Cauvery turbidity halts Hogenakkal water supply; Dharmapuri, Krishnagiri told to use local sources

Drinking water supply from the Hogenakkal project has been suspended temporarily after heavy rain in Karnataka pushed turbidity in the Cauvery to more than double the level the pumping system is designed to handle, the district administrations of Dharmapuri and Krishnagiri have said.

Krishnagiri Collector C. Dinesh Kumar said supply under the Hogenakkal Drinking Water and Fluorosis Mitigation Project had been stopped because of high turbidity — the cloudiness caused by suspended silt, clay and other particles carried in the water.

The turbidity reading at Hogenakkal on Monday morning was 220 NTU (Nephelometric Turbidity Units), according to the district administration. The system is designed to pump water with turbidity of no more than 100 NTU. With the inflow well above that limit, pumping at the Central Pumping Station in Hogenakkal was halted, officials said.

High turbidity makes both pumping and purification difficult. Suspended particles clog pumps and filters and increase the amount of treatment needed before water is fit for drinking. Plants therefore stop drawing water rather than risk damage to equipment or compromise the quality of supply.

The spike follows heavy rain in the Cauvery catchment in Karnataka, which washes soil and sediment into the river and its tributaries. River-based supply schemes commonly face such interruptions during periods of heavy inflow, when sediment loads rise sharply.

Residents in the areas served by the project have been advised to use available local water sources until turbidity levels fall and pumping restarts. The administrations did not indicate how long the interruption would last, saying resumption depends on the river settling to levels the treatment system can manage.

The Hogenakkal project draws water from the Cauvery at Hogenakkal, on the border between Dharmapuri and Krishnagiri districts, and supplies treated drinking water to towns and villages across both. It was taken up in part to address fluorosis, a health condition caused by long-term consumption of groundwater containing excess fluoride, which affects parts of these districts.

Officials monitor turbidity at the intake so that pumping can resume once readings return to permissible levels. Until then, households dependent on the scheme will have to rely on wells, borewells and other local sources, and are likely to face inconvenience if the disruption continues.