Can you suggest methods and procedures for estimating the reliability for different sources (river, borewell, open well, lake) while planning a water supply project for a town/region. How to estimate the safe withdrawal limit and allocate withdrawal share for different sources?
Very good and meaningful question. My appreciations for posing such a question. I have also many times wondered whether any such studies are being carried out before finalizing and implementing water supply schemes, as many of the public water supply schemes are a failure or non-functional or non-sustainable. Reasons may be many, but one of the important factors is the absence of studies on the source availability and its sustainability. Many times the schemes are implemented because of the compulsions (public or political), without giving any importance on other factors, including the water availability.
Because of the above reasons, for the first time a systematic study was conducted in Kerala State, India, to assess the sub-surface water availability in the riverbed material for a regional water supply scheme. It gave rise to the conclusion that only certain months in a given year the water supply scheme can give the proposed amount of water and during summer months it can give only 50% of the proposed yield.
Reference:
Rajagopalan.S.P and Narasimha Prasad.N.B, 1989, Subsurface Water in River Beds as Source for Rural Water Supply Schemes, Journal of Water Resources Planning And Management, American Society of Civil Engineers, New York, Vol.115, No.2.
Borewell or Openwell based water supply schemes should be finalized / implemented only after a detailed long duration pump tests; determination of time for full water level recovery and safe yield for a given depth of drawdown / fall in water level in the well due to certain rate of pumping. The yield and recovery rate vary from region to region and depends on various hydraulic properties of the underlying aquifer material. Most of the time the reason for failure in well yield sustainability is due to lack of pumping tests and related safe withdrawal assessment. Sometimes, because of the humans greed, the pumping rate will be more than the aquifer yield thereby creating interference with the adjoining wells or reduction in the yield or drying up of the aquifer / well.
Dear Dibakar,
Thank you for your appreciations. Yes it is a result / reflection of 37 years of R & D experience.
Best wishes.
Dear Dibakar,
If you really see most of the projects in India are implemented by the Government agencies and majority of them have to be working well. Very few projects of late are implemented with the help NGOs through participatory approach. As there are so many projects which are working, it is not fair to put such a blame on the Government agencies. However if you talk in terms of failure percentage then in 'some fields of development' Government agencies have failed in more instances. Yes I agree with you that in Government projects there is lack of accountability, periodic monitoring and maintenance. One of the reason stated is absence of very limited financial allotment for monitoring and maintenance. Any way even today we depend more on Government agencies, at least in the field of water resources. But with the recent trend of public awareness and vigilance, the act of media - print as well as TV, etc., we can look forward to better tomorrow.
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