World Hydrography Day - June 21
(Last Updated On: November 8, 2022)


On June 21st, World Hydrography Day highlights the importance of surveying and charting bodies of water. The day also encourages the general public to learn more about the science of hydrographs.

It’s a known fact that 71 percent of the earth is covered with water. While most of the earth’s water is found in the oceans, it is also found in lakes, rivers, swamps, glaciers, and aquifers. It even exists in the air in the form of water vapor. Water is important for a number of reasons. Without water, humans and animals could not survive. We also use water for irrigating crops, keeping things clean, and providing recreational opportunities.

Water also plays a key role in transportation. To navigate the earth’s waterways, scientists find out specific information. This information allows ships and other vessels to navigate the waters safely and efficiently. This falls under the science of hydrography. The information these scientists look for include:

  • Water depth
  • Shape of the seafloor and coastline
  • Location of possible obstructions
  • Physical features of water bodies

Scientists use all this information to update nautical charts. These charts cover 95,000 miles of shoreline. Additionally, the charts cover 3.6 million square nautical miles of waters in the U.S. alone. Besides transportation and navigation, hydrography also helps in other areas. These areas include seafloor construction, anchoring, understanding fish habitats, and laying pipelines and cables.

HOW TO OBSERVE #WorldHydrographyDay

Every year the International Hydrographic Organization (IHO) hosts a variety of activities that focus on the annual theme. These activities include workshops, educational seminars, and conferences. To participate:

  • Learn more about hydrography and the importance of this science.
  • Find some nautical chart posters on the internet.
  • Do some educational activities with your kids, such as the build a boat challenge or making a compass.
  • Watch a documentary about water, such as Liquid Assets: The Story of Our Water Infrastructure or Watermark.

Share this day on social media with #WorldHydrographyDay.


The IHO created World Hydrography Day in 2005. That same year, the United Nations General Assembly adopted a resolution that recognized the establishment of this day. The date of June 21st coincides with the anniversary of the founding of the IHO in 1921 under the name International Hydrographic Bureau. The name changed to the IHO in 1970.

Past themes for this day have included:

2021: One hundred years of international cooperation in hydrography.
2020: Hydrography enabling autonomous technologies.
2019: Hydrographic information driving marine knowledge.
2018: Bathymetry – the foundation for sustainable seas, oceans, and waterways.
2017: Mapping our seas, oceans, and waterways – more important than ever.


Join the

Stay up to date on upcoming national days and Celebrate Every Day!