This is a question near to my heart because I'm a resident of the Connecticut River Valley myself, and I have done a lot of research on water quality in the river and its tributaries.
The main issue facing most of the valley is sprawl. Tourists who expect to enjoy big-city, high-end amenities while on vacation here drive developers to build bigger, fancier facilities that increase pressure on our infrastructure. Bigger hotels, fancier restaurants, golf courses, and the like mean local taxes have to rise to help pay for things like improvements to water systems, upgrades to waste treatment facilities, and road widening. The increasing taxes hurt the farmers and landowners in the valley, who then sell off land to the developers, creating a vicious circle that eventually destroys the very things the tourists came to enjoy in the first place.
Tourists need to recognize that the Connecticut River Valley is famous for its forests, open land, wildlife, small towns, and farms. The best way to preserve its beauty for future generations is to partake of these things, rather than simply being an observer. That means staying in a small, locally-owned inn and patronizing the small, local businesses nearby. Ideally, tourists should embrach an ecotourism approach, and should feel like they have traveled back in time to a simpler era when they visit.