Environment and Ecology

The ecosystem of a river consists of its natural environment, which includes biotic (living) interactions amongst plants, animals and micro-organisms, as well as abiotic (nonliving) physical and chemical interactions. Environment and ecosystem of Indian rivers have suffered from intense human intervention resulting in loss and degradation of their natural habitat and as a consequence many fresh water species including fish etc. have become heavily endangered, particular in Ganges basin where heavy fresh water demands are ever-increasing. River conservation and management activities in most countries including India suffer from inadequate knowledge of the constituent biota. The main causes of the loss of biodiversity in freshwaters are habitat degradation and fragmentation, exotic species introduction, water diversions, pollution, and global climate change impacts.


The River Ganga is facing challenges of maintaining its ecological integrity due to declining flow and degrading water quality due to pollution and construction of dams and barrages mainly to divert the river water for irrigation in unsustainable manner. Besides, the ongoing and proposed constructions of hydroelectric projects on the main stem of Bhagirathi, Alaknanda and their tributaries in the Himalaya are declining the flow as well as water quality of the river thus adversely affecting the ecosystem functions of the Ganga. Managing upper-watershed forests in the catchment areas wisely, adopting alternative non-structural measures to control floods and droughts and regulating discharge of pollutants into the river waters are essential to maintain ecological health of the Ganga. Efforts would have to be made for sustainable utilization of the river water and its bio-resources. Also since the river basin covers China, Nepal, India and Bangladesh; the best way to protect and manage the river would be by close international co-operation among all the countries within the river basin bringing together all interests upstream and downstream. Apart from this, there is an urgent need for research to pursue and promote for conservation planning to protect freshwater biodiversity and river ecosystem.


In India, majority of the tributaries of the Ganges are being controlled by barrages and diversion for diverting flow for irrigation, hydro-electric projects etc. and as a result fish catch has been declined, and thereafter, loss of species diversity have been reported. This has badly affected the ecological integrity of the rivers. The fast flowing pristine water of the Ganga and tributaries with thousands of rapids has been converted into reservoirs of stagnant water or several portions of rivers have completely been devoid of flow. Moreover, twenty nine freshwater fish species been recently listed as threatened under vulnerable and endangered categories. Therefore, conservation and restoration of river have become vital for the overall development and nutritional and livelihood security of the Indo-Gangetic region. The ecosystem services of a river are not confined to providing water and fish but probably the most important service lies in the assimilation of wastes from their catchments including those from anthropogenic sources. Practically all components of biodiversity contribute to this waste processing function, and thereby result in maintaining high water quality and productivity.




In the Ganga river basin, alterations in biota diversity and community structure are mainly due to hydro-logical alterations, dam constructions, over fishing, pollution, water diversions, changing land use pattern, exotic species invasion, rapid sedimentation, deforestation, climatic changes and land erosion etc. Assessing impacts and threats directly informs conservation strategies, management options and priorities for actions. Freshwater ecosystem conservation plans rely mainly on assessing ecological integrity of ecosystems, based on the notion that ecosystems of high ecological integrity support and maintain the full natural range of biological features and ecological processes. A series of barrages and dams have been commissioned in the upper segment of river Ganges from Rishikesh to Narora and the Tehri dam constructed in the hills of Uttarakhand has considerably reduced the water flow and have shown detrimental effects on physical attributes and destruction of feeding, spawning, and migration routes of Mahseer and  the other migratory species like dwarf goonch(Bagariusbagarius), yellowtail catfish (Pangasiuspangasius), pangas catfish (Siloniasilondia), hilsa(Tenualosailisha) and long whiskered catfish (Sperataaor).


The main eco-hydrological alterations are constructions of dams and barrages on the river, loss of wetlands and floodplain habitat and water diversions. Alterations of water quantity, seasonal flows and patterns of flow variability such as by damming and abstractions, or inter-basin transfers (IBTs) have substantial and negative consequences for the maintenance of biodiversity in many rivers.


Pollution Status

A study done by CPCB for the period 2006-2011 it has been found that the River Ganga in Uttarakhand is relatively clean and complying with the criteria, except for Total Coliform (TC) and Fecal Coliform (FC) which is higher. However the location Haridwar D/s appears as a critical location. Spatial and temporal of water quality in Uttar Pradesh upper stretch (from Garhmukteshwar to Kanpur D/s) of River Ganga was found polluted. Water Quality Assessment in Uttar Pradesh Lower Stretch (from Dalmau to Trighat) was also found polluted. Water Quality Assessment in Bihar (from Buxar to Khalgaon)is comparatively clean in the stretch of Bihar with respect to organic pollution. Fecal contamination was observed high and beyond the criteria at most of the locations. Water Quality Assessment in West Bengal was polluted with respect to organic and coliform pollution the stretch of West Bengal at most of the monitoring locations. CPCB identified three polluted stretch in river Ganga D/s of Haridwar to Garhmukteshwar, from Kannauj to Varanasi D/s and few locations at West Bengal (Dakshineshwar, Uluberia and Diamond Harbour).


Toxic Chemical

The River receives approximately 12,000 million litres per day (MLD) municipal sewage throughout its stretch for which presently there is a treatment capacity of only around 4,000 MLD. There are acknowledged fifty cities (Class I (36 No.) & Class II (14 No.)) along the mainstream of Ganga, discharging 2723.3 Million Litre/day wastewater out of which 1208.8 MLD has the treatment capacities i.e. 44 %.The river water is polluted with toxic chemicals and microbes. There are 764 grossly polluting industries discharging wastewater to main stem of River Ganga (either directly or through drains) and its two important tributaries Kali-east and Ramganga in Uttarakhand, Uttar Pradesh, Bihar and west Bengal. Out of 764 industries, 687 are located in Uttar Pradesh. The water consumed by grossly polluting industries is 1123 MLD. Total wastewater generated by grossly polluting industries is 501 MLD. This is 45% (approx) of total water consumed. In terms of number of industrial units, tannery sector is dominating where as in terms of wastewater generation Pulp & paper sectors dominate followed by chemical and sugar sector.


Large number of indus­tries located in the basin discharge enormous amounts of toxic wastes to the Ganges. The severe impacts of industrial effluents disposed into the river have resulted in fish kills reported from time to time. Bio-accumulation of heavy metals was observed in fishes in the lower stretch of the river and at Varanasi.


Indiscriminate use of organo-chlorine pesticides like DDT, Eldrin, Dieldrin, BHC, HCH etc. both in agriculture and health sectors in Ganga Basin has led to bio-concentration and bio-magnification of these toxic chemicals in fishes and other endangered animals like the Ganges dolphins.The agriculture sector drains about 134.8 million waste into the river basin. Similarly, 2,573 tonnes pesticides, mainly DDT and BHC-Y are applied annually for pest control. The Ganges Basin is reported to carry some 200 tonnes of biological oxygen demand (BOD) per day gross pollution. However, it is still relatively localized and focused on urban centers including Hardwar, Kanpur, Varanasi and Diamond Harbour near Kolkata.


All such anthropogenic activities in the Ganga Basin are not only declining biodiversity in the basin but the rivers are facing threats of their survival. So it is of utmost importance that we must allow ‘Aviral Dhara’ and ‘Nirmal Dhara’ (uninterrupted quality flow) in the rivers. We should try to minimize wastage of waters being supplied for irrigation purposes so that rivers can have maximum possible flow. For this various technology of irrigation like sprinkler irrigation, drip irrigation etc. should be adopted.



·        The creation of specially targeted fish protected areas is an important step in the conservation of Ganges and its biodiversity. There is a need to identify the tributaries in the upper stretch of river Ganges which are important habitats of fish to breed and spawn so that can be declared as protected areas in consultation with local communities.

·        A proper environment assessment is required before taking up any hydro projects in the Ganges.

·        It is necessary that minimum flow throughout the year is maintained to support eco-system of river and aquatic life. It would be advisable to create more water storage facility for Ganga riverine system and release water in the lean period to effectively maintain minimum flow in the river.

·        Major industrial sector namely, Tannery, Sugar & Distillery, Pulp and Paper mills contributes significant pollution load to river Ganga and its tributaries. There is immediate need of firm environment surveillance in order to check their compliance with environmental standards.

·        There is a large gap between the wastewater generation and treatment capacity. More and more sewerage treatment facilities at towns along the Ganga and its tributaries/ sub- tributaries may be created under Ganga Action Plan (GAP), National Mission on Clean Ganga (NMCG), etc.

·        In the middle and lower stretches of the river Ganges the conservation strategies for fishes must take into account the life history traits and habitat requirements of migratory species.

·        Biological characters of the many species are still unknown and therefore studies are needed.

·        Restoring the natural stocks of the species should be a priority, which includes ensuring minimum flow requirements and revival of lost breeding grounds and thereby restoring the failed recruitment process. This may be achieved by negotiation with the stake-holders so that the required flow and depth of the river is maintained.

·        In addition, restoration of floodplain and associated wetlands should be a priority for conservation because floodplains play an integral part of riverine ecosystem. Many floodplains have already lost their connection with main channel due to heavy siltation. Floodplains serve as breeding and nursery grounds for several species.

·        Towards restoring those critical habitats, research efforts should be translated into social and political actions as early as possible.

·        Efforts should be made to check the sediment flow by extensive plantation of native trees, shrubs, etc. on the riverbank and adjoining catchment area.

·        Effective construction of fish passage structure is necessary. Conventional fish ladders designed may not be successful because most fishes do not jump. In the middle stretch of the river Ganges (Allahabad), Hilsa (Tenualosailisha), which used to form a good share in catches below Allahabad has almost disappeared after inception of Farakka barrage despite fish ladders were installed. Steps should be taken to improve fish pass way so that the fishes may negotiate upstream areas.

·        Research efforts on generating the life history of threatened fishes in the river are necessary for successful conservation. Information on the role of species diversity is the functioning of ecosystems should be incorporated into comprehensive environmental management policies of the large Indian rivers.


It is a high time to introspect and analyse the cost-benefits of the so called developmental activities in the name of flood control and water resource development in Ganga Basin. We should have minimum interference with our natural systems especially rivers which are not only our life line but have been cradle of our civilization.


The River Ganga has been not only the cradle of the Indian civilization, but is the life line for the people of this part of the world. The river created vast plains of fertile land which attracted people from Central Asia to settle. Over the time several urban settlements came on the banks of the river. The river basin is one of the most thickly populated areas of the world. It remained source of pure freshwater and that of economic, spiritual and cultural activities since time immemorial. It sustains thousands of aquatic species of flora and fauna including many endemic and charismatic mega-fauna like the Ganges dolphin, Gavialis etc. However, since 1950s the river is facing threats of erosion of its ecological integrity due to anthropogenic pressures in the form of construction of dams, barrages and embankments; loss of forest cover in its catchment area leading to heavy siltation, pollution from industrial effluents and domestic sewage degrading the water quality to the extent that the river water is not fit for even bathing purposes what to talk about drinking purposes. The river has very reduced flow, worst between Narora and Allahabad where river has more effluents than freshwater. The declining flow has badly affected the assimilative capacity of the river and the river has lost its self-purifying capacity.


Nevertheless, the river harbours rich and abundant aquatic biodiversity. Recent ongoing and completed hydroelectric projects in the Himalayan region are likely to worsen the situation. Invasion of exotic species is another big threat for the river biota. Apparently, the biota and river both have resilient capacity. There is immediate need to take measures to increase flow and reduce pollution load in the river. This is possible only if water-efficient agricultural practices are opted which will reduce abstraction of river water in irrigation canal, mass scale plantation is undertaken in catchment area of the river, wetlands in the river basin are conserved, stringent measures are taken for pollution abatement, and peoples participation is ensured in 'Save Ganga Movement'.


Lakra, W. S., Sarkar, U. K., Kumar, R. S., Pandey, A., Dubey, V. K., & Gusain, O. P. (2010). Fish diversity, habitat ecology and their conservation and management issues of a tropical River in Ganga basin, India. Environmentalist, 30(4), 306–319. https://doi.org/10.1007/s10669-010-9277-6

2. Sarkar, U. K., Gupta, B. K., & Lakra, W. S. (2010). Biodiversity, ecohydrology, threat status and conservation priority of the freshwater fishes of river Gomti, a tributary of river Ganga (India). Environmentalist, 30(1), 3–17. https://doi.org/10.1007/s10669-009-9237-1

3. Sarkar, U. K., Pathak, A. K., Sinha, R. K., Sivakumar, K., Pandian, A. K., Pandey, A., … Lakra, W. S. (2012). Freshwater fish biodiversity in the River Ganga (India): Changing pattern, threats and conservation perspectives. Reviews in Fish Biology and Fisheries, 22(1), 251–272. https://doi.org/10.1007/s11160-011-9218-6