Upload
samuel-davis
View
215
Download
0
Embed Size (px)
Citation preview
8/13/2019 Planning & Designining Rain Water Harvesting Syst.
1/64
1
PROJECT REPORT
ON
Planning and Designing Rain Water Harvesting System
Premnagar dehradun
DEPARTMENT OF CIVIL ENGINEERING
JB INSTITUTE OF TECHNOLOGY
DEHRADUN, UTTRAKHAND (248007)
[2013-2014]
Submitted By:
ABHIRAJ KUMAR PATHAK
Aditya Painyuli Amit Purohit
Balkrishana Tamta Deepak Singh
Himanshu Negi Sonali Rawat
Guided By:Mr. Subhash Chamoli
8/13/2019 Planning & Designining Rain Water Harvesting Syst.
2/64
2
On
Planning and Designing Rain Water Harvesting System
Premnagar dehradun
In partial fulfilment of requirements for the degree of
Bachelor of Technology
In
CIVIL ENGINEERING
SUBMITTED TO: SUBMITTED BY:
Prof. Sanjeev Gill (H.O.D) Abhiraj Kumar Pathak
Civil Engineering Department. Aditya Painyuli
JBIT,Dehradun Amit Purohit
Balkrishana Tamta
Deepak Singh
Himanshu Negi
Sonali Rawat
8/13/2019 Planning & Designining Rain Water Harvesting Syst.
3/64
3
DECLARATIONWE HEREB Y CERTIFY THAT THE REPORT EN TITLED PLANNING DESIGNING RAIN WATER HARVESTING SYSTEM
PREMNAGAR DEHRADUN IS SUB MITTED ,IN PARTIAL FULFILMEN T OF THE REQUIREMEN T FOR THE AW ARD O F DEGREE OFB ACHELOR OF TECHN OLOGY IN C IVIL EN GIN EERIN G ,T O JB INSTITUTE O F T E C H N O LO G Y U N D E R U T T A R A K H A N DT E C H N I C A L UNIVERSITY),DEHRADUN COMPRISES ON LY ORIGIN AL W ORK .
T HE MATTER EMB EDDED IN THIS REPORT IS O RIGIN AL AN D HAS N OT B EEN SUB MITTED EARLIER FOR THE AW ARD OF AN YOTHER DEGREE O F THIS OR AN Y UN IVERSITY.
ABHIRAJKUMARPATHAK (61530107002)ADITYAPAINYULI (10530107005)AMITPUROHIT (10530107008)BALKRISHANATAMTA (61530107004)HIMANSHUNEGI (10530102015)DEEPAKSINGH (10530107013)SONALIRAWAT (61530107012)
CERTIFIC TE
8/13/2019 Planning & Designining Rain Water Harvesting Syst.
4/64
4
his is to certify that the project work entitled
PLANNING DESIGNING RAIN WATER HARVESTING SYSTEM PREMNAGARDEHRADUN is a bonafide work carried out by ABHIRAJ KUMAR PATHAKcandidates of the B.Tech Civil Engineering from JB Institute of
Technology , Dehradun, affiliated to Uttarakhand Technical
University, Dehradun, under my guidance and supervision.
Mr. Subhash Chamoli Prof. Sanjeev Gill
{ Assistant Professor} {HOD Civil Engineering}
ExternalExaminer
(Signature)
Abstract
8/13/2019 Planning & Designining Rain Water Harvesting Syst.
5/64
5
Along the path of water flowing in a river basin are many water-related human
interventions that modify the natural systems. Rainwater harvesting is one such
intervention that involves harnessing of water in the upstream catchment. Increased water
usage at upstream level is an issue of concern for downstream water availability to
sustain ecosystem services. . To address this problem a technique was developed for
small scale farmers with the objective of harnessing rainwater for crop production.
However, the hydrological impact of a wider adoption of this technique by farmers has
not been well quantified. In this regard, the SWAT hydrological model was used to
simulate the hydrological impact of such practices. The scenarios studied were: (1)
Baseline scenario, based on the actual land use of 2000, which is dominated by pasture
(combination of natural and some improved grass lands) (PAST); (2) Partial conversion
of Land use 2000 (PAST) to conventional agriculture (Agri-CON); and (3) Partial
conversion of Land use 2000 (PAST) to in-field rainwater harvesting which was aimed at
improving the precipitation use efficiency (Agri-IRWH).
8/13/2019 Planning & Designining Rain Water Harvesting Syst.
6/64
6
CKNOWLEDGEMENTThe satisfaction and euphoria that accompanies the successful completion of any taskwould be incomplete without the mention of the people who made it possible whoseconstant guidance encouragement and support fructified my effort with success.
I consider it my privilege to express my gratitude and respect to all those who guidedme in the completion of my seminar report.
I would like to thank Prof.Sanjeev Gill Head of Department Civil Engineering forproviding me this valuable opportunity of presenting the seminar on Assessment ofPlanning and Designing Rain Water Harvesting System which has not onlyenhanced my knowledge about the subject but also increased my confidence level.
I am indebted to my mentor Mr. Subhash Chamoli for guiding me throughout thepreparation of my seminar. Last but not the least I would like to thank God myparents and colleagues for helping me directly or indirectly in the successfulcompletion of the project.Abhiraj Kumar pathak Aditya Painyuli
Amit Purohit Balkrishana Tamta
Deepak Singh Himanshu Negi
Sonali Rawat
8/13/2019 Planning & Designining Rain Water Harvesting Syst.
7/64
7
CONTENTS
1.1 Introduction
1.1.1 Rainwater Harvesting1.1.2 Why Rain Water Harvesting?
1.2. Rainwater Harvesting Feasibility Criteria
1.2.1 Plumbing Code1.2.2 Mechanical, Electrical, Plumbing (Mep
1.2.3 Water Use
1.2.4 Available Space
1.2.5 Site Topography
1.2.6 Available Hydraulic Head1.2.7 Water Table
1.2.8 Soils
1.2.9 Proximity Of Underground Utilities1.2.10 Contributing Drainage Area
1.2.11 Contributing Drainage Area Material
1.2.12 Water Quality Of Rainwater1.2.13 Hotspot Land Uses
1.2.14 Setbacks From Buildings
1.2.15 Vehicle Loading
1.2.16 Discharge To Combine Sewer System
1.3. Rainwater Harvesting Conveyance Criteria1.3.1 Collection And Conveyance
1.3.2 Overflow1.4. Rainwater Harvesting Pretreatment Criteria
1.4.1 First Flush Diverters
1.4.2 Leaf Screens1.4.3 Roof Washers
1.4.4 Vortex Filters
1.5 Criteria For Selection Of Rainwater Harvesting Technologies
1.6 Components Of A Rooftop Rainwater Harvesting System1.6.1 A Collection Or Catchment System
1.6.2 A Conveyance System Is Required To Transfer The Rainwater From The Roof
1.7 The Design Criteria Of A Sorage Tank
1.7.1 Available Space1.7.2 Site Topography1.7.3 Available Hydraulic Head
1.7.4 Water Table1.7.5 Soil
1.7.6 Proximity Of Underground Utilities
8/13/2019 Planning & Designining Rain Water Harvesting Syst.
8/64
8
1.7.7 Contributing Drainage Area
1.7.8 Water Quality Of Rainwater
1.7.9 Hotspot Land Uses1.7.10 Contributing Drainage Area Material
1.8 Rainwater Harvesting In Lpu Complex
1.9 Design Capacity Of Storage Tank2.1 Rainwater Harvesting Pretreatment Criteria2.2 Filtration Systems And Settling Tanks
2.3 Primary Treatment Of Rain Water
2.4 Secondary Treatment
2.4.1 Lab Testing On Rain Water Harvesting In prem nagar2.5 Experiment-2
2.6 Tertiary Treatment
Disinfection Technologies
Storage Tank Or Cistern To Store Harvested Rainwater2.6.3 Delivery System
2.6.3 Storage Tanks Or Reservoirs2.7 Storage Reservoirs For Domestic Rainwater Harvesting Are Classified In Two Categories
3.1 Rain Water Harvesting Techniques3.2 Urbanization Effects On Groundwater Hydrology
3.2.1 Methods Of Artificial Recharge In Urban Areas
3.2.2 Computation Of Artificial Recharge From Roof Top Rainwater Collection3.2.3 Benefits Of Artificial Recharge In Urban Areas
3.3 How It Works
Roof Catchments
Section Through Typical Gutter3.4 Harvesting Rainwater Harnessing Life
3.5 Attributes Of Groundwater3.5.1 Recharge Shafts3.5.2 Lateral Shafts With Bore Wells
3.5.3 Spreading Techniques
3.5.4 First Flush And Filter Screens3.5.5 Rainwater Harvesting Efficiency
3.6 Some Useful Data
3.6.1 Climatological Data
3.6.2 Irrigation3.6.3 Ground Water Potential (As On 31.03.2004)
4.1 Geomorphology And Soils
4.2 Hydrometeorology4.3 Hydrology And Surface Water Utilisation4.4 Agriculture
4.5 Hydrogeology
4.6 Water Level Behavior4.7 Ground Water Flow
4.8 Drinking Water Supply
4.9 Tube Well Irrigation
8/13/2019 Planning & Designining Rain Water Harvesting Syst.
9/64
9
5.1 Designing A Rainwater Harvesting System
5.2 Typical Domestic Rwh Systems
5.2.1storage Tanks And Cisterns5.2.2 Domestic Storage Tanks
5.2.3 Ferro Cement Tanks
5.2.4 Rock Catchments5.2.5 Cultural Acceptability5.6 Maintenance
5.6.1 Regulations And Technical Standards
5.6.2 Types Of Rainwater Use5.7 Advantage Of Rainwater Harvesting
5.8 Disadvantages
5.9 Effectiveness Of Technology
Reference
Name of figure. Page No.Vortex Filters
Components of a rooftop rainwater harvesting system
Rainwater harvesting in prem nagar dehradunBlock 55
Block 56
Water supply by pipeSand filter
PH meter
Turbidity meterStorage reservoirs for domestic rainwater harvesting
Rock catchmentsGraphical methode of determine the required storage volume for a rain water
1.1 Introduction:
8/13/2019 Planning & Designining Rain Water Harvesting Syst.
10/64
10
1.1.1 Rainwater Harvesting
Rainwater harvesting systems store and release rainfall for future use. Rainwater that falls on
a rooftop or other impervious surface is collected and conveyed into an above- or belowground
storage tank (also referred to as a cistern or rain tank), where it can be used for nonpotablewater uses and on-site storm water disposal/infiltration. Non-potable uses may
include landscape irrigation, exterior washing (e.g. car washes, building facades, sidewalks,
street sweepers, fire trucks), flushing of toilets and urinals, fire suppression (sprinkler
systems), supply for cooling towers, evaporative coolers, fluid coolers and chillers,
supplemental water for closed loop systems, steam boilers, replenishment of water features
and water fountains, distribution to a green wall or living wall system, laundry, and delayed
discharge to the combined sewer system.
In many instances, rainwater harvesting can be combined with a secondary (down-gradient)
storm water practice to enhance storm water retention and/or provide treatment of overflow
from the rainwater harvesting system. Some candidate secondary practices include:
Disconnection to a pervious or conservation area
Overflow to bio retention practices
Overflow to infiltration practices
Overflow to grass channels or dry swales
By providing a reliable and renewable source of water to end users, rainwater harvesting
systems can also have environmental and economic benefits beyond storm water
management (e.g. increased water conservation, water supply during drought and mandatory
municipal water supply restrictions, decreased demand on municipal or groundwater supply,
decreased water costs for the end-user, potential for increased groundwater recharge).
Seven primary components of a rainwater harvesting system include:
(1) Drainage area
(2) Collection and conveyance system (i.e. gutter and downspouts)
(3) Pre-screening and first flush diverter
(4) Storage tank
(5) Water quality treatment (as required by TRAM)
(6 )Distribution system
(7) Overflow, filter path or secondary storm water retention practice
8/13/2019 Planning & Designining Rain Water Harvesting Syst.
11/64
11
1.2.4 Available Space: - Adequate space is needed to house the storage tank and any
overflow. Space limitations are rarely a concern with rainwater harvesting systems if they are
considered during the initial building design and site layout of a residential or commercial
development. Storage tanks can be placed underground, indoors, on rooftops that are
structurally designed to support the added weight, and adjacent to buildings. Designers can
work with architects and landscape architects to creatively site the tanks. Underground
utilities or other obstructions should always be identified prior to final determination of the
tank location.
1.2.5 Site Topography: - Site topography and storage tank location should be considered
as they relate to all of the inlet and outlet invert elevations in the rainwater harvesting system.
The final invert of the outlet pipe from the storage tank must match the invert of the receiving
mechanism (e.g. natural channel, storm drain system) that receives this overflow. The
elevation drops associated with the various components of a rainwater harvesting system and
the resulting invert elevations should be considered early in the design, in order to ensure that
the rainwater harvesting system is feasible for the particular site.
Site topography and storage tank location will also affect pumping requirements. Locating
storage tanks in low areas will make it easier to get water into the cisterns; however, it will
increase the amount of pumping needed to distribute the harvested rainwater back into the
building or to irrigated areas situated on higher ground. Conversely, placing storage tanks at
higher elevations may require larger diameter pipes with smaller slopes but will generally
reduce the amount of pumping needed for distribution. It is often best to locate a cistern close
to the building or drainage area, to limit the amount of pipe needed.
1.2.6 Available Hydraulic Head: - The required hydraulic head depends on the
intended use of the water. For residential landscaping uses, the cistern should be sited upgradient
of the landscaping areas or on a raised stand. Pumps are commonly used to convey
stored rainwater to the end use in order to provide the required head. When the water is being
routed from the cistern to the inside of a building for non-potable use, often a pump is used to
feed a much smaller pressure tank inside the building, which then serves the internal water
demands. Cisterns can also use gravity to accomplish indoor residential uses (e.g. laundry)
8/13/2019 Planning & Designining Rain Water Harvesting Syst.
12/64
12
that do not require high water pressure.
1.2.7 Water Table:- Underground storage tanks are most appropriate in areas where the
tank can be buried above the water table. The tank should be located in a manner that is not
subject it to flooding. In areas where the tank is to be buried partially below the water table,
special design features must be employed, such as sufficiently securing the tank (to keep it
from floating), and
Conducting buoyancy calculations when the tank is empty, the tank may need to be secured
appropriately with fasteners or weighted to avoid uplift buoyancy. The tank must also be
installed according to the tank manufacturers specifications.
1.2.8 Soils: - Storage tanks should only be placed on native soils or on fill in accordance
with the manufacturer's guidelines. The bearing capacity of the soil upon which the cistern
will be placed must be considered, as full cisterns can be very heavy. This is particularly
important for above-ground cisterns, as significant settling could cause the cistern to lean or
in some cases to potentially topple. A sufficient aggregate, or concrete base, may be
appropriate depending on the soils. The pH of the soil should also be considered in relation to
its interaction with the cistern material.
1.2.9 Proximity of Underground Utilities: - All underground utilities must be taken
into consideration during the design of underground rainwater harvesting systems, treating all
of the rainwater harvesting system components and storm drains as typical storm water
facilities and pipes. The underground utilities must be marked and avoided during the
installation of underground tanks and piping associated with the system.
1.2.10 Contributing Drainage Area:- The contributing drainage area (CDA) to the
cistern is the impervious area draining to the tank. Rooftop surfaces are what typically make
up the CDA, but paved areas and landscaped areas can be used with appropriate treatment
(oil/water separators and/or debris excluders). Areas of any size, including portions of roofs,
can be used based on the sizing guidelines in this design specification. Runoff should be
8/13/2019 Planning & Designining Rain Water Harvesting Syst.
13/64
13
routed directly from the drainage area to rainwater harvesting systems in closed roof drain
systems or storm drain pipes, avoiding surface drainage, which could allow for increased
contamination of the water.
1.2.11 Contributing Drainage Area Material: - The quality of the harvested
rainwater will vary according to the roof material or drainage area over which it flows. Water
harvested from certain types of rooftops and CDAs, such as asphalt sealcoats, tar and gravel,
painted roofs, galvanized metal roofs, sheet metal, or any material that may contain asbestos
may leach trace metals and other toxic compounds. In general, harvesting rainwater from
such surfaces should be avoided. If a sealant or paint roof surface is desired, it is
recommended to use one that has been certified for such purposes by the National Sanitation
Foundation (ANSI/NSF standard).
1.2.12 Water Quality of Rainwater: - Designers should also note that the pH of
rainfall in the District tends to be acidic (ranging from 4.5 to 5.0), which may result in
leaching of metals from roof surfaces, tank lining or water laterals, to interior connections.
Once rainfall leaves rooftop surfaces, pH levels tend to be slightly higher, ranging from 5.5 to
6.0. Limestone or other materials may be added in the tank to buffer acidity, if desired.
1.2.13 Hotspot Land Uses: - Harvesting rainwater can be an effective method to
prevent contamination of rooftop runoff that would result from mixing it with ground-level
runoff from a storm water hotspot operation. In some cases, however, industrial roof surfaces
may also be designated as storm water hotspots.
1.2.14 Setbacks from Buildings: - Storage tank overflow devices should be designed
to avoid causing ponding or soil saturation within 10 feet of building foundations. Tanks
must be designed to be watertight to prevent water damage when placed near building
foundations.
1.2.15 Vehicle Loading: - Whenever possible, underground rainwater harvesting
systems should be placed in areas without vehicle traffic or be designed to support live loads
8/13/2019 Planning & Designining Rain Water Harvesting Syst.
14/64
14
from heavy trucks, a requirement that may significantly increase construction costs.
1.2.16 Discharge to Combine Sewer System: - Discharge of harvested rainwater to
the combined sewer system is considered an acceptable drawdown method to achieve
retention value. However, the drawdown must be limited to a rate which releases the SWRv
over at least 72 hours.
1.3. Rainwater Harvesting Conveyance Criteria
1.3.1 Collection and Conveyance: - The collection and conveyance system consists of
the gutters, downspouts, and pipes that channel rainfall into storage tanks. Gutters and
downspouts should be designed as they would for a building without a rainwater harvesting
system. Aluminum, round-bottom gutters and round downspouts are generally recommended
for rainwater harvesting. Minimum slopes of gutters should be specified. Typically, gutters
should be hung at a minimum of 0.5% for 2/3 of the length and at 1% for the remaining 1/3
of the length in order to adequately convey the design storm (e.g. Storm water Retention
Volume (SWRv)). If the system will be used for management of the 2-yr and 15-yr storms,
the gutters should be designed to convey the appropriate 2-yr and 15-yr storm intensities.
Pipes, which connect downspouts to the cistern tank, should be at a minimum slope of 1.5%
and sized/designed to convey the intended design storm, as specified above. In some cases, a
steeper slope and larger sizes may be recommended and/or necessary to convey the required
runoff, depending on the design objective and design storm intensity. Gutters and downspouts
should be kept clean and free of debris and rust.
1.3.2 Overflow: - An overflow mechanism should be included in the rainwater harvesting
system design in order to handle an individual storm event or multiple storms in succession
that exceed the capacity of the tank. Overflow pipe(s) should have a capacity equal to or
greater than the inflow pipe(s) and have a diameter and slope sufficient to drain the cistern
while maintaining an adequate freeboard height. The overflow pipe(s) should be screened to
prevent access to the tank by rodents and birds.
1.4. Rainwater Harvesting Pretreatment Criteria
8/13/2019 Planning & Designining Rain Water Harvesting Syst.
15/64
15
Pre-filtration is required to keep sediment, leaves, contaminants, and other debris from the
system. Leaf screens and gutter guards meet the minimal requirement for pre-filtration of
small systems, although direct water filtration is preferred. All pre-filtration devices should
be low-maintenance or maintenance-free. The purpose of pre-filtration is to significantly cut
down on maintenance by preventing organic buildup in the tank, thereby decreasing
microbial food sources.
For larger tank systems, the initial first flush must be diverted from the system before
rainwater enters the storage tank. Designers should note that the term first flush in
rainwater harvesting design does not have the same meaning as has been applied historically
in the design of storm water treatment practices. In this specification, the term first flush
diversion is used to distinguish it from the traditional storm water management term first
flush. The amount can range between the first 0.02 to 0.06 inchesand typically applies to
rooftop runoff.
The diverted flows (i.e. first flush diversion and overflow from the filter) must be directed to
an acceptable flow path that will not cause erosion during a 2-yr storm or to an appropriate
BMP on the property.
Various first flush diverters are described below. In addition to the initial first flush diversion,
filters have an associated efficiency curve that estimates the percentage of rooftop runoff that
will be conveyed through the filter to the storage tank. If filters are not sized properly, a large
portion of the rooftop runoff may be diverted and not conveyed to the tank at all. A design
intensity of 1 inch/hour (for design storm = SWRv) should be used for the purposes of sizing
pre-tank conveyance and filter components. This design intensity captures a significant
portion of the total rainfall during a large majority of rainfall events (NOAA, 2004). If the
system will be used for channel and flood protection, the 2-yr and 15-yr storm intensities
should be used for the design of the conveyance and pre-treatment portion of the system. For
the SWRv, a minimum of 95% filter efficiency is required. This efficiency includes the first
flush diversion. The Cistern Design Spreadsheet, discussed more in Section 1.2 assumes a
filter efficiency rate of 95% for the SWRv design storm. To meet the requirements to manage
the 2-year and 15-year storms, a minimum filter efficiency of 90% should be met.
1.4.1 First Flush Diverters: - First flush diverters direct the initial pulse of rainfall
8/13/2019 Planning & Designining Rain Water Harvesting Syst.
16/64
16
away from the storage tank. While leaf screens effectively remove larger debris such as
leaves, twigs, and blooms from harvested rainwater, first flush diverters can be used to
remove smaller contaminants such as dust, pollen, and bird and rodent feces. Simple first
flush diverters require active management, by draining the first flush water volume to a
pervious area following each rainstorm. First flush diverters may be the preferred pretreatment
method if the water is to be used for indoor purposes. A vortex filter (see Figures
3.2.2) may serve as an effective pre-tank filtration device and first flush diverter.
1.4.2 Leaf Screens: - Leaf screens are mesh screens installed over either the gutter or
downspout to separate leaves and other large debris from rooftop runoff. Leaf screens must
be regularly cleaned to be effective; if not maintained, they can become clogged and prevent
rainwater from flowing into the storage tanks. Built-up debris can also harbor bacterial
growth within gutters or downspouts (TWDB, 2005).
1.4.3 Roof Washers: - Roof washers are placed just ahead of storage tanks and are used
to filter small debris from harvested rainwater (see Figure 3.2.3). Roof washers consist of a
tank, usually between 25 and 50 gallons in size, with leaf strainers and a filter with openings
as small as 30-microns. The filter functions to remove very small particulate matter from
harvested rainwater. All roof washers must be cleaned on a regular basis.
8/13/2019 Planning & Designining Rain Water Harvesting Syst.
17/64
17
1.4.4 Vortex Filters: - For large scale applications, vortex filters can provide filtering of
CDA rainwater from larger CDAs.
Rooftop rainwater harvesting at the household level is most commonly used for domestic
purposes. It is popular as a household option as the water source is close to people and thus
requires a minimum of energy to collect it. An added advantage is that users own maintain
and control their system without the need to rely on other community members.
1.5 Criteria for selection of rainwater harvesting technologiesSeveral factors should be considered when selecting rainwater harvesting systems for
domestic use:
Type and size of catchment area
Local rainfall data and weather pattern
Family size
Length of the drought period
Alternative water sources
Cost of the rainwater harvesting system.
When rainwater harvesting is mainly considered for irrigation, several factors should be taken
into consideration.
These include:
rainfall amounts, intensities, and evaporate-transpiration rates
8/13/2019 Planning & Designining Rain Water Harvesting Syst.
18/64
18
soil infiltration rate, water holding capacity, fertility and depth of soil
crop characteristics such as water requirement and length of growing period
hydrogeology of the site
Socio-economic factors such as population density, labour, costs of materials and
regulations governing water resources use.
1.6 Components of a rooftop rainwater harvesting system
Although rainwater can be harvested from many surfaces, rooftop harvesting systems are
most commonly used as the quality of harvested rainwater is usually clean following proper
installation and maintenance. The effective roof area and the material used in constructing the
roof largely influence the efficiency of collection and the water quality.
Rainwater harvesting systems generally consist of four basic elements:
1. A collection (catchment) area
2. A conveyance system consisting of pipes and gutters
3. A storage facility,
8/13/2019 Planning & Designining Rain Water Harvesting Syst.
19/64
19
4. A delivery system consisting of a tap or pump.
1.6.1 A collection or catchment system: - is generally a simple structure such as
roofs and/or gutters that direct rainwater into the storage facility. Roofs are ideal as
catchment areas as they easily collect large volumes of rainwater. The amount and quality of
rainwater collected from a catchment area depends upon the rain intensity, roof surface area,
type of roofing material and the surrounding environment. Roofs should be constructed of
chemically inert materials such as wood, plastic, aluminum, or fiberglass. Roofing materials
that are well suited include slates, clay tiles and concrete tiles. Galvanized corrugated iron
and thatched roofs made from palm leaves are also suitable. Generally, unpainted and
uncoated surface areas are most suitable. If paint is used, it should be non-toxic (no leadbased
paints).
1.6.2 A conveyance system is required to transfer the rainwater from the
roof: - catchment area to the storage system by connecting roof drains (drain pipes) and
piping from the roof top to one or more downspouts that transport the rainwater through a
filter system to the storage tanks. Materials suitable for the pipe work Include polyethylene
(PE) polypropylene (PP) or stainless steel. Before water is stored in a storage tank or cistern,
and prior to use, it should be Filtered to remove particles and debris. The choice of the
filtering system depends on The conditions. Low-maintenance filters with a good filter output
and high Water flow should be preferred. First flush systems whichfilter out the first rain
and diverts it away from the storage tank should be also installed. This will remove the
Contaminants in rainwater which are highest in the first rain shower.
1.7 THE DESIGN CRITERIA OF A SORAGE TANK
1.7.1 Available Space: - Adequate space is needed to house the storage tank and any
overflow. Space limitations are rarely a concern with rainwater harvesting systems if they are
considered during the initial building design and site layout of a residential or commercial
development. Storage tanks can be placed underground, indoors, on rooftops that are
structurally designed to support the added weight, and adjacent to buildings. Designers can
work with architects and landscape architects to creatively site the tanks. Underground
8/13/2019 Planning & Designining Rain Water Harvesting Syst.
20/64
20
utilities or other obstructions should always be identified prior to final determination of the
tank location.
1.7.2 Site Topography: - Site topography and storage tank location should be considered
as they relate to all of the inlet and outlet invert elevations in the rainwater harvesting system.
The final invert of the outlet pipe from the storage tank must match the invert of the receiving
mechanism (e.g. natural channel, storm drain system) that receives this overflow. The
elevation drops associated with the various components of a rainwater harvesting system and
the resulting invert elevations should be considered early in the design, in order to ensure that
the rainwater harvesting system is feasible for the particular site.
Site topography and storage tank location will also affect pumping requirements. Locating
storage tanks in low areas will make it easier to get water into the cisterns; however, it will
increase the amount of pumping needed to distribute the harvested rainwater back into the
building or to irrigated areas situated on higher ground. Conversely, placing storage tanks at
higher elevations may require larger diameter pipes with smaller slopes but will generally
reduce the amount of pumping needed for distribution. It is often best to locate a cistern close
to the building or drainage area, to limit the amount of pipe needed.
1.7.3 Available Hydraulic Head: - The required hydraulic head depends on the
intended use of the water. For residential landscaping uses, the cistern should be sited upgradient
of the landscaping areas or on a raised stand. Pumps are commonly used to convey
stored rainwater to the end use in order to provide the required head. When the water is being
routed from the cistern to the inside of a building for non-potable use, often a pump is used to
feed a much msmaller pressure tank inside the building, which then serves the internal water
demands. Cisterns can also use gravity to accomplish indoor residential uses (e.g. laundry)
that do not require high water pressure.
1.7.4 Water Table: - Underground storage tanks are most appropriate in areas where the
tank can be buried above the water table. The tank should be located in a manner that is not
subject it to flooding. In areas where the tank is to be buried partially below the water table,
8/13/2019 Planning & Designining Rain Water Harvesting Syst.
21/64
21
special design features must be employed, such as sufficiently securing the tank (to keep it from
floating), and conducting buoyancy calculations when the tank is empty. The tank may
need to be secured appropriately with fasteners or weighted to avoid uplift buoyancy. The
tank must also be installed according to the tank manufacturers specifications.
1.7.5 Soil: - Storage tanks should only be placed on native soils or on fill in accordance
with the manufacturer's guidelines. The bearing capacity of the soil upon which the cistern
will be placed must be considered, as full cisterns can be very heavy. This is particularly
important for above-ground cisterns, as significant settling could cause the cistern to lean or
in some cases to potentially topple. A sufficient aggregate, or concrete base, may be
appropriate depending on the soils. The pH of the soil should also be considered in relation to
its interaction with the cistern material.
1.7.6 Proximity of Underground Utilities: - All underground utilities must be taken
into consideration during the design of underground rainwater harvesting systems, treating all
of the rainwater harvesting system components and storm drains as typical storm water
facilities and pipes. The underground utilities must be marked and avoided during the
installation of underground tanks and piping associated with the system.
1.7.7 Contributing Drainage Area: - The contributing drainage area (CDA) to the
cistern is the impervious area draining to the tank. Rooftop surfaces are what typically make
up the CDA, but paved areas and landscaped areas can be used with appropriate treatment
(oil/water separators and/or debris excluders). Areas of any size, including portions of roofs,
can be used based on the sizing guidelines in this design specification. Runoff should be
routed directly from the drainage area to rainwater harvesting systems in closed roof drain
systems or storm drain pipes, avoiding surface drainage, which could allow for increased
contamination of the water.
1.7.8 Water Quality of Rainwater: - Designers should also note that the pH of
rainfall in the District tends to be acidic (ranging from 4.5 to 5.0), which may result in
leaching of metals from roof surfaces, tank lining or water laterals, to interior connections.
8/13/2019 Planning & Designining Rain Water Harvesting Syst.
22/64
22
Once rainfall leaves rooftop surfaces, pH levels tend to be slightly higher, ranging from 5.5 to
6.0. Limestone or other materials may be added in the tank to buffer acidity, if desired.
1.7.9 Hotspot Land Uses: - Harvesting rainwater can be an effective method to prevent
contamination of rooftop runoff that would result from mixing it with ground-level runoff
from a storm water hotspot operation. In some cases, however, industrial roof surfaces may
also be designated as storm water hotspots.
1.7.10 Contributing Drainage Area Material: - The quality of the harvested
rainwater will vary according to the roof material or drainage area over which it flows. Water
harvested from certain types of rooftops and CDAs, such as asphalt sealcoats, tar and gravel,
painted roofs, galvanized metal roofs, sheet metal, or any material that may contain asbestos
may leach trace metals and other toxic compounds. In general, harvesting rainwater from
such surfaces should be avoided. If a sealant or paint roof surface is desired, it is
recommended to use one that has been certified for such purposes by the National Sanitation
Foundation (ANSI/NSF standard).
1.8 Rainwater harvesting in Prem nagar
Location-block number 55, 56, 57
These three blocks are situated behind the prem nagar.
8/13/2019 Planning & Designining Rain Water Harvesting Syst.
23/64
23
Block 55
Block 56
General data about rainfall in prem nagar
8/13/2019 Planning & Designining Rain Water Harvesting Syst.
24/64
24
Area of one block = 1800m^2
Number of Block=03
Now total area =1800*3
=5400 m^2
Annual rainfall depth =.700m
Total number of peoples = 8000(approx)
1.9 Design capacity of storage tank
Total water collection= area *rain fall depth
=5400*0.7= 3780 m^3
Now total amount of water =3780000 liter
There will be 60% of rainfall used for rainwater harvesting= (3780000*60)/100=>2268000 lit
So loss of rain water => 3780000-2268000=1512000 liter
Total number of peoples= 8000
Per capita water demand =15 liter/person/day
Total water demand for drinking => 8000*15= 120000 liter/day
Total water demand for gardening and cleaning purpose =>2268000-120000= 2148000 liter
So total storage tank capacity =3780000 liter
Now we will install the tank in each block = (2268000/3) = 756000 liter
2.1 Rainwater Harvesting Pretreatment Criteria
Pre-filtration is required to keep sediment, leaves, contaminants, and other debris from the
system. Leaf screens and gutter guards meet the minimal requirement for pre-filtration of
small systems, although direct water filtration is preferred. All pre-filtration devices should
be low-maintenance or maintenance-free. The purpose of pre-filtration is to significantly cut
down on maintenance by preventing organic buildup in the tank, thereby decreasing
microbial food.
2.2 Filtration systems and settling tanks
There are a wide variety of systems available for treating water before, during and after
storage .The level of sophistication also varies, from extremely high-tech to very
8/13/2019 Planning & Designining Rain Water Harvesting Syst.
25/64
25
rudimentary. A German company, WISY, have developed an ingenious filter which fits into a
vertical downpipe and acts as both filter and first-flush system. The filter, s cleverly takes in
water through a very fine (~0.20mm) mesh while allowing silt and debris to continue down
the pipe. The efficiency of the filter is over 90%. This filter is commonly used in European
systems The simple trash rack has been used in some systems but this type of filter has a
number of associated problems: firstly it only removes large debris; and secondly the rack
can become clogged easily and requires regular cleaning. The sand-charcoal-stone filter is
often used for filtering rainwater entering a tank. This type of filter is only suitable, however,
where the inflow is slow to moderate, and will soon overflow if the inflow exceeds the rate at
which the water can percolate through the sand. Settling tanks and partitions can be used to
remove silt and other suspended solids from the water. These are usually effective where
used, but add significant additional cost if elaborate techniques are used. Many systems found
in the field real simply on a piece of cloth or fine mosquito mesh to act as the filter (and to
prevent mosquitoes entering the tank). Post storage filtration include such systems as the up
flow sand filter or the twin compartment candle filters commonly found in LDCs .Many
other systems exist and can be found in the appropriate water literature.
8/13/2019 Planning & Designining Rain Water Harvesting Syst.
26/64
26
Water supply by pipe
Rainwater harvesting is one of the most promising alternatives for supplying water in the face
of increasing water scarcity and escalating demand. The pressure on water supplies, increased
environmental impact from large projects and deteriorating water quality, constrain the ability
to meet the demand for freshwater from traditional sources. Rainwater harvesting presents an
opportunity for the augmentation of water supplies allowing t the same time for self-reliance
and sustainability.
2.3 Primary Treatment of Rain Water
Sand Filters
A sand bed filter is a kind of depth filter. Broadly, there are two types of filter for separating
particulate solids from fluids:
Surface filters, where particulates are captured on a permeable surface
Depth filters, where particulates are captured within a porous body of material
In addition, there are passive and active devices for causing solid-liquid separation such as
settling tanks, self-cleaning screen filters, hydro cyclones and centrifuges.
8/13/2019 Planning & Designining Rain Water Harvesting Syst.
27/64
27
There are several kinds of depth filter, some employing fibrous material and others
employing granular materials. Sand bed filters are an example of a granular loose media
depth filter. They are usually used to separate small amounts (
8/13/2019 Planning & Designining Rain Water Harvesting Syst.
28/64
28
Requirements: Buffer solutions pH 4 & 7, Digital pH Meter, Beakers, Conical Flask,
Glass Stirrer, Burette 50 ml, Standard Hydrochloric acid solution 0.001 M, Methyl orange
indicator.
Principle: The original definition of the PH = -log [H] is not exact, & cannot be determined
exactly by electrometric methods. The activity rather than the concentration of an ion
determines the e.m.f of a galvanic cell of the type commonly used to measure PH, hence PH
may be defined as PH = -log OH+
Where OH+ is the activity of the hydrogen ion, but even this quantity, as defined, is not
capable of precise measurement, since any cell of the type
H2, Pt | H+ (unknown) || salt bridge || reference electrode
Used for the measurement inevitably involves a liquid junction potential of more or less
uncertain magnitude.
Measurement of PH by the e.m.f. method gives values corresponding more closely to the
activity than the concentration of hydrogen ion. It can be shown that the PH value is nearly
equal tolog 1.1 OH+, hence
PH = PCH + 0.04
The modern definition of PH is an operational one and is based on the work of standardization
and the recommendation of USNBs. In UPAC definition the difference in PH between two
solutions a std and an unknown at the same temperature with the same reference electrode
and with hydrogen electrodes at the same hydrogen pressure is
PH (X) - PH (S) = EX - ES /2.3026RT/F
Where EX is the emf of the cell
H2, Pt | solution S || 3.5M KCL | reference electrode
& ES is the emf of the cell
Two Helectrode may be replaced by a single glass electrode which is transferred from one
cell to the other. The PH difference thus determined is a pure number. The PH scale is defined
by specifying the nature of the standard solution & assigning a PH value to it.
The modern PH meter is an electronic digital voltmeter, sealed to read PH directly, & may
8/13/2019 Planning & Designining Rain Water Harvesting Syst.
29/64
29
range from a comparatively simple hand-hold instrument, suitable for use in the field to more
elaborate bench models. A PH meter therefore, always includes a control so that with the
electrode assembly placed
In a buffer solution of known PH, the scale reading of the instrument can be adjusted to the
correct value.
If the cell emf is measured over a range of PH, all measurements at the same temp. & if the
readings are then repeated for a series of different temperatures, then on plotting the results as
a series of isothermal curves, we find that at same PH value (PHi) the cell emf is independent
of temp, PHi is called the isopotential PH.
Procedure
Preparation of buffer solutions
1. Dissolve 1 buffer (pH 4 or 7) tab/cap in 50ml Double distilled water taken in a glass
beaker.
2. Transfer the liquid into a 100ml volumetric flask.
8/13/2019 Planning & Designining Rain Water Harvesting Syst.
30/64
30
3. Wash twice the beaker with 20ml of double distilled water and add washings in
volumetric flask.
4. Make up the volume of volumetric flask up to the mark with double distilled water.
Calibration of instrument
1. Switch on & adjust temperature knob at ambient temp and set Calibrate & Slop knob
at mid position. Set instrument at pH mode.
2. Put pH 7 buffer solution below clean, activated & dry pH electrode attached with the
instrument.
3. Adjust the Calibrate knob till reading displays 7.00 & then remove and wash the pH
electrode and gently wipe with tissue paper.
4. Put the pH electrode in pH 4 buffer solution & adjust the slop know till reading
displays 4.00.
5. Now the instrument is calibrated and no any knob is disturbed till end of experiment.
Calculation of pH value
1. Filter the water sample if there is any visible turbidity or precipitate.
2. Put the pH electrode in water sample taken in a beaker & note the reading of display.
3. Repeat the process for 3 times and Note down the average of all 3 values.
Calculation of alkalinity of water sample
1. Fill burette with standard hydrochloric acid (0.001M)
2. Take 100ml filtered water sample in a conical flask and add 1-2 drops of methyl
orange indicator, the color of water becomes yellow.
3. Add drop wise standard HCl to the conical flask & view over white background till
8/13/2019 Planning & Designining Rain Water Harvesting Syst.
31/64
31
color changes from Yellow to Reddish
4. Note the reading & repeat the process for three times.
Observation Table
Calculations
Water sample = HCl Solution
N1 x V1 = N2 x V2
N1 x 100 = 0.001 x 11.0
N1= (0.001 x 11)/100
N1= 0.00011
Result
The value of water sample was recorded 10.04 and the alkalinity (Hydroxyl Ion
Concentration) of given water sample was found to be 0.00011 N.
8/13/2019 Planning & Designining Rain Water Harvesting Syst.
32/64
32
2.5 Experiment-2
Object To determine the turbidity of water sample using coagulant treatment.
Requirements Digital Nephlo Turbidity Meter, Beakers, Conical Flask, Glass Stirrer, 0.1M
Potash Alum soln.
Procedure
Addition of coagulant
1. Add 5.0ml of 0.1M Potash alum solution in 250ml of filtered water sample and stay
for 5 minutes.
2. Shake well the precipitate if formed to make a turbid solute
Calibration of instrument
1. Switch on & adjust NTU range button at 1000 NTU.
2. Put double distilled water in sample tube up to the mark for reference and set the NTU
reading with ZERO calibrate button to 0.00.
3. Replace the blank with Standard 100 NTU Solution and set the NTU reading with
NTU calibrate button to 100.
4. Again replace distilled water followed by standard turbid solution and set 0.00 &
100.0 receptively with corresponding knobs.
8/13/2019 Planning & Designining Rain Water Harvesting Syst.
33/64
33
Calculation of Turbidity
1. Fill the sample tube with coagulant treated water sample.
2. Note down the display reading.
3. Repeat the process for 3 times and Note down the average of all 3 values.
Observation Table
Calculations
Average NTU Value= (212+210+211)/3 = 211
Result
The Turbidity of water sample was found to be 211 NTU
8/13/2019 Planning & Designining Rain Water Harvesting Syst.
34/64
34
2.6 Tertiary Treatment
2.6.1 Disinfection Technologies :- Although there are numerous disinfection
technologies, some of them are more appropriate for home use than others. We recommend
that you consider using a combination of ultraviolet light and chlorine for the following
reasons.
Ultraviolet light (UV) is extremely effective against Cryptosporidium, but high doses are
required to inactivate some viral pathogens. In addition, UV systems do not maintain a
Disinfectant residual in your plumbing system.
Free chlorine is very effective against viruses but is virtually ineffective against
Cryptosporidium. In addition, it is easy to maintain and measure free chlorine residual in your
plumbing system.
If you do not want to maintain a disinfectant residual in your plumbing system, you may want
To consider using ozone as an alternative to UV, Like UV, ozone does not produce a longlasting
residual and will not provide any protection against bacterial regrowth in your
plumbing. However, it is effective against both parasites and viruses. The major reason that
we are not recommending ozone is that there is no ANSI/NSF standard for evaluating the
safety of ozone generators used for potable water applications. If you do decide to use ozone
as your disinfectant, be sure to use an ozone contact vessel that is certified in accordance with
ANSI/NSF Standard 61 requirements.
2.6.2 Storage tank or cistern to store harvested rainwater: - for use when
needed. Depending on the space available these tanks can be constructed above grade, partly
underground, or below grade. They may be constructed as part of the building, or may be
built as a separate unit located some distance away from the building. The storage tank
should be also constructed of an inert material such as reinforced concrete, Ferro cement
(reinforced steel and concrete), fiberglass, polyethylene, or stainless steel, or they could be
made of wood, metal, or earth. The choice of material depends on local availability and
affordability. Various types can be used including cylindrical Ferro cement tanks, mortar jars
(large jar shaped vessels constructed from wire reinforced mortar) and single and battery
8/13/2019 Planning & Designining Rain Water Harvesting Syst.
35/64
35
(interconnected) tanks. Polyethylene tanks are the most common and easiest to clean and
connect to the piping system. Storage tanks must be opaque to inhibit algal growth and
should be located near to the supply and demand points to reduce the distance water is
conveyed. Water flow into the storage tank or cistern is also decisive for the quality of the
cistern water. Calm rainwater inlet will prevent the stirring up of the sediment. Upon leaving
the cistern, the stored water is extracted from the cleanest part of the tank, just below the
surface of the water, using a floating extraction filter. A sloping overflow trap is necessary to
drain away any floating matter and to protect from sewer gases. Storage tanks should be also
kept closed to prevent the entry of insects and other animals.
2.6.3 Delivery system: - which delivers rainwater and it usually includes a small pump, a
Pressure tank and a tap, if delivery by means of simple gravity on site is not feasible.
Disinfection of the harvested rainwater, which includes filtration and/or ozone or UV
disinfection, is necessary if rainwater is to be used as a potable water source.
2.6.4 Storage tanks or reservoirs: - The storage reservoir is usually the most
expensive part of the rainwater harvesting system such that a careful design and construction
is needed. The reservoir must be constructed in such a way that it is durable and watertight
and the collected water does not become contaminated.
All rainwater tank designs should include as a minimum requirement:
1. A solid secure cover
2. A coarse inlet filter
3. An overflow pipe
4. A manhole, sump, and drain to facilitate cleaning
5. An extraction system that does not contaminate the water, e.g. a tap or pump.
8/13/2019 Planning & Designining Rain Water Harvesting Syst.
36/64
36
2.7 Storage reservoirs for domestic rainwater harvesting are classified in
two categories: -
1. Surface or above-ground tanks, most common for roof collection,
2. Sub-surface or underground tanks, common for ground catchment systems.
Materials and design for the walls of sub-surface tanks or cisterns must be able to resist the
soil and soil water pressures from outside when the tank is empty. Tree roots can also damage
the structure below ground. The size of the storage tank needed for a particular application is
mainly determined by the amount of water available for storage (a function of roof size and
local average rainfall), the amount of water likely to be used (a function of occupancy and
use purpose) and the projected length of time without rain (drought period).
3.1 Rain water harvesting techniques
8/13/2019 Planning & Designining Rain Water Harvesting Syst.
37/64
37
There are two main techniques of rain water harvestings.
(1) Storage of rainwater on surface for future use.
(2) Recharge to ground water.
(1) The storage of rain water on surface is a traditional techniques and structures used were
underground tanks, ponds, check dams, weirs etc. Recharge to ground water is a new concept
of rain water harvesting and the structures generally used are: -
Pits: - Recharge pits are constructed for recharging the shallow aquifer. These are
constructed 1 to 2 m, wide and to 3 m. deep which are back filled with boulders, gravels,
coarse sand.
Trenches: - These are constructed when the permeable stream is available at shallow
depth. Trench may be 0.5 to 1 m. wide, 1 to 1.5m. Deep and 10 to 20 m. long depending up
availability of water, these are back filled with filter materials.
Dug wells: - Existing dug wells may be utilized as recharge structure and water should
pass through filter media before putting into dug well.
Hand pumps: - The existing hand pumps may be used for recharging the shallow/deep
aquifers, if the availability of water is limited. Water should pass through filter media before
diverting it into hand pumps.
Recharge wells: - Recharge wells of 100 to 300 mm. diameter are generally constructed
for recharging the deeper aquifers and water is passed through filter media to avoid choking
of recharge wells.
3.2 Urbanization effects on Groundwater Hydrology: -
Increase in water demand
More dependence on ground water use
Over exploitation of ground water
Increase in run-off, decline in well yields and fall in water levels
Reduction in open soil surface area
Reduction in infiltration and deterioration in water quality
3.2.1 Methods of artificial recharge in urban areas: -
Water spreading
8/13/2019 Planning & Designining Rain Water Harvesting Syst.
38/64
38
Recharge through pits, trenches, wells, shafts
Rooftop collection of rainwater
Road top collection of rainwater
Induced recharge from surface water bodies.
3.2.2 Computation of artificial recharge from Roof top rainwater
collection: -
Factors taken for computation.
Roof top area 100 sq .m. for individual house and 500 sq .m. for multi
storied building.
Average annual monsoon rainfall - 780 mm.
Effective annual rainfall contributing to recharge 70% - 550 mm.
3.2.3 Benefits of Artificial Recharge in Urban Areas: -
Improvement in infiltration and reduction in run-off.
8/13/2019 Planning & Designining Rain Water Harvesting Syst.
39/64
39
Improvement in groundwater levels and yields.
Reduces strain on Special Village Panchayats/ Municipal/Municipal Corporation
water supply.
Improvement in groundwater quality.
Estimated quantity of additional recharge from 100 sq. m. roof top area is 55.000
liters.
3.3 How it works
3.3.1 Roof catchments: -
Rainwater can be collected from most forms of roof. Tiled roofs, or roofs sheeted with
corrugated mild steel etc are preferable, since they are the easiest to use and give the cleanest
water. Thatched or palm leafed surfaces are also feasible; although they are difficult to clean
and can often taint the run-off. Asbestos sheeting or lead-painted surfaces should be avoided.
The rainwater is collected in guttering placed around the eaves of the building. Low cost
guttering can be made up from 22 gauge galvanized mild steel sheeting, bent to form a V
and suspended by galvanized wire stitched through the thatch or sheeting.
3.3.2 Section through typical gutter: -
8/13/2019 Planning & Designining Rain Water Harvesting Syst.
40/64
40
The guttering drains to a down-pipe which discharges into a storage tank. The down-pipe
should be made to swivel so that the collection of the first run-off can be run to waste (the
first foul flush), thus preventing accumulated bird droppings, leaves, twigs and other
vegetable matter, as well as dust and debris, from entering the storage tank. Sometimes a
collecting box with a mesh strainer (and sometimes with additional filter media) is used to
prevent the ingress of potential pollutants.
8/13/2019 Planning & Designining Rain Water Harvesting Syst.
41/64
41
Alternatively, a foul flush box, which can be drained separately, may be fitted between the
down-pipe and the storage tank. The run-off from a roof is directly proportional to the
quantity of rainfall and the plan area of the roof. For every one millimeter of rain a square
meter of roof area will yield one litter of water, less evaporation, spillage losses and wind
effects. The guttering and downpipes should be sized so as to be capable of carrying peak
volume of run off; in the tropics this can occur during high intensity storms of short duration.
3.4 harvesting rainwater harnessing life:A noble goal a common responsibility: - Ground water exploitation is
inevitable is Urban areas. But the groundwater potential is getting reduced due to
urbanization resulting in over exploitation. Hence, a strategy to implement the
groundwater recharge, in a major way need to be launched with concerted efforts by
various Governmental and Non-Governmental Agencies and Public at large to build
up the water table and make the groundwater resource, a reliable and sustainable
source for supplementing water supply needs of the urban dwellers.
3.5 Attributes of groundwater:
There is more ground water than surface water.
Ground water is less expensive and economic resource.
Ground water is sustainable and reliable source of water supply.
Ground water is relatively less vulnerable to pollution.
8/13/2019 Planning & Designining Rain Water Harvesting Syst.
42/64
42
Ground water is usually of high bacteriological purity.
Ground water is free of pathogenic organisms.
Ground water needs little treatment before use.
Ground water has no turbidity and color .
Ground water has distinct health advantage as art alternative for lower
sanitary quality surface water.
Ground water is usually universally available.
Ground water resource can be instantly developed and used.
There are no conveyance losses in ground water based supplies.
Ground water has low vulnerability to drought.
Ground water is key to life in arid and semi-arid regions.
Ground water is source of dry weather flow in rivers and streams.
3.5.1 Recharge Shafts: - For recharging the shallow aquifer which is located below
clayey surface, recharge shafts of 0.5 to 3 m. diameter and 10 to 15 m. deep are constructed
and back filled with boulders, gravels & coarse sand.
3.5.2 Lateral shafts with bore wells: - For recharging the upper as well as deeper
aquifers lateral shafts of 1.5 to 2 m. wide & 10 to 30 m. long depending upon availability of
water with one or two bore wells is constructed. The lateral shafts are back filled with
boulders, gravels & coarse sand.
3.5.3 Spreading techniques: - When permeable strata start from top then this technique
is used. Spread the water in streams/Nalas by making check dams, nala bunds, cement plugs,
gabion structures or a percolation pond may be constructed.
3.5.4 First flush and filter screens: -The first rain drains the dust, bird droppings,
leaves, etc. which are found on the roof surface. To prevent these pollutants from entering the
storage tank, the first rainwater containing the debris should be diverted or flushed.
Automatic devices that prevent the first 20-25 liters of runoff from being collected in the
storage tank are recommended. Screens to retain larger debris such as leaves can be installed
8/13/2019 Planning & Designining Rain Water Harvesting Syst.
43/64
43
in the down-pipe or at the tank inlet. The same applies to the collection of rain runoff from a
hard ground surface. In this case, simple gravel-sand filters can be installed at the entrance of
the storage tank to filter the first rain.
3.5.5 Rainwater harvesting efficiency :- The efficiency of rainwater harvesting
depends on the materials used, design and construction, maintenance and the total amount of
rainfall. A commonly used efficiency figure, runoff coefficient, which is the percentage of
precipitation that appears as runoff, is 0.8. For comparison, if cement tiles are used as a
roofing material, the year-round roof runoff coefficient is about 75%, whereas clay tiles
collect usually less than 50% depending on the harvesting technology. Plastic and metal
sheets are best with an efficiency of 80-90%. For effective operation of a rainwater
harvesting system, a well-designed and carefully constructed gutter system is also crucial.
90% or more of the rainwater collected on the roof will be drained to the storage tank if the
gutter and down-pipe system is properly fitted and maintained. Common materials for gutters
and down-pipes are metal and plastic, but also cement-based products, bamboo and wood can
be used.
3.6 Some useful data
Geographical Area : 2662 Sq. km
Blocks : 10 (prem nagar west)
Rural Population as % of Total Population: 52.52%
8/13/2019 Planning & Designining Rain Water Harvesting Syst.
44/64
44
Urban Population as % of Total Population: 47.48%
Prem nagar, the central most city of dehradun is located between 30o 59: 31o 37 north
latitudes and 75o 04 : 75o 57 east longitudes. Total geographical area of the district is 2662
sq.km. Administratively, the district is controlled by dehradun division. . The total population of
8/13/2019 Planning & Designining Rain Water Harvesting Syst.
45/64
45
district was 19,53,508 as per 2001 Census, which constitutes 8.04 % of the total population of
the prem nagar. dehradun district has observed a growth (1991-2001) rate of 18.40 %. Population
density of district is 742 person/sq.km having a literacy rate of 77.91%
4.1 Geomorphology and soils
The district forms a part of Beas Sub basin of Indus basin.The district is part of Bist Doab
Tract, which is inter alluvial plain tons River. Physiographically, the
district is characterised by two distinct features i.e. vast upland plain and Satluj flood plain.
The width of the flood plain varies according to the amount of shift experienced by the river.
It is widest in the dehradunr tehsil. The district is mainly drained by the river tons and dehradun has two
types of
soils viz-tropical arid brown and arid brown soils (solonized). Tropical brown soils are found
In major parts of the district whereas arid brown soils are found in south western part of the
district especially in dehradun .
Type of soil is found.
4.2 Hydrometeorology
Climate of the district can be classified as tropical and dry sub humid. The area receives
normal annual rainfall is about 701 mm which is spread over 35 rainy days. 70% of rainfall
occurs during south-west monsoon.
4.3 Hydrology and surface water utilization
The Bist Doab Canal System is the major source of canal irrigation. The network of dehradun
branch (irrigate northern and central parts) and Phillaur distributary of dehradun branch
((irrigate southern parts of the district). In all there are 41 canals having total length of 604.40
km. of which Best Doab canal is 43 km long. Out of 2,27,423 ha net irrigated area, 26,755 ha
is irrigated by canal and rest by ground water. At present, two irrigation projects are in
operation. One project is for Remodeling of Phillaur distributry system in prem nagar area and
8/13/2019 Planning & Designining Rain Water Harvesting Syst.
46/64
46
other project is for Construction of super passage over Nasrala choe near prem nagar. The main
purpose of the irrigation project is to increase the capacity of the channel by 20% and to
avoid the damages to the crops and adjoining abadies during flood season.
4.4 Agriculture
Net area sown in the district is 2,27,994 ha which constitutes 86% of the total area. Area
sown more than once is 1,85,285 ha bringing the total cropped area (Gross sown area) to
4,13,279 ha. Paddy constitutes main kharif crop whereas the wheat is the main Rabi crop.
Perusal of historical data reveals that the paddy cultivation has increased about 85 times since
1950-51 against wheat cultivation, which has increased only 1.7 times. Average yield of
paddy cultivation has increased from 806 kg/ha to 3588 kg/ha where as wheat crop average
yield has increased from 958 kg/ha to 4925 kg/ha over the period of last 50 years. Thus, it has
given further stress on ground water.
4.5 Hydrogeology
The district is occupied by geological formations of Quaternary age comprising of Recent
alluvial deposits belong to the vast Indus alluvial plains. Central Ground Water Board has
drilled one exploratory borehole and 15 piezometers to delineate and determine potential
aquifer zones, evaluation of aquifer characteristics etc.
Ground water exploration undertaken by CGWB has revealed the presence of 4 sets of
aquifer groups down to a depth of 312 m. These zones
8/13/2019 Planning & Designining Rain Water Harvesting Syst.
47/64
47
8/13/2019 Planning & Designining Rain Water Harvesting Syst.
48/64
48
4.6 Water level behavior
43
Depth to water level in the area ranges from 6.0 to 29.0 m bgl during pre-monsoon period and
is shallow in northern part and deeper in southern part. Deepest water levels are normally
reported from parts of Shahkot block.
8/13/2019 Planning & Designining Rain Water Harvesting Syst.
49/64
49
In major part of the district water level varies between 10 and 15m. Long-term net change of
water levels indicates a general decline (negative change) in the large part of the district and
it is up to 8.18m. The maximum fall is observed in parts of Nakodar and Shahkot blocks.
4.7 Ground water flow
Elevation of the water table in the district varies from 205m to 240m above msea level.
Average gradient of the water table is of the order of 1.08 m/km. Overall flow of ground
water is towards south- west direction.
4.8 Drinking water supply
Entire drinking water supply to all the rural as well as urban sectors of the district is based on
only ground water through deep tube wells drilled down to the depth of 150 m. These tube
wells tap aquifer zones from a depth range of 55 m to 143m. On an average 35m thick aquifer
is tapped for extracting Ground water.
4.9 Tube well irrigation
There are 92,734 shallow tube wells ranging in depth from 25 to 60m and provide irrigation
to 200349 ha area which constitutes about 88.09% of the total irrigated area. Discharge of
these shallow tube wells ranged between 100 and 800 lpm with a drawdown of 1.0 to 3.5m. A
large number of shallow tube wells generally exist in the blocks lying in southern parts and
deep
Tube wells exist only in Shahkot and Lohian blocks of the district. This is primarily due to
occurrence of relatively finer grained sediments in these blocks.
5.1 Designing a rainwater harvesting system
For the design of a rainwater harvesting system, rainfall data is required preferably for a
period of at least 10 years. The more reliable and specific the data is for the location, the
better the design will be. Data for a given area can be obtained at the meteorological
departments, agricultural and hydrological research centers and airports. One simple method
of determining the required storage volume, and consequently the size of the storage tank, is
shown below:
8/13/2019 Planning & Designining Rain Water Harvesting Syst.
50/64
50
With an estimated water consumption of 20 L/C*d, which is the commonly accepted
minimum, the water demand will be = 20 x n x 365 l/year, where n=number of people in the
household. If there are five people in the household then the annual water demand is 36,500
liters or about 3,000 l/month. For a dry period of four months, the required minimum storage
capacity would be about 12,000 litters. As rainwater supply depends on the annual rainfall,
roof surface and the runoff coefficient, the amount of rainwater that can be collected =
rainfall (mm/year) x area (m2) x runoff coefficient.
As an example: a metal sheet roof of 80 m2 with 800 mm rainfall/year will yield = 80
x800x0.8= 51,200 l/year. Demonstrates the cumulative roof runoff (m3) over a one-year
period and the cumulative water demand (m3). The greatest distance between these two lines
gives the required storage volume (m3) to minimize the loss of rainwater.
5.2 Typical domestic RWH systems
5.2.1 Storage tanks and cisterns
The water storage tank usually represents the biggest capital investment element of a
domestic RWH system. It therefore usually requires careful designto provide optimal
storage capacity while keeping the cost as low as possible. The catchment area is usually the
existing rooftop or occasionally a cleaned area of ground , as seen in the courtyard
Collection systems in China ,and guttering can often be obtained relatively cheaply, or can be
manufactured locally.
There are an almost unlimited number of options for storing water. Common vessels used for
very small-scale water storage in developing countries in clued such examples as plastic
Bowl sand buckets, jerry cans, clay or ceramic jars, cement jars, old oil drums, and empty
food Containers, etc. For storing larger quantities of water the system will usually require a
tank or a cistern. For the purpose of this document we will classify the tank as an aboveground
storage vessel and the cistern as a below-ground storage vessel. These can vary in size
from a cubic me tree or so (1000 liters) up to hundreds of cubic meters for large projects, but
typically up to a maximum of 20 or 30 cubic meters for a domestic system. The choice of
8/13/2019 Planning & Designining Rain Water Harvesting Syst.
51/64
51
system will depend on a number of technical and economic considerations silted below.
Space availability
Options available locally
Local traditions for water storage
Costof purchasing new tank
Costof materials and labor for construction
Materials and skills available locally
Ground conditions
Style of RWH-: the system will provide total or partial water supply One of the main
choices will be whether to use a tank or a cistern. Both tanks and cisterns have their
advantages and disadvantages.
8/13/2019 Planning & Designining Rain Water Harvesting Syst.
52/64
52
8/13/2019 Planning & Designining Rain Water Harvesting Syst.
53/64
53
8/13/2019 Planning & Designining Rain Water Harvesting Syst.
54/64
54
5.2.3 Ferro cement tanks
Above ground level, tanks are constructed with a plain or reinforced concrete base,
cylindrical walls of Ferro cement and a roof of Ferro cement, or sometimes mild steel
sheeting. The construction of Ferro cement walls is carried out by first assembling a
cylindrical mesh of chicken wire and/or fence wire reinforcement, with or without the aid of
formwork. On to this, a cement-rich mortar of 3:1 sand: cement is applied by trowel and built
up in layers of about 15 millimeters to a finished thickness of between 30 to 100 millimeters,
depending on wall height and tank diameter. Thicker walls may have two layers of mesh. The
mesh helps to control local cracking and the higher walls may call for the provision of small
diameter vertical steel reinforcing bars for bending resistance. Sometimes barbed fence wire
is wound spirally up the wall to assist with resistance to ring tension and stress distribution.
Effective curing of the mortar between the trowel ling of each layer is very important and
affects the durability of the material and its resistance to cracking. Mortar should be still
green when the next layer is placed. This means that the time gap between layers should be
between 12 and 24hours. The finished material should then be cured continuously for up to
10 days under damp hessian, or other sheeting. A ferrocement tank is easy to repair and, if the
mortar has been properly applied and cured, should provide long service as a water-retaining
structure at a fraction of the cost of a reinforced concrete structure.
5.2.4 Rock catchments
Just as the roofs of buildings can be exploited for the collection of rainwater, so can rock
outcrops be used as collecting surfaces. Indeed, if access to the catchment area by animals,
children etc, can be prevented, a protected catchment can collect water of high quality, as
long as its surfaces are well flushed and cleaned before storage takes place. A significant
proportion of Gibraltars water is obtained from sloping rock catchments on the Rock. At the
foot of the slopes, collecting channels drain into pipes which lead to tanks excavated inside
the rock. Some artificial collection surfaces have also been formed: cracks and voids in rock
surfaces have been filled in and at large, soil covered, sloping area has been covered in
corrugated mild steel sheeting supported on short piles driven into the subsoil. This is a huge
example of what may be possible on a smaller domestic or village scale. Sometimes it proves
difficult to prevent the collected water from being polluted. If so, it is sensible to use this
8/13/2019 Planning & Designining Rain Water Harvesting Syst.
55/64
55
water for purposes that do not require a potable water supply, such as house cleaning,
laundry, horticulture etc, and reserve for drinking water, cooking and personal hygiene the
better quality water which has been collected from a clean roof .Use can also be made of
other forms of ground catchment where, although the collection coefficient can be as low as
30%, useful volumes of water can be collected and used for agriculture and animals.
5.2.5 Cultural acceptability
Rainwater harvesting is an accepted freshwater augmentation technology in many parts of the
world. While the bacteriological quality of rainwater collected from ground catchments is
8/13/2019 Planning & Designining Rain Water Harvesting Syst.
56/64
56
poor, rainwater from properly maintained rooftop catchment systems, which are equipped
with tight storage tanks and taps, is generally suitable for drinking and often meets the WHO
drinking water standards. This water is generally of higher quality than most traditional water
sources found in the developing world. Rooftop catchment of rainwater can provide good
quality water which is clean enough for drinking, as long as the rooftop is clean, impervious
and made from non-toxic materials and located away from over-hanging trees.
5.6 Maintenance
Maintenance is generally limited to the annual cleaning of the tank and regular inspection and
cleaning of gutters and down-pipes. Maintenance typically consists of the removal of dirt,
leaves and other accumulated material. Cleaning should take place annually before the start
of the major rainfall season. Filters in the inlet should be inspected every about three months.
Cracks in storage tanks can create major problems and should be repaired immediately.
5.6.1 Regulations and technical standards
The most important aspect during the construction of a rainwater harvesting system is to
completely separate the rainwater and drinking water networks. All rainwater pipe work and
tapping points should be clearly designated and secured against unauthorized use. In
Germany, the construction of a rainwater harvesting system does not require a building
approval but it is advisable to report it to the local public health office as well as the local
water supplier. Some regulations and standards should be taken into consideration during
construction and maintenance of a rainwater harvesting system
8/13/2019 Planning & Designining Rain Water Harvesting Syst.
57/64
57
(Graphical methode of determine the required storage volume for a rain water)5.6.2 Types of rainwater use
Rainwater systems can be classified according to their reliability, yielding four types of user
regimes:
Occasional - water is stored for only a few days in a small container. This is suitable
when there is a uniform rainfall pattern with very few days without rain and when a
reliable alternative water source is available.
Intermittent - in situations with one long rainy season when all water demands are
met by rainwater. During the dry season, water is collected from other sources.
Partial - rainwater is used throughout the year but the 'harvest' is not sufficient for all
domestic demands. For example, rainwater is used for drinking and cooking, while
for other domestic uses (e.g. bathing and laundry) water from other sources is used.
Full - for the whole year, all water for all domestic purposes comes from rainwater. In
8/13/2019 Planning & Designining Rain Water Harvesting Syst.
58/64
8/13/2019 Planning & Designining Rain Water Harvesting Syst.
59/64
59
5.8 Disadvantages
The main disadvantages of rainwater harvesting technologies are the limited supply and
uncertainty of rainfall. Rainwater is not a reliable water source in times of dry periods or
prolonged drought. Other disadvantages include:
Low storage capacity which will limit rainwater harvesting, whereas, increasing the
storage capacity will add to the construction and operating costs making the
technology less economically feasible
Possible contamination of the rainwater with animal wastes and organic matter which
may result in health risks if rainwater is not treated prior to consumption as a drinking
water source
Leakage from cisterns can cause the deterioration of load-bearing slopes
Cisterns and storage tanks can be unsafe for small children if proper access protection
is not provided.
8/13/2019 Planning & Designining Rain Water Harvesting Syst.
60/64
60
5.9 Effectiveness of technology
The feasibility of rainwater harvesting in a particular locality is highly dependent on the
amount and intensity of rainfall. As rainfall is usually unevenly distributed throughout the
year, rainwater harvesting can usually only serve as a supplementary source of household
water. The viability of rainwater harvesting systems is also a function of the quantity and
quality of water available from other sources, household size, per capita water requirementsand available budget. Accounts of serious illness linked to rainwater supplies are few,
suggesting that rainwater harvesting technologies are effective sources of water supply. It
would appear that the potential for slight contamination of roof runoff from occasional bird
droppings does not represent a major health risk. Nevertheless, placing taps at about 10 cm
above the base of the rainwater storage tanks allows any debris entering the tank to settle on
8/13/2019 Planning & Designining Rain Water Harvesting Syst.
61/64
61
the bottom, where it will not affect the quality of the stored water, provided it remains
undisturbed.
Finally, effective water harvesting schemes require community participation which is
Enhanced by:
sensitivity to peoples needs
indigenous knowledge and local expertise
full participation and consideration of gender issues,
Taking consideration of prevailing farming systems as well as national policies and
community by low
8/13/2019 Planning & Designining Rain Water Harvesting Syst.
62/64
62
Conclusions
The cheap but invaluable natural resource of water in the way of floods have to be effectively stored, to
ensure safety of the people besides more importantly its effective utility for alround development
Rainwater harvesting
With the ever increasing concrete jungles besides metalling of ever increasing road metalling,
Rainwater harvesting is the ultimate method of ensuring ground water table for the benefit of all living
beings on this earth besides its flora and fauna.
8/13/2019 Planning & Designining Rain Water Harvesting Syst.
63/64
63
Bibliography:
Nissen-Petersen E(2007) Water from roofs,Danida
Gould G, Nissen-Petersen E(1999) Rainwater catchment systems,IT
Publications, London
Pacey A, Cullis A(1986) Rainwater harvesting: The collection of rainfall
and run-off in rural areas, IT Publications, London
https://www.rain water harvesting
https://www.Rain water harvesting & overview,
8/13/2019 Planning & Designining Rain Water Harvesting Syst.
64/64