Hydroelectric power is a clean, renewable, non-emitting source of energy. Thus source of energy is generated mainly from hydroelectric dams, and it provides low cost electricity and helps reduce carbon emission.

Hydroelectric power is the world's largest renewable energy source. It is clean and renewable - it doesn't pollute the air because no fuels are burned and it's renewable because it uses the earth's water cycle to generate electricity. Hydro power turbines are capable of converting more than 90% of available energy into electricity. By comparison with fossil fuel plants - which is another source of renewable energy - fossil fuel plants are only approximately 50% efficient.

Hydro power has a lot of positives. Firstly, it is important to other intermittent renewable sources such as wind and solar. Hydro output can be used to keep the electric grid in balance as daily doses of sunshine and wind fluctuate and wane. Moreover, river waters are purely domestic resources, as the result, there almost no conflicts with foreign suppliers and no interruptions as the result of labor strikes. In addition, multi purpose dams provide water for irrigation, wildlife, recreation, and flood control benefits.

However, critics claims that their reluctance to call hydroelectric power a renewable source of energy is based on the impact of dams on fisheries and water flows. Several large dams block migrating fish from reaching their spawning grounds. Nevertheless, hydroelectric power remains the most efficient source of renewable energy.

Reference:

https://naturalresources.house.gov/issues/issue/?_e_pi_=7%2CPAGE_ID10%2C6840251613

https://www.governing.com/topics/transportation-infrastructure/gov-hydropower-renewable-energy.html