"Existing dams" refers to dams that are already built and in place. These are not new or future dams, but ones that are currently present and serving a specific purpose such as water storage, flood control, or power generation. Full definition
Much of what one often hears about greenhouse gas emissions from dams being minimal is based on the world's existing dams with measurements of emissions. (internationalrivers.org)
To understand Site C's true impact on First Nations, you first had to look at the distressing impacts of the two existing dams on... (theenergymix.com)
One approach is to create campaigns against new dams to save fish, or to create campaigns to have existing dams removed (as in the Snake River dams in the USA). (dotearth.blogs.nytimes.com)