SOFTWARE TO QUENCH THIRST OF PARCHED INDIAN VILLAGERS

In Rajasthan, India, a non-governmental organisation has developed a new software program which will help villagers predict their drinking water supplies, so that the ever-receding dream of providing every human being with a reliable and safe source of water, can confidently take a step forward.

By Frederick Noronha

RURAL India's developmental efforts could get an unexpected boost from the computer software field. To kick off such attempts, the first program of its kind has just been launched by public-spirited citizens, which offers to simulate the performance of rainwater collection tanks. Called SimTanka, this free computer software is aimed at simulating the performance of rainwater harvesting sysems with covered water storage tanks under the influence of a fluctuating rainfall. Such systems are called Tanka in the western parts of Rajasthan.

Western Rajasthan - the region's inhospitable desert tract - is known to have once had prosperity, wealth and habitability in medieval times. This is believed to have been based on the extremely sagacious use of its natural resource base, which has got badly eroded over time. Now, the search is on for a software fix which could help offer a solution.

'Traditional water harvesting techniques have been severely eroded, thrown into disuse and even eliminated in most parts of the country,' warns the Citizens' Report on the State of India's Environment, recently published by the Centre for Science and Environment, New Delhi.

Most desert-tract villages have small ponds, which gave them enough drinking water for up to eight months in a good season. Villages also have used 'tankas'. These are circular holes in the ground lined with fine polished lime (chunam), in which water was collected during rainfall and used only when other supplies failed.

Using computer simulation, this software will predict the performance of this rainwater harvesting system, based on a mathematical model of the actual system. SimTanka simulates the fluctuating rainfall on which the water harvesting system relies.

Rainwater harvesting systems are often designed using some statistical indicator of the rainfall for a given place, like the average rainfall. When the rainfall is meagre and shows large fluctuations - as is the case in India's desert tracts - then a design based on any single statistical indicator can be misleading. But SimTanka takes into account the fluctuations in the rainfall, giving each fluctuation its right importance for determining the size of the rainwater harvesting system.

'The result of the simulation allows you to design a rainwater harvesting system that will meet your demands reliably. It lets you find the minimum catchment area and the smallest possible storage tank that will meet your demand, with a probability of 95%, in spite of the fluctuations in the rainfall,' says Vikram Vyas of the Ajit Foundation in Jaipur, which developed this software.

One can even use SimTanka to find out what fraction of the total demand can be met reliably by one's system. SimTanka uses the rainfall record of approximately 15 of the immediate past years to obtain probabilities of the future rainfall. If not available, then rainfall records from the nearest place with the same rainfall pattern can be used. Simulation results however give a guideline based on past rainfall record, not a definite prediction of future performance. SimTanka has an included utility, RainRecorder, to enter and update the rainfall data.

'SimTanka is free and is being developed by the Ajit Foundation in the spirit that it might be useful for meeting the water needs of small communities in a sustainable and reliable manner,' adds Vyas, whose next model will aim to simulate rainwater harvesting systems with open storage tanks, tentatively named SimTalab.

Vyas told this writer, 'The dream of providing every human being with a reliable and safe source of water seems to be ever receding. In pursuit of this vision the traditional rainwater harvesting systems, as developed in the arid and semi-arid regions of India, have an important and unique role to play.'

Such systems can provide water in a sustainable and energy-efficient manner. Yet, the use of these systems has declined. One serious technical shortcoming in these systems is that they are unreliable, since they are dependent on a meagre and fluctuating rainfall. To solve this problem, SimTanka the computer-based approach attempts to meet the villagers' needs with as much as 95% confidence.

Primary users of SimTalab and SimTanka are individuals and organisations - governmental and non-governmental - involved in developing water resources for rural communities. The software SimTanka and SimTalab will also be useful to organisations funding the development of traditional water harvesting systems. - Third World Network Features

About the writer: Frederick Noronha is a Goa-based journalist.

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