Storing the Monsoon: Reservoirs and Water

How dams and reservoirs capture monsoon rain for irrigation, drinking water and power, how their levels are tracked, and the debates over big dams.

Because India’s rain falls mainly in a few months, storing water is essential. Dams and reservoirs capture monsoon rain for use through the dry months.

What reservoirs do

Irrigation, especially for rabi crops in winter.
Drinking water for cities.
Hydropower generation.
Flood control by holding back water during heavy rain.

Tracking levels

The Central Water Commission publishes weekly bulletins on storage in about 150 major reservoirs across India, comparing current levels with the previous year and the ten-year average. After a weak monsoon, low reservoir levels warn of trouble for rabi crops and drinking water.

Big dams: benefits and costs

India has built thousands of large dams since independence, such as Bhakra Nangal, which supported the Green Revolution in Punjab and Haryana.

Benefits include irrigation, power and flood control. But large dams also:

Displace people, often tribal communities and farmers.
Submerge forests and farmland.
Affect river ecosystems and downstream flows.
Can lead to disputes between states over water sharing, such as over the Kaveri river.

The Narmada dam projects, including Sardar Sarovar, became the focus of long protests over displacement and rehabilitation.

Smaller-scale storage

Check dams, farm ponds and tanks store water locally.
Rainwater harvesting on rooftops.
Groundwater recharge structures.

These can be cheaper and faster to build and involve communities, though they store less water.

Managing releases

Reservoir operators must balance storing water for dry months with keeping space for floods. Poorly timed releases during heavy rains have worsened floods in some cases.

The winter wheat

After a strong monsoon, reservoirs in Madhya Pradesh are nearly full. Canal irrigation lets farmers grow a large wheat crop in winter. The following year, a weak monsoon leaves reservoirs half-empty, and farmers plant less.

Thinking the monsoon's benefits end in September

Water stored in reservoirs and aquifers during the monsoon supports farms, cities and power plants for months afterwards.

Key takeaways

Reservoirs store monsoon rain for irrigation, drinking water, power and flood control.
The Central Water Commission tracks storage in about 150 reservoirs weekly.
Big dams bring benefits but also displacement and disputes.
Check dams, ponds and rainwater harvesting offer local storage.