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Reducing pollution, safeguarding floodplains: Can ‘greening’ help Indian rivers?


By Manoj Misra* 
The Indian Council of Forestry Research and Education (ICFRE) under the union Ministry of Environment, Forest and Climate Change (MOEFCC) has recently prepared Detailed Project Reports (DPRs) for the rejuvenation of 13 Indian rivers and released a document called the ‘overview of Detailed Project Reports for rejuvenation of major Indian rivers through forestry interventions’. These rivers are Jhelum, Chenab, Ravi, Beas, Sutlej, Yamuna, Brahmaputra, Luni, Narmada, Godavari, Mahanadi, Krishna and Cauvery (Kaveri). This article is in the nature of a caveat on the overview DPR report and the plans.
Process of greening or re-vegetation means raising or creating conditions for growth of vegetation (herbs, shrubs, grasses, lianas and trees, big or small) at locations which once carried it in a natural manner. It is different from ‘plantations’ marked by growing of tree seedlings, which in due course may or may not become forests. Also it is a fact that while tree seedlings and soil binders like bamboo can be planted, other forms of plant life usually comes up on its own under suitable conditions of soil, climate and safety from adverse influences.
A river is a channel (one or many in number) which drains its catchment of all the runoff it receives during a storm period. In a country like India there is a specific time in the year called the ‘monsoon’ when storm events are far more frequent than during other months of the year unlike in many parts of the world where storm events with high or low rainfall are well distributed over the year. So rivers in India carry high to very high runoff during the monsoon months (June-October) and then almost abruptly lean down to what are called the ‘base’ flows. Plants and animals associated with Indian rivers are thus adapted to this sudden change in its flow over the year.
Source: https://www.bedfordcountyconservation.com/
Furthermore a river does not exist in isolation nor is homogenous in structure over its entire length. What is commonly understood as ‘the river’ (main-stem like Ganga, Yamuna, Narmada, Mahanadi or Kaveri etc) is actually the end result of a complex woven system of hundreds and even thousands of smaller streams, called ‘tributaries’ that combine to produce the main-stem. For convenience of understanding these smaller streams are classified according to their ‘order’. A river looks uncannily like a tree where two ‘first’ order streams meet up to form the ‘second’ order and so on to ‘third’, ‘fourth’, ‘fifth’ order… etc., but only two similar order streams on meeting will form a higher order and not otherwise.
The entire spread of land with its natural and man altered variations that a main-stem river system drains is called its ‘catchment’ or ‘basin’. Most large or main-stem rivers have three distinct sections:
1. Hilly catchments or founder basin: the streams here are hemmed in within valleys with natural, agricultural and urbanized stretches. Flow is the master variable and is dependent on rain, runoff, springs, nallas and waterfalls. Lean season flow has little dependence on groundwater supplies in the valleys except from snow melt in glacial zones. As the founder basin of any major river this constitutes a critical but small portion of the overall basin of the river. This section of the basin is also full of lower order streams feeding the river main-stem. Here the longitudinal gradient is steep and the river speed is high. So is the eroding power of the stream. Here ridge to valley differentiation is pronounced and most hill slopes are wooded with the tree cover density dependent on the influence of ‘aspect’. In case of Himalayas the northern aspects and valleys are often denser than the southern aspects and ridges, while in the Western and Eastern Ghats the western aspects are denser.
2. Plains (river channel here is braided, often has multi-channel, is meandering, spread over wide channel width and pronounced floodplains) have natural, agricultural and urbanized stretches. Flow as the master variable is dependent primarily on monsoon and return flows from the aquifers during the lean (non monsoon) season. This constitutes the major section of any major Indian river. Here several higher order tributaries might meet at various places along the length of the main stem but the presence of lower order streams is low. This stretch is primarily made up of deep alluvial deposits with rich aquifer presence. In some stretches ravine formations and wide valleys are conspicuous. Longitudinal gradient is moderate and so is the river speed. Here ridge to valley morphology is not always discernible although one bank is often higher than the other. Natural vegetation is of the pioneering nature where grasses score over trees although the higher bank might carry more number of trees than the lower bank. Most riparian vegetation is flood dependent and incidences of large scale changes in vegetation and channel morphology following floods are common. Erosion and deposition of silt during and post floods is a natural phenomenon.
3. Delta (river channel distributes itself into several streams, called the distributaries, as they proceed to meet the sea). This is a very dynamic section of the river and here the master variable is the sea’s tidal action. This section of river basin is also called the mouth of the river. Here too exist the natural, agricultural and urban stretches although there is often significant overlap amongst them. The longitudinal gradient here is hard to fathom and the river speed is slow and variable under the tidal influence. Natural vegetation is typical of the brackish estuarine environment dominated by ‘mangrove’ species in places where the land is still left to nature. The key role of mangrove forests is not ground water recharge but morphological stability of river mouth amongst other ecological functions. Deposition of silt is the marked characteristic of the streams here.

How can re-vegetation augment stream flows?

It is no secret that Indian rivers are in bad shape. Reasons are many but ‘dwindling flows’ in them is the main one since flow is the master variable in a river system. Rivers have lost their flows to diversion by dams and barrages and loss of vegetation in their hilly catchments where smaller order streams predominate. Now while removal of such dams and barrages that are past their ‘life’ (every manmade thing comes with a finite life span) is an option that we in India must seriously begin to consider, re-vegetation of hilly catchments is something that can be readily taken up with benefits much beyond augmentation of stream flows.
You might notice that I keep mentioning about ‘hilly’ catchments and not the other sections of the river for re-vegetation and there is a reason behind it. While a forest with its full complement of undergrowth, middle and upper canopy is a boon in hilly catchments the same could be a disaster in the floodplains of a river lower down in the plains section of the same river. While the delta section of the same river is a totally different ball game.
Let us not forget that a tree is also a water guzzler, it draws water from the underground to fulfill it biological functions. The same tree as part of forest on hill slopes helps lessen the speed of storm period runoff, percolate part of it underground and prevents soil loss, consequently regenerating springs, waterfalls and stream flows down in the valley; in the plains it can quickly dry up soil moisture and shallow aquifers which are essential for ensuring base flows in the river post monsoon.
So a word of caution here is that while we should go all out to appropriately (this is very important caveat) re-vegetate our hilly catchments keeping in mind the ‘aspect’ factor of hill slopes and also green all our hills big and small wherever existing as they form the catchment of one or the other small stream feeding a bigger stream, we must scrupulously avoid drying up our already precariously placed shallow aquifers in our ‘plains’ sections of the rivers by planting trees on them. In the delta, plantation of mangroves wherever land is available is of course a dire necessity.

How to go about it?

River rejuvenation is not and cannot be an overnight or project driven phenomenon. The secret of success of any sustainable river rejuvenation lies in restoration of its lower order streams which together shall rejuvenate the higher order streams. Our focus for greening should thus be on the hilly catchments of first, second and third order streams. In plains stand alone hills which abound in central and peninsular India should be taken up for such appropriate greening.
While for the main-stem the process of reduction of pollution, safeguarding of floodplains and removal of dams and barrages (or where not feasible immediately, ensuring adequate flows down these structures) can go on as part of a basket of river rejuvenation strategies aimed at aviral, nirmal and swacch kinara triad, we as a nation must go all out to first establish ‘working models’ on a mission mode of augmenting flows in the first, second and third order ‘hilly’ streams strategically and representatively selected and spread all over the country. These re-vegetation efforts leading to documented enhanced flows against initially established baselines must be carried out not as any government departmental project but by groups of local people, communities at the gram sabha level as the frontline stakeholders. Appropriate methodologies and local level institutions can be found or devised. GIS and other experts can be made to partner these local groups. Even some startups could take this up as a worthwhile enterprise. Funds from MGNREGA, GREEN INDIA MISSION and CAMPA etc could be utilized for establishing these initial working models. Local forest departments may have facilitating role in it all but all the planning and execution should be led by local gram sabha groups. Later a river basin level, state wise well funded mission could be created to upscale the various already established working greening models. Such an effort shall not only be natural and sustainable but can have huge and sustained employment generation potential on long term basis. To begin with the DPRs prepared by the ICFRE may appropriately be revised with focus shifted away from the main-stem onto lower order tributaries and their catchments. The DPRs should in any case be all in public domain, open to review and changes.

Manoj Misra (yamunajiye@gmail.com), a former forester, is the Convener of Yamuna Jiye Abhiyaan. Courtesy: sandrp.in

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