How much do we need?
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In urban areas, BIS suggests 135 litres for a person a day.
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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 3 litres and water required for cooking is 5 litres, for bathing 15 litres, for ablution 10 litres and for washing utensils 7 litres. In the event of this being reached for a large number of habitations, the 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 metro cities such as Bangalore, Chennai or Hyderabad, this amount is likely to be higher and, therefore, it suggests 150 litres per person per day.
Design factor
Designs of water supply systems, such as pumps, pipes, storage reservoirs and distribution pipes, as well as sewage systems, such as collection and treatment systems, depend on per capita consumption. If the actual consumption is less than that anticipated, then there can be redundancy in design, making the capital investment costlier.
If a full cost recovery model is then set in place, this can 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 means that a source such as a borewell or storage system such as a sump or overhead reservoir will dry up quicker than anticipated. Sewage treatment systems can 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 and whether you live in a flat or 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 giving incentives for 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.
S. VISHWANATH
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