Change sometimes takes a while, but steady pressure can bring about results in the long run. You can learn a lot about the health of your watershed with the help of a standard water quality testing kit. Use a pH test to determine if water is acid or alkaline. Healthy waters are often slightly alkaline because of carbon dioxide content. Too much alkalinity may indicate sewage pollution.
Acidity often points to industrial pollution.
Tests for nitrates and phosphates show if plant nutrients are present, and may indicate pollution from sewage or fertilizer run-off. It measures the amount of light available to aquatic plants. High turbidity may point to serious erosion or other pollution. Testing the temperature of water gives a clue to its oxygen content, since cooler water contains more oxygen. Your biology text or a fisheries biologist can tell you what temperatures are suitable for different fish species.