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How much do we need?

TOUGH TIMES: Residents lining up at a roadside tap for drinking water

This is a question of water for domestic use in urban and rural India and not about the virtual use of water that, say for example, is needed to grow the food that we need or for the goods that we consume. So, how much water does an individual need every day?

The standard for water supply for domestic use in rural India is agreed as 40 litres per capita per day. This was on the understanding that drinking water requirement is three litres, water required for cooking is five litres, for bathing 15 litres, for ablution 10 litres and for washing utensils seven litres. In the event of this being reached for a large number of habitations, States are free to increase this quantum. Karnataka set a standard of 55 litres per capita per day for its rural habitations.

In the urban areas, the BIS or the Bureau of Indian Standards suggests 135 litres as the requirement of a person per day. This is also accepted by the Manual on Water Supply Design brought out by the Central Public Health Engineering Organisation (CPHEEO). In metros such as Bangalore, Chennai or Hyderabad, this amount is likely to be higher and, therefore, the CPHEEO suggests a figure of 150 litres per person per day.

Designs of water supply systems including pumps, pipes, storage reservoirs and distribution pipes as well as sewage systems including collection and treatment systems are dependent on per capita consumption. If the actual consumption is less than that anticipated, then there could be redundancy in design, making the capital investment costlier.

If a full cost recovery model is then set in place, this could mean higher tariff. Sewage systems may under-perform because there is not enough scouring velocity or self-cleaning velocity in the pipes meant to collect them. Sewage treatment systems may also suffer from the same problem of “over-design,” making the systems costlier and the treatment and recycled water costlier too.

On the other had, underestimating demand or per capita consumption would mean that a source such as a borewell or storage system such as a sump/overhead reservoir would dry up quicker than anticipated. Sewage treatment systems could collapse because of the inability to treat the larger-than-expected volumes of flow.

While it is generally accepted that weather, climate, cultural practices, individual habits, price, whether you live in a flat or an independent house et al have a bearing on water consumption, we need further empirical and statistical evidence on real consumption across India. As the economic boom kicks in at least in a certain segment of the population, demand for water seems to be changing rapidly.

Richer areas of cities generally report larger consumption and poorer areas get lower water and report less consumption.

While incentivising good behaviour or punishing bad behaviour is the job of the State, this cannot be done in a paradigm of absence of information. The drive towards efficiency demands that we reduce per capita consumption to its optimum as many countries globally are attempting.

Germany and Australia represent two notable examples. Germany has brought down per capita consumption to around 105 litres from a high of 160 litres.

At the local level, in our homes and flats, we can meter water and calculate per capita consumption. Where do we stand with regard to standards would be a question then answered.

An optimum level of 100 to 105 litres seems possible. This will enable less resource to be distributed more equitably.

A combination of technology, economic incentives and disincentives, metering and volumetric pricing and education and awareness can achieve this from a household level to apartments to the city itself.

www.rainwaterclub.org

www.arghyam.org

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