How it works:
Ideally the trench is constructed across the land slope along the boundary walls of the house. The trench may be 0.5 to 1 m wide, 1 to 1.5 m deep and 10 to 20 m long, depending upon the availability of land and rooftop area. The trench is filled with boulders at the bottom followed by pebbles and by sand on the top (filler material).
The collected water from the roof is diverted through the drain pipe to the trench.
Recharge trenches, by their nature of larger area, charge larger amount of water compared to recharge pits. Hence it is better used in rooftop areas that collect large amount of water.
Step by step construction of Recharge Trenches
Dig a trench about 0.5 to 1 m wide, 1 to 1.5m. deep and 10 to 20 m. long depending upon availability of water to be recharged
Fill the trench with boulders (5-20cm), gravel (5-10 mm) and coarse sand (1.5-2 mm) - the boulders at the bottom (bottom most layer), gravel in between and coarse sand at the top.
Provide a mesh around the outlet at the roof so that leaves or any other solid waste debris is prevented from entering the trenches. A desilting/ collection chamber may also be provided on ground to arrest the flow of finer particles to the trench.
Provide a by-pass arrangement before the collection chamber to reject the first showers.