What does "watershed" mean?

A mountain or river highland between adjacent water systems (or rivers). The precipitation falling on both sides of the watershed is injected into different water systems or rivers along the slopes on both sides. For example, the Qinling Mountains are the watershed between the Yangtze River and the Yellow River. The precipitation in the north of the Qinling Mountains flows to the Yellow River, and the precipitation in the south of the Qinling Mountains flows to the Yangtze River. Dabie Mountain is the watershed of the Yangtze River and Huaihe River systems, and Nanling Mountain is the watershed of the Yangtze River and Pearl River systems.