Drinking Water Supply System Gravity Fed

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Drinking Water Supply System Gravity Fed

We were discussing about development of future plan for our city Skardu respect to safe drinking water coverage to all citizens. I have suggested them to allocate fund for consultancy of feasibility, topography and designing for master plan of drinking water supply system for entire city for next fifty years.

But at this stage we need to brief the authorities to highlight the current water crises and and to suggest alternate options to meet the demand the of next fifty years.  

Therefore I want to get some technical feed back on the following matter.

1. Currently there are 150,000 population in the entire city, can you please tell me the current total demand in cusecs. (on the basis of liter per capita per day assuming 80 LPCPD)

(According to an anthropological study it was 40 to 70Ltr per capita per day consumption in the rural communities in 1996, now due to behaveral changes it can be increased up to 80 Ltr per capita per day in the same community) 

2. Total demand in cu secs for next 50 years. 

Do any one have suggestions to incorporate for the concept of development of master plan, it would be very nice help to develop concept to make a successful master plan in future.  

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12 Answers

  1. The population forecast is done by various methods given in Reference books and manuals. Some of them are Demographic method, Arithmetical progression method, Geometrical progression method etc. You can refer any method to get population forecast. Some time the real figures may differ from calculated figures because of many factors that promote migration in or out of the town. In India National Building Code recommends 135 lpcd water supply. However you may safely consider 90 lpcd. Rest of the calculations is very simple. For further details please contact on rvsveipl@gmail.com. Prof. Rajendrakumar V Saraf, Chairman Viraj Envirozing India Pvt. Ltd. Pune, India

  2. The information desired is not clear.Quantity of water requirement for the present or future population will have to based on availability of in the source of water whether surface or ground.Depending on availability, per capita supply may be considered as 135 lpcd for urban areas.Distribution system be designed with a peak factor of 2.5 for continuous supply.For a master plan of 50 Years , a proper land development  plan for next  50 years would be essentially required.

     

  3. One further note:  In order to give you a continuous supply of water for your growing population , you will need a very large reservoir or lake as a source.  One hectare-Meter of water will last about 3.37 days at the maximum usage rate.  So for a year's supply you will need something with a volume of about 115 ha at a depth of at least 2 meters or more.  You work out the cubic volume but plan for 25% evaporation losses during dry season from a reservoir. 

  4. Dear Abbas,

    It seems we are many steps far from what is needed for framing even a very rough Master plan for a city of 150K resident. There are many parameters to be considered alongside the quantity. Not to talk about SDG commitments which your country is also a signatory to.

    My suggestion in this connection is: "Any water and sanitation engineer from your locality can better come up with realistic suggestions than 'distant experts'. "

    Good luck in finding a useful solution!

    Kabindra

  6. Please consider a consumption of 100-125 lit per head  per day for design calculations.

  7. Munawar

    Your question is a little basic - just calculating the demand is a very small part of the process and, perhaps, the simplest. I have given you some links to papers which deal with the business and strategic planning processes in some detail and will be happy to explain more if you get back to me.

  10. Sir, your estimates for daily consumptions per family our pretty good for master planning purposes. There are two sides as you know well - the supply and demand.  You will need to estimate population growth and multiple that with per capita consumption. For population growth, you can estimate the growth based on previous growth in the region. I think the Pakistan government or the UN shows have this data on their website. Use the current population and the growth rate to project future water needs. It is a simple excel calculation. As noted below by Dave, assume a peaking factor for increased usage as population increases and people become more prosperous.  

    On the supply side, you will need to estimate what you can get from your surface sources  - rivers, lakes, etc. Usually, there is safe and sustainable limit for withdrawal from these sources established by local and national govt (but no one obeys that in our regions). If you can get flow rate of a year (average) you can estimate the volume that flows through your City. Assume you can safely use 20-40% of the volume as supply. For lakes, you can also assume a percentage of volume for use based on the rainfall or snow melt that recharges the lake. Estimation of groundwater is not easy for this effort unless you have more data. 

    I believe you can show a nice story with these calculations. As you noted, the current supplies might not support future growth. Hope this helps. Goodluck! 

    1 Comment

  11. As far as i know, mostly drinking water need of Skardu population is being fulfilled by the Satpara lake,There should be some other grounded horizons of water, like filtration of spring water.This is not truly the answer of asked question but an observation to be shared.

    1 Comment

    1. You are right, currently due to rapid growth of urbanization the Satpara lack is not fullfilling the requirement of power generation as well as Agriculture and drinking purposes in winter and spring season. As it is the only single source, therefore the public has demanded to divert a stream from Deosai which was the part of Satpara Dam project. But unfortunately it was excluded from the Project during implementation phase. Public opinion seems justified that without diversion of Shatong Nullah the purpose of Dam is totally useless and ineffective and the huge investment over construction of Dam and right bank canal (RBC) and left bank canal (LBC).

      Your idea is good, there are several morain type springs below the Satpara Dam which can be further purified and filtered to ensure reliable to drinking purposes and can supply. But unfortunately due to lack of planning and lack of human and financial resources there is no proper drinking water supply system yet in Skardu city. Majority of piped water is being used to irrigate gardens, construction and other commercial purposes without any regulation. 

  12. If we assume a peaking factor of about 1.5 that would give you about 18,000,000 liters/ day peak demand, and that translates to about 7.35 cubic feet per second.  Assuming a 50% growth in population and an increase in water demand of about 25%, that would mean that your future growth would increase by just under double to about 13.8 cubic feet per second. 

    1 Comment

    1. We have already calculated similar to the idea of Mr. David, we considered 80 L/Day per capita demand based on climatic and cultural practices of water consumption. In this way 4.9 Cusecs is the current demand of a population of 1.5K. Whereas it would increased to 9 cusecs after 30 years based on the annual growth rate of maximum 2% of current population.