ROOF TOP RAIN WATER HARVESTING

             The rapid pace of growth of population and consequent urbanisation has led to stress on available water resources due to over use of surface supplies and over-exploitation of ground water. Dependence on ground water, to meet various requirements, is so heavy that water levels are declining rapidly and the dug wells and bore wells are even drying up. On the other hand, in urban settlements, the natural recharge to ground water has diminished considerably due to shrinkage of open land consequent to urbanisation activities. Therefore, in the present day scenario there is utmost need to augment ground water storage by arresting the roof top rain-water which drains off in to the sewerage of urban settlement.

1.WHAT IS ROOF TOP HARVESTING

          In Urban areas, the roof top rainwater can be conserved and used for recharge of ground water. This approach requires connecting the outlet/drop pipe from roof of the building to divert the rainwater to either existing wells/tubewells/bore well or specially designed structure.

2.WHY IT IS REQUIRED

a.To meet ever increasing demand for water in urban area.

b.To reduce the runoff, which is choking the storm drains.

c.To avoid the flooding of roads.

d.To augment the ground water

e.To reduce the ground water pollution.

f.To improve the quality of ground water.

g.To reduce the soil erosion..

3.WHAT ARE THE ADVANTAGES

          1.This is an ideal solution of water problems where there is inadequate ground water supply or surface resources are either lacking or insignificant.

2. To utilise the rainfall runoff, which is going to sewer or storm drains.

3.Rainwater is bacteriologically pure, free from organic matter and soft in nature.

4. It will help in reducing the flood hazard.

5. To improve the quality of existing ground water through dilution.

6. To remove bacteriological and other impurities from sewage and waste water so that the water is suitable for re-use.

7. Rainwater may be harnessed at place of need and may be utilised at time of need.

8. The structures required for harvesting the rainwater are simple, economical and eco-friendly.

4.HOW TO DO IT

       Roof top rainwater is recharge of ground water reservoir through

1.Abandoned dug well.

2. Abandoned/running hand pump.

3. Recharge pit. Recharge trench.

4.Gravity head recharge well. Recharge shaft.

5.DESIGN GUIDELINES

      ABANDONED DUG WELL (Fig.-1)

A dry/unused dug well can be used as a recharge structure.

The recharge water is guided through a pipe to the bottom of well or below the water level to avoid scouring of bottom and entrapment of air bubbles in the aquifer.

Before using the dug well as recharge structure, its bottom should be cleaned and all the fine deposits should be removed.

Recharge water should be silt free.

It should be cleaned regularly.

It is suitable for large building having the roof area more than 1000 sq.m.

Periodic chlorination of water should be done for controlling the bacteriological contamination.