Lower reservoir levels, silt hit power generation

Lower water levels in the reservoirs coupled with the heavy quantity of silt in the water fed to hydropower plants has caused India’s hydropower generation to decline this year, according to the latest data compiled by the Central Electricity Authority (CEA).

The data show that India’s total hydropower generation since the beginning of the current year (about 89,900 Mw) is about 5,000 Mw less than the generation achieved in the same period last year.

Lower generation from hydropower plants in the country has happened even as there has been an overall capacity addition of about 2,087 Mw in hydropower generation in India in the last one year.

“The heavy dependence of hydropower projects on monsoon and rainfall patterns is a serious concern. High silt concentration drastically reduces a plant’s efficiency, added to the fact that renovation of hydel projects takes much longer and affects machine availability,” said Shubhranshu Patnaik, senior analyst from accounting and consultancy firm PricewaterhouseCoopers. “With increasing climate change, the silt levels will only increase,” he added.

The current water storage level in the 81 reservoirs that feed the country’s hydropower plants, stands at 108 billion cubic metres (bcm), about 47 bcm or 30 per cent lower than the total capacity of these reservoirs, according to the data released by the Central Water Commission (CWC).

The Union power ministry, while confirming the concerns over depleted water availability threatening hydropower generation, has said that it is keeping a watch on the matter. “We have reviewed the available resources and ensured that all the usable water has been utilised. The constraints though are uneven rainfall and high silt concentration in the water, especially in two projects — Teesta-5 and Naphtha Jhakhri,” said Anil Razdan, power secretary.

He also said that the modification work carried out in the Naphtha Jhakhri project and the huge landslides occurring in the catchment area of the Teesta-5 project had led to silt accumulation in the water fed to them, due to which the projects had to be stalled for some time.

“A run-of-the-river (RoR) project is a handicap. Although its benefit is that it avoids displacement of the local populace, it accumulates huge amounts of silt because the water flows directly into the project,” he said.

At the Naphtha Jhakhri project, located in the Kinnaur district of Himachal Pradesh, whenever the silt concentration in the Sutlej river feeding the plant exceeds the permissible limit of 4,000 parts per million (PPM), the 1,500 Mw plant has to be shut down to avoid erosion in underwater parts of the turbine.

Razdan also mentioned the case of Madhya Pradesh where the water levels in the reservoirs feeding the hydel projects had depleted to critical levels in past months, owing to prioritised supply for irrigation and drinking purposes. “Reservoir levels have not been good, especially in Omkareshwar and Indira Sagar projects. We wanted to conserve water.

But we can generate (power) only when we get the clearance (for water supply). So, availability was reduced,” he said.

Experts in the industry have also confirmed the increased level of threat that India’s hydropower plants are facing owing to environmental and technical concerns.

In the current Plan period, 57 hydel projects have been identified by the power ministry for renovation and modernisation of their machinery, according to the CEA. The renovation of these plants, which have a total capacity of 10,833 Mw, will require about Rs 4,100 crore, out of which Rs 498 crore have already been spent.