Choosing a Water Poster for the City Underpass

A Poster for People on the Move

A pedestrian underpass connects two busy streets in a city neighborhood. People walk through it on their way to shops, apartments, and offices. A neighborhood team is choosing a science poster for a notice panel inside the underpass. The poster will answer a question: How is water distributed across Earth? Readers may stop for just a moment, so the team wants a graph with clear labels. Several designers have suggested ways to make the small amounts easier to notice without changing what the data mean.

The team uses rounded scientific estimates rather than counting water in the neighborhood. Imagine Earth's total water divided into 1,000 equal model units. The planning record lists these amounts:
Salt water: 975 model units
Fresh water: 25 model units
Total water: 1,000 model units
These units represent shares of the planet's water, not actual buckets or gallons. Salt water contains much more dissolved salt than fresh water. A photograph of a nearby drinking fountain would show one local use of fresh water, but the planning record includes water across the planet.

Fresh water occurs in several places and forms. It includes water frozen in glaciers and ice sheets, fresh water stored underground, and water in lakes, rivers, and other places. To help readers explore that smaller group, the team prepares a second model. Divide just Earth's fresh water into 100 equal parts. About 69 parts are frozen in glaciers and ice sheets, about 30 parts are underground, and about 1 part is in other places combined. These rounded amounts describe the fresh water group, not the larger group containing Earth's total water.

The team will check each proposed poster against its planning records. A draft may have a familiar title and neatly drawn bars yet still give the wrong impression. The team must decide which features to keep, which numbers to correct, and how to explain the water that people do not see flowing along the surface.