This is largely addressed by the article. Improved biodiversity (more fish, more native vegetation and the bugs/wildlife that go with it) as well as improvement of the water itself like the elimination of dangerous algae blooms.

From the article: The dams also had a severe impact on water temperature and quality – growth of toxic algae behind two of the dams resulted in health warnings against water contact.

Also from the article: "where we've seeded is green, we're seeing flowering plants teeming with life. I counted eight different butterflies in the areas we hand-seeded. There's moths, hoverflies, bees, birds. It's been a really exciting first year."