Common Tributary Water Measurements
Taking water measurements can reveal very important information about a body of water and the plants and animals that inhabit it. The results of a single measurement of a water’s properties are less important than looking at how the properties vary over time. So, often, the changes in water measurements will tell more than the actual single measurement. This is why our Lake and Tributary monitoring programs are so valuable. We are watching changes over periods of time, to enable us to anticipate problems and respond more quickly if we see any occurrences of concern.
Water temperature is not only important to swimmers and fishermen, but also to fish and algae. Temperatures can affect the entire water habitat. Temperature can also affect the ability of water to hold oxygen as well as the ability of organisms to resist certain pollutants.
pH is a measure of how acidic/basic water is. The range goes from 0 – 14, with 7 being neutral. Measurements of less than 7 are acidic, and greater than 7 basic. Since pH can be affected by other chemicals in the water, pH is an important indicator of water that is changing chemically.. pH is reported in “logarithmic units,” like the Richter scale, which measures earthquakes. In other words, each number represents a 10-fold change in the acidity/basicness of the water. Water with a pH of 5 is ten times more acidic than water having a pH of six – so, for example, you can see that slight changes could have a great impact on fish who cannot tolerate acidity. Any type of pollution, such as acid rain or phosphorous from fertilizers or soils, can harm animals and plants living in the water.
Specific conductance is a measure of the ability of water to conduct an electrical current. It is highly dependent on the amount of dissolved materials (such as salt) in the water. Pure water, such as distilled water, will have a very los specific conductance, and sea water will have a high specific conductance. You probably remember the experiment where you hold up a battery to a light bulb and run two wires into a beaker of water. When the wires are put into distilled water, the light will not respond, but when put in salt water, lights up because the water is conducting an electrical current!
Rainwater often dissolves airborne (atmospheric) gasses and airborne dust, and thus often has a higher specific conductance that distilled water. This is why acid rain has been such a problem is causing water bodies to absorb chemicals from air pollution. However, the nation’s efforts over the past decade to reduce air pollution from mid-western power plants has actually begun to make a difference in reducing acid rain over New England. This shows in our testing results over time.
Turbidity is the amount of Particulate matter that is suspended (not dissolved) in water. Turbiduity measures the scattering effect that suspended solids have on light: the higher the intensity of scattered light, the higher the turbidity. Materials that cause water to be turbid include:
Finely divided organic (live) and inorganic matter
Soluble colored organic compounds
Plankton (microscopic plants)
Microscopic animals (fish food!)
Turbidity makes the water cloudy (“opaque”). This may occur from soil erosion – either from some sort of construction activity, or flooding – when the amount and velocity of water can have an erosive effect on the stream beds and banks. During a rainstorm particles from the surrounding land are washed into the river making the water a muddy brown color, indicating water that has higher turbidity values.
Turbidity can be measured on site with a hand held meter as well as in the lab.
Dissolved Oxygen (DO)
Although water molecules contain an oxygen atom, this oxygen is not what’s needed by aquatic organisms living in our natural waters. A small amount of oxygen, up to about 10 molecules per million of water, is actually dissolved in water. This DO is breathed by fish and zooplankton (plants) and is needed for their survival. The Newfound Lake and streams are known for their very good fishery, so this is one of the most important reasons to keep this habitat very high quality – it affects local recreation and businesses! (See “Fisheries”)
Rapidly moving water, such as in a mountain stream or large river, tends to contain a lot of dissolved oxygen, while stagnant water contains little. Bacteria in water can consume oxygen as organic matter decays. Thus, excess organic material in our lakes and rivers can cause an oxygen-deficient situation. Aquatic life can have a hard time in stagnant water that has a lot of rotting, organic material in it, especially in late summer, when DO levels are at a seasonal low. Low DO also causes some of the odors you can sense when water levels have been low, and organic material is decaying at the end of the summer.
Suspended sediment is the amount of soil moving along in a stream. It is highly dependent on the speed of the water flow, as fast-flowing water can pick up and hold more soil than calm water. During storms, soil is washed from the stream banks into the stream and then the lake. The amount depends of the land in the watershed, and the vegetation surrounding the river or lake. The Newfound Lake Watershed is very steep, and therefore considered “flashy.” This means that when it rains hard, the water quickly rushes down the steep slopes, potentially causing “flash” flooding and erosion.
If land is disturbed along a stream, and protection measures (see “Best Management Practices”) are not taken, excess sediment can impact the stream and the lake, along with all the critters living in them. “Erosion control silt fences” are supposed to be installed wherever there is disturbance near a water body, to trap sediment and keep it from washing into a stream.