Today is World Water Day, and this year’s theme is “Water and Food Security.” UN Water explains why we should care:

Each of us needs to drink 2 to 4 litres of water every day. But it takes 2 000 to 5 000 litres of water to produce one person’s daily food.

Today, there are over 7 billion people to feed on the planet and this number is expected to reach 9 billion by 2050.

To be able to feed everybody, we first need to secure water, in sufficient quantity and adequate quality.

We will also need to produce more food using less water, reduce food wastage and losses, and move towards more sustainable diets.

Climate change is making it even harder to reach the goal of ensuring adequate food and water for all. “To the extent that climate change increases the variability of rainfall and increases the frequency of extreme weather events, it will hinder food security,” explains a UN Food and Agriculture Organization fact sheet. Changes in temperature and rainfall patterns may benefit agriculture in some areas but will harm it in others; FAO predicts that China could increase its cereal production by 100 million tonnes, but India will likely lose 30 million tonnes of cereal and Mozambique could lose 25% of its agricultural productive capacity.

While the outlook for water in agriculture is disturbing, water advocates got some good news this month about drinking water.

One of the targets of the “Ensure Environmental Sustainability” Millennium Development Goal is “Halve, by 2015, the proportion of the population without sustainable access to safe drinking water and basic sanitation.” (Background on Millennium Development Goals is here.) Earlier this month, the Joint Monitoring Programme for Water Supply and Sanitation released its 2012 update report and announced that the drinking water target has been met ahead of schedule. Over the past two decades, more than two billion people gained access to improved drinking water sources, which include household connections, public standpipes, boreholes, protected dug wells, protected springs, and rainwater collection.

Access to improved drinking water is important for reducing water-related diseases, which kill more than three million people each year. It can also reduce the time people have to spend collecting water — and since women and girls do most of this work, the time savings can help them achieve education and other goals and lead to reductions in gender inequality.

These gains still need to be expanded: 783 million people still lack access to safe drinking water, and 40% of them are in sub-Saharan Africa. It will also take work to ensure that the people who’ve gained access to improved drinking water are able to maintain it.

It’s also troubling that the world is not on track to achieve the sanitation target. The Joint Monitoring Programme reports that 2.5 billion people still lack improved sanitation. (Here‘s more on what constitutes improved sanitation and why it can be hard to achieved.) Water and sanitation are part of the same target for a reason: human waste can contaminate drinking water supplies if not handled properly. Failing to achieve sanitation goals can prevent people from getting the full benefit of improved drinking water supplies.

This World Water Day is both a celebration of an achievement and a reminder that we still have a long way to go before everyone has the water, sanitation, and food needed to live healthy lives.