What is a Watershed (continued)

A watershed is a good example of how the living and nonliving things within an ecosystem depend upon each
other. Altering a watershed will affect all the living things within that watershed. People can alter a watershed by paving over land
and constructing buildings. This will affect how water flows over the land and may cause harmful materials to flow directly into
the water. This will have an effect on the organisms that depend on the water for survival. For example, some fish feed on
organisms in the water. Polluted water may cause these organisms to die, leaving the fish with no food. This is why we must
understand these relationships and protect our water resources.  You share your watershed with all other living things
within the ecosystem.

 Source:
Project Oceanography