Some FAQS about city water supply that must be known

Q. Will our cities become short of water with expansion?

As cities expand a greater pressure is being put on water resources required to meet the needs of urban populations in cities around the world. There is a need to maintain adequate water supply as well as the quality of the water supplied so that health of urban dwellers does not deteriorate. It must be remembered that water for the most part is not destroyed by use. With proper recycling and management, urban dwellers need not suffer water shortage. This point needs to be highlighted before we proceed,

With proper management and recycling, urban areas can avoid shortages and poor quality of water

Q. What is the proper and inexpensive way to recycle water?

There is a proper way to recycle water and an improper way. The proper way mimics natural processes through which water has been recycled on land for millions of year, which is collecting it in ponds where an initial purification takes place by aerobic and anaerobic bacterial processes. The water then seeps into the ground whereby it gets filtered. The water can then be pumped out and supplied with minimal treatment. Similarly rainwater too can be fed into lakes in and around the city for recharging ground water.

Q. How about just taking water from the ground without building lakes and ponds

The water will then run out sooner or later. Ground water table will go down if it is not recharged. A few lucky areas, especially those close to mountains, may have swift underground streams and it may be possible to extract ground water without the water table going down. In that case it is not necessary to build rain fed lakes. However, it is still a good idea to make waste water lakes and ponds to prevent dirty water from reaching rivers and polluting them.

Q. How about taking water from rivers or natural lakes for urban supply?

If a city is lucky enough to be near a river it can take water from it but it must not be so much that down stream life is adversely affected. It must be remembered that water from lakes and rivers needs to be treated before supply and the process can be more expensive than just taking pure ground water. In addition, many methods of chemical purification of water that are not very expensive have adverse side effects on  environment. For example, chemical purification with chlorine can lead to production of  harmful dioxins in environment.

As regards lakes near cities, the water may be much too polluted to supply even after usual treatment. An example is Nainital town situated at 2000 meters height around a lake in the Himalayas. Even here it is necessary to pump out ground water for urban supply.

There are many cities around the world that do not have a river nearby for water supply. Often water is pumped in from dams and rivers far way. It can be more expensive than simply taking local ground water, provided of course that water table could be maintained.

As regards the electricity required to pump out ground water, use of alternative solar or wind energy needs to be considered. It is cheaper than electricity required for domestic use because in this case the use of expensive electricity storage devices are not as necessary. 

How about Rain Water Harvesting?

Unfortunately some types of water harvesting that is being proposed in some cities is harmful.

They propose directing rainwater close to the ground water through deep shafts. This directs surface pollution into ground water without the benefit of natural filtration through ground. This is a fast route to polluting ground water and spoiling underground sources for long periods of time.

Should rainwater be wasted then?

NO, as said earlier, it should be directed to lakes and ponds near the city from where it will return into the ground water after natural purification.This is the proper way to harvest rain water.

Can all the water used by a city be recycled? Doesn’t some get lost?

Yes some is lost through evaporation but it is not a full loss because some returns again to ground as rain. The real loss is when water flows into a river that flows into the sea or very far away from the city. Some water is also converted to biomass such as trees but this is not a loss because trees improve environment of a city greatly. The benefit of trees far outweighs any possible loss.

Can ground water level fall in an some areas and rise in some other area around a city?

Yes, that happens often. Monitoring stations and pump houses are required in and around a city to draw water from areas where ground water level is rising, not falling.

Isn’t ground water bad some times?

Yes, in some areas ground water has harmful contents such as too much salt or even very harmful components such as arsenic, fluorides and nitrates.

What can be done in areas where ground water is bad?

When ground water is unfit or harmful for humans in any city or village then it is necessary to have two types of water supply. One purified by expensive methods such as reverse osmosis for drinking and cooking and the rest for washing etc. Nitrates and pesticides in water can be prevented by an advisory for organic farming in a buffer zone around the city.

Is it possible to ration water such as a supply for limited hours in a city?

Many cities do that, but this is a harmful practice. During hours when supply is shut down, polluted urban seepage gets in through pipe joints and mixes in good water.

A round the clock twenty four-hour supply prevents that because it is near impossible to prevent seepage otherwise. Occasional shutdowns for maintenance can be managed easily by warning the city dwellers not to use water for cooking and drinking for a few hours after supply is restored so that pollutants are washed out.

It must be remembered that fluids flow from areas of high pressure to low pressure and not the other way around. Therefore when a supply line is pressurized for 24 hours then pollutants do not leak in, only some water may seep out.

How else to manage if water is in short supply if not by rationing?

The easy and natural way to limit water consumption and wastage is to have a differential rate of water use i.e. beyond a certain usage a penal rate of use that is twice or four times can be applied. However, as said at the outset, with proper management, water need not be short because water is not destroyed by use. The small loss that takes place through evaporation, chemical conversion etc. is easily made up by rain or water supply from a distant river.

Can Ground water level rise too fast if it is too well managed?

Yes that has happened in some cities. In some cities water table went up so much that it began to seep into basements. It may also lead to collapse of buildings. If that happens, the best solution is to pump it out and direct it away from the cities through canals to distant rivers or wetlands. Incase the surroundings of the city are not forested then this is an ideal opportunity to pump out water from the city to surrounding areas to create such forests. Jodhpur city in Rajasthan, India is an example of a city where water table has been rising over the last several years.