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K Salim Ali
Friday , December 07, 2012 at 17 : 02

The water antiphone : mini overflow dams


"If there is magic on this Planet, it is contained in Water"

- Loran Eisley, The Immune Journey, 1957

Water is the most abundant compound we find encompassing our earth's surface, constituting a major 70 per cent in its liquid, solid & gaseous states. The Human body is said to contain anywhere between 55 and 78 per cent of water. So, it may be rightly said that, it is not just an indispensible necessity to life; but rather life itself. DH Lawerence quotes in the "Pansies", "Water is H2O, Hydrogen two parts, Oxygen one part, but there is also a third thing that makes water & nobody knows that". Is it any wonder then, that it is very aptly called "the Elixir of life?"

History tells us of Man creating civilizations in & around water bodies. Even today, modern societies are concentrated on the world's seaboards; but, the future definitely appears bleak & bizarre with the soaring population still soaring higher, the inevitable global warming simmering, the pollution, mankind's callousness & much more.

The importance of water is hardly valued until we realise our well has gone dry. It is the same water that existed a billion years back, but our population has tripled over the years. Water may cover 70 per cent of the Earth, but only 3 per cent of it is fresh water, of which a meagre 1 per cent is readily accessible to mankind. This has been very well summed up by the World Bank Institute's Water Policy Reform Program - 1999.

Water is essential for all dimensions of life. Over the past few decades, use of water has increased, and in many places water availability is falling to crisis levels. More than eighty countries, with forty percent of the world's population, are already facing water shortages, while by year 2020 the world's population will double. The costs of water infrastructure have risen dramatically. The quality of water in rivers and underground has deteriorated, due to pollution by waste and contaminants from cities, industry and agriculture. Ecosystems are being destroyed, sometimes permanently. Over one billion people lack safe water, and three billion lack sanitation; eighty per cent of infectious diseases are waterborne, killing millions of children each year.

Since the problem is alarming & its countdown begun, the time has come to review & devise innovative means to conserve water for our future generations. Modern ways of water conservation like rain water harvesting, & drip irrigation should be strongly reinforced as part of the social system. Awareness & responsibility of all citizens ought to be brought on board, to highlight this problem. Ambitious initiatives of linking rivers has been in growing demand , but may not be a reality with the political bickering & cost factor in tow, to deal with.

One ideal solution to tackle this grave problem through unconventional means would be to utilise the water resources which go waste into the sea. Rain-fed rivers in our country discharge a phenomenal amount of fresh water into the Bay of Bengal to a tune of 126x1010m3/year & the Arabian Sea 29.7x1010m3/year, without being utilised for constructive purposes like irrigation & replenishing the ground water level.

Our country is in a phase where pressure on land is acute. It precludes the option of constructing dams to conserve the discharge. The best way to conserve the water discharge is to perhaps make optimum use of the gradient and the banks that border the river to store water by constructing a series of mini over-flow concrete gravitational dams of 10 to 20 metres height which commence from the river mouth and proceed upwards. The embankment along the banks should be raised to the extent of one metre higher than the dam along the gradient till it tapers off to zero height so that this dam can hold on to the substantial amount of water. The mini over flow dam should also have sluices for regulating the movement of silt during the peak period so that the base of the dam is not silted nor the nature of the river flow tampered.

The Dam series structure pictorially should be as follows:

Indian peninsula rivers have a gradient of 20 cms/Km at the mouth of the river, 40 to 280 cms/km based on the terrain through which it flows. An average of 200 mts width of the river can be used to construct a 10 metres dam for a river with a gradient of 20 cm/Km. To do this, the embankment has to be raised by 10 mts which would taper to zero height at 50 km point of the river. The storage capacity of one such dam would be to the extent of 5x107 cubic meter per year. Similarly, for 40 cms/Km gradient river, the embankment has to be raised by 10 mts which would taper to zero height at 25 kms point of the river.    

At the zero point another mini over-flow dam of 10 mts height can be constructed and the series can continue throughout the length of the dam based on the river structure and its tributaries.

A table to calculate the exact water stored as per gradient can be developed as given below:

Sl.NoGradientZero height point on the river bank10mt ht x 200 mt width
120cm/Km50 Km5x107 cu mts
240 cm/Km25 Km2.5x107 cu mts
3200 cm/Km5 Km5x106 cu mts

The benefits which will accrue are multifarious. Some are given below:

5X107 cu mts of water can irrigate 12,000 hectares of land for paddy or 30,000 hectare of pulses/oilseed as per details obtained from Ministry of Agriculture.

Results in enormous increase in the ground water on either side of the banks.

If the water is being stored at a particular height, the gravitational irrigation system can be evolved based on the capacity and requirement.

It provides portable water to all in the villages along the banks.

The stored water can be utilized to ensure a Blue Revolution.

River Banks are to be raised and constructed along the river flow which will not disturb the river ecology and prevent flooding of the area.

These mini dams can also be constructed on the banks of all the tributaries which feed the major rivers that lead to flooding of various deltas.

A river water transport system can be evolved.

De-silting during the dry season through NREGA will also facilitate maintenance of these banks.

De-silting can lead to scientific sand mining.

Agrarian population on either side of the river can be given employment for raising the mudfield embankment from 10 mts to 0 height on either side of the banks, and also the responsibility to maintain it.

In this innovative method only the excess flow, is being tapped and, hence, would not trigger any inter-state disputes as the work progresses with the construction of the dam from the river mouth, upwards.

Masonry structures can be given to construction companies under CSR projects as the cost would vary from 20 to 30 Crores per dam.

This indigenous project can be implemented with the funds from MNREGA, CSR, World Bank and ADB.

It can also be modest beginning for linking the rivers using the gravitational methods without disturbing the environment.

Thus, a novel project of solving the water problem of our country which has a growing demand of amazing magnitude could be tackled very deftly by making use of this dynamic concept which defies the cost factor.


More about K Salim Ali

K Salim Ali is an IPS officer of the 1978 batch, Tripura cadre. He is now special director, CBI, and a part-time research scholar at IP University, New Delhi.



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