Artificial aeration helped revive Naini Lake after decades of decline: IIT Roorkee study

Nainital: A long-term study by Indian Institute of Technology (IIT), Roorkee researchers has found that artificial aeration has significantly improved the water quality of Naini Lake, helping reverse decades of ecological decline marked by toxic algal blooms, low dissolved oxygen levels and winter fish mortality.The study, published in Environmental Monitoring and Assessment in 2026, found that bubble aeration reduced the duration of thermal stratification, improved oxygen levels and helped control harmful algae. However, researchers cautioned that low oxygen levels still develop near the lake bed in summer and that pollution and climate-related factors continue to threaten full recovery. The research was carried out by Stuti Shah, Sumit Sen and Karan Adhikari of IIT-Roorkee.Naini Lake, located at an altitude of 1,937m, is a major source of drinking water and a key tourism hub. For nearly three decades, it has faced severe environmental stress due to rapid urbanisation and nutrient-rich runoff, which pushed the lake towards hyper-eutrophication, causing repeated blooms of toxic blue-green algae, oxygen depletion in deeper waters and fish deaths in winter.In 2007, the district development authority installed a diffused air aeration system with 30 bubble plume aerators across the lake bed to improve water circulation and oxygen levels.

The IIT-R study assessed how this system changed the lake’s thermal structure and water quality compared with pre-aeration conditions between 1977 and 1995.Researchers found that the lake now remains largely well-mixed, with only weak layering during peak summer. Strong thermal layering has reduced from 8-9 months a year to less than four months, while temperature differences between surface and bottom waters have fallen from over 9°C to under 2°C. Shah said the long-term analysis showed that artificial aeration had “substantially improved” Naini Lake’s water quality by reducing stratification, increasing dissolved oxygen and limiting harmful algal blooms.

“But these benefits depend on continuous operation and proper maintenance,” she said.