per day = 320x0.1 = 32 cu.m /day

•

Total no. of days we can utilize preserved water = stored water/water demand

•

For Magadha village, volume of water stored in tank was taken approx. = 37760.14x0.66=24921.69 cu.m

•

Hence finally, no of days = 24921.69/32 = 778 days (or 25.9 months)

For long term storage of preserved water in good condition, preserving chemical should be added. 5.2.2. Rapid Depletion Method (RDM): In Rapid Depletion method, there is no restriction on the use of harvested rainwater by consumer. Consumer is allowed to use the preserved rain water up to their maximum requirement, resulting in less number of days of utilization of preserved water. The rainwater tank in this method is considered to be only source of water for the consumer, and alternate source of water has to be used till next rains, if it runs dries. •

For example if we assume per capita water demand = 150 lt/day = 0.15 cu.m /day

•

Total amount of water consumption per day = 320 x 0.15= 48cu.m /day

•

Total no. of days, preserved water can be utilize = stored water/water demand =24921.69 /48 = 519 days (17.3 months) 58  

 

Hence, finally it is observed that, if the amount of water stored is equal to 24921.69 cu.m, then applying 1. RDM, consumer can only utilize the preserved stored water for about 778 days (25.9months), 2. Where as in RM, preserved stored water can be utilized for a period of 519 days (17.3 months).

5.3. Runoff Coefficients: •

The design of water harvesting schemes requires the knowledge of the quantity of runoff to be produced by rainstorms in a given catchment area. It is commonly assumed that the quantity (volume) of runoff is a proportion (percentage) of the rainfall depth. Runoff [mm] = K x Rainfall depth [mm]  

•

In rural catchments where no or only small parts of the area are impervious, the coefficient K, which describes the percentage of runoff resulting from a rainstorm, is however not a constant factor. Instead its value is highly variable and depends on the above described catchment-specific factors and on the rainstorm characteristics

•

For example, in a specific catchment area with the same initial boundary condition (e.g. antecedent soil moisture), a rainstorm of 40 minutes duration with an average intensity of 30 mm/h would produce a smaller percentage of runoff than a rainstorm of only 20 minutes duration but with an average intensity of 60 mm/h although the total rainfall depth of both events were equal.

5.3.1. Determination of Runoff Coefficients: •

For reasons explained before, the use of runoff coefficients which have been derived for watersheds in other geographical locations should be avoided for the design of a water harvesting scheme. Also runoff coefficients for large watersheds should not be applied to small catchment areas.

59    

•

An analysis of the rainfall-runoff relationship and subsequently an assessment of relevant runoff coefficients should best be based on actual, simultaneous measurements of both rainfall and runoff in the project area.

•

As explained above, the runoff coefficient from an individual rainstorm is defined as runoff divided by the corresponding rainfall both expressed as depth over catchment area (mm):

•

Actual measurements should be carried out until a representative range is obtained. Shanan and Tadmor recommend that at least 2 years should be spent to measure rainfall and runoff data before any larger construction programme starts. Such a time span would in any case be justified bearing in mind the negative demonstration effect a water harvesting project would have if the structures were seriously damaged or destroyed already during the first rainstorm because the design was based on erroneous runoff coefficients.

5.3.2. Assessment of annual or seasonal runoff: •

The knowledge of runoff from individual storms as described before is essential to assess the runoff behavior of a catchment area and to obtain an indication both of runoff-peaks which the structure of a water harvesting scheme must withstand and of the needed capacity for temporary surface storage of runoff, for example the size of an infiltration pit in a micro catchment system.

•

It is necessary to assess either the annual (for perennial crops) or the seasonal runoff coefficient. This is defined as the total runoff observed in a year (or season) divided by the total rainfall in the same year (or season).

60    

•

The annual (seasonal) runoff coefficient differs from the runoff coefficients derived from individual storms as it takes into account also those rainfall events which did not produce any runoff. The annual (seasonal) runoff-coefficient is therefore always smaller than the arithmetic mean of runoff coefficients derived from individual runoff-producing storms.

5.4. Design suitability conditions for all the recharge structures: 5.4.1. Abandoned dug well: •

It is suitable for large buildings having the roof area more than 1000 sq.m.

•

Before using the dug well as recharge structure, its bottom should be cleaned and all the fine deposits should be removed.

5.4.2. Abandoned/Running hand pump: •

These structures are suitable for small buildings having roof area up to 150 sq.m.

•

Water is diverted from rooftop to the hand pump through pipe of 50 to 100mm dia.

5.4.3. Recharge pit: •

These are constructed generally 1 to 2 m wide and 2 to 3 m deep.

•

It is suitable for small buildings having the roof top area up to 100sq.m.

5.4.4. Recharge trench: •

The trench may be 0.5 to 1m wide 1 to 1.5m depth and 10 to 20m long depending upon the availability of land and roof top area.

•

It is suitable for the buildings having rooftop area of 200 to 300 sq.m.

•

It is constructed when permeable strata of adequate thickness are available at shallow depth.

•

These are constructed across the land slope.

61    

5.4.5. Gravity head recharge well: •

This technique is suitable where land availability is limited.

•

Recharge water should be silt free as possible.

5.4.6. Recharge shaft: •

Diameter of recharge shaft varies from 0.5 to 0.3m depending upon the availability of water to be recharged.

•

Depth of recharge shaft varies from 10-15m below ground level.

62    

CHAPTER 6 CALCULATIONS AND DESIGN 6.1. Determination of catchment area at Magadha village: The rooftop surface area is nothing but the catchment area which receives rainfall. This measurement was done manually with the help of reinforced fiber tape which is the simplest technique known as “tape survey”. Before using tape, tape was checked for any zero error and also length of the tape was also carefully checked for its accuracy. •

Total rooftop area= 37760.148 sq.m

•

Runoff coefficient is=0.4 to 0.6 (say 0.5)[obtained from CPWD manual]

•

Average rainfall (from annual rainfall data)=0.66m

•

So, capacity of tank=area x rainfall x runoff coefficient =37760.148 x 0.66 x 0.5 =12460.85 cu.cm =1246085litres

•

Considering 10% losses, the capacity of tank would be=12, 00,000litres.

6.1.1. Storage tank optimum dimensions: Two types of tank can be used for storing of rainwater discharged from the roof. They are: a) LINED STORAGE TANK b) UNLINED NATURAL STORAGE TANK In lined storage tank, earth work excavation is done and underground RCC water storage tank is constructed which is completely covered from the top. The land above the tank can be used for serving as playground or parking slot, etc. In unlined natural storage tank, earth excavation is done and all the water being allowed to fall directly in that pit and store it. In this method, we get two advantages. 63    

Firstly, our natural water gets recharged leads to augmentation of water level and ground condition, increasing prospects for better future cultivation and plantation. Secondly, underground water can be extracted anywhere within some limited areas from that pit and can be used to satisfy daily water demand. 6.1.2. Optimum dimensions: •

Total amount of water collected in one year=size of the tank=37760.148 x 0.66 =24921.69cu.m

•

Taking height of tank=3m

•

Mostly excess amount of water assumed to be collected during the period of maximum rainfall- July and august.

•

Assuming amount of water consumed per month (assuming 100litre/day per capita water demand)=320x0.1x30=960cu.m

•

Amount of water collected during July and August=960+1125 =2085cu.m

•

(1125 m^3 is the maximum rainfall recorded during these two months i.e. July and august)

•

And, amount of water consumed during this two month=2x960=1920cu.m

•

Hence, total amount of water to be stored=size of tank=2085-1920=165cu.m

•

Fixing the height of tank to be 3m

•

Area of the base=165/4=55sq.m

•

But as a rectangular tank is more economical and feasible the dimensions of the tank are taken as 10.5mx6mx3m which is easy to construct and more feasible.

64    

6.1.3. Structural Design of 1200KL Capacity RCC Sump: I. Given Data: •

Capacity = 1200KL

•

Soil Bearing Capacity = 25 Tonnes/sq.m

Sections and Data Assumed: •

Grade of Concrete = M-30

•

Grade of Steel = Fe- 415

•

Dead Storage = 15cm

•

Free Board = 30cm

•

Size of the Compartment = 10.5mx6m

•

Depth of Water = 3m

•

Size of columns = 0.3m x 0.3m

•

Assumed Size of Beams = 0.3m x 0.45m

•

No. of Internal Columns = 2 No’s

Capacity Calculations: •

Volume Proposed =10.5x6x3 m^3 = 189 Cu.m.

•

Deduct for Volume of Columns = 2x0.3x0.3x3 = 0.54 Cu.m

•

Net Capacity = 188.56 Cu.m or 190 Cu.m >165 Cu.m HENCE OK

II. Design Coefficients: •

For members in bending бcbc=100kg/cm^2, бst=1300kg/sq.cm

•

Modular Ratio, m = (280/3x100) =0.93 o K = (0.933x100/0.933x100+1300) = 0.417 o Lever Arm, J = 1−(0.417/3) = 0.86 o R = 17.931kg/sq.cm

65    

III. Design of Roof Slab: a) Panels •

Assuming that the interior panel Sizes = 3mx3m So design the roof slab interior panel as a two way slab.

•

Assume the thickness of the slab to be 150mm

•

Effective Span = 3.5+(0.3/2)+(0./2) = 3.8m

Loading: •

Self weight = 0.15 x 2550 = 382.5 Kg/sq.m

•

Live load = 150 Kg/sq.m

•

Floor Finishes = 167.5 Kg/sq.m

•

Total load = 700 Kg/sq.m

Moment Coefficients •

As ly/lx = 1, the moment coefficients for long span and short span are same.

•

From IS- 456, Table 26, Coefficients for Negative Moment at continuous edge = 0.032

•

Positive Moment at edge = 0.024

•

Maximum Negative Moment = 0.0032x700x2.81^2= 176.87 Kg-m

•

Maximum Positive Moment = 0.024x700x2.81^2= 132.65 Kg-m

•

Effective Depth required = √M/R b=3.14cm

•

Effective Depth required from deflection, consideration with 0.3% tension reinforcement

•

Span to depth ratio =26 (Continuous)

•

L/d = 26

•

Modification factor is 1.4 for 0.3% reinforcement (fig -4, IS 456)

•

d = (3x100/26x1.5) = 7.69cm (<11cm) So Ok.

•

Over all depth required using 8mm bars =11+3+0.4 = 14.4cm < (15cm) Hence the depth chosen is OK.

•

Ast required at the top = (M/ бst x J x d) = (176.87x100/1300x0.872x11) =1.42sq.cm

•

Ast required at the mid span = (132.65x100/1300x0.872x11) =1.06sq.cm 66  

 

•

But Min Ast as per code (IS 3370 part II – 8.1)

•

For 150 mm, Ast minimum = (0.35x15x100/100) = 5.25 So provide, 10mm bars @ 140mm c/c both ways, at bottom of mid span and crank alternate bars at support in both directions to cater for the negative reinforcement. Also provide 10mm diameter extra bars at top of supports @280mm c/c

(b) End Panels: Provide the same reinforcement as that of corner panel for end panel also. IV. Design of Roof Beam: •

Assume Size of the beam proposed = 30x45sq.cm

•

Depth = 45cm

•

Effective Span = 3.8 m

Loading: Dead Loads: •

Equivalent UDL from Slab = (2/3) x550x3=1100kg/m

•

Self Weight = 0.3x0.45x2550=459 kg/m

•

Total Dead load = 1559 kg/m

Live Load: •

Equivalent UDL from Slab = (2x150x3/3)=300 kg/m

Span Moments: •

Bending moment near middle of end span = (1559x3^2/12) + (300x3^2/10) =1439.25 Kg-m

•

Bending moment at middle of interior span =(1559x3^2/16) + (300x3^2/12) =1101.94 kg-m

Support moments: •

Bending moment at support next to end support = (1559x3^2/10) + (300x3^2/9) = 1703.1 kg-m

•

Bending moment at other interior supports = (1559x3^2/12) + (300x3^2/9) = 1469.25 Kg-m

•

Max moment = 1703.1 Kg-m

•

Effective depth = √(1703.1x100/17.931x30) = 15.41cm

67    

•

Provided depth of 45cm is sufficient and effective depth available = 45− 4 − (1.2/2) =40.4cm

•

Ast required near middle of end span at bottom = (1439.25x100/1300x0.872x40.4) = 3.15sq.cm Provide 2 No. of 12mm dia bars running through and 2 no. of 12mm dia cranked at bottom (Ast provided = 4.52 sq.cm)

•

Ast required middle of interior span at bottom=(1101.94x100/1300x0.872x40.4)=2.41sq.cm Provide 2 No. of 12mm dia bars running through and 2 no. of 12mm dia cranked at bottom (Ast provided = 3.14 sq.cm)

•

Ast required at support next to end support at top = (1703.1x100/1300x0.872x40.4) =3.72sq.cm Provide 2 No’s of 12mm dia bars at top, Straight and running through, One 12 mm dia extra bar on the top of interior supports in addition to 2 cranked bars of 12mm dia from bottom. (Ast Provided = 5.65sq cm)

•

Ast required at other interior supports at top = (1469.25x100/1300x0.872x40.4) =3.21sq.cm Provide 2 No’s of 12mm dia bars at top. The two numbers of 12mm dia bars taken from bottom of adjacent spans will be sufficient (Ast provided = 4.52 sq cm)

•

Ast Provided = (3.72x100/30x40.4)=0.23

•

Max Shear Force = (1559+300) x4x0.6 =4461.6 kg

•

Shear stress = (4461.6/30x40.4) =2.76kg/sq.cm

•

From table 23 of IS: 456-2000,

•

Balance shear to be carried by stirrups = 4461.6−2.28x30x40.4 = 777.12kg

•

Spacing of 8mm 2-legged stirrups, Asv=2x(∏/4)x0.8^2 = 1.005 sq.cm

•

Taking fy= 1300 kg/cm^2 , spacing of stirrups is given by, Sv=(1300x1.005x45/777.12) =20cm So provide 8mm-tor 2-legged stirrups at 150mm C/C

V. Design of Side Wall: Dead storage including bell mouth weight = 30cm The wall is designed as cantilever 68    

•

Maximum water pressure at bottom = 1000 x 3 = 3000kg/sq.m

•

Moment = (3000 x 3^2 / 6) =4500 kg-m

•

Uncracked thickness = √ (4500 x 100 x 6 / 20 x 100 ) = 36.74cm Provide 40cm overall depth of sidewall at bottom.

•

Effective depth at bottom = 40 −2 −1− 0.5 = 36.5cm

•

Ast required on water face at bottom = ( 4500 x 100 / 1500 x 0.875 x 36.5) = 9.39sq.cm Provide 16mm dia bars @ 140mm c/c &12mm dia bars at 140mm c/c.

•

Ast required at 1.45m from bottom =( 2663.265 x 100 / 1500 x 0.875 x 34.2) = 5.93sq.cm Provide 16mm dia bars @ 280mm c/c &12mm dia bars at 140mm c/c.

•

Ast required at 2.45cm from bottom = ( 1891.304 x 100 /1500 x 0.875 x 28.49 ) = 5sq.cm Provide 16mm dia bars @ 280mm c/c &12mm dia bars at 280mm c/c.

Stabilizing moments: Overturning moment = (1/2) x 1000 x 3.5^2 x (3.5/3 + 0.5) = 10208.33kg-m COMPONENT

WEIGHT IN KG

LEVER ARM IN MOMENT @ A IN METERS

KG-M

1759.5

0.3

527.85

W2→0.5 x 0.18 x 3 x 1800

486

0.66

320.76

W3→3 x 0.6 x 1800

3240

0.3

972

879.75

0.73

642.21

W5→2.5 x 3.45 x 1000

8625

2.25

19406.25

W6→3.5 x 0.5 x 2550

4462.5

1.75

7809.38

W1→0.2 x 3.45 x 2550

W4→0.5 x 0.2 x 3.45 x 2550

Weight in kg = 19452.75kg Moment @ A = 29678.445kg-m •

Net stabilizing moment = 29678.445 – 10206.33 = 19470.115 kg-m

•

Eccentricity from A = (19470/19452) = 1m

•

Eccentricity from center = (3.5/2) – 1 = 0.55 < (b/6) 69  

 

•

Maximum stresses = (19452/3.5 x 1) x [1 + (6 x 0.55/3.5)] = 10797 kg/sq.m < SBC of soil

•

Minimum stress = (19452/3.5 x 1) x [1 − (6 x 0.55/3.5)] = 317 kg/sq.m (no tension) OK

Net upward pressure: •

Max = 10797 – 0.5 x 2550 = 9522 kg/sq.m

•

Min = 317 – 0.5 x 2550 = 958 kg/sq.m

•

Mxx = (7742.18 x 0.62 /2) + (1779.82 x 0.6 /2) x (2/3) x 0.6 = 1607.17 kg-m

•

Myy = (3.45 x 100 x 2.5^2/2) – (6555.64/2) x (1/3) x 1.66^2 = 13792.03 kg-m

•

Uncracked depth required = √ (13792.06 x 100 x 6 / 20 x 100) = 64.32cm

•

Provide 50 cm thick base slab

•

Effective depth available = 50 – 5 – (1.6/2) = 44.2cm

•

Ast required at bottom = (1607.17 x 100 / 1900 x 0.893 x 44.2) =2.14sq.cm

•

Ast required at top = (13792.03 x 100/ 1900 x 0.893 x 44.2) = 18.39sq.cm

•

Provide 16mm dia extra bars @140mm c/c at top in addition to floor slab bars of 10mm dia @ 300mm c/c.

•

Ast min = (0.2 x 0.8 x 50 x 100/100) = 8sq.cm

•

Ast min in each face = 8/2 = 4sq.cm

•

Provide 12mm dia extra bars @ 150mm c/c at bottom in addition to floor slab bars of 10mm dia @ 300mm c/c. provide 12mm dia distributors @ 150mm c/c at top & bottom.

Distribution Steel: •

Minimum Reinforcement = (0.12x300x1000/100)=360sq.mm Provide 10mm Dia bars at a spacing of 130mm C/C

VI. Design of Internal Columns: •

Column Size = 30*30sq.cm Provide 4 no’s of 12mm Dia bars tied with 8mm dia links

•

Height of the column = 3.15+0.3 = 3.45m

•

Leff /L = 1.2 Leff= 1.2x3.45= 4.14m 70  

 

Leff/d = 4.14/0.3 =13.8 >12 It is designed as a long column •

So, Reduction Coefficient = 1.25−(4.14/48x0.3) =0.9 Load on Column

•

Due to Slab = 700x3x3 =6300kgs

•

Due to roof beams = (0.4x0.45x4) x2x2550 =3672kgs

•

Due To self weight of the column = 0.3x0.3x3.45x2550 = 791.77 Kgs

•

Total Load on the column = 10763.77 Kgs

•

Load Carrying Capacity of the column (P) = бcc x Acc+ бsc x Asc =74413kg>>10763.77kgs Hence the provided section is safe

VII. Check for Uplift (Base slab Design) for Sump Empty Condition: A) Load from Roof slab = (10.5+0.6) x (6+0.6) x 700 = 51282kgs B) Weight of Roof Beams a) 1 x 10.5 x 0.3 x 0.3 x 2550 =2410 kgs b) 3 x 6 x 0.3 x 0.3 x 2550 =4131kgs C) Weight of Side Wall a) 2 x 10.5 x 0.3 x 3.45 x 2550 =55424kgs b) 2 x 6.6 x 0.3 x 3.45 x 2550 = 34838kgs D) Weight of floor Slab = 1 x 1 x 12.3 x 7.8 x 2550 =244647 kgs E) Weight due to columns = 3 x 3.45 x 0.3 x 0.3 x 2550 = 2375 kgs •

Total Load = 345225 Kgs

•

Upward Pressure due to uplift = 1000 x 12.3 x 7.8 x 3 = 287820 kgs

•

Factor of Safety against uplift = (345225/287820) = 1.25 > 1.2 Hence Ok

•

Intensity of Upward Pressure = (345225/12.3 x 7.8) = 3598 kg/sq.m

•

Deduct Self weight = 1.0 x 2550 = 2550 kg/sq.m

•

Net Upward Pressure = 1048 kg/sq.m

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Designing of Base slab considering it as flat slab: •

Bending moment= Wl/8 = [(1048 x 3 x 3) x 3]/8 =3537 kg-m

•

Negative Design Moment=0.65Mc= 0.65 x 3537 = 2299.05 kg-m

•

Positive Design Moment=0.35Mc= 0.35 x 3537 = 804.66 kg-m

Bending Moment for Column Strip: •

Negative Bending moment for column Strip is generally taken as 75% of the total negative moment in the panel. Negative Design Moment= 0.75 x 2299.05 =1724.28 kg-m

•

Positive Bending moment for column Strip is generally taken as 60% of the total positive moment in the panel. Positive Design Moment= 0.6 x 804.66 = 482.79 kg-m

Bending Moment for middle Strip: •

Negative Bending moment for middle Strip is generally taken as 25% of the total negative moment in the panel. Negative Design Moment= 0.25 x 2299.05 = 574.76 kg-m

•

Positive Bending moment for middle Strip is generally taken as 40% of the total positive moment in the panel Positive Design Moment= 0.4 x 804.66 = 321.86 kg-m

•

Depth of the slab = 1000mm

Reinforcement: •

Column Strip: Steel for Negative moment = (1724.28 x 1000/1300 x 0.87 x 967) = 15.7 sq.mm Provide 8mm Dia bars at a spacing of 150mm c/c for negative reinforcement and 150mm c/c for positive reinforcement.

VIII. Design of Internal Column Footing: •

Load from Column = 10763.77 Kgs

•

Assuming the self weight of footing equal to 10% of the super imposed load

•

Self Weight = 1076.3 Kgs

•

Total load = 11840.07 Kgs or 11.84 tonnes

•

Given Soil bearing Capacity = 25t/sq.m

•

Area of footing = 11.84/25 = 0.47 sq.m 72  

 

•

But Provide size footing 1.4 x 1.4 sq.m

•

Net Upward Pressure = (10763.77/1.4 x 1.4) = 5491.71 kg/sq.m

•

Moment = 5491.71 x {(1.4−0.3)^2/ 2} x 1.4 = 2460.28 kg-m

•

Uncracked Depth = √ (2460.28 x 100 x 6) / (20 x 100) = 27.16cm

•

Provided over all depth of 100cm is sufficient

•

Providing 10mm dia bars,

•

Effective depth = 100-5-1.0/2 = 94.5cm

•

Ast required = (2460.28 x 100 / 130 x 0.872 x 94.5) = 2.29sq.cm Provide 4no.s of 10mm tor bars at bottom both ways as mesh, in addition to floor slab bars of 10mm dia tor bars at 300mm c/c.

Leveling course: Provide 200mm thick leveling course below base slab and footing with CC (1:3:6) mix.

6.2. Filtration: Because the majority of bacteria enters rainwater from a roof and gutter system (where the water picks up fecal matter from squirrels, birds, etc., as well as other organic matter), prefiltration is a VITAL step in creating and storing a fresh water supply. First, you’ll want to consider installing first flush filters. A first flush filter works under the principle that the most contaminated water is the first bit of water that falls from a roof during a rain event (because this is the water that’s flushing off the fecal matter and organics). Please note that the downpipe component on first flush filters should be sized according to the type of roof you have (e.g., asphalt shingle roofs will need more first flush diversion -- and therefore a larger downpipe on the first flush filter -- than metal roofs because they are more gritty and it takes longer for fecal matter to be cleaned from the surface from a rain event). For roofs that in a clean environment (i.e., not many trees/birds around), it is recommended to flush 12.5 gallons/1,000 sq. ft. of roof area. For roofs that are more susceptible to organic material and/or roofs with asphalt shingles, a flushing of 50 gallons/1,000 sq. ft. of roof is recommended.

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Figure. 32 First flush mechanism

Figure .33 simple cloth filter

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6.3. Gutter design: A channel which surrounds edge of a sloping roof to collect and transport rainwater to the storage tank is called gutter. Gutters can be semi-circular or rectangular and generally of PVC or galvanized iron sheet type of material. Gutter shape is semicircular withdiameter150mm. The efficiency of gutter is highly influenced by its choice of optimal size, width and position relative to the roof edge and its slope. Hence, this parameter is cautiously chosen. So, in order to collect maximum water, it is highly required to build the gutter with large dimensions. However, it is economical to make large gutter with reasonable dimension because the value of water collected from it is much higher than the cost of constructing the gutter. Considering the throw wind and pulsating effects, gutter width was frozen on the basis of the roof size and the ideal positioning was found out. Keeping the present case in mind, results of various studies were

extensively

analyzed,

and

a

suitable

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gutter

design

was

proposed.

CHAPTER 7 RESULTS & DISCUSSIONS 1. Storage tank capacity =12, 00,000 liters 2. Optimum dimensions of the storage tank =10.5m x 6m x 3m To store 12,00,000 liters of water the dimensions of the tank 10.5m x 6m x 3m is

•

sufficient 3. Number of days supported by stored harvested water in tank to consumer S.No

Rational method (RM)

1.

778 days

Rapid Depletion Method (RDM) 519days

4. Optimum location of storage tank: at the dead end of venture. •

At the dead end there are no villas and free space is available. So, location of storage tank is at the dead end.

5. From direct shear test •

C=0 ( since C=0 type of soil is sand)

•

Ф=43.6

6. Specific gravity of soil = 2.59 7. Bulk density of soil

= 1.349g/cc

8. Dry density of soil

= 1.285g/cc

9. Large roof area is found to be available in the JNTUH campus & three rooftop rainwater harvesting structures each with a capacity of 1,00,000 liters & one reuse structures with a capacity of 2,00,000 liters have been found. Total water recharged in the campus through construction of rooftop rainwater harvesting structures is 14, 00,000 liters up to august 2014.

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CHAPTER 8 CONCLUSION This project dealt with all aspect of improving the water scarcity problem at Magadha village by implementing ancient old technique of rainwater Harvesting. Two alternatives have been suggested for tank design, which takes separate approaches towards the consumption of harvested rainwater. Hence we can draw out a conclusion that a huge amount of water gets collected from the rooftop surfaces of all the villas. And if, this project is being done seriously and implemented to the villas, then the tank would have a huge harvesting potential. This reservoir should have to build for the storage of 12 lakh liters of water. Hence this tank has huge capacity of getting rainwater and on proper storage, this tank can supply almost throughout the year for about 320 consumers having a consuming rate of 100liter/day as calculated by rational depletion method. It is concluded that RCC tank which is to be constructed should be an underground one, so that upper surface of the tank can be utilized economically for any land purpose such as playground or cycle stands or any such small structure. The other component of the harvesting systems such as Guttering, First-Flush, and Filtration mechanism have also been reviewed and designed for all the villas. Hence it was finally concluded that implementation of RAINWATER HARVESTING PROJECT to the Magadha village will be the best approach to fight with present scenario of water scarcity in all aspects, whether it is from financial point of view or from optimum utilization of land surface. Therefore, water is highly a precious natural resource which is always in high demand in the Magadha village and thus, RAINWATER HARVESTING AT MAGADHA VILLAGE is highly recommended.

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REFERENCES: 1. Artificial recharge to groundwater-guidelines Indian standard IS15792-2008 2. CPWD manual on rainwater harvesting and conservation 3. Case study: Rainwater harvesting at JNTUH 4. Case study: NIT Rourkela- Rainwater harvesting. 5. Case study: NIT Warangal- Rainwater harvesting 6. Environmental Engineering by G.S.Birdie 7. Geotechnical engineering by C.Venkatramiah. 8. http://as.ori.nic/balangir/rainfall/pubNormaldtl.asp 9. http://www.rainwaterharvesting.org/ 10. http://www.tn.gov.in/dtp/rainwater.htm 11. http://www.aboutrainwaterharvesting.com/ 12. http://www.rainwaterharvesting.org/People/innovators-urban.htm#svis 13. Irrigation and water resources & water power by P.N.Modi 14. Plain and reinforced concrete - code of practice:IS456-2000 15. Rainfall data – Ground water department 16. Structural design of RCC sump - Guidelines from IS 3370 part 2 : 1967 17. Structural design of RCC sump - Guidelines from IS 3370 part 4 : 1967 18. Watershed management by JVS Murthy 19. Wikipedia.com

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