Fish Deaths at Durgam Cheruvu Linked to Oxygen Depletion
Healthy fish‑bearing waters typically maintain DO at 5 mg/l or higher.
Hyderabad:Hundreds of fish deaths at Durgam Cheruvu have been traced to severe oxygen depletion and high levels of organic and nutrient pollution. Data released by the Telangana Pollution Control Board (TGPCB) in May 2026 showed dissolved oxygen (DO) levels at just 0.3 mg/l, far below the CPCB’s minimum 4 mg/l requirement for fisheries. Healthy fish‑bearing waters typically maintain DO at 5 mg/l or higher.
Chemical Oxygen Demand (COD) was recorded at 123 mg/l, indicating a heavy load of oxidisable substances. Biochemical Oxygen Demand (BOD) stood at 12 mg/l, six times the Class A parameter and four times the Class B and C limits set by CPCB. High BOD levels mean microorganisms consume oxygen rapidly, leaving fish and aquatic life starved.
The US Environmental Protection Agency notes: “The greater the BOD, the more rapidly oxygen is depleted… aquatic organisms become stressed, suffocate, and die.” Together, the figures point to a deficient oxygen system in the lake, worsened at night or in poorly mixed waters.
Nutrient pollution is also significant. Total phosphate was 0.91 mg/l and orthophosphate 0.83 mg/l, levels that drive eutrophication. Excess phosphorus fuels algal blooms, which on decomposition strip oxygen further, compounding fish mortality.
Environmental scientist Srikanth Rao said mass fish deaths rarely occur due to a single factor. “It mostly happens when a collective system goes wrong. Cutting off sewerage inflows must be the first step. Continuous monitoring of DO, BOD, COD, ammonia and nutrients is essential. Aeration can provide short‑term relief, but the long‑term solution is preventing pollutants and restoring ecological balance,” he said.