AI-ASSISTED · EDITOR-REVIEWED
Theme brief
Water offers scale from a street drain to the global ocean. Think in connected systems — watershed, flow, storage, risk and access — and distinguish observed water from modeled flood zones or long-term averages.
Official prompt“About 71% of the Earth's surface. That wet thing, you know?”
30DayMapChallenge 2026
WAYS IN
Four map ideas
- 01
Trace a watershed from ridge to river mouth.
- 02
Compare river networks with political borders they ignore.
- 03
Map seasonal surface-water change from satellite imagery.
- 04
Visualize bathymetry as a landscape beneath the sea.
IN THE DIRECTORY
Recommended tools
QGIS
Combines hydrology tools, raster terrain analysis and strong water cartography.
Open source · View detailsGoogle Earth Engine
Supports multi-date surface-water and flood analysis from satellite archives.
Freemium · View detailsCopernicus Browser
Quickly inspects recent imagery for coasts, rivers and inundation.
Free · View detailsWhiteboxTools
Offers a focused open toolkit for watershed and terrain processing.
Open source · View detailsSTART WITH A CLEAR LICENSE
Data sources
Global catchments, rivers, lakes and hydrographic derivatives.
Free for non-commercial and commercial use · cite source GEBCO global bathymetryGlobal gridded ocean and land elevation.
Free use with acknowledgment USGS Water Data for the NationStreamflow, groundwater and water-quality observations.
U.S. government dataLicenses are a planning aid, not legal advice. Check the source record and version you actually download; terms can vary within a catalog.
BEFORE YOU EXPORT
Cartography check
Show the date or season prominently. Water extent is often dynamic, and a timeless map can be misleading.
COMMUNITY MAPS
Selected work
First participate officially by posting publicly with #30DayMapChallenge. You can then suggest that original post for our independent MapTools picks. We link to the source, credit every author and use images only with permission.
Suggest for MapTools picks