Inputs sought by the Lions Club Chairman about water management

Dear Sri Ranganathan,                                                                                 

Greetings and good wishes. I am glad that my website has elicited interest in you.

My clarifications are :

• “1Q) Why are you trying to prevent percolation? Is the ground water saline or unfit in some way? In my opinion catching rainfall to re-charge ground water is the most suitable option. The sheer quantity of rain water would improve the ground water quality. It would be a good idea for you to get a realistic quotation for digging storage tanks for harvested rain water with plastic lining. You are likely to find the cost quite high and it may make the idea unviable. Spraying light mineral oil on the water will create a new problem of seperating water and oil. I am also not so sure if this is such a good idea to prevent evaporation.”
  • 1A) There is no question of preventing percolation. I agree with you that maximum amount of rainwater should be allowed to percolate to recharge ground water as far as possible.  Storm water often  floods  city roads for days together is not going to help ground water recharge because of concrete jungle in cities.  
  • What I want to impress is this storm water should be transferred fast to pre arranged water bodies for better reuse latter. Out of the normal 140 rainy days in a season,  rains normally occur only in about 50 to 100 hours. During these short span  of time frame the sewage component is very less and the storm water is fit for recycling and reuse. Rain water harvesting to augment village water supply is altogether a different issue  and dealt below.
  • For solving  village drinking water problem, I advocate rain water harvesting in an open level areas and this rain water has to be stored  in tanks with plastic lining to prevent percolation losses and spraying with suitable  mineral oil as thin film to minimize evaporation losses.  The practice of lining of irrigation canals with polethene sheet is common. Spraying non reactive mineral oil is also possible.
• “2Q) Building dykes to keep fresh water from draining into the sea may also be a very expensive proposition, unless the quantity of fresh water saved is large enough to warrant such a measure and also if it is possible to use this water as a town water supply at a cost that will help fund the cost of construction dykes”
  • 2A)  I do not know how you   concluded  that construction of  a subsurface dyke (a  simple vertical masonry wall a  few feet below the ground surface) parallel to the sea coast in city limits,  to prevent ground water discharge into sea is very expensive.
  • For example, at Visakhapatnam (Andhra Pradesh), the terrain is steep sloping towards  sea coast and drinking  water is a problem.   So it might be feasible to construct suitable dyke.  Central Ground Water Board advocated this concept in their  website and you can see relevant  picture in my website.  Any way if the concept is good, feasibility  studies  and estimates could be undertaken before the actual construction.
• “3Q) Harvesting roof top rain water extensively in any city would first of all substantially reduce the storm water volume. Unfortunately storm water drains in most cities and towns in our country also carry sewage. If this can be prevented, storm water can be harvested as proposed by you.”
  •  3A) Harvesting roof top Rain water has many advantages   like reduce dependence of city water Supply and  reduce Storm Water in the City. The excess water collected could be utilized for ground water recharge through an unused well.

You are again mixing up two different issues like Roof Top Harvesting and Recycling Storm Water.  The issue of sewage component in storm water is dealt above.

Regards

P.Nukaiah Chetty