Damned by old age

Ageing dams and shrinking canal command area are the blind spots in the management of impending water and food crises

- J HARSHA

THE PARADOX is perplexing. Bhagwant Singh is a farmer from Punjab, who owns a 2-hectare plot in the Bhakra Canal command area. Though his plot falls under the command area of one of the most iconic dams of Independent India, he depends on a tubewell for irrigation. Similarly, farmers in the Tungabhadra canal command in south India are unaware that the live storage of the Tungabhadra dam has shrunk by over 20 per cent and concomitantly, the canal command area is shrinking. Whenever farmers see their field channels dry, they believe that it is due to drought! So it should not come as a surprise that millions of farmers across command areas of large and medium dams depend on groundwater for irrigation. They neither are aware of the storage position in these dams nor the loss of live storage or sedimentation and age of the dams.

STATIC THINKING

India has 5,264 large dams, and hundreds and thousands of medium and minor dams—a majority of them provide water for irrigation through a maze of canal network. About 64 large dams are 120 years old, 300 large dams are between 70 and 120 years old, and cumulatively, about 600 large dams are at least 55 years old. The scenario will become alarming in 2030, when about 2,000 large dams will be 50-120 years old, as the envisaged benefits from these dams will reduce substantially.

The reason is, as a damages, the live storage capacity designed for reservoirs will not remain static. It changes with time. The live storage of the Krishnarajasagar dam built-in 1931 cannot remain the same in 2020. This is because reservoirs get silted over time.