**Executive Summary**
This document addresses a parliamentary question regarding pollution in the Thenpennai River, focusing on untreated sewage discharge from Karnataka and its impact on Tamil Nadu. It outlines measures taken for water quality monitoring, compliance with National Green Tribunal (NGT) directives, and the absence of the river in the National River Conservation Plan. The response was provided on 08.12.2025.
**Key Points / Main Content**
* **Water Quality Monitoring:**
* The Central Pollution Control Board (CPCB), with State Pollution Control Boards (SPCBs) and Pollution Control Committees (PCCs), monitors water quality at 4922 locations under the National Water Quality Monitoring Programme (NWMP).
* CPCB monitors water quality at the Karnataka-Tamil Nadu border.
* **Sewage and Effluent Treatment:**
* States/Union Territories (UTs) and Urban Local Bodies are primarily responsible for treating sewage and industrial effluents before discharge.
* The Central Government sets standards for treated sewage and industrial effluent, enforced by SPCBs/PCCs.
* **Karnataka's Contribution:**
* The estimated sewage generated in the Thenpennai river catchment area in Karnataka is 1329 MLD.
* Bengaluru Water Supply and Sewerage Board (BWSSB) has 26 STPs with an installed capacity of 958.5 MLD and treats 830 MLD sewage; 12 STPs are under proposal.
* The river's water quality in Karnataka meets the "E" category (Irrigation, Industrial Cooling, Controlled waste disposal).
* **NGT Involvement:**
* The NGT is addressing the issue of toxic foam in Tamil Nadu's Hosur and has directed responses from relevant parties.
* The "Dakshina Pinakini along Mugaluru" stretch is identified as a Polluted River Stretch (PRS).
* The Chief Secretary to the Government of Karnataka has filed action taken/compliance reports before the NGT.
* **Tamil Nadu's Actions:**
* The Thenpennai River is not covered under the National River Conservation Plan (NCRP).
* Tamil Nadu conducts regular water quality monitoring at the entry point under the National Water Quality Monitoring Programme.
* Tamil Nadu has installed a Real Time Water Quality Monitoring station on the river.
* **Sampling Results:**
* Sampling of six locations at River Thenpennai found Dissolved Oxygen (DO) as BDL (less than 0.3 mg/L), pH in the range of 7.24 - 8.1, Bio-chemical Oxygen Demand (BOD) in the range of 17 - 52.4 mg/L and Fecal Coliform in the range of 2,80,000 - 79,00,000 MPN/100 ml.
**Impact Analysis**
**Karnataka State Pollution Control Board (KSPCB)**
* **Impact**
* Required to monitor river water quality at Mugalur bridge once a month.
* Responsible for enforcement of treated sewage and treated industrial effluent standards.
* **Action Required**
* Continue monitoring water quality and report on compliance.
**Tamil Nadu State Pollution Control Board (TNPCB)**
* **Impact**
* Responsible for downstream monitoring and ensuring water quality.
* **Action Required**
* Maintain real-time water quality monitoring and coordinate with upstream agencies.
**Central Pollution Control Board (CPCB)**
* **Impact**
* Coordinates national water quality monitoring and sets water quality standards.
* **Action Required**
* Continue to monitor water quality at the Karnataka-Tamil Nadu border and provide technical support to SPCBs.
**States/Union Territories (UTs) and Urban Local Bodies**
* **Impact**
* Responsible for ensuring treatment of sewage and industrial effluents before discharge into rivers and other water bodies.
* **Action Required**
* Ensure required treatment of sewage and industrial effluents to meet prescribed norms.
Key Entities Referenced
National Green Tribunal (NGT): A statutory body responsible for environmental protection and conservation, playing a significant role in addressing the pollution of the Thenpennai River and overseeing compliance.
Central Pollution Control Board (CPCB): The primary regulator monitoring water pollution in India and setting water quality standards. CPCB is involved in monitoring the Thenpennai River's water quality.
Karnataka State Pollution Control Board (KSPCB): The state-level agency responsible for monitoring and reporting pollution levels in the Thenpennai river within Karnataka's jurisdiction.
National Water Quality Monitoring Programme (NWMP): A nation-wide program under which water quality monitoring is conducted at various locations in the country.
Thenpennai River: The river that is the subject of the policy, facing pollution from untreated sewage discharge from Karnataka and causing public health risks in Tamil Nadu. The focus of the government’s interventions for remedial and enforcement measures.
GOVERNMENT OF INDIA
MINISTRY OF ENVIRONMENT, FOREST AND CLIMATE CHANGE
LOK SABHA
UNSTARRED QUESTION NO. 1299
TO BE ANSWERED ON 08.12.2025
Pollution in Thenpennai River
1299. THIRU DAYANIDHI MARAN:
SHRI S JAGATHRATCHAKAN:
Will the Minister of ENVIRONMENT, FOREST AND CLIMATE CHANGE be pleased to
state:
(a) whether the Government is aware of untreated sewage discharge from Karnataka into
the Thenpennai river, and the estimated volume of sewage entering in to the river on a
daily basis;
(b) the official estimate of daily volume entering Tamil Nadu along with the assessed
impact on downstream districts—Krishnagiri, Dharmapuri, Thiruvannamalai,
Villupuram and Cuddalore— including incidents of toxic foam, water contamination
and public-health risks;
(c) the status of compliance by Karnataka and the Central Government with the National
Green Tribunal (NGT’s) directions on preventing sewage discharge into the
Thenpennai, including dates of action-taken reports submitted.
(d) whether the Government has conducted or reviewed water-quality testing at inter-State
entry points and downstream reservoirs, and if so, the details and the current status
thereof; and
(e) the remedial and enforcement measures taken under the National River Conservation
Plan to prevent further contamination and safeguard drinking water, agriculture and
ecosystems in Tamil Nadu?
ANSWER
MINISTER OF STATE IN THE MINISTRY OF ENVIRONMENT, FOREST AND
CLIMATE CHANGE
(SHRI KIRTI VARDHAN SINGH)
(a) to (e) To monitor the pollution of water bodies in the country, Central Pollution
Control Board (CPCB) in association with State Pollution Control Boards (SPCBs) and
Pollution Control Committees (PCCs) has established a Water Quality Monitoring Network
under the National Water Quality Monitoring Programme (NWMP). Currently, water quality
monitoring is carried out at 4922 locations in the country. It is the primary responsibility of
States/Union Territories (UTs) and Urban Local Bodies to ensure required treatment of sewage
and industrial effluents to the prescribed norms before discharging into the rivers and other
water bodies. The Central Government has laid down standards for the quality of treated sewage
and treated industrial effluent to be discharged into rivers and these standards are enforced by
State Pollution Control Boards/Pollution Control Committees (SPCBs/PCCs).As per the information provided by Karnataka State Pollution Control Board (KSPCB), the total
estimated quantity of sewage generated in the Thenpennai river catchment area is 1329 MLD.
Presently, Bengaluru Water Supply and Sewerage Board (BWSSB) is having 26 STP's with
installed capacity of 958.5 MLD & is treating 830 MLD sewage and 12 STP’s are reported to
be under proposal.
Further, It is reported by KSPCB that KSPCB is monitoring the river water quality at Mugalur
bridge once in a month regularly apart from various locations along river Thenpennai. As per
the analysis report of river Thenpennai submitted by KSPCB, the river water quality meets the
criteria “E” (Irrigation, Industrial Cooling, Controlled waste disposal) category, as per the
Designated Best Use Water Quality Classification set by the Central Pollution Control Board
(CPCB).
Hon’ble National Green Tribunal (NGT) vide order dated 18.12.2024 in Original Application
No. 1374/2024 (Principal Bench) while hearing the issue of Toxic Foam in Tamil Nadu’s Hosur
after Dam Discharges Surplus Water, on suo-moto basis, directed all the respondents to file
their responses before the appropriate bench of the Hon’ble Tribunal and transferred the case
to Hon’ble NGT Southern Zone, Chennai. Subsequently, the case was re-numbered as O.A No.
14 of 2025 (Southern Zone).
In compliance of the Hon’ble NGT’s order dated 18.12.2024, CPCB submitted report dated
01.04.2025, in which, while referring about the report prepared for “Polluted River Stretches
for Restoration of Water Quality - 2022” for identification of polluted river stretches in the
country, it is stated that the "Dakshina Pinakini along Mugaluru" stretch is identified as one of
the Polluted River Stretch (PRS) along Mugaluru under Priority I, as the maximum BOD
observed as 111 mg/L during the period 2019 & 2021. The location is downstream of Bengaluru
city in Karnataka.
CPCB - Regional Directorate, Bengaluru monitors water quality at Karnataka-Tamilnadu inter-
state location at river “Thenpennaiyar” at Chokkarasanapalli Bridge under National Water
Quality Monitoring Programme (NWMP) on quarterly basis. The location is further
downstream of Bengaluru city in Karnataka
The officials of CPCB, Regional Directorate, Bengaluru along with officials of Karnataka State
Pollution Control Board and Tamil Nadu State Pollution Control Board (TNPCB) carried out
sampling of six locations at River Thenpennai, namely, Channasandra bridge (01), Mugaluru
bridge (01) in Karnataka State, Chokkarasanapalli (01), Kelavarapalli dam (dam
water/upstream, downfall near gate/downstream, Mitteganahalli bridge/ Marasandra) (03) in
Tamil Nadu State on 28.10.2024. . The assessment of water quality data for the year 2024
indicates that Dissolved Oxygen (DO) is observed as BDL (less than 0.3 mg/L), pH in the range
of 7.24 - 8.1, Bio-chemical Oxygen Demand (BOD) in the range of 17 - 52.4 mg/L and Fecal
Coliform in the range of 2,80,000 - 79,00,000 MPN/100 ml.
Further, as per the information provided by KPCB, pursuant to the directions of the Hon'ble
NGT in O.A No. 111/2020, the Chief Secretary to the Government of Karnataka has filed action
taken/compliance reports dated. 01.04.2025, 20.08.2025 and 13.11.2025 before the Hon'ble
NGT, Chennai Bench.
As per input provided by TNPCB, The Thenpennai River stretch is not covered under the
National River Conservation Plan (NCRP). However, as per NGT (SZ) order dated 20.07.2020,regular water-quality monitoring at the Tamil Nadu entry point is carried out under National
Water Quality Monitoring Programme. Further Government of TamilNadu reported that they
have installed Real Time Water Quality Monitoring station at Thenpennai River for real time
monitoring of the river water. TNPCB coordinates with CPCB and upstream agencies for
regulatory compliance and improvement of river water quality.
***