RAIN WATER HARVESTING

BY

KRISHNA VAMSY

REASONS OF SHORTAGE OF WATER• POPULATION INCREASE

• INDUSTRIALIZATION

• URBANIZATION

- INCREASE IN PER CAPITA UTILIZATION

• IN PLACES WHERE RAIN FED/ IRRIGATION BASED CROPS ARE CULTIVATED THROUGH GROUND WATER

• DECREASE IN SURFACE AREA OF LAKES, TANKS ETC.

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WHAT IS THE SOLUTION ?

• RAIN WATER IS THE 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 ANSWER3

WHY RAIN WATER BE HARVESTED

• TO OVERCOME THE SHORTAGE OF WATER.

• TO REDUCE WATER TABLE DEPLETION.

• TO IMPROVE THE QUALITY OF GROUND WATER.

• TO REDUCE PRESSURE ON OTHER WATER RESOURCES.

Rain Water Harvesting?.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

•

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

RAIN WATER HARVESTING

Rain

Roof Top

Filtration

or

Recharge to ground water

Storage

Rooftop Water

RECHARGE TO GROUND WATER: Structures generally used arePits :- 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.

Technology of Rainwater Harvesting

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 utilised as recharge structure and water should pass through filter media before putting into dug well.

TRENCH

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.

THE TYPICAL ROOF TOP RAIN WATER HARVESTING SYSTEM

COMPRISES

• ROOF CATCHMENT

• GUTTERS

• DOWN PIPE & FIRST FLUSHING PIPE

• FILTER UNIT

• STORAGE TANK

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ROOF CATCHMENTThe roof of the house is used as the catchment for collecting rain water.

The style,construction and material of the roof effect its sustainability.

Corrugated iron sheet, asbestos sheet, tiles or concrete can be utilized for harvesting rainwater.

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THE ROOF CATCHMENT ARE SELECTIVELY CLEANER WHEN COMPARED TO THE GROUND LEVEL CATCHMENT

LOSSES FROM ROOF CATCHMENT ARE MINIMUM

NO CHEMICAL CONTAMINATION & ONLY REQUIRED FILTRATION

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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.

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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 POSSIBLE20

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’ JUNCTION21

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.

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STORAGE TANK

IT IS USED TO STORE THE WATER THAT IS COLLECTED FROM THE ROOF THROUGH FILTER.

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.

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Water Source Setup Cost Running Cost Yield Applicable in

Tubewells Medium Medium Medium Places with Deep Aquifers

Hand-dug wells

Low Medium Low-Medium Places where water table is not lower than six metres

Reverse Osmosis

High High High Only in Urban regions

Rainwater Harvesting

Low-Medium Low-Medium High Only in regions which receive moderate-high rainfall once a year

Comparison With Other Methods

No land is wasted for storage purpose and no population displacement is involved.

Improves the quality of ground water through dilution when recharged

Reduces soil erosion & flooding.Mitigates the effect of drought.The rooftop rain water harvesting is less expensive &

easy to construct, operate and maintain In saline or coastal areas & Islands, rain water

provides good quality water

ADVANTAGES:

DISADVANTAGES:-Unpredictable rainfall

Storage limits

Regular maintenance

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