This is a tough one. The best answer is to try and change the environment so it isn't as favorable for mosquitos. However there isn't anything you can do regarding the stream.
Mosquitos prefer standing water for breeding purposes. Be sure to eliminate any sources of standing water around the property. This springs wet conditions have been perfect for mosquitos. I don't think any area in Northern Ky. is not seeing lots of this insect.
Obviously sprays and repellents applied before going out and keeping as much skin
covered as possible will help.