Reservoirs store fresh drinking water for millions of people.  However, these artificial lakes also provide extensive habitat for a variety of creatures.  

Reservoirs' calm, slow-moving waters support several species of water-breeding insects, like dragonflies and damselflies.  Their far-reaching tributaries allow semi-aquatic critters, like frogs and salamanders, to venture deep into the woods, where their main predators (fish and herons) do not follow.  

Armies of game fish, originally stocked for fishermen's pleasure, also feed the hungry beaks of herons, egrets, eagles, and ospreys and many other piscivorous (fish-eating) animals.

These are just a few examples of reservoirs' (and, ultimately, humans') positive impact on the environment.  By creating reservoirs, we have formed vibrant ecosystems that shelter and support billions of animals worldwide.