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How and where can ‘greener’ help Indian Rivers? – IMPRI Impact and Policy Research Institute

How and where can ‘greener’ help Indian Rivers? - IMPRI Impact and Policy Research Institute

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.  

The process of greening or re-vegetation means raising or creating conditions for the 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 the growth 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 their own under suitable conditions of soil, climate and safety from adverse influences.   

A river is a channel (one or many in number) that 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 is called the ‘base’ flows. Plants and animals associated with Indian rivers are thus adapted to this sudden change in their flow over the year.

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 the 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 the 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:

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 for snowmelt 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’s 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 the case of the 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. 

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 a rich aquifer presence.

In some stretches ravine formations and wide valleys are conspicuous. The 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 a pioneering nature where grasses score over trees although the higher bank might carry more trees than the lower bank.

Most riparian vegetation is flooded 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.    

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 the river basin is also called the mouth of the river.

Here 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 groundwater recharge but morphological stability of river mouths among 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 the 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 the augmentation of stream flows.

You might notice that I keep mentioning ‘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 fulfil its biological functions. The same tree as part of the 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 streamflow 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 a 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 overnight or project-driven phenomenon. The secret to the success of any sustainable river rejuvenation lies in the 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 were 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 with 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 to facilitate a 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 a long term basis. To begin with, the DPRs prepared by the ICFRE may appropriately be revised with the focus shifted away from the main stem onto lower order tributaries and their catchments. The DPRs should in any case be all in the public domain, open to review and changes.

First published on South Asia Network on Dam, River and People, titled How and where can ‘greening’ help Indian Rivers?, on 27 March 2022

Read another piece on the Forest survey by Manoj Misra, Why Does The Forest Survey Disappoint Everyone, Except Forest Ministry? on IMPRI Insights

Read another piece on Accountable Development by Manoj Misra titled “A Hope To Make Development Accountable To Planet In 2022” at IMPRI insights.

Read another piece on River pollution by Manoj Misra “Making Yamuna Flow Again” at MPRI insights

About the Author

Manoj Misra, a former forest officer is the Convener of Yamuna Jiye Abhiyaan (Campaign for a Living Yamuna), a civil society consortium.

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