Generally, rivers are divided into two types. One is snow-fed and the other rain-fed. The ecology of the one always differs from the other.
The flora and fauna as well the avifauna of these rivers vary because of the prevalence of distinctive climatic conditions. In case of snow-fed rivers, the pine trees are noticed, but the broad-leaved species are seen in rain-fed rivers.
In Odisha, all the rivers are rain-fed and contain tropical board leaf species. The trees found along the river banks are mostly evergreen.
The evergreen trees mean the green leaves are seen in the tree throughout the year. The examples are Jamun, Hinjal, Panasa, Mango, Phasi, Neem, Chakunda, Kanta and bamboo etc. Other than tree species, some grasses and reeds also grow naturally in the river banks. These species create a cool climate favourable to the growth of various wild lives.
Generally, varieties of land animals, right from mammals to egg laying reptiles and ground birds settle in these grasses. Different types of flowering and non-flowering orchids also are found. Besides, avifaunas of different nature also settle in the environment. The massive food chains help them grow.
The riverine ecology can be divided into three parts. The first part covers the catchment areas and the lands of hilly terrains, where mostly deciduous trees and shrubs are seen. The ground floras are massive. This is most important part of ecological wealth of riverine land. Most of the tributaries of the principal rivers join the mainstream within this portion of terrain. This part is very much susceptible to soil erosions and washout of top mother soils. It is here that special measures should be taken to check soil erosions and conserve soil moisture.
In case of the recent devastating flood of Kerala and Odisha’s Malkangiri, we can attribute the disaster to improper management of drainage system. Rivers are an integral part of the drainage system of State or country.
By ignoring the drainage system, the ecological resources cannot be managed proficiently. There are 45 tributaries and sub-tributaries of the Mahanadi, but all the major tributaries come under Chhattisgarh State and two important tributaries like Ib and Tel come under Odisha.
The Mahanadi is a most important drainage system of Chhattisgarh and Odisha, which entirely commands the ecology of both the States. The drainage system is quite responsible for ecological potentialities.
The rich ecological potentialities of a State imply rich heritage of the same. The Eastern Ghat of India is the mother of the Mahanadi.
Similarly, the Western Ghat is the mother of all rivers in Kerala, Tamil Nadu and Karnataka.
The variations in topographical gradient or the stiffness command the speed of the stream water. The richness of ecological wealth of catchment areas and watershed areas of river controls the acceleration of stream flow. The destruction of the ecological wealth of the catchment areas and watershed areas for the purpose of industrialisations leads to disasters, like the one in Kerala. Hence, needless to say, the catchment areas and the watershed areas are responsible for cause of flood and by all accounts, we need to maintain the ecology in these areas.
The total catchment areas of Mahanadi is 1,40,716 sq km, which is also vulnerable to flood. Hence, scientific management of catchment areas is very important for protection and conservation of ecological base of the river. Total 65, 580 sqkm of catchment area of the river come within Odisha.
The total length of the Mahanadi is 960 km, but the length of the river from source to delta head is 853 km. The most vulnerable distance of the stream is from upper point of delta to river mouth which is 107 km. The delta area is most critical during flood period.
These areas are very much known as flood ravaged areas and flood plains. This comes under second category of riverine areas.
Now, the Government of Odisha has planned to raise plantations of indigenous trees on banks of all the rivers in the State. Such an attempt leads to ecological management of river. This also amounts to forest and natural resource management. The plantations in both sides of river banks will boost the ecological and economical development of the people.
They also can promote the natural resource managements like pisciculture of stream based fisheries. Generally, the riverine fish get ample of herb-based food material from the stream waters. So the nature’s grown ecological systems of riverine land are to be protected and conserved. Such activities can promote fishing and protect the livelihood of lakhs of people.
These days sand mafias are active in banks of rivers and streams. The extensive scale of sand lifted from river beds for construction activities with and without the permission of State Government has posed a grave threat to the rivers. Similarly, earth from banks of river and streams are removed for construction works and brick making.
Scores of illegal brick kilns are mushrooming up every now and then. The trees from river banks are felled and foliages cleared for burning the bricks.
Such unlawful activities lead to the bank erosions of rivers and streams and must be stopped for healthy management of rivers. Again, a number of industries is also established for different purposes in the banks of river, creating pollution.
Some of them not only unlawfully use the water beyond their permissible level, but spoil the water resources by releasing waste water and dumping indusial garbage.
The third part of a river is its mouth, where it meets with the sea.
Here, very rich bio-diversities of flora and fauna are found. The coral reefs are also found in the region. Right from micro-organisms to oceanic mammals, all kinds of faunas are found in this part.
The unique floras like mangroves are seen in intertidal region of river mouths. Here the fresh water from rivers joins the oceanic water and from a unique ecological system. The species here have special adaptations to thrive in brakish water and in silt depositions.
Because of rich diversified eco-systems, the socio-economic conditions of the region are also rich. But due to industrialisation, these regions also are facing huge degradations.
(The writer is a former forest officer and environmentalist. Email:nadiya.kanungo@gmail.com, M-9937460649)