Check out the Mystic River website, and some of the data you can find there.
As well as some of the work they are doing.
The business case from "Building Community Resilience with Nature-Based Solutions: A Guide for Local Officials" by FEMA:
The Quabbin and Wachusett Reservoirs serve 2.5 million people in central Massachusetts and the Boston area. Over 20 years, the Massachusetts Water Resources Authority spent $130 million on nature-based solutions. The nature-based solutions protect 22,000 acres of the watershed that drains into these reservoirs. A water filtration plant would have cost $250 million to build and $4 million annually to operate and maintain.