Water News: Millions of women and children spend several hours a day collecting water from distant, often polluted sources.
Water News: Much more fresh water is stored under the ground in aquifers than on the earth’s surface.
Water News: Somewhere between 70 and 75 percent of the earth’s surface is covered with water.

Rain Water Harvesting (RWH)

Rainwater harvesting may be done by adopting various methods and some of the types are listed hereunder

  • Pebble bed method
  • Percolation pits
  • Recharge wells
  • Ridges and furrows
  • Check dams
  • Gully control/stone wall structures
  • Contour bunding, trenching
  • Land Flooding
  • Rainwater harvesting service wells
  • Recharge water through soak pits
  • Traditional water harvesting through Lakes
  • Rainwater harvesting through watershed management

By using existing well: The run-off water from rooftops can be led into the existing well through pipes and a small settling pit to filter the turbidity and other pollutants. In this cost-effective process we not only conserve the precious rainwater but also help to increase the local ground water table. Even an abandoned well can be used for this purpose.

Through percolation pits: Percolation pits (1m x 1m x 3m) may be dug a little away from the building. The pit is then filled with brick jelly/pebbles followed by river sand for the purpose of better percolation. The top layer of sand may be cleaned and replaced once in two years to remove the settled silt for improving the percolation.

Decentralized percolation trenches: This method can be adopted by those who reside in houses with large open areas. Run-off water from the rooftop can be diverted into bare soil/ garden in the premises. Apart from this a longitudinal trench of 1.0m depth and 0.5 m width may be dug at the periphery of the plot and filled with pebble stones and sand in order to store the excess run-off during rainy season that will eventually percolate into the ground.

Other methods of utilizing rain water

  • Run-off should be diverted into suitably designed structures near pavements, parking lots, parks, play grounds, etc.
  • Rainwater can also be stored in underground storage tanks (water sumps) for a few months and used directly for washing, flushing and other domestic purposes. Industries, multi storied buildings, various offices, etc., can implement this cost effective method, as they depend mostly on ground water for their needs.

I.               Excess/ surplus water should be used for recharging the ground water using the existing open well/ bore well after filtering the water through filter media of 3ft x 3ft x 6ft size and back filled with washed aggregates of size 40mm and 20mm, covered with a thin layer of sand. 

II.             Rainwater harvesting for recharge of ground water may be done through a bore well around which a pit of one meter width may be excavated up to a depth of at least 3.00 meters and refilled with washed stone aggregate and sand. The filtered rain water may be channeled to the refilled pit for recharging the bore well. Another method of recharging the Bore wells is by the V-Wire Screen Technique wherein 

  •                A well of 1.5-m diameter and 3-m depth is dug around the bore.

  •                The well is lined with cement rings as in the conventional system.

  •                A layer of gravel put at the bottom.

  •                The casing pipe is cut just above the gravel layer, and the pump and casing pipe are removed.

  •                A section of the casing pipe, equal to the height of the

  •                V-wire screen is cut and the screen fitted to the pipe.

  •                The casing pipe with the V-wire screen is fitted back to the cut section of the casing pipe at the bottom of the well.

  •                A perforated reinforced concrete slab is placed at the level of the third ring from the top and then filled with sand, charcoal, and crushed stones.

  •                The empty space between the third ring and the bottom allows the water to collect and also increases the pressure with which it enters the bore through the V-wire screen. 

III.            In the event of non availability of open well/ bore well, if the plinth area exceeds 4000 sq m, construction of Recharge pit is mandatory. Recharge pit shall be constructed for recharging the shallow aquifers. These shall be constructed 1 to 2 m. wide and 2 to 3 m. deep which are back filled with boulders, gravels & coarse sand. The size of filter material is generally taken as below:

         Coarse sand:    < 2 mm

         Gravels:            5 - 10 mm

         Boulders:          5 - 20 cm

The filter material shall be filled in graded form. Boulders at the bottom, gravels in between & coarse sand at the top so that the silt content that will come with runoff will be deposited on the top of the coarse sand layer and can easily be removed. If clay layer encountered at shallow depth, it shall be punctured with auger hole and that auger hole shall be refilled with fine gravel of 3 to 6 mm size. 

IV.          If the open space surrounding the building is more and it is not paved, the surface run off may be recharged into ground through percolation pits or trenches or combination of pits and trenches. Depending on the geomorphologic, topographical and soil condition, the pits may be of the size of 1.20 m width x 1.20 m length x 2.00 m to 2.50 meter depth. The trench shall be of 0.60 m. width x 2.00 to 6.00 meter length x 1.50 to 2.00 meter depth. The surface run off shall be channeled to pits or trenches. Such pits or trenches shall be backfilled with filter media comprising the following materials: 

         40 mm stone aggregate as bottom layer up to 50% of the depth

         20 mm stone aggregate as lower middle layer up to 20% of the depth

         Coarse sand as upper middle layer up to 20% of the depth; a thin layer of fine sand as top layer

         Top 10% of the pit/ trench shall be empty and a splash is to be provided in this portion in such a way that roof top water falls on the splash pad

         Brick masonry wall is to be constructed on the exposed surface of pit/ trench and the cement mortar plastered. The depth of wall below ground shall be such that the wall prevents lose soil entering into pit / trench. The projection of the wall above ground shall at lease be 15 cm height

         Perforated concrete slabs shall be provided on the pit / trench

         If the open space surrounding the building is not paved, the top layer up to a sufficient depth shall be removed and refilled with course sand to allow percolation of rainwater into ground 

In the event of non availability of open well/ bore well, if the plinth area exceeds 4000 sq ft, construction of Recharge well is mandatory. The recharge well shall be with 3ft dia and 15-18ft depth. The well shall be lined by concrete rings with intermittent weep holes. Bottom of the well shall be covered with 1ft thick broken brick for cushioning. The well may be covered with RCC slab of 1 to 1.5 inch thickness and connected with down take pipe from the roof top 

Existing open well: Rainwater from the sump/ tank’s surplus shall be diverted to the existing open well by using PVC pipes connecting to a filter chamber. The minimum size of the filter chamber shall be with 2.5ft x 2.5ft x 2.5ft and filled with washed broken bricks / blue metal / pebbles and sand on the top. The chamber may be covered with RCC slab. 

Existing bore well: Filter tank of 3ft x 3ft x 6ft size shall be constructed at the surrounding of bore well keeping the well in middle, and back filled with washed aggregates of size 40mm and 20mm, covered with a thin layer of sand and charcoal. Perforations shall be put on casing pipe to make casing porous. Overflow water from the sump/ tank may be diverted to this tank to get water slowly percolated