WATER MANAGEMENT FORUMThe Institution of Engineers (India)http://www.wmf-iei.org/index.php/

• Process of arresting and storing rain water for efficient application and conservation • An effective way of utilising large quantum of water which otherwise goes as surface runoff. • RWH has 2 components:

1) Rain water collection for storage 2) Recharging groundwater What is artificial recharge to ground

water?• Process of enhancing ground water storage artificially at a rate exceeding natural rate of recharge

• Possible by putting up small structure enabling storage and infiltration

What are the advantages of RWH & recharge?

Improvement in ground water levels

Enhancement of water availability in wells/ tube-wells

Improvement in the quality of ground water through dilution

Saving energy in lifting ground water – one meter rise in level saves 0.40 KWH of electricity

Reduction in soil erosion due to reduced surface water runoff

What are the Rain Water Harvesting techniques for urban areas?

• Suitable for buildings having roof area of 100 square meters

Constructed for recharging shallow aquifers

Pit width 1 to 2 meter, depth 2 to 3 meter

Pits to be backfilled with

boulders at bottom --5 to 20 cmsize,

gravel in between 5-10 mm sizeand

coarse sand at the top --1.5 to 2mm size in graded form.

• Backfill pits for smaller roofs with brickbats/ cobbles.- Mesh to be provided at top to prevent leaves etc from falling & choking- Top sand to be cleaned periodically.- Bye-pass arrangements to be provided before collection chamber to reject first showers

Abandoned Tube –wells

Can be utilised for recharging as shallow aquifers have dried up

Water channelized for recharging, after silt removal from such wells

10 cm diameter PVC pipes connected to roof drains. First rains allowed to pass through bottom of drain pipe, which is closed thereafter.

Recharge Trench

• Suitable for buildings having roof area of 200 square meters or more

• Suited at places where shallow permeable strata exists

• Half to one meter wide, one to one and a half meter deep and 10 to 15 meter long trenches

Backfilled with boulders at bottom --5 to 20 cm size, gravel in between 5-10 mm size and coarse sand at the top --1.5 to 2 mm size in graded form.

Mesh to be provided at top to prevent leaves etc from falling & choking

Top sand to be cleaned periodically.

Bye-pass arrangements to be provided before collection chamber to reject first showers

RECHARGE WELLS/ SHAFTSSuited at places, where deeper permeable strata exists.

100 to 300 mm diameter recharge well, constructed 3 to 5 meter below water level.

Trench for channelizingwater to well – 1.5 to 3 mwide, 10 to 30 m in lengthconstructed.

Shaft of 2 to 5 m diameter, 3 to 5 m depth is constructed if aquifer is located at greater depth.

Recharge well mentioned above, is to be constructed within this shaft.

Inputs : Courtesy Central Ground Water Board