The scale is logarithmic. A change of one pH unit means 10 times the acid or base concentration. For instance, a change from 7.0 to 6.0 indicates water 10 times more acidic; a change from 7.0 to 5.0 indicates water 100 times more acidic.

Typically nitrogen levels in natural waters are low (below 1 ppm nitrate nitrogen). Nitrogen released by decomposing animal excretions, dead plants, and animals is rapidly consumed by plants. In water bodies with high nitrogen levels, eutrophication can occur. Nitrogen levels can become elevated from natural or human-related activities. Ducks and geese contribute heavily to nitrogen in the water where they are found. Man-made sources of nitrogen include sewage dumped into rivers, fertilizer washed into streams or leached into groundwater, and runoff from feedlots and barnyards.

Nitrate levels are measured in parts per million (ppm) nitrate nitrogen. Remember that nitrate levels can change over time. So it is best to test fresh samples (less than 2 hours old) or refrigerated samples. 

Macroinvertebrates can tell us a lot about the conditions within a water body. Many macroinvertebrates are sensitive to changes in pH, dissolved oxygen, temperature, salinity, transparency, and other changes in their habitat. Habitat is a place that includes everything that an animal needs to live and grow. 

Ashley J. Rust A C , Terri S. Hogue A B , Samuel Saxe A and John McCray A B

International Journal of Wildland Fire 27(3) 203-216 https://doi.org/10.1071/WF17115
Submitted: 8 March 2017  Accepted: 28 January 2018   Published: 28 March 2018 

 

And here is a link to the USGS website that describes how you measure streamflow. This is the research method but it can be done with a measuring tape, something that floats (like an orange peel) and a timer too so it is a fun activity with students. These links give a great overview and the detailed specifics of how you do it.