RAIN WATER HARVESTING

BySANJAY SINGH

CIVIL ENGINEERING

WHAT IS RAINWATER HARVESTING ?

RAINWATER HARVESTING IS AN INNOVATIVE ALTERNATIVE WATER SUPPLY APPROACH ANYONE CAN USE. RAINWATER HARVESTING CAPTURES, DIVERTS, AND STORES RAINWATER FOR LATER USE

Process of Rainwater Harvesting• Rainwater harvesting is a way of

catching rain, filtering it, and using it for drinking and non-drinking purposes

Type of Rain water Harvesting

Type of rain water harvesting

Rooftop Rainwater Harvesting

Underground System

Advantages

• Rainwater harvesting provides an independent water supply during regional water restrictions and in developed countries is often used to supplement the main supply.

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Advantages

It provides water when there is a drought, prevents flooding of low-lying

areas, replenishes the ground water table, and enables dug wells and bore wells to yield in a sustained manner. It also helps in the availability of clean

water by reducing the salinity and the presence of iron salts.

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Advantages

• Makes use of a natural resource and reduces flooding, storm water runoff, erosion, and contamination of surface water with pesticides, sediment, metals, and fertilizers

•Promotes both water and energy conservation•No filtration system required for landscape irrigation

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Advantages

•Excellent source of water for landscape irrigation, with no chemicals such as fluoride and chlorine, and no dissolved salts and minerals from the

soil.•Home systems can be relatively

simple to install and operate and it may reduce your water bill.

Quality•The concentration of contaminants is reduced significantly by diverting the initial flow of runoff water to waste.• Improved water quality can also be obtained by using a floating draw-off mechanism (rather than from the base of the tank) and by using a series of tanks, with draw from the last in series. The stored rainwater may need to be analyzed properly before use in a way appropriate to its safety.

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Quality

The quality of collected rainwater is generally better than that of 

surface water. Contamination is always possible by airborne dust and mists, bird feces, and other debris, so some treatment is necessary,

depending on how the water will be used.

System setupRainwater harvesting systems can be

installed with minimal skills The system should be sized to meet the water demand throughout the dry season since it must be

big enough to support daily water consumption. Specifically, the rainfall

capturing area such as a building roof must be large enough to maintain adequate flow. Likewise, the water storage tank should be large enough to contain the captured water

Present day RWH in india

In the state of Tamil Nadu, rainwater harvesting was made compulsory for every building to avoid ground water depletion. It proved excellent results

within five years, and every other state took it as role model. Since its implementation, Chennai saw a 50 percent rise in water level in five

years and the water quality significantly improved

Present day RWH in india

In Rajasthan, rainwater harvesting has traditionally

been practiced by the people of the Thar Desert. There are

many ancient water harvesting systems in Rajasthan, which

have now been revived Kerala

Present day RWH in india•At present, in Pune (in Maharashtra), rainwater harvesting is compulsory for any new society to be registered•An attempt has been made at Dept. of Chemical Engineering, IISc, Bangalore to harvest rainwater using upper surface of a solar still, which was used for water distillation

Harvested Rainwater Application

• Residential/Small Commercial

• Multi-family Residential

• Commercial/Industrial

Residential/Small Commercial

Large Commercial/Industrial

RECHARGECOOLINGCAR WASHING

FOUNTAINSIRRIGATION

RECHARGECOOLINGCAR WASHING

FOUNTAINSIRRIGATION

ComponentsVortex Filters for fine filtration and oxygenation

Floating Filter takes the cleanestwater

Smoothing Inlet stable sedimentationand oxygenation

Multifunction overflowfor a clean water surfaceprotects water quality

Harvesting SystemBroadly rainwater can be harvested for two purposes• Storing rainwater for ready use in containers above or below ground 

• Charged into the soil for withdrawal later (groundwater recharging)

                                                                                

            

                                                                                

            

Source: A Water Harvesting Manual For Urban Areas

RAIN WATER HARVESTING TECHNIQUES :

There are two main techniques of rain water harvestings.

• Storage of rainwater on surface for future use.

• Recharge to ground water.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 stram 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 utilised 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.

Recharge Shafts :- For recharging the shallow aquifer which are 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.

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 are constructed. The lateral shafts is back filled with boulders, gravels & coarse sand.

Reasons of Shortage of Water

• Population increase• Industrialization• Urbanization

(a) Increase in per capita utilization(b) Less peculation area

• In places where rain fed/ irrigation based crops are cultivated through ground water

• Decrease in surface area of Lakes, talab, tanks etc.

Reasons of Shotrage of Water• Deforestation(i) Less precipitation(ii) Absence of Barriers

(a) Rain drops checked by leaves of tree

(b) Water slowly descends through twigs & trunk

© Humus – acts as reservoir(d) Tiny creatures – helps percolation

1 hectare of forest-6-7 Lac ton of water

(after filtering) top layer can hold 1.2 Lac tons of water

What is the solution ?

• Rain water is the ultimate source of fresh water

• Potential of rain to meet water demand is tremendous

• Rain water harvesting helps to overcome water scarcity

• To conserve ground water the aquifers must be recharged with rain water

• Rain water harvesting is the ultimate answer

Why Rain water be harvested• To conserve & augment the

storage of ground water• To reduce water table

depletion• To improve the quality of

ground water • To arrest sea water intrusion

in coastal areas • To avoid flood & water

stagnation in urban areas

What is rain water harvesting ?

• It is the activity of direct collection of rain water

• Rain water can be stored for direct use or can be recharged into the ground water aquifer

Rain Water Harvesting?. • Rain Water Harvesting RWH- process of collecting,

conveying & storing water from rainfall in an area – for beneficial use.

• Storage – in tanks, reservoirs, underground storage- groundwater

• Hydrological Cycle

Rain Water Harvesting?.

• RWH - yield copious amounts of water. For an average rainfall of 1,000mm, approximately four million litres of rainwater can be collected in a year in an acre of land (4,047 m2), post-evaporation.

• As RWH - neither energy-intensive nor labour-intensive

• It can be a cost-effective alternative to other water-accruing methods.

• With the water table falling rapidly, & concrete surfaces and landfill dumps taking the place of water bodies, RWH is the most reliable solution for augmenting groundwater level to attain self-sufficiency

Rain Water Harvesting– Advantages

1.Provides self-sufficiency to water supply

2.Reduces the cost for pumping of ground water

3.Provides high quality water, soft and low in minerals

4.Improves the quality of ground water through dilution when recharged

5.Reduces soil erosion & flooding in urban areas

6.The rooftop rain water harvesting is less expensive & easy to construct, operate and maintain

7. In desert, RWH only relief

8. In saline or coastal areas & Islands, rain water provides good quality water

Appropriate Technology

Water conservation and groundwater recharge techniques

Water harvesting cum supplementary irrigation techniques

The roof catchment are selectively cleaner when compared to the ground level catchment

• Losses from roof catchment are minimum

• Built & Maintained by local communities

• No Chemical contamination & only required filtration

• Available at door step with least cost

Rain water harvesting system

The typical roof top rain water harvesting system comprises

• Roof catchment• Gutters• Down pipe & first flushing pipe• Filter Unit• Storage Tank

Roof catchment

The roof of the house is used as the catchment for collecting rain water. The style construction and material of the roof effect its suitability as a catchment, Roofs made of corrugated iron sheet , asbestos sheet, Tiles or Concrete can be utilized for harvesting the rain water

Gutters

Gutters are channels fixed to the edges of roof all around to collect & transport the rainwater from the roof. Gutters can be made in semi-circular and rectangular shape with cement pipe, plain galvanized iron sheet, PVC pipes, bamboos etc. Use of locally available material reduce the overall cost of the system.

Down Pipe

It is the pipe which carries the rainwater from the gutters to the filter & storage tank. Down pipe is joined with the gutters at one end & the other end is connected to the filter unit of the storage tank. PVC or GI pipe of 50mm to 75mm (2 to”) are commonly used for down pipe. Bamboo can be also used wherever available and possible

First Flush Pipe

Debris, dust & dirt collect on the roof during non rainy periods when the first rain arrive. A first flush system arrangement is made to avoid the entering unwanted material into the Filter media & storage tank. This is a simple manually operated arrangement or semi-automatic system with a valve below the ‘T’ junction

Filter Unit

The filter unit is a container or chamber filled with filter media such as coarse sand, charcoal, coconut fiber, pebbles & gravels to remove the debris & dirt from water that enters the tank. The filter unit is placed over the storage tank or separately. It may be of Ferro cement filter unit, Aluminum, Cement rings or Plastic bucket etc.

Storage TankIt is used to store the water that is collected from the roof through filter. For small scale water storage plastic buckets, jerry cans, clay or cement jars, ceramic jars, drums may be used. For larger quantities of water, the system will require a bigger tank with cylindrical or rectangular or square in shape constructed with Ferro cement or cement rings or plain cement concrete or reinforced cement concrete or brick or stone etc. The storage tank is provided with a cover on the top to avoid the contamination of water from external sources. The storage tank is provided with pipe fixtures at appropriate places to draw the water to clean the tank & to dispose of extra water. A provision for keeping the vessel to collect the water is to be made.

Size of Storage Tank

• Based on – No. of person in the House hold– Per capita water requirement– No. of days for which water is required

Water available from RoofAnnual rainfall (in mm) x roof area (in sq. m) x co-efficient of run off for roof

co-efficient of run off GI sheet 0.9Asbestos 0.8Tiled 0.75Plaster on bricks/ Concrete 0.7

Cost of Material for Filtration Tank• 1. P/fabricated cement rings 5*Rs. 40.00 200.00• 2. Cement 2 bags*Rs. 140.00 280.00• 3. Sand 2 bags 50.00• 4. Grit 4 bags 50.00• 5. Charcoal 20 Kg*Rs. 8.00 160.00• 6. Sand for Plastering 4 bags 100.00• 7. Mason/ Labor 500.00• 8. White washing 40.00• 9. Transportation 50.00

Total 1430.00

Cost of Material for Tank• 1. Cement 8 bags*Rs. 140.00 1120.00• 2. Grit .25 Cum 200.00• 3. Sand .4 Cum 100.00• 4. Perforated Cement rings 5 No. 1000.00• 5. P/fabricated Cement rings 4 No. 400.00• 6. PVC pipe 63mm dia.*10M 200.00• 7. P/fabricated Asbestos 10mm dia.*10mm

Gutters250.00

8. Mason/ Labor charges. 1000.009. Transportation 130.00

Total4400.00

• Total Cost of construction Rs. 4400.00+Rs. 1430.00= Rs. 5830.00

The cost on O/ M-1. White washing 100.002. Water testing 200.00

(2 times a year) 300.00

Water available from Roof continued……

Size of Tank =1.2 m dia 1.8 m heightNo. of Tanks 4Volume of Tanks 3.14x1.2x1.2x1.5/4

2.03 cum2000 liters

Volume of of 4 tanks =4x20008000 Liters

(this can be designed as per requirement)

How the problem can be minimized

1 By providing pipe water system with source (electric based)

(a) Surface water(b) Deep tubewells2 Recharging stratas through rainwater

harvesting methods(No. of villages of lower range concentration can be

decreased)3 Storing rain water for drinking purpose

(a) In areas where electricity problem is more(b) In areas where concentration is more © In areas where PWS is uneconomical (d) In areas where dependable source is not

available

• 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• 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 colour.• 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 is 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.

THANKS

Tky gS rks dy gS