Water erodes the landscape creating streams and waterfalls producing gravel, sand, clay, and moss
Water escapes from lakes and aquifers. Dirt and sand wash away to deepen stream beds and cut river banks. Find Forest brooks and Mountain creeks in your explorations. Pass through a dry Desert valley one day and find it flooded the next.
This mod looks really neat.
https://www.curseforge.com/minecraft/mc-mods/water-erosion