I agree Robert Caro’s The Power Broker will answer many of the issues your researching. Like the biblical Moses, Robert Moses parted Inwood Hill Park, Riverdale and Van Cortlandt Park with the Henry Hudson Parkway and is covered in the book.
Filtration plant was a polictical decision supported by the then mayor Bloomberg and trade unions. There was a location perfectly located in North White Plains that the Westchester community actually wanted the filtration plant.
Much of what you seeking can be found searching the internet. The link that Nick included has much info.
Another is this one https://www.nycgovparks.org/about/history/timeline/park-planning-for-greater-ny
The local Riverdale Press news paper has had many articles over the years covering some of these issues.
NYC parks do not have as much protection as everyone would believe. The Parks Dept is not supported financially as they had been a generation ago. Now they get operational funds for minimal maintenance and look for handouts from private sponsors who will pay for improvements.
Good luck with your research. The society would appreciate a copy ofrlink to whatever you publish.