Watershed

Watershed is an educational sandbox for real terrain. Draw an area anywhere on Earth, pick a storm, and watch real elevation data fill its valleys, carve rivers, and run to the sea. Then drain the oceans back to the Ice Age, roll the atlas back to the Bronze Age, and send a caravan across what remains.

Weather. Six storm presets with their real order of magnitude, from a desert cloudburst to a monsoon week, or set every number yourself. A GPU shallow-water solver runs the physics live: water races down steep faces, ponds in basins, drains to real sinks, and recedes after the rain stops through infiltration and evaporation. Cloud shadows, rain and lightning play over readable ground; a procedural soundscape follows the millimetres and, as you zoom in, the speed of the rivers.

Ocean. Lower or raise the world's sea level from −500 m to +80 m on real bathymetry. The Persian Gulf drains into a river valley, Dover joins Calais, deltas drown.

Time. A year slider from 3000 BC to today: historical city names, ancient peoples, trade routes and empire borders. Discoveries shows every mapped historic site in view, plus curated atlases of Arabian stone monuments and world rock art.

Journey. Place two flags, choose a camel or an ox, a party and a cargo. The route threads the valleys, walks around lakes and the sea, crosses rivers only where it must, and hops between the oases, wells and cities of the chosen year. Watch the caravan travel day by day, with camps, fords, thirst warnings and a survivability verdict. Lower the sea and it takes the land bridge.

Era scenes set the sea level, the year and a matching storm in one click. Share links reproduce an entire scenario for someone else.

Every layer is real data with its source shown. Every number has a reason. Nothing is a calibrated engineering model, and the app says so.

System requirements

• Windows 10 or 11, 64-bit
• A graphics card or laptop chip with WebGPU support (any card from the last ~6 years; the app locks the highest detail on small chips and lets you unlock it at your own risk)
• Internet connection for map and terrain data (revisited areas are cached)
• About 25 MB of disk space plus the terrain cache

Installing Run the installer. Windows may show "Windows protected your PC" because it is not yet code-signed: click More info, then Run anyway. The app installs per user, needs no administrator rights, and adds "Watershed" to the Start Menu.