Conductivity
What is it? Conductivity is water's ability to pass an electrical flow and measures the amount of ions dissolved in the water (such as chloride, nitrate, sulfate, sodium, magnesium, calcium, or iron).
Why is it important? Every body of water has a unique conductivity level based on its bedrock. Establishing a baseline is important as some bodies of water have naturally high levels due to their geology and geography.
What does it mean? We can use conductivity as an early warning system for potential problems that warrant further testing. If we see a variance (either lower or higher) from our baseline readings, we know something may have gone wrong. Sometimes high conductivity is from natural sources (certain rockbeds create high readings, for example). But if an area acquires unusual readings, it could mean that that area is in trouble: too high or too low conductivity for an area means local species cannot survive.