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This project hub will be updated as analyses are completed and new material is published.
Project Purpose
The project critically examines polluted river stretches in the Cauvery River Basin, state responses, judicial interventions, and governance gaps, translating these findings into an action agenda for citizens, governments, and policymakers.
The State of the Cauvery River System project examines polluted river stretches in the Cauvery Basin using official Polluted River Stretches (PRS) data. It traces long-term pollution trends, critically assesses the limitations of the PRS framework, reviews government responses under National Green Tribunal orders, and analyses the laws, policies, regulatory mechanisms, and institutions governing river pollution.
The analysis draws on Mapping Malnad’s more than a decade of engagement with pollution control boards, on-ground fact-finding, and information obtained through the Right to Information (RTI) Act.
This analysis is translated into an action agenda outlining concrete legal, institutional, and policy measures required to restore river health and ensure accountability. The findings are presented through maps, timelines, analytical articles, and culminate in a consolidated report.
The project is organised into the following sections, each examining a distinct dimension of polluted river stretches and river governance in the Cauvery Basin:
- Polluted River Stretches (PRS): Framework, Evolution, and Spatial Mapping
- Cauvery Basin Polluted River Stretches: A Decadal Data Review (2015–2025)
- A Critical Review of the PRS Assessment Framework
- Judicial & Government Responses to Polluted River Stretches
- A Review of Law, Policy, Regulations, and Institutions Governing River Pollution
- Implications for Drinking Water Security, Wildlife, and the Mekedatu Dam
- Citizen Action Agenda for Improving River Health
Each of the above sections is elaborated below, with links to analyses, maps, and timelines.
This project hub will be updated as analyses are completed and new material is published.
To contribute to the project, write to: Editor@MappingMalnad.com
1.1 PRS framework based on Biochemical Oxygen Demand (BOD)
How does the government decide whether a river is polluted?
An overview of the Polluted River Stretches (PRS) framework and how Biochemical Oxygen Demand (BOD) is used to identify and classify polluted river stretches.
1.2 Timeline: Evolution of PRS Assessments framework
How has the identification of polluted river stretches evolved over time?
A chronological overview of how Polluted River Stretches (PRS) have been identified, assessed, and reported by the Central Pollution Control Board across successive assessment cycles.
1.3 Map: Spatial extent of Polluted River Stretches in Karnataka (2025)
Where are the Polluted River Stretches across Karnataka?
A state-wide spatial mapping of 14 Polluted River Stretches (PRS) identified in the 2025 assessment, showing their distribution across river basins in Karnataka—namely Arkavathi, Bhima, Bhadra, Cauvery, Dakshina Pinakini, Ghataprabha, Kagina, Kabini, Krishna, Lakshmantirtha, Malaprabha, Shimsha, Tunga, and Tungabhadra.
1.4 Map: Spatial extent of Polluted River Stretches in the Cauvery Basin of Karnataka (2025)
Where are the Polluted River Stretches within the Cauvery Basin?
A basin-scale spatial mapping of Polluted River Stretches (PRS) in the Cauvery Basin, as identified in the 2025 assessment—namely the Cauvery, Arkavathi, Kabini, Lakshmantirtha, and Shimsha rivers.
What does the data say?
The assessment is ongoing. Preliminary findings from a decadal analysis of Central Pollution Control Board Polluted River Stretch (PRS) data indicate a worsening pattern of river pollution across the Cauvery Basin between 2015 and 2025. Polluted stretches along major rivers—Cauvery, Arkavathi, Kabini, Shimsha, and Lakshmantirtha—have expanded significantly in length, while organic pollution has intensified, as reflected in rising Biological Oxygen Demand (BOD) levels.
Do official PRS assessments capture the true extent of river pollution?
The assessment is ongoing. Preliminary findings indicate that the CPCB’s PRS framework significantly underestimates the extent and severity of river pollution due to structural and methodological limitations. Key shortcomings include the exclusion of state-level monitoring data, inconsistent reporting of polluted stretch lengths, weak data-collection practices, and an over-reliance on BOD that obscures industrial and emerging contaminants. Together, these gaps distort both the assessment of river health in the Cauvery Basin and the national picture of river pollution.
What are the NGT Orders & Government Responses to Polluted River Stretches?
The assessment is ongoing. Preliminary findings indicate that government actions undertaken pursuant to National Green Tribunal orders on polluted river stretches in the Cauvery Basin have been largely procedural and ineffective. Despite the preparation of river rejuvenation action plans and regular progress reporting, interventions remain narrowly focused on sewage infrastructure, while industrial pollution, floodplain protection, ecological flows, and catchment-level drivers are routinely ignored or misrepresented. Across the Arkavathi, Cauvery, Shimsha, Kabini, and Lakshmantirtha rivers, the persistence and expansion of polluted stretches suggest systemic governance failures rather than gaps in information or intent.
How have policy and regulation affected river protection capacity?
Data collection & review ongoing. Preliminary findings indicate a systematic erosion of legal, regulatory, and institutional safeguards governing river protection in the Cauvery Basin. This erosion is driven by policy dilutions, regulatory re-interpretations, weakening of pollution control institutions, and project approvals that displace pollution rather than address it at source. Together, these changes have transformed environmental law from a protective framework into a facilitative tool, accelerating ecological degradation while creating an illusion of compliance and reverence for rivers.
What are the implications for drinking water, ecosystems, and proposed dams?
The assessment is ongoing. Preliminary findings indicate that drinking-water security and ecological water needs remain critical blind spots in river pollution governance in the Cauvery Basin. Polluted rivers continue to supply drinking water to millions of people and flow through legally protected wildlife sanctuaries, exposing both human and ecological systems to chronic risks from organic pollution, industrial contaminants, and emerging pollutants. These risks are further compounded by large infrastructure proposals such as the Mekedatu Dam, which would impound and concentrate toxic flows, raising serious concerns for public health, wildlife conservation, and long-term water security.
What actions do citizens propose to improve river health and ensure accountability?
This section presents a citizen action agenda emerging from ongoing consultations with civil society groups, researchers, and affected communities across the Cauvery Basin. It seeks to consolidate citizen concerns and proposals in response to the erosion of legal safeguards, regulatory failures, and worsening river pollution.
