Follow lower ground
Both south and east lead downhill. The bottom-right tile is the stream outlet.
Watershed Runoff
Guide rainfall downhill to a stream and let soil absorb part of the moving water.
Grades 3–5 · Earth Science
Your goal
Guide 12 rainfall units downhill to the stream. Let soil absorb water along the path so exactly 10 units reach the outlet.
Reduced motion is on. The controls still update the scene.
0 units entered soil, 12 are still on the surface, and 0 reached the stream. The sum is always 12.
The blue parcel represents runoff from a single rain event. You choose between equally downhill south and east paths on a simple slope. Each green soil tile can absorb two units, while remaining water joins the stream at the outlet. Real watersheds contain divides, many flow paths, groundwater and changing infiltration. This board shows routing and conservation, not a rainfall or flood forecast.
Related resources
Related simulations
Learn with Watershed Runoff
Watershed Runoff helps elementary students trace a rain parcel through a small catchment. Guide twelve water units toward lower ground using south and east movement buttons. At selected tiles, let soil absorb two units before moving on. The stream receives the remaining surface water when the parcel reaches the outlet. Goals ask for different amounts at the stream, so students must plan where infiltration happens. Height numbers, a visible route and water totals connect the path across land with the water arriving downstream.
What to look for
Choose infiltration sites
Each soil tile absorbs two units once. Absorb water before leaving that tile.
Balance the rainfall
Soil water, moving water and stream water always add to twelve units.
For teachers and curious learners
Trace downhill runoff and account for rainfall divided between soil and a stream outlet. Ask students to predict what will happen, change one setting, and explain what they observe. Learn gives a starting point. Practice and Challenge offer new goals with the same scene.
A single parcel moves on a fixed four by four slope. Soil absorbs two units per selected tile. Real divides, branching flows, groundwater and changing infiltration are omitted; this is not a forecast.