On 04-05-2024: 42.70/120 அடி/Feet
Inflow: 50 கன அடி/Cusecs
Outflow: 500 கன அடி/Cusecs
Available Water: 13.523/93.47 T.M.C
Water Level: Increasing
கட்ட துவங்கிய நாள்: 20.071925
கட்டி முடித்த நாள்: 21.08.1934
கட்டி முடிக்க ஆன செலவு : ரூ.4.80 கோடி
கொள்ளளவு: 93.50 டி.எம்.சி
அதிகபட்ச உயரம்: 214 அடி
அதிகபட்ச அகலம்: 171 கீ.மீ 
சேமிப்பு உயரம்: 120 அடி
நீர்ப்பிடிப்பு பரப்பளவு: 59.25 சதுர மைல்
1 Cusecs=28.317 Liters Per Second
1 T.M.C=28,316,846,592 Liters
மரம் வளர்ப்போம்...!!! மழை பெறுவோம்...!!!

Saturday 9 June 2018

Do You know How to Calculate Dam Water Capacity in Real Time?

1 comment
Do you know how to calculate Dam Water Capacity in Real Time?

Water Measuring Technique

1 liter of water = 1000milli liter water

1 cusecs =?

Cusec is a measure of flow rate and is informal shorthand for "cubic feet per second"(28.317 litres per second).

1 cusec = Flowing or Running 28.37 litre – per second.

1 cusec = 1 கன அடி

How do I calculate 1 TMC water?

TMC refers to “Thousand Million Cubic Feet”.


1 Cubic Feet = 1ft x 1ft x 1ft = 0.3048 m x 0.3048 m x 0.3048 m = 0.02831684 m^3.

Since, 1 m^3 = 1000 litres.

Therefore, 0.0283164 m^3 = 0.0283164 x 1000 = 28.3164 litres.

Also, Thousand = 1000 = 10^3

And, Million = 1000000 = 10^6


1 TMC = 10^3 x 10^6 x 28.3164 = 28.3164 x 10^9 litres of Water.

I cubic feet of water corresponds to 28 litres approximately.

1 thousand million means 1 billion

Hence 1 TMC corresponds to 28 billion litres of water

How To Calculate Dam Water Storage Capacity ?
  • Land managers need to know how much water is stored in their dams to manage water supply for livestock, spraying and other uses.
  • The critical supply period is over summer and autumn when evaporation is high, and demand from livestock, irrigation or household use increases.
  • Knowledge of your dam(s) storage capacity is also required if you plan to develop or expand an existing or new enterprise on the property. This page provides the steps needed to accurately calculate dam capacity and water volume in small farm dams (excavated tanks).
Measuring the dimensions of your dam

With a few tools and some preparation, this method gives a good estimate of dam capacity. You will need:
  • 20–30m of surveyor tape (depending on the size of the dam)
  • lightweight rope — long enough to reach from one side of the dam to the other
  • binoculars
  • an assistant
  • notebook and pencil.
Step 1

Take half the length of rope and make loops every metre. The rope serves 2 purposes: it will support the surveyors tape and is a measuring device. The loops should be large enough to easily thread the tape.

Step 2

Thread the tape through the loops, so the rope can support it for most of the distance across the longest side of the dam. Be careful to avoid twisting the rope and tape, which will prevent the free movement of the tape through the loops.

Step 3

Tie a weight to the end of the tape to help it sink.

Step 4

Ask your assistant to take one end of the rope and walk to the opposite side of the dam. Your end will have the loops and the threaded tape.

Step 5

When in position let out the tape until it hits the bottom of the dam. Read the water depth on the tape at the water surface using the binoculars.

Step 6

Move the equipment and measure the depth again until you find the edge of the deepest part of the dam (the edge of the rectangle/square base). Count how many rope loops are suspended over the water.

Step 7

Repeat the procedure across the dam until you find the edge of the base on the other side — closer to your assistant. Again count the number of loops that are suspended over the water.

The difference in the number of loops suspended over the water from one side of the base to the other will give you the length of the base of the dam.

Step 8

Record the length and depth of the base.

Step 9

Repeat steps 4–8 at right angles to your first measurement line.

You now have measurements for the base of the dam (length and breadth) and the dam depth.

Step 10

Measure the surface dimensions of the water. Pace the length and breadth of the bank at the water surface for rectangular or square dams.

Round dams can be measured by pacing the circumference of the bank at water level. Then divide this distance by 3.142 (π) to calculate the diameter.

Step 11

Insert the figures into the following equations to estimate the current water volume. The equations vary according to the type and shape of the dam.

Calculating full capacity

The full capacity of a dam can be calculated using the dam's dimensions measured earlier.

Step 1

Measure or pace the sides or circumference of the dam at the elevation of the spillway discharge. This gives you the top measurements when the dam is full.

Step 2

Measure the difference in height between the current water surface and the spillway discharge.

Step 3

Add this measurement to the current depth to calculate the water depth when the dam is full.

Step 4

Insert the new measurements into the appropriate equation below to give you the volume of the dam at full capacity.

Volume of a square or rectangular dam

Volume (m3) = [A + B + (√ (A x B)] x D ÷ 3

Where: A = top surface area (m2)

B = base area (m2)

D = depth (m)

Volume of a circular dam

Volume (m3) = 0.2619 x D x [Td2 + Bd2 + (Td x Bd)]

Where: Td = top diameter (m)

Bd = base diameter (m)

Note: diameter = circumference ÷ 3.142

This simple, cheap and quick technique for measuring dam volumes should be added to your armoury of farm management tools to provide you with an early warning of water shortage problems. You also need to monitor the water quality so you know that the water you have is suitable for what you need it for.

Useful Links:

Mettur Dam Water Level Today

Mettur Dam Water Level History

Tourism in Mettur Dam

About Mettur

About Mettur Dam

Mettur Dam History

About Diabetes and Treatments

List of Important Government Websites

How to Increase Bike Mileage

Importance of Insurance

Major Reserviors in Tamilnadu

Tamil units of Measurements

Methods of Rain Water Harvesting

Mettur Park Timings

Arulmigu Padrakali Amman Temple Mecheri

Tourist Places in Mettur

About Dengue Fever

Contact Us


Read More

Tamil Units of Measurements (அளவீட்டு தமிழ் அலகுகள்)


Tamil Measuring Units

Measurements in ancient Tamil land were of seven kinds. They were number counts, balance weights, fluid volumes, grain volumes, length, time and the likeness. Ancient tamils were used only mind-calculation for their daily necessaries. Their life is mixed up with calculation for everything. They have enough tables of units for all kind such as weighing, counting, measuring, etc.,. which is similar to the Indus Valley Civilization. They have fractional tables which includes divisor of 2, 5, 8 & etc.,. 

The Tamil peoples are using still their basic unit of distance measurement called muzham to measure the length of jasmine garland. Ancient tamils also used muzhakkuchi (scale/tape) which is the basic measuring instrument to build a temple or other building. One of the temple which used muzhakkuchi is Tanjore Big Temple from Tamil Nadu, India. 


1 kuzhi(kuRRuzhi) = குழி (குற்றுழி)= 6.66 millisecond-the time taken by the Pleiades stars(aRumin) to glitter once. 

12(base 8) or 10 kuzhigaL= 1 miy= 66.6666 millisecond-the time taken by the young human eyes to flap once. 

2 kaNNimaigaL (கண்ணிமைகள்)= 1 kainodi (கைநொடி)= 0.125 second 

2 kainodi= 1 maatthirai (மாத்திரை) = 0.25 second 

6(base 8) or 6 miygaL= 1 siRRuzhi(nodi) சிற்றுழி (நொடி)= 0.40 second-the time taken for a bubble (created by blowing air through a bamboo tube into a vessel 1 saaN high, full of water) to travel a distance of one saaN (சாண்). 

2 maatthiraigaL= 1 kuru (குறு) = 0.50 second 

2(base 8) or 2 nodigaL= 1 vinaadi வினாடி = 0.80 second-the time for the adult human heart to beat once 

21⁄2 nodigaL= 2 kuru= 1 uyir உயிர் = 1 second 

5 nodigaL= 2 uyir= 1 saNigam சாணிகம் = 1/2 aNu அணு = 2 seconds 

12(base 8) or 10 nodigaL= 1 aNu= 4 seconds 

6(base 8) or 6 aNukkaL= 12 saNigam= 1 thuLi துளி = 1 naazhigai-vinaadi நாழிகை வினாடி = 24 seconds 

12(base 8) or 10 thuLigaL= 1 kaNam கணம் = 4 minutes 

6(base 8) or 6 kaNangaL= 1 naazhigai= 24 minutes 

12(base 8) or 10 naazhigaigaL= 4 saamam சாமம் = 1 siRupozhuthu சிறுபொழுது = 240 minutes= 4 hours 

6(base 8) or 6 siRu-pozhuthugaL= 1 naaL நாள் (1 day)= 24 hours 

7 naaTkaL= 1 kizhamai கிழமை (1 week) 

15 naaTkaL= 1 azhuvam அழுவம் (1 fortnight ) 

29.5 naaTkaL= 1 thingaL திங்கள் (1 lunar month) 

2 thingaL= 1 perum-pozhuthu பெரும்பொழுது (1 season) 

6 perum-pozhuthugaL= 1 AaNdu ஆண்டு (1 year) 

64 aaNdugaL= 1 vattam வட்டம் (1 cycle) 

4096(=8^4) AaNdugaL= 1 Oozhi ஊழி (1 epoch) 


1 Marakkal vaedaipadu (seeds required for planting rice) = 8 cents 

12.5 Marakkal vaedaipadu = 100 cents (one acre) 

Area calculation and Measurement Chart 

1 hectare = 2 acre 47 cent 

1 hectare = 10,000 sq.m. 

1 acre = 0.405 hectare 

1 acre = 4046.82 sq.m. 

1 acre = 43,560 sq.ft. 

1 acre = 100 cent = 4840 sq.gejam 

1 cent = 435.6 sq.ft. 

1 cent = 40.5 sq.m 

1 ground = 222.96 sq.m. = 5.5 cent 

1 ground = 2400 sq.ft. 

1 kuzhi = 10x10 ft. (although some say that 1 kuzhi is approximately equal to 12x12 ft. i.e., 144 sq.ft.) 

1 Mā = 100 kuzhi = 10000 sq.ft. 

1 Kāni = 4 Mā = 40000 sq.ft. 

1 kāni = 92 cents = 0.92 acre 

1 kāni = 400 kuzhi = 40000 sq.ft. 

1 acre = 436 kuzhi 

1 Veļi = 7 kāni = 6.43 acres = 2.6 hectares 

1 dismil =2.5 cent 

1 furlong = 660 feet = 220 kejam 

1 kilometre = 5 furlong 

1 link / chain = 0.66 foot = 7.92 inch 

1 kejam = 9.075 sq.ft. 

1 mile = 8 furlong 

1 ares = 1076 sq.ft. = 2.47 cent 

1 chain = 22 kejam 

1 furlong = 10 chain 

1 kejam = 0.9144 metre 

1 township = 36 sq.mile 

1 sq.mile = 640 acre 

1 cent = 48 kejam 


Balance weights 

Gold weights 

4 nel edai= 1 kunRimaNi 

2 kunRimaNi= 1 manjaadi 

1 manjaadi= 1 paNavedai 

5 paNavedai= 1 kazhanju 

8 paNavedai= 1 varaaganedai 

20 paNavedai= 4 kazhanju = 1 kaqhsu 

80 paNavedai= 16 kazhanju= 4 kaqhsu= 1 palam. 

1.5 Kazhanji = 8 gram or one pown 

Goods weights 

32 kunRimaNi= 1 varaaganedai 

10 varaaganedai= 1 palam 

40 palam= 1 veesai 

1000 palam =1 kaa 

6 veesai= 1 thulaam 

8 veesai= 1 maNangu 

20 maNangu= 1 paaram. 

Grain volume 

1 kuNam= smallest unit of volume 

9 kuNam= 1 mummi 

11 mummi= 1 aNu 

7 aNu=1 immi 

7 immi= 1 uminel 

1 sittigai= 7 uminel 

360 nel= 1 sevidu 

5 sevidu= 1 aazhaakku 

2 aazhaakku= 1 uzhakku 

2 uzhakku= 1 uri 

2 uri= 1 padi 

8 padi= 1 marakkaal(kuRuNi) 

2 marakkaal(kuRuNi)= 1 padhakku 

2 padhakku= 1 thooNi 

5 marakkaal= 1 paRai 

80 paRai= 1 karisai 

96 padi= 1 kalam 

120 padi= 1 pothi(mootai) 

21 marakkal = 1 Kottai 

22 maakaani = 100 gms 

1 padi, = 1800 avarai pods = 12,800 miLagu seeds = 14,400 nel grains = 14,800 payaRu grains = 38,000 arisi grains = 115,200 sesame seeds 

Fluid volume 

5 sevidu= 1 aazhaakku 

2 mahani = 1 aazhakku (arai kal padi) 

2 aazhaakku= 1 uzhakku (Kal padi) 

2 uzhakku= 1 uri (Arai padi) 

2 uri= 1 padi 

8 padi= 1 marakkaal 

2 marakkaal(kuRuNi)= 1 padhakku 

2 padhakku= 1 thooNi 

21 Marakkal = 1 Kottai 


10 koaN= 1 nuNNaNu 

10 nuNNaNU= 1 aNu(atom) 

8 aNu= 1 kathirtthugaL 

8 kathirtthugaL= 1 thusumbu 

8 thusumbu= 1 mayirnuni 

8 mayirnuni= 1 nuNmaNal 

8 nuNmaNal= 1 siRu-kadugu 

8 siRu-kadugu= 1 eL 

8 eL= 1 nel 

8 nel= 1 viral= 8^8 aNu(atom)= 1.9444 centimetre 

12 viral= 1 saaN= 100 immi= 23.3333 centimetre 

2 saaN= 1 muzham= 46.6666 centimetre 

2 muzham= 1 kajam

4 muzham= 1 paagam 

625 paagam= 1 kaadham= 5000 saaN= 1166.66 metres= 1.167 kilometre 


Likeness has attributes of tone, sound, colour and shape for comparison of a given substance with a known standard. 


1= onRu 

10= patthu 

100= nooRu 

1000= aayiram 

10,000= pathaayiram 

100,000= nooRaayiram 

1000,000= meiyiram 

10^9= thoLLunn 

10^12= eegiyam 

10^15= neLai 

10^18= iLanji 

10^20= veLLam 

10^21= aambal 

Tamil texts elaborate the following version: 

1 = ONDRU -one 

10 = PATHU -ten 

100 = NOORU-hundred 

1,000 = AAYIRAM-thousand 

10,000 = PATHAAYIRAM -ten thousand 

100,000 = LATCHAM-hundred thousand 

1,000,000 = PATHU LATCHAM - one million 

10,000,000 = KODI-ten million 

100,000,000 = ARPUTHAM-hundred million 

1,000,000,000 = NIGARPUTHAM- one billion 

10,000,000,000 = KUMBAM-ten billion 

100,000,000,000 = KANAM-hundred billion 

1,000,000,000,000 = KARPAM-one trillion 

10,000,000,000,000 = NIKARPAM -ten trillion 

100,000,000,000,000 = PATHUMAM -hundred trillion 

1,000,000,000,000,000 = SANGGAM -quadrillion 

10,000,000,000,000,000 = VELLAM -ten quadrillion 

100,000,000,000,000,000 = ANNIYAM - 

1,000,000,000,000,000,000 = ARTTAM - 

10,000,000,000,000,000,000 = PARARTTAM - 

100,000,000,000,000,000,000 = POORIYAM - 

1,000,000,000,000,000,000,000 = MUKKODI - 

10,000,000,000,000,000,000,000 = MAHAYUGAM - 


1= onRu 

3/4= mukkaal 

1/2= arai 

1/4= kaal 

1/5= naalumaa 

3/16= moonRu veesam 

3/20= moonRumaa 

1/8= araikkaal 

1/10= irumaa 

1/16= maakaaNi (veesam) 

1/20= orumaa 

3/64= mukkaal veesam 

3/80= mukkaaN 

1/32= araiveesam 

1/40 araimaa 

1/64= kaal veesam 

1/80= kaaNi 

3/320= araikkaaNi munthiri 

1/160= araikkaaNi 

1/320= munthiri 

1/102,400= keezh munthiri 

1/2,150,400= immi 

1/23,654,400= mummi 

1/165,580,800= aNu 

1/1,490,227,200= kuNam 

1/7,451,136,000= pantham 

1/44,706,816,000= paagam 

1/312,947,712,000= vintham 

1/5,320,111,104,000= naagavintham 

1/74,481,555,456,000= sinthai 

1/1,489,631,109,120,000= kathirmunai 

1/59,585,244,364,800,000= kuralvaLaippidi 

1/3,575,114,661,888,000,000= veLLam 

1/357,511,466,188,800,000,000= nuNNmaNl 

1/2,323,824,530,227,200,000,000= thaertthugaL 


1 pal (wooden discs/sea shellots)= (approximately) 0.9 grain 

8 (or 10 base 8) paRkaL =1 senkaaNi (copper/bronze) = 7.2 grains(misinterpretted by Roman accounts as 10 base 10 paRkal =9 grains) 

1/4 senkaaNi =1 kaalkaaNi (copper) =1.8 grains(misinterpretted by Roman accounts as 2.25 grains) 

64 (or 100 base 8) paRkaL = 1 KaaNap-pon a.k.a. Kaasu panam(gold) = 57.6 grains 

1 Roman dinarium was traded on par with 2 KaaNappon plus 1 SenkaaNi(=124 grains). 

18 Ana = 2.5 Rupee, 16 Ana = 1 Rupee, 1 Ana = 3 Thuttu, 1/4 Ana = 3/4 (mukkal) thuttu

Useful Links:

Mettur Dam Water Level Today

Mettur Dam Water Level History

Tourism in Mettur Dam

About Mettur

About Mettur Dam

Mettur Dam History

About Diabetes and Treatments

List of Important Government Websites

How to Increase Bike Mileage

Importance of Insurance

Major Reserviors in Tamilnadu

Tamil units of Measurements

Methods of Rain Water Harvesting

Mettur Park Timings

Arulmigu Padrakali Amman Temple Mecheri

Tourist Places in Mettur

About Dengue Fever

Contact Us


Read More

Tuesday 5 June 2018

Methods of Rainwater Harvesting | How to Save Rain Water

Methods of Rainwater Harvesting

mettur dam water harvestingsystem
Save Rain Water

rain water harvesting methods and tricks
Save Rain Water

Broadly there are two ways of harvesting rainwater
  1. Surface runoff harvesting
  2. Roof top rainwater harvesting
Rainwater harvesting is the collection and storage of rainwater for reuse on-site, rather than allowing it to run off. These stored waters are used for various purposes such as gardening, irrigation etc. Various methods of rainwater harvesting are described in this section.

1. Surface runoff harvesting

In urban area rainwater flows away as surface runoff. This runoff could be caught and used for recharging aquifers by adopting appropriate methods.

2. Rooftop rainwater harvesting

It is a system of catching rainwater where it falls. In rooftop harvesting, the roof becomes the catchments, and the rainwater is collected from the roof of the house/building. It can either be stored in a tank or diverted to artificial recharge system. This method is less expensive and very effective and if implemented properly helps in augmenting the groundwater level of the area.

Rooftop Rainwater Harvesting System

Components of the Rooftop Rainwater Harvesting

The illustrative design of the basic components of roof top rainwater harvesting system is given in the typical schematic diagram shown in Fig 1.

best rain water harvesting methods and technique
Fig 1: Components of Rainwater Harvesting

The system mainly constitutes of following sub components:
  • Catchments
  • Transportation
  • First flush
  • Filter

The surface that receives rainfall directly is the catchment of rainwater harvesting system. It may be terrace, courtyard, or paved or unpaved open ground. The terrace may be flat RCC/stone roof or sloping roof. Therefore the catchment is the area, which actually contributes rainwater to the harvesting system.


Rainwater from rooftop should be carried through down take water pipes or drains to storage/harvesting system. Water pipes should be UV resistant (ISI HDPE/PVC pipes) of required capacity. Water from sloping roofs could be caught through gutters and down take pipe. At terraces, mouth of the each drain should have wire mesh to restrict floating material.

First Flush

First flush is a device used to flush off the water received in first shower. The first shower of rains needs to be flushed-off to avoid contaminating storable/rechargeable water by the probable contaminants of the atmosphere and the catchment roof. It will also help in cleaning of silt and other material deposited on roof during dry seasons Provisions of first rain separator should be made at outlet of each drainpipe.


There is always some skepticism regarding Roof Top Rainwater Harvesting since doubts are raised that rainwater may contaminate groundwater. There is remote possibility of this fear coming true if proper filter mechanism is not adopted.

Secondly all care must be taken to see that underground sewer drains are not punctured and no leakage is taking place in close vicinity.

Filters are used for treatment of water to effectively remove turbidity, colour and microorganisms. After first flushing of rainfall, water should pass through filters. A gravel, sand and ‘netlon’ mesh filter is designed and placed on top of the storage tank. This filter is very important in keeping the rainwater in the storage tank clean. It removes silt, dust, leaves and other organic matter from entering the storage tank.

The filter media should be cleaned daily after every rainfall event. Clogged filters prevent rainwater from easily entering the storage tank and the filter may overflow. The sand or gravel media should be taken out and washed before it is replaced in the filter.

A typical photograph of filter is shown in Fig 2.
how to save rain water during raining season
Fig 2: Photograph of Typical Filter in Rainwater Harvesting

There are different types of filters in practice, but basic function is to purify water. Different types of filters are described in this section.

Sand Gravel Filter

These are commonly used filters, constructed by brick masonry and filleted by pebbles, gravel, and sand as shown in the figure. Each layer should be separated by wire mesh. A typical figure of Sand Gravel Filter is shown in Fig 3.
use of rain water harvesting methods
Fig 3: Sand Gravel Filter

Charcoal Filter

Charcoal filter can be made in-situ or in a drum. Pebbles, gravel, sand and charcoal as shown in the figure should fill the drum or chamber. Each layer should be separated by wire mesh. Thin layer of charcoal is used to absorb odor if any. A schematic diagram of Charcoal filter is indicated in Fig 4.
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Fig 4: Charcoal Filter

PVC –Pipe filter

This filter can be made by PVC pipe of 1 to 1.20 m length; Diameter of pipe depends on the area of roof. Six inches dia. pipe is enough for a 1500 Sq. Ft. roof and 8 inches dia. pipe should be used for roofs more than 1500 Sq. Ft. Pipe is divided into three compartments by wire mesh.

Each component should be filled with gravel and sand alternatively as shown in the figure. A layer of charcoal could also be inserted between two layers. Both ends of filter should have reduce of required size to connect inlet and outlet. This filter could be placed horizontally or vertically in the system. A schematic pipe filter is shown in Fig 5.
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Fig 5: PVC-Pipe filter

Sponge Filter

It is a simple filter made from PVC drum having a layer of sponge in the middle of drum. It is the easiest and cheapest form filter, suitable for residential units. A typical figure of sponge filter is shown in Fig 6.
save rain water by rain water harvesting methods
Fig 6: Sponge Filter

Methods of Rooftop Rainwater Harvesting

Various methods of using roof top rainwater harvesting are illustrated in this section.

a) Storage of Direct Use

In this method rainwater collected from the roof of the building is diverted to a storage tank. The storage tank has to be designed according to the water requirements, rainfall and catchment availability.

Each drainpipe should have mesh filter at mouth and first flush device followed by filtration system before connecting to the storage tank. It is advisable that each tank should have excess water over flow system.

Excess water could be diverted to recharge system. Water from storage tank can be used for secondary purposes such as washing and gardening etc. This is the most cost effective way of rainwater harvesting.

The main advantage of collecting and using the rainwater during rainy season is not only to save water from conventional sources, but also to save energy incurred on transportation and distribution of water at the doorstep. This also conserves groundwater, if it is being extracted to meet the demand when rains are on. A typical fig of storage tank is shown in Fig 7.
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Fig 7: A storage tank on a platform painted white

b) Recharging groundwater aquifers

Groundwater aquifers can be recharged by various kinds of structures to ensure percolation of rainwater in the ground instead of draining away from the surface. Commonly used recharging methods are:-

a) Recharging of bore wells

b) Recharging of dug wells.

c) Recharge pits

d) Recharge Trenches

e) Soakaways or Recharge Shafts

f) Percolation Tanks

c) Recharging of bore wells

Rainwater collected from rooftop of the building is diverted through drainpipes to settlement or filtration tank. After settlement filtered water is diverted to bore wells to recharge deep aquifers. Abandoned bore wells can also be used for recharge.

Optimum capacity of settlement tank/filtration tank can be designed on the basis of area of catchment, intensity of rainfall and recharge rate. While recharging, entry of floating matter and silt should be restricted because it may clog the recharge structure.

First one or two shower should be flushed out through rain separator to avoid contamination. A schematic diagram of filtration tank recharging to bore well is indicated in Fig 8 .
how to measure rain water harvesting quadity
Fig 8 :Filtration tank recharging to bore well

d) Recharge pits

Recharge pits are small pits of any shape rectangular, square or circular, contracted with brick or stone masonry wall with weep hole at regular intervals. Top of pit can be covered with perforated covers. Bottom of pit should be filled with filter media.

The capacity of the pit can be designed on the basis of catchment area, rainfall intensity and recharge rate of soil. Usually the dimensions of the pit may be of 1 to 2 m width and 2 to 3 m deep depending on the depth of pervious strata.

These pits are suitable for recharging of shallow aquifers, and small houses. A schematic diagram of recharge pit is shown in Fig 9.
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Fig 9: Recharge pit

e) Soakway or Recharge shafts

Soak away or recharge shafts are provided where upper layer of soil is alluvial or less pervious. These are bored hole of 30 cm dia. up to 10 to 15 m deep, depending on depth of pervious layer. Bore should be lined with slotted/perforated PVC/MS pipe to prevent collapse of the vertical sides.

At the top of soak away required size sump is constructed to retain runoff before the filters through soak away. Sump should be filled with filter media. A schematic diagram of recharge shaft is shown in Fig 10
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Fig 10 : Schematic Diagram of Recharge shaft

f) Recharging of dug wells

Dug well can be used as recharge structure. Rainwater from the rooftop is diverted to dug wells after passing it through filtration bed. Cleaning and desalting of dug well should be done regularly to enhance the recharge rate. The filtration method suggested for bore well recharging could be used. A schematic diagram of recharging into dug well is indicated in Fig 11 shown below.
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Fig 11: Schematic diagram of recharging to dug well

g)Recharge trenches

Recharge trench in provided where upper impervious layer of soil is shallow. It is a trench excavated on the ground and refilled with porous media like pebbles, boulder or brickbats. it is usually made for harvesting the surface runoff.

Bore wells can also be provided inside the trench as recharge shafts to enhance percolation. The length of the trench is decided as per the amount of runoff expected.

This method is suitable for small houses, playgrounds, parks and roadside drains. The recharge trench can be of size 0.50 to 1.0 m wide and 1.0 to 1.5 m deep. A schematic diagram of recharging to trenches is shown in Fig below 12.
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Fig 12: Recharging to trenches

h) Percolation tank

Percolation tanks are artificially created surface water bodies, submerging a land area with adequate permeability to facilitate sufficient percolation to recharge the groundwater. These can be built in big campuses where land is available and topography is suitable.

Surface runoff and roof top water can be diverted to this tank. Water accumulating in the tank percolates in the solid to augment the groundwater. The stored water can be used directly for gardening and raw use. Percolation tanks should be built in gardens, open spaces and roadside greenbelts of urban area.

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