Aquatic

• Temperature

  Thermometer
• Water Flow Rate

  Flowmeters give river's discharge at various points/depths as water isn't consistent throughout the channel.
• Dissolved Oxygen Content

  Colorimetric methods show oxygen in a sample. Chemical reagents react with oxygen and change colour. Quick and inexpensive but limited and subject to error.
• Biological Oxygen Demand

  Amount of oxygen needed for aerobic biological organisms to break down organic material. Indicator of pollution.
• Salinity

  Hydrometers measure gravity of liquids to measure salinity. Refractometer is more reliable but expensive, and measures how light bends/refracts when entering liquid. More salt means more resistance light will meet and the more it will bend and vice versa.
• pH

  Using a pH meter, make sure to rinse and clean after. Using litmus papers pH is measured from 0-14. 0 is most acidic, 14 is most alkaline, and 7 is neutral.
• Tidal Effects

  Recorders send an audio signal down a tube and measure the time it takes for the reflected signal to travel back from the surface.