RAIN WATER CONSERVATION

&

HARVESTING

R.N. Yadav, SDE (BS-C), 9412739253 (M)

E-mail ID: yadavrn68@gmail.com

• Rakhiyo – To Protect

• Soon – Empty

• Ubre – Not Survive

• Moti – Pearl

Rain Water Conservation & Harvesting

jfgeu ikuh jkf[k;¨] fcu ikuh lCk lwuA

ikuh Xk;s u mCkjs] e¨rh ekul PkwuAA

• Rahiman Pani Rakhiyo, Bin Pani Sab Soon

• Paani Gaye Na Ubre, Moti Maanas Choon.

• Rakhiyo – To Protect

• Soon – Empty

• Ubre – Not Survive

• Moti – Pearl

• Manas – Man

Rain Water Conservation & Harvesting

jfgeu ikuh jkf[k;¨] fcu ikuh lCk lwuA

ikuh Xk;s u mCkjs] e¨rh ekul PkwuAA

• Next to air, water is the only other resource in the nature which sustains life on

Earth. If we cannot live without air for more than a few minute, we cannot live

without water form more than a few hours. Life without water is impossible, with

scare water extremely hard and with abundant water a blessing. In recognition of

this fact Nature has covered two-third of our planet with water, but rapid

industrialization leading to its indiscriminate use has already made it a scarce

commodity which is getting scarcer day by day.

• Indiscriminate mining of water due to rapid industrialization as led to its acute

shortage at an alarming rate.

• Although our country has been blessed with an above average rain fall, the

availability of water has become scarcer over the years.

• Lowering of water table leading to drying up of bore wells has become common

occurrence.

• Government of India has since undertaken a number of steps aimed at preventing

its excessive mining and harvesting and conservation. Ministry of water

resources has voiced its concern vide his D.O. No. 11-2-2000-GW-II dated May

17, 2001 address to secretary department of telecommunication suggesting

various measures of water harvesting. In pursuance of the same Dr. D.P.S.Seth,

the then CMD, vide his D.O. No. 4859/CMD (BSNL)/2001 dated June 21, 2001

issued direction to “- -Take up roof top rain water harvesting in our own building

in including residential area”, with this single step begin the journey of a thousand

miles in search of water solution.

Rain water harvesting is the technique of collection and storage of rain water of

surface or in sub-surface aquifer by recharging it for future requirement so that it

is not lost as surface run-off. Rain water is the purest form of raw water available

on the earth. In fact the total freshwater available on earth is only 3% as against

97% saline water in Oceans. Out of this 3% fresh water, 77% water is in the form

of glaciers and icecaps, 11% water is in deep aquifers which is 800 meters below

ground and only 12% is available for drinking and other purpose out of which

11% is in acquires which are up to 800 meters below ground and remaining 1% is

available in rivers, lakes, ponds and streams

The solution of drinking water problem of the vast majority of population in our country

lies in the appropriate use of Rain water harvested through roof and from built up

catchments where annual rainfall is sufficient. It has been estimated that the amount of

rain water that falls on the terrace of a medium house can take care of the drinking-

water requirement of an average family of four members for one year.

3%

97%

Fresh water

saline water

77%

11%

11%

1%

Glaciers 77%

Deep Aquifers>800 m 11% Deep Aquifers<800 m 11% rivers, ponds, streams 1%

Advantages of Rainwater Harvesting:

• Conservation of valuable ground water and enhancing the availability.

• Recharge ground water level and improve it.

• Provides sufficient water for home needs

• Reduction in flooding and drainage problems.

• To arrest seawater ingress.

• Conserve urban water waste.

• Controls soil erosion.

• Improves the underground water quality.

• Saves the energy for lifting ground water.

Rainwater Harvesting Systems:

• There are basically two main techniques for harvesting rainwater:

• Conservation by providing storage tank on the ground or underground and

recharge of aquifer. A rain water harvesting structure can incorporate either of

these two techniques or a combination of both depending upon various factors as

shown below.

RAIN WATER HARVESTING

SYSTEMS

CONSERVATION

GROUND WATER

RECHARGE

STORAGE

TANK

CHECK

DAMS

LAKES &

PONDS

CONSERVATION

& RECHARGE

RECHARGE

PIT

RECHRGE

TRENCH

RECHARGE

SHAFT

RECHARGE

BORE WELL

DUG

WELL

CAVITY

WELL

HAND

PUMP

Conservation of rainwater by storing it on the surface is a traditional technique and

structure used are storage tanks, ponds, check dams, weirs etc. while recharging is a new

concept of rainwater harvesting.

Methods of Rainwater Harvesting:

• In houses and flat complexes rainwater falls on both the

• Terrace as well as on the open area all around.

• It is this water which will have to be led into the ground

• wherever possible, this can broadly be done in two ways:-

1) Direct the terrace rainwater drain pipes directly into open wells through a filter

tank.

2) Direct these pipes to percolation / absorption pits and wells constructed

specifically for this purpose.

• A similar thing will have to be done for the water falling on the open area

around.

A. Percolation/Absorptions Pit

A percolation/absorption pit is a hand bore made in the soil with the help of an

augur and filled up with pebbles and river sand on top. The depth of these pits will be

anywhere between 4 and 8 meters depending on the nature of the soil if the soil is clayey

the pit has to be dug to a depth till a reasonably sandy stratum is reached. These pits will

be 25 cm. (10 in.) A square/ circular collection chamber with still arrestor is provided at

the top.

B. Percolation/Absorption Well

These wells are constructed using cement rings readily available in the market.

The diameter of these rings from 2ft.to 6 ft. the depth to which these wells are dug

depends on the nature of the soil and the diameter depends on the number of roof top

pipes that are likely to be connected to each one of these wells. These wells are left

unfilled and are covered with RCC slabs of suitable thickness to facilitate free pedestrian

and vehicular movement on the ground

C. Percolation Well cum Borepit (for clayey soil)

In areas where the soil is likely to be clayey up to say 15 ft.and more, it is

advisable to go in for a percolation well up to 10 ft or 15 ft. and a hand bore pit within

this well up to a depth of 10 ft to 15 ft. from its bottom. A PVC pipe of 6 in. diameter is

inserted into the bore for the entire length.

• There are different structure for rain water harvesting which singly or in

combination with structures are employed depending upon various factors as

described below:

1. Recharge Pit

• It is suitable for areas where sandy formations occur within 1-2m from the ground

surface.

• This is ideally suited for small buildings up to 100 sq. m roof top area.

• It can be circular, square or rectangular in shape.

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

• After excavation the pits are refilled with pebbles and boulders.

2. Recharge Trench

• It is suitable when permeable strata of adequate thickness are available at shallow

depth and the roof area of the building is 200-300sqm.

• Recharge trench can be of any dimensions. Generally it is 1-1.5m deep, 0.5-1m

wide and of any length depending upon the availability of water to be recharged.

• Recharge trench can be straight, zig-zag, L-shaped, U shaped.

• The recharge trench should be filled with filter media which can grade from

boulders (5-20cm) at the top for filtration of water.

• The sides of the trench should slope at low angle for stability.

3. Recharge Shaft:

• This is the most efficient and cost effective technique to recharge unconfined

aquifer overlain by poorly permeable strata.

• This is like an open well but filled with filter media.

• Diameter of the shaft generally varies from 1-3m depending upon the availability

of the water to be recharged.

• It is constructed where the aquifer to e recharged is located at medium depth.

• The recharge shaft end in permeable strata to be recharged. It may not touch the

water table.

• In the upper portion of 1-2m depth, the brick masonry work carried out for the

stability of the structure.

4. Dug Well:

• Dug wells may be utilized as recharge structure after cleaning & desilting the

same.

• A filtration chamber may be constructed so that the water can be made silt free

before entering the dug well.

• The recharge water is guided through a pie to the bottom of the dug well and it is

converted into dug-cum-bore well.

• It is suitable for large buildings preferably having the roof area more than

1000sqm from where the rain water can be diverted and recharged.

• Periodic chlorination should be done for controlling the bacteriological

contaminations.

5. Recharge/Injection Well:

• This is used to recharge deep aquifer or where multiple aquifers are met

interspersed with impervious strata.

• In case of recharge well single diameter pipe assembly is used and it should have

the provision of slotted pipes against the water bearing strata.

• The rainwater is allowed to pass through the filter media before it is channeled to

the well under gravity flow conditions.

• The number of recharging wells depends upon the roof top area and aquifer

characteristics.

6. Abandoned Tube wells/Hands Pumps:

• These water abstraction structures act as good recharge structure.

• The hand pump is suitable for small building having roof area up to 150sqm.

• Water is diverted from the roof top to the hand pump through pipe of 100 mm dia.

7. Cavity Wells:

• Cavity wells in use also form good recharge structures.

• Cavity wells are constructed by drilling boreholes with hand boring and pipes are

driven up to the bottom of the clayey bed.

• Cavity is formed within the underlying sand bed with the help of the high capacity

pumps.

• Filter/screen is not used in these wells and the bottom of the pipe is not closed but

kept open for entering water.

• The filtered water is recharged under gravity through these wells.

• Cavity well can be constructed in the areas where overlying aquifer layer to be

charged is hard and plastic in nature.

• The recharge capacity of the cavity well is generally 5 to 10 liters/Sec.

• It is cheap structure compared to recharge well.

• The water to be recharged should be silt free.

• The cavity should be developed periodically whenever it is found that the

recharge capacity is reduced.

• It can be used as pumping well.

8. Contour Bunds:

• These are suitable in low rainfall areas where monsoon runoff can be impounded

by constructing bunds on the sloping ground all along the contour of equal

elevation.

• Flowing water is intercepted before it attains the erosive velocity by keeping

suitable spacing between the bunds.

• Spacing between the two contour bunds depends on the slope of the area as well

as the permeability of soil.

• Contour bunds are suitable on lands with moderate slopes without involving

terracing.

• Contour bunds are effective methods to conserve soil moisture in watershed for

long duration.

9. Rainwater Harvesting in Individual Houses

Dig a number of 3 to 6 meter deep and 30 cm diameter -percolation pits at 3 meter

intervals all around the house. Lead the terrace pipes into the open well if any, through a

60cm x 60cm x 60cm filter (filled with pebbles) under the ground level.

Rain Water Harvesting Methods

10. Rainwater Harvesting in a Flat Complex (Service Well cum Recharge Well

Method)

Utilize the open well if any within the complex to divert the rainwater from the

terrace into it. If not, construct a well for this purpose. The rainwater falling on the open

space around the complex can be collected near the gate by providing a gutter with

perforated lid. The collected water can be led through necessary piping arrangements into

a recharge well of 1 meter diameter and 5 meter deep.

Maintenance of Rain Water Harvesting Systems

The key to satisfactory performance of a RWH system lies in its periodic

maintenance. If not maintained properly, the system may not only not work at all but or

silting of drains etc. which will have to be tackled on emergent basis. As such a RWHS

should be provided only when its periodic maintenance can be ensured.

Expenditure on maintenance of RWHS may be booked under maintenance head

as there is no need for submitting the estimate for obtaining A/ A & E/ S.

imple measure given below so a long way for a trouble free service for RWHS.

1. It is desirable to preclude first shower from the RWHS as it as known a contain

pollutants from the atmosphere and excessive silt.

2. All terrace and drains may be cleaned before the onset on the monsoon.

3. Filter may be removed and washed with clean water in a drum and placed back.

This may be before monsoon or more frequently as per the requirement.

4. Silt collected in the buffer/storage tank or sedimentation tank may be removed

prior to monsoon.

5. Bore well may also be developed before monsoon as silt and fine sand present in

runoff may clog the gravel and the aquifer immediately surrounding the screen. If

development operation is to be effective, it must cause reversal of flow through

the screen opening of the formation immediately around the well. Development

may be done every alternate year before monsoon or less frequently as per the

need. Date of development as well as annual maintenance may be displayed on

the parapet of the buffer tank.

6. Reading water table should be recorded before and after the monsoon.

Glossary of Terms

1. Aquifer/Ground water aquifer: Any underground formation of soil or rack which

can yield water.

2. Artificial recharge: Any man scheme or facility that adds water to an aquifer.

3. Bore well: small diameter wells which are generally deeper than open well.

4. Dug Wells: large diameter pits excavated in the ground until water table is

reached.

5. Ground Water: The water retained in the inter-granular pores of the soil or

fissures of rock below the water table.

6. Runoff: water that flows away from a surface after falling on the surface in the

form of rain.

7. Recharge: the process of surface water joining the ground water aquifer.

8. Water Table: The level of water within the granular pores of the soil or fissures of

rock below which the pores of the host are saturated.

9. Buffer tank/Storage Tank: Tank used for storing of rain water. Storage tanks can

be of any size, shape and capacity depending upon requirement.

10. Sedimentation tank: A tank is used to settle down/retain the impurities of water.

11. Detention Period: Period for which the water is retained in a sedimentation tank.

12. Rate of infiltration: The speed by which the water is absorbed by the natural

soil/earth.

13. Rainfall Intensity: Rainfall intensity is the rate fall measured in mm per hour in

any particular area.

14. Peak rainfall intensity/Peak flow: The maximum intensity of rain fall in any

particular area which lasts for a very short period and given a peak flow of water.

15. Rain Water Harvesting Structure: The whole system fabricated/Constructed for

rain water harvesting is termed as Rain Water Harvesting structure.

16. Permeable Strata: A strata through which water can pass. It depends upon the size

of the voids and uniformity coefficient of the particles in the strata.

17. Filter Media: A media consisting of granular particles, which retains the

impurities of water when passed through it.

18. Catchment Area: A small piece of land which collects the surface runoff and

produces a stream flowing through its deepest through it.

19. Well Screen/ Strainer: Screens/strainers are long slotted pipes fitted at proper

elevation according to the depth of the water bearing strata. They allow the

ground water to enter into the well but not the sand or silt around. They are made

of brass, iron, copper, galvanized iron or steel, various alloys and concrete.

20. Injection Well: Used to recharge deep aquifer or water multiple aquifers are met.

• Cost of Rain water Harvesting

The cost of implementation of rainwater harvesting systems in a house/flat complex

will vary from Rs.5000 - Rs.50, 000 depending on the size of the premises as well the

nature of the soil. Once put in place, the harvesting structure does not require any

serious maintenance and hence there is no recurring expenditure involved.

QQuueessttiioonnss::--

1. What is Rain Water Harvesting? Please elaborate.

2. Describe various rain water harvesting systems?

3. List the advantages of rain water harvesting.

4. Describe in brief Injection Well Method of RWH.

5. What is Aquifer? What are its characteristics?

6. What do you understand by Run off?

7. Describe the ground water recharge systems.

8. Explain the recharge pit.

9. What is water table?

10. Explain the injection well for Rain Water Harvesting system.