NOAA Education Resources: Water Cycle Collection.
The basic water cycle is relatively simple and is taught as early as elementary school. However, the water cycle is one of NOAA’s Grand Science Challenges.
Like the accompanying diagram, the water cycle is often shown and taught as a simple circular cycle. Although this can be a useful model, students should understand that the reality is very different.
The paths and influences of water through Earth’s ecosystems are extremely complex and are not completely understood.