What are Polluted River Stretches?
How are Polluted River Stretches identified?
The Central Pollution Control Board (CPCB) in collaboration with State Pollution Control Boards (SPCBs) and Pollution Control Committees (PCCs) monitors the quality of rivers and other water bodies across the country through the National Water Quality Monitoring Programme (NWMP). The monitoring helps assess the state of water quality and identify water bodies where pollution needs to be addressed.
CPCB began identifying Polluted River Stretches (PRS) in 2009, using water-quality monitoring data from 2002–2008. The exercise has since been repeated periodically as the monitoring network and available data have expanded.
PRS are identified using Biochemical Oxygen Demand (BOD) as the criterion parameter.
BOD is an indicator of organic pollution in water. Locations where BOD exceeds 3 mg/L, the prescribed limit under the Primary Water Quality Criteria for outdoor bathing, are identified as polluted. Two or more polluted monitoring locations occurring consecutively along a river are identified as a Polluted River Stretch
How are the Priority River Stretches (PRS) Classified?
CPCB classifies these stretches into five priority classes based on the maximum BOD observed:
Priority |
BOD |
What it indicates |
|---|---|---|
Priority I |
> 30 mg/L |
Highest level of BOD pollution |
Priority II |
20.1–30 mg/L |
Very high BOD pollution |
Priority III |
10.1–20 mg/L |
High BOD pollution |
Priority IV |
6.1–10 mg/L |
Moderate BOD pollution |
Priority V |
3.1–6 mg/L |
Lowest PRS priority, but still above the 3 mg/L criterion |
The higher the priority, the greater the BOD pollution, with Priority I representing the most severely polluted stretches.
What is the integrated Governance Framework for Restoring the Polluted Stretches?
Restoring polluted river stretches requires coordinated action across multiple sectors and levels of government. Over the years, an integrated governance framework has evolved through environmental laws, judicial directions, regulatory guidelines and compliance mechanisms aimed at preventing pollution at its source and restoring river water quality to a BOD of less than 3 mg/L.
Together, these measures define the responsibilities of different agencies, require time-bound action for restoration and provide the basis for tracking progress through Action Plans and Monthly Progress Reports.
A series of important judicial directions have played a key role in shaping this framework, strengthening accountability and establishing mechanisms for monitoring river restoration. Some of the key directions are highlighted below.
Key Judicial Directions Governing Polluted River Stretch Restoration
Table giving highlights of the key Judicial directions that shaped the governance framework
How is restoration progress monitored by the government?
The primary mechanism for monitoring the restoration of polluted river stretches is the Monthly Progress Reports (MPRs), prepared by States and Union Territories under the directions issued in OA No. 673/2018. These reports document the actions taken under the Polluted River Stretch Action Plans and are reviewed by the Central Monitoring Committee under the National Mission for Clean Ganga (NMCG) to monitor implementation and recommend corrective actions.
In a separate proceeding (OA No. 360/2018), the National Green Tribunal also directed every district to prepare a District Environment Plan (DEP) as a comprehensive roadmap for addressing environmental challenges. A river basin typically extends across multiple districts. As a result, understanding the status of a river basin requires bringing together information from each district through which the river and its tributaries flow. District Environment Plans therefore provide an important source of district-level information that complements the river basin-wide assessment of polluted river stretches.
The DEPs cover many of the same areas that influence river health including sewage management, industrial pollution, solid and liquid waste management, hazardous waste, biomedical waste, groundwater, water bodies and air quality creating a significant overlap with the Polluted River Stretch restoration framework. All the environmental plans related to the districts of Karnataka are here.
A Mandate for River Basin-wise Assessment
In its order dated 28 August 2019 in OA No. 593/2017, the National Green Tribunal directed CPCB to develop a river basin-wise macro picture of pollution and its management. This was to bring together information on ETPs, CETPs, STPs, municipal solid waste facilities, legacy waste sites and other pollution sources, helping identify gaps and interventions required across an entire river basin.
To implement this direction, CPCB developed a framework for a River Basin Portal and, in May 2020, asked State Pollution Control Boards and Pollution Control Committees to populate it with basin-wise information.
This establishes an important principle within the governance framework that river restoration requires information on pollution sources, treatment infrastructure and implementation gaps to be brought together and assessed at the scale of the river basin.
River Basin-wise Assessment Dashboard – A spatial lens on the state of river restoration
The official reporting provides a way to track progress on individual actions and interventions. But we wanted to look at restoration through a wider spatial lens: does the reporting capture all the potential sources of pollution that could be affecting a Polluted River Stretch?
Building on the principle of a river basin-wise assessment, we developed a spatial dashboard that maps the Polluted River Stretches and brings together relevant information on settlements, sewage treatment infrastructure, industrial areas, waste facilities and other potential pollution sources within their catchments.
The question we are asking
Do the Action Plans and Monthly Progress Reports comprehensively address all potential pollution contributors within each Polluted River Stretch (PRS) catchment?
