RIVER POLLUTION IN ASSAM
Dr. Bidyut Bikash Sharma
When we talk about the rivers in Assam, we usually talk about the geomorphological and the hydrological characteristics of the Brahmaputra and Barak river systems. We tend to discuss more about the ill effects of the recurring flood and erosion caused by the rivers. We blame the rivers for the economic devastation they cause to our state annually and also for the loss of lives and livelihood of the people. But, we rarely discuss how we human beings are silently killing the rivers by polluting them. River pollution is an insidious problem and we never discuss it or take any curative action until it manifests into a major civic problem. River pollution at large draws very little attention of the society. In India it is only because of a series of reports by the CPCB and subsequent court directives, that the Govt. and civil society is taking up the issue of river pollution at fore. Same is the situation in Assam.
As per the CPCB report of 2018, there are 44 pollution river stretches across Assam falling in the priority classes from I to V; river and water bodies falling in priority class I are the most highly polluted warranting immediate action. Assam stands at the second position in the country after Maharashtra for having the second highest numbers of polluted river stretches. It is interesting to note that although Assam is comparatively a less developed state in terms of industrial infrastructure when compared to other states like Gujarat, UP, Haryana etc., yet the rivers of Assam are highly polluted. The level of pollution in river stretches has been determined on the basis of some key parameter like the Biological Oxygen Demand (BOD) among others.
Let us go into depth of the technical details of the CPCB report. Firstly, out of the 44 ‘‘Polluted river stretches’’, there are 39 actual river stretches and the rest 5 are wetlands. Again among the rivers, there are two stretches that are within the main channel of Brahmaputra and the Barak river. Rest of the river stretches fall within various tributaries of these two rivers. Thus, different stretches of river in both Brahmaputra and Barak valley are polluted leading to unacceptable level of BOD values. According to the CPCB report, the river stretch in Brahmaputra (from Kherghat to Dhubri) had BOD levels upto 6.4 mg/L and in the Barak (the river stretch from Panehgra to Silchar), the BOD values ranged from 3.5-4.2 mg/L. According to CPCB criterion, the particular stretch of Brahmaputra fell in the Priority class III and the stretch within Barak river was categorized as Priority Class V.
Now among all the tributaries of Brahmaputra-Barak river systems, the CPCB has identified the Bharalu river to be the highest polluted with maximum BOD value reaching upto 52 mg/L. This resulted in the Bharalu river being categorized as a Priority Class I waterbody. Similarly, in the same report, CPCB has identified the Borsola & Silsako wetlands of Guwahati city as Priority Class I waterbodies owing to very high BOD values reaching upto 30 mg/L. Also, the Sorusola Beel and Deepor Beel (both wetlands) have been placed in priority class II and priority class III respectively due to high BOD values. Now, the Bharalu, river, Silsako, Borsola, Sorusola and the Deepor Beel are all located in the city of Guwahati. Rapid urbanization and unsustainable way of city management is the main culprit behind the pollution of these once pristine freshwater ecosystems. One must also take note of the fact that Deepor Beel is a protected area - a wildlife sanctuary and the lone Ramsar Site of Assam. Yet, owing to unsustainable practices of the citizens and apathy of the Government agencies, the BOD levels were at beyond acceptable limits with a mean value of 10.6 mg/L. Now the question arises as to what has contributed to so much of high levels of BOD in rivers and other water bodies of Assam.
The main reason behind such high BOD levels is nothing else but pollution due to high input of organic matter load. The readers must be aware of the fact that the state of Assam does neither have a public sewerage system, nor any installed sewage treatment plant (STP). Therefore, all the domestic sewage alongwith other industrial effluents and other wastewater are directly fed to the storm water drainage system which ultimately carries the mixture directly to the rivers and waterbodies.
Let me explain the situation with the case of Bharalu river. Basically, Guwahati city has a natural drainage system- a network of natural streams - which I preferably call as the Bahini-Bharalu-Basistha river system or network. These individual streams flow through an entirely densely populated residential, industrial and commercial areas of the city. All these 3 rivers are highly impacted in terms of pollution. In terms of geomorphology, Bahini constitutes the upstream stretch of the Bharalu river. During the 70’s, the river water was clean and people used to catch fish and also used the water for religious rituals. However, the water quantity started to deteriorate after 1983-85. We can attribute this sudden change to the diversion of a part of Bahini to Basistha by excavating a channel and setting up a sluice gate. This was done in the year 1983 by the erstwhile Flood Control Department. The project significantly altered the natural hydrological condition of the downstream of Bahini river, i.e. - the Bharalu river. Simultaneously, there was tremendous population growth and unregulated settlement within the city since the govt. had shifted its capital from Shillong to Dispur in Guwahati. In the absence of a dedicated sewerage system and due to weak or non-existent environmental regulations during that period, the Bharalu river started receiving untreated wastewater, sewage and dumping of solid wastes which still continues unabated. In the absence of environmental flow of the river, Bharalu turned into a sewage canal. In my own research it was observed that there is total absence of fish fauna and presence of only pollutant tolerant species in the pollution impacted stretches of the drainage network. Water quality analysis shows that Dissolved Oxygen (DO) ranged from 0.0 - 5.40 mg/l with a mean of 3.71 mg/l. Thus, there are many stretches within the B-B-B river network which are technically ‘‘hypoxic’’ (absence of dissolved oxygen in water). According to Govt. reports, BOD values were found to be as high as 54 mg/l. BOD was above the permissible limit and it significantly deteriorated as we proceed downstream. Another, important water quality parameter is the ‘P’ (Phosphorous) - determined as Phosphate (PO43-) which was found to be maximum of 11.37 mg/l, which in above the permissible limit of 5.0 mg/l. The reason behind such pollution is the direct entry of about 70 MLD (million litres per day) of sewage which is further projected to increase to 280 MLD by 2025 and all of these are carried down by around 330 drains.
Further, as per CPCB and other Govt. agency reports, the bacteriological contamination was very high as indicated by the water quality parameter - Fecal Coliform count. Fecal coliform count in the river water was found to be 3000 MPN/1000 ml which is way above the permissible limit.
Apart from the above categories or types of pollution, rivers in Assam also faces same other serious forms of pollution like oil spillage, heavy metal contamination etc. There have been increasing numbers of instances of oil spills in the past 10-15 years. More than 100 incidents ranging from small to moderate to major oil spills have been reported in the state in past 10 years. As far as heavy metal contamination of Brahmaputra river in concerned, a recent study by researchers from Cotton University have found that the concentrations of Nickel, Chromium, Mercury and Cadmium were very high in the river water, the concentration being highest in the stretch along Guwahati city. Another serious pollution of river water in Assam is due to the occurrences of pesticides and polycyclic aromatic hydrocarbons (PAH). In a research conducted in 2011, the mean concentration of DDT was 5402 mg/L and 6121 mg/L in Dibrugarh and Nagaon surface water sampler. According, to the study 93% of the samples for DDT exceeded the WHO permissible limits for drinking water. Thus, from the above discussion we can say that the main sources of river pollution in Assam can be categorized as -
i. Municipal solid wastes
ii. Raw domestic sewage
iii. Contaminated storm water
iv. Untreated or inadequately treated industrial effluents
v. Atmosphere deposition
The Way Forward
Controlling river pollution is definitely not an easy task. It involves not only whole hearted efforts of the govt. but also active cooperation from the public in general. A broad strategic plan would be required to mitigate the pollution of Brahmaputra and Barak river system and the connected wetlands. Until a long term plan in derived, some actions can definitely be taken up by the Govt. as short term measures. These may be both structural & non-structural. Structural measures should be taken up keeping in view the longer term plans, so that there doesn’t occur any duplicity of work and public fund is not wasted. Keeping in view, the condition of the rivers of Assam, the following measures should be taken up urgently for mitigating the pollution problem:
i. Strict enforcement of environmental laws/rules; specifically, those related to municipal solid waste handling and management, Industrial effluents, e-waste and Biomedical wastes
ii. Installation of sewage treatment plant (STPs) in specific locations based on water quality data & the projected population growth.
iii. Construction of sewerage network separately from the storm water drainage system and taking into consideration the projected population growth for atleast next 50 yrs.
iv. Re-structuring the existing storm water drainage system according to natural topography of the region
v. Establishing state of the art Municipal Solid Wastes management facilities across all the major towns and cities of the state
vi. All restoration activities concerning the rivers and wetlands should be carried out taking into consideration of the entire catchment area instead of only the polluted stretches
vii. Land settlements in urban and peri-urban areas must be regulated and should be solely based on modern town planning concepts
Conservation of rivers and riverine habitat is the need of the hour and availability of unpolluted water for human sustenance is at the core of majority of the activities that are targeted towards achieving sustainable development goals in the state of Assam.
---------------------------------------------
