STATUS OF COOUM RIVER
The Cooum River originates from the surplus course of Cooum tank in Tiruvallur District.
It runs east for a distance of about 65 kilometres and confluences with the Bay of Bengal downstream of Napier Bridge, traversing a distance of 20 kilometres within Chennai city limits.
Cooum River is fed by Kosasthalaiyar and Palar river surpluses
Cooum River also supplies water to Chembarambakkam lake in the Adyar Sub-basin from Korattur Anicut.
Cooum River is connected to its adjoining basins through the Buckingham Canal.
Cooum River supports a substantial portion of irrigation and additional rain fed agriculture in its upper part and also provides water supply to Chennai city and its adjoining areas.
Cooum River also acts as the major flood carrier for Chennai city with its arms viz., Otteri Nallah in the north (10.8 km) and Virugambakkam to Arumbakkam drain in the south (6.4 km).
The upper catchment of Cooum River is primarily rural
As it enters the peri-urban areas and Chennai City, the river is constrained in channels before draining into the Bay of Bengal.
The Cooum River in its upstream rural areas shows issues of catchment degradation and tank siltation. There is also no minimum flow maintained in the river during the lean season.
As the river flows through peri-urban areas and municipalities, there are increasing problems of water quality. The highly polluted reputation of the river also leads to public apathy and disposal of solid waste on the river bed that impacts downstream water quality and oxygen levels in the water.
When it enters the city, the river is basically an urban sewer receiving
*municipal and industrial wastewater
*solid waste (especially near bridges)
*refuse from slums.
This results in the direct impact of polluted anoxic stretches, as well as raises public health (including from mosquito breeding in stagnant waters) and odour concerns and secondary groundwater pollution.
The river mouth is subject to blockage by sand bars.
INTEGRATED COOUM RIVER ECO-RESTORATION PROJECT
It was proposed to take up the restoration from Paruthipattu as the major sources of pollution have been observed to be downstream of Paruthipattu, in the densely populated urban areas.
The Project area presently being covered for restoration comprises the stretch from Paruthipattu to the river mouth in the Bay of Bengal as the major sources of pollution have been observed to be downstream of Paruthipattu, in the densely populated urban areas.
To ensure effective abatement of pollution and protection of rivers by adopting a sustainable approach to promoting inter-sectoral co-ordination through comprehensive planning and management.
To maintain ecological flows into the river with the aim of ensuring water quality and sustainable development.
To develop the river front within urbanized areas, wherever possible.
To explore potential future uses of the river after restoration.
Project Implementation
the Integrated Cooum River Eco-Restoration Project (ICRERP) was taken up by the Government under the aegis of the Chennai Rivers Restoration Trust (CRRT).
The ecological restoration of Cooum River from Paruthipattu check dam to the river mouth in the Bay of Bengal for a length of 32 km was taken up and the Government have accorded Administrative Sanction of Rs.735.08 crore for the implementation of Integrated Cooum River Eco-Restoration Project.
Various pollution abatement measures are proposed such as
Interceptors and diversion of sewage to improve the water quality,
river channel improvement to enhance ecological flow of the river development of parks and maintenance pathways.
River bank vegetation and mangrove plantations are planned to enhance the diversity of flora and fauna in the Cooum riverine system.
Study
• The River Cooum, once a fresh water source is today a drainage course collecting surpluses of 75 small tanks of a minor basin. The length of the river is about 65 km, of which 18 km, fall within the Chennai city limits. This once fishing river & boat racing ground has borne the brunt of the city's population explosion.
• The water quality as we are all aware is bound to degrade progressively as the river takes the untreated sewage but unable to flush it into the sea.
• Even if the planners succeed in limiting the disposal of untreated sewage at some point in future, the water discharge in the river is insufficient to improve the water quality
• The purpose of this study is to explore means of enhancing the flushing capability through appropriate engineering intervention as there is little scope for natural flushing.
Reasons for degradation
• Littoral sediment transport along coast line results in the formation of sand bar at mouth.
• The little river discharge is not sufficient for preventing the bar formation.
• Tidal range is small at Chennai coast (1.2m) reducing the possibility of tidal prism induced flushing in the estuary
• The terrain is very gentle leading to stagnation
Suggestion for improvement
• Considering the other waterways of Chennai city viz. Adyar and Buckingham canal, it will be possible to create a network with sea and let the tidal flow do the flushing job.
• To enable tidal flow, the network needs to be designed for sufficient cross section and minor alterations may be required at mouths of Cooum and Adyar rivers.
• After achieving optimum channel dimensions, the flushing action would be a continuous process maintained by regular tidal movement and will have very little seasonal variation
Summary & Conclusion
• Assuming 10 km length for waterway network, approximately 0.7 Mm3 material will be required to be removed
• With canal section lined with geosynthetic material, the cost of creating network will be of the order of Rs. 30 Cr. (based on assumed approximate quantities and rates)
• Based on model results an attempt is made to achieve on average a residual flow of 0.001m/s for entire network. At this rate of residual flow, a complete replacement of water mass within the network will take place in about 4 months time.
• The water quality improvement will be gradual and remain steady with fresh sea water entering continuously within the network.
Anticipated problems and means to minimize their effects
• It may be noted that even if the scheme is successful and we transfer the sewage from within the Cooum to open sea, it may end up polluting along the shoreline (Marina beach) due to open sea flow pattern.
• In long run, it is desirable to arrest the untreated sewage input to the river network as a permanent solution so that the problem is not merely shifted from river to sea.
• The river mouths will need continuous maintenance to avoid closure due to littoral drift.
• A combination of Groynes and dredging / sand by-passing will be needed to maintain the river mouth opening.
• Settlements and Elevated railway track along the network may deter the smooth implementation.