The above video from Oregon State University permaculture professor Andrew Millison is a great introduction to watersheds.

And in this TED talk Alan Savory explains how to reverse desertification by planned holistic grazing:  bunching and moving herds of domestic animals such as sheep and cattle.

Just below is a screen shot of land that healed using planned holistic grazing.

Snake River Music Gardens adds another element to planned holistic grazing:  log dams, also called beaver dam analogues.  These "leaky weirs" mimic the work of beavers, placing dams across gullies to slow the flow of water and spread the water into the lands above the dam.