Since 2009, the Central Pollution Control Board (CPCB) has been identifying Polluted River Stretches (PRS) across Indian rivers using Biochemical Oxygen Demand (BOD) as the indicator of organic pollution, based on data from its national water-quality monitoring network.

The PRS framework thus provides a national snapshot of river pollution, highlighting stretches that require urgent regulatory intervention. This page critically examines the PRS framework to assess whether regulatory interventions are effective, whether the condition of Karnataka’s rivers is improving over time, and whether polluted stretches are genuinely being restored.