Criticism of large dams
Topic: Water Resources of India: Availability, Use and Conservation · NCERT: Class 10, Ch 3 "Water Resources"
Meaning
Large dams bring irrigation and power, but they also cause harm. They change a river's natural flow. Silt (fine soil carried by water) piles up in the reservoir. As a result, the river bed below the dam turns rocky and floodplains lose their fertile silt. Dams also break rivers into pieces, so fish cannot swim upstream to breed. Reservoirs drown forests and soil and push people out of their homes and livelihoods. A reservoir filled with silt holds less floodwater, so a dam can fail to stop floods. Reservoirs can also trigger earthquakes and spread water-borne diseases. Canal irrigation pushes farmers towards thirsty cash crops, and over time this makes the soil salty (salinisation).
Example
In 1967 an earthquake struck near the Koyna dam in Maharashtra. It is linked to the weight of water in the reservoir (reservoir-induced seismicity). The Narmada Bachao Andolan opposed the Sardar Sarovar dam in Gujarat because of mass displacement.
Don't confuse with
- "Dams always reduce floods": this is a common exam trap. Silting reduces a reservoir's storage, so a dam's power to control floods weakens over time.