Do not kill a river

Before we think of linking rivers it is a good idea to understand that a living and healthy river must flow. If the flow is obstructed or diverted the river cannot perform its natural functions and will degrade and become sick — much like the blood flow in our bodies. In a study on ecological flow, it has been found rain-fed Indian rivers need over 50 per cent of rainfall to transport the silt that is washed down during the monsoon to avoid the riverbed getting clammed. And they need 60 per cent of their virgin flow in the lean season to avoid algal choking.

Most rivers are running below the norm. At this time, the lean rainfall season, the Krishna in southern India has no flow at Vijayawada and is just a medley of scattered stagnant pools of water. The Yamuna in Delhi is down to only 16 per cent of its flow and is reduced to cesspools of sewage. The Ganga, after Haridwar, is not doing much better.

The reduced flow has terminal consequences on the delta ecology. The Colorado river was dammed and its flow diverted. The consequence: its coastal ecology was destroyed and its delta in the Gulf of California desiccated.

It is now being slowly revived by a new treaty between Mexico and the US. Sea ingress from low flows has freshwater retreating back into the delta in all our rivers. Livelihoods of millions have been hit. The fresh water line has retreated 50 km for the Indus and over 25 km for the Ganga delta. This is also true for peninsular rivers. We are surely heading into a human and ecological dead-end.

An oft repeated seemingly logical fiction is that all the flood water is wasted and so we should impound it and store it. As we have shown above, in this event, all rivers will get completely silted and deltas recede. Actually most flood disasters like the Mithi channel disaster in Mumbai, the Jhelum flood in Kashmir and even the more recent Chennai floods are due to silted and choked river channels which disturb the flow of water. Flood water flow is not wasted but essential. The river must flow.

Floodplains: Rivers in India are monsoon rivers which have deep and wide extended floodplain aquifers that run for thousands of kilometres and are an enormous natural storage for water that gets recharged by the river flow and flood especially during the monsoon. Floodplains for the Himalayan rivers are sand banks that are 5 to 20 km wide and a 100 metres deep, and about 40 per cent of this huge volume all along their course is water. They are naturally recharged by rain and floods during the monsoon. The water that is replenished every year, but no more, can be used to supply hundreds of cities on their banks. Floodplains feed groundwater aquifers in their environs and, steadily and slowly, feed the river in the lean season. Given the increasing scarcity of water they are likely to be one of the few perennial local water resources of the future.

If not polluted by human intervention, the water in the river is the best mineral water. In millions of years of flow, a river has washed down salinity and other salts to give really good quality water, which makes a river a special and vital survival resource. Diversion of water into canals or interlinking with other rivers runs counter to the natural watercourse and will disturb the water balance created by nature.

River-linking and water transfer: There are many working agreements on river water sharing like the Mekong and Indus river treaties. But treaties often emphasise simply the engineering and legal and social aspects of equitable division in the flows of river water. They do not address the adverse long-term ecological effects. A conspicuous example is the Indus water treaty. 

The Indus water agreement: The Indus water agreement was made about 60 years ago when environmental concerns were not well articulated. By allocating the waters of the three northern rivers, the Indus, Jhelum and Chenab to Pakistan and allocating the waters of the southern rivers, the Ravi, Sutlej, Beas water to India, the flow of these latter rivers in Pakistan has been effectively stopped, except during the monsoon. As has been pointed to before, this is a disaster for river ecology as a minimum flow has to be maintained. Now, a canal system from the Chenab feeds Lahore on the Ravi and the Ravi, Sutlej, Beas feed a canal network that services Punjab (Indian) and Rajasthan agriculture. 

The consequences are: 1) The Ravi river channel is dead, as it is being used as a sewage dump and is full of city sewage, polluting the floodplain and adjoining aquifers. Empty rivers invite invasion of rivers and their floodplains by gravity flow from their surroundings that can do permanent damage. 

2) Lahore gets non-local water through canals, run off from the Chenab, in the north. This has the unforeseen effect of increasing salinity and waterlogging along canals as good river water dissolves salt and passes into the groundwater. Once water is saline it cannot be restored to good water in any sensible timescale. Many such unforeseen events will certainly accompany river-linking.

Another kind of disaster is exemplified by the recent extinction of the Aral sea and the rivers flowing into it, the Amu Darya and the Syr Darya. Canals were run off from the source-rivers of the sea, to irrigate a vast area for cotton cultivation. Scant attention was paid to the ecology of the sea. The sea’s surface has now shrunk by 70 per cent and its volume by 80 per cent. Its enhanced salinity can no more support any life. River basin policies and treaties must avoid such losses. 

The answer clearly is not to destroy healthy rivers but to change our agricultural praxis around the overdrawn rivers by having more water-efficient irrigation and less water intensive crops. Or, we can irreversibly damage the evolutionary resource of the river and the floodplain. Killing a river is not only a permanent loss of a living resource created by millions of years of evolution but a crime against humanity. These are potent reasons to avoid tampering with river ecology by linking them.

The author is emeritus professor of physics and ecological wisdom at Jamia Millia Islamia and Jawaharlal Nehru University, New Delhi