The WaterwayMap

The WaterwayMap is a visually beautiful interactive map that uses OpenStreetMap data to visualize the structure and flow of rivers around the world.

At its core, WaterwayMap utilizes the directional data of waterways recorded in OpenStreetMap (OSM). In OSM, waterways are represented as ways - ordered lists of nodes that indicate the sequence and direction of flow. WWM uses this directional information and calculates additional hydrological details to provide a comprehensive visualization of water systems.

Thanks to a recent update by Amanda McCann, the map's creator, the widths of rivers now represent cumulative stream lengths. This means that the width of a river segment on the map reflects the total cumulative length of all upstream waterways feeding into that segment. Thicker lines represent rivers with larger upstream networks, such as major rivers fed by extensive tributary systems.

The colors of the rivers indicate grouped waterways and are randomly assigned. These colors help users visually separate different river systems or watersheds on the map. Each color corresponds to a connected network of waterways, typically a river and its tributaries. This allows users to easily identify which rivers and streams belong to the same system.

You can also explore watersheds on the Global Watersheds interactive map. By clicking anywhere on the map, you can view a visualization of the upstream watersheds calculated from your selected location. The map enables you to quickly see the origin and destination of water at any point on Earth.

The screenshot above shows the vast 1 million km² watershed flowing from the Andes into the Solimões River in Brazil. To explore the world's largest watersheds, you can click downstream in the Amazon Basin (the world's largest watershed) or in the Mississippi River Watershed in the United States.

If you're interested in tracing the flow of a watercourse, you can select the 'downstream' option on the map. This will display the flow path of the selected river from your chosen location to the ocean. Other options allow you to download watershed data in geoJSON, shapefile, or KML formats.

Also See:

River Runner and River Runner Global - uses elevation and hydrology data to calculate and animate the probable ultimate journey of a drop of water from any location to the sea.