A pH of 6.3 is just 0.2 less than what is considered normal range of pH for natural waters. "Aquatic life and recreational uses of lakes and streams are not affected when the pH varies between 6.5 and 9.0. When you see a pH value ask these questions because how and when the sample was taken can affect the measurement or reading." A difference of 0.2 could easily be due to error.
� Was the test performed correctly? Was the reading taken directly in the stream or was the sample handled correctly?
� Was the test performed during the summer in very productive waters (many aquatic plants)? Water containing many aquatic plants may have raised pH values on summer afternoons because of plant photosynthesis where readings will be lowest in early morning when plants have released carbon dioxide and highest mid or late afternoon when the CO2 has been abosrbed. CO2 addition makes water more acidic.
� Does the watershed contain a lot of granite-like rock, dense conifer forests, or acidic soil? If so, it will likely have relatively acidic waters. Limestone based soils will result in surface waters that are more basic or alkaline aka 'hard'.
Unpolluted rain water normally has a range of pH between 5 and 6.
Last edited by Bill Cody; 11/20/13 08:02 PM.
