World Water Day is celebrated every year on March 22 to recognize the importance of fresh water around the world.
From the UNESCO website at https://en.unesco.org/commemorations/waterday:

World Water Day is held annually on 22 March as a means of focusing attention on the importance of freshwater and advocating for the sustainable management of freshwater resources. This Day is an opportunity to learn more about water related issues, be inspired to tell others and take action to make a difference. Water is an essential building block of life. It is more than just essential to quench thirst or protect health; water is vital for creating jobs and supporting economic, social, and human development.
A new World Water Development Report is released each year on or near World Water Day, to provide decision-makers with tools to formulate and implement sustainable water policies. This report is coordinated by UNESCO’s World Water Development Programme (WWAP) on behalf of UN-Water.

The theme for this years’ World Water Day is “Valuing Water” to encourage the public to join the global conversation for water and water quality.