The primary source of irrigation in Tamil Nadu is:

Canals
Tanks (small reservoirs)
Groundwater
Rainwater harvesting

The primary source of irrigation in Tamil Nadu is canals. In 2018, canals accounted for 57% of the total irrigation in the state. Tanks (small reservoirs) accounted for 27%, groundwater accounted for 14%, and rainwater harvesting accounted for 2%.

Canals are a type of artificial watercourse that is used to transport water from a source to a destination. They are typically constructed by digging a trench in the ground and lining it with a material such as concrete or clay. Canals can be used for a variety of purposes, including irrigation, transportation, and flood control.

Tanks are small reservoirs that are used to store water. They are typically constructed by building a dam across a stream or river. Tanks can be used for a variety of purposes, including irrigation, drinking water, and fish farming.

Groundwater is water that is found beneath the surface of the Earth. It is stored in aquifers, which are layers of rock or sand that are saturated with water. Groundwater can be used for a variety of purposes, including irrigation, drinking water, and industrial use.

Rainwater harvesting is the process of collecting and storing rainwater for later use. It can be used for a variety of purposes, including irrigation, drinking water, and domestic use.

In Tamil Nadu, canals are the primary source of irrigation because they are a reliable and efficient way to transport water to crops. Canals are also relatively inexpensive to construct and maintain. Tanks are another important source of irrigation in Tamil Nadu, but they are not as reliable as canals because they are more susceptible to drought and flooding. Groundwater is also used for irrigation in Tamil Nadu, but it is becoming increasingly scarce due to overpumping. Rainwater harvesting is a promising alternative to canals and tanks, but it is not yet widely used in Tamil Nadu.