Test the pH of the water both times. Note any changes. Test the water on or near trees in your schoolyard, home etc. The acidity of a soil is a prime indication of the health of the forest. Soils that are acidic in nature cannot support a wide diversity of plant and animal life.
Fish are particularly sensitive to small changes to the water.
Acid present in soils eventually reaches lakes and rivers through the groundwater table or by runoff and erosion of the soil. The increasing amount of acid rain has severely damaged some of the nations prime wilderness land. Include all the parties that may be affected, such as farmers, the weekend fisherman who can no longer fish, government agencies, etc.