Climate and water are inextricably linked. Water evaporates from the planet’s surface to the atmosphere, where it condenses into clouds that are transported around the globe. They then release rain and snowfall that returns fresh water to Earth’s land, rivers, lakes and glaciers. This is what sustains life on our planet. Climate drives the hydrological cycle, and it in turn defines our climate.

This cycle is often taken for granted. But it lies at the heart of many of our global Sustainable Development Goals — from ending hunger, to ensuring health and well-being, enabling productive industries, sustaining thriving communities and unlocking the potential of affordable and clean energy for all.

Climate change is disrupting our hydrological cycle and redistributing water availability around the world. This means increased floods for some and more prolonged droughts for others. Our planet already faces great hydrological challenges from unsustainable use, with more than half the world’s population facing severe water scarcity during at least one month of the year. With global demand for water continuing to increase, we face a grave water crisis.

That is why, this year, World Meteorological Day and World Water Day share the theme of climate and water. We need to manage climate and water in a more coordinated and sustainable manner to address the urgent need for improved forecasting, monitoring and management of water supplies and to tackle the problem of too much, too little or too polluted water. We cannot manage what we do not measure. Improved hydrological monitoring and forecasting are vital to underpin effective water management policies and flood and drought early warning services.

Let us mark World Meteorological Day this year by appreciating the inextricable link between climate and water and the importance of our hydrological cycle. Let us intensify our efforts to support our meteorological and hydrological communities to further the effective management of water resources. Let us count every drop, because every drop counts.