Water Quality Results Defined
Key Terms:
ppm: parts per million
ppt: parts per thousand
oC: degrees Celsius
mg/L: Milligrams per Liter of solution.
Meter: SI (International system of Units) unit of length one meter is equal to 3.3 ft.
μS (micro-siemens): Unit of measure for conductivity.
JTU (Jackson Turbidity Units): Unit of measure for water clarity.
SIU ( Significant Industrial Users): Unit of measure for pH.
O2: Short hand the elemental oxygen (O), on the Periodic Table of elements.
D.O. : Short hand for dissolved oxygen
Interpreting Water Results
Water Temperature: temperature affects the physical and chemical properties of water and greatly influences aquatic organisms by affecting their feeding, reproduction, and metabolic rates. Drastic changes in temperature can cause thermal stress, in general temperatures above 32oC (89.6oF) are considered lethal for marine life.
Dissolved Oxygen: One requirement of aquatic life is oxygen. Fish and other organisms, like us, need oxygen to survive. D.O. decreases in higher temperatures (spring ,summer) and increases in colder temperatures (fall, winter). Plants and other microorganisms can increases the amount of oxygen available to aquatic organisms, on the other hand decaying plant life removes oxygen from the water. D.O. value for healthily lakes, streams, and rivers must be at least 5.0ppm or more, below 5.0ppm "fish kills" can occur.
Dissolved Oxygen percent saturation: The amount of oxygen a body of water can hold based on: temperature, elevation, and salt content. In general D.O. percent saturation below 60% is poor, 60-79% is considered acceptable for most bodies of water, 80-125% excellent for most bodies of water, above 125% oxygen content is too high and maybe dangerous to fish.
pH : Is the measure of how acidic (Hydrogen ions H+) or basic (Hydroxide ion OH-) a body of water is. A pH of 7 is considered neutral (neither acidic or basic). A pH below 7 is considered acidic, above 7 are considered basic. Optimal pH is considered to be between 6.5 and 8.5. A pH reading less than 4.0 or more than 10.0 is usually lethal to fish and other aquatic organisms. Click here for a view of the pH scale.
Alkalinity: Is a measure of a body of water's resistance to rapid change in pH. The higher the alkalinity the better the water can resist changes to pH thus making the water "stable" for aquatic life. However alkalinity usually follows pH, the higher the alkalinity the higher the pH.
Hardness: Is a measure of the amount of dissolved Calcium and Magnesium in the water. When the presence of Calcium and Magnesium are high "hard water" is the result (soap is hard to lather). This test is an indirect measure of pollution, streams lacking salt and other pollutants have a "soft" value (0-60 mg/L). Brackish waters can range from 20-180 mg/L due to a tidal influence of salt in fresh water.
Turbidity and Secchi depth: Turbidity is a measure of water "cloudiness" caused by suspended matter (soil, silt, plankton, algae, etc). Runoff and erosion is one of biggest contribution toward water "cloudiness". High turbidity limits the amount of sunlight reaching the bottom of a lake, river or steam, and inhibits the growth of aquatic plants, and other organisms. A Secchi disk is one way to measure the turbidity of a body of water. It is a black and white disk with a string attached marked off every 0.1 (one tenth) of a meters. The disk is lowered into the water until it can not be seen. The farther down the disk goes, the lower the turbidity (the clearer the water).
Conductivity: Measures the ability of water to conduct an electrical current, and is directly related to the total dissolved salts and other solids dissolved in the water.
