What You'll Be Testing For
On World Water Monitoring Day
During the Water Monitoring Day event, you will be testing your water samples for temperature, dissolved oxygen (DO), percent saturation (DO Percent Saturation), pH (hydrogen ion concentration) and turbidity. Some of you may also take a "bug" count report that tells how many and what types of macroinvertebrates live in the body of water from where you took the sample, giving an overall snapshot of the water's quality.
The following explains why these are important indicators of water quality, how varying levels of these indicators can affect the water quality of the body of water you are testing and how that water quality affects its aquatic life.
- Temperature: Temperature is a measurement of how warm or cold the water is. This is important because it affects dissolved oxygen, photosynthesis, and the food supply. Fish are ectotherms or poikilotherms. These are both terms that describe animals that have a body temperature that is dependent upon the water temperature.
Waters that are too hot or too cold can have severe effects on fish and other aquatic life because water temperature affects such things as the fish's immune system, wound healing and digestion.
What constitutes a 'good' temperature depends on the type of stream you are monitoring. Lowland streams, known as "warmwater" streams, are different from mountain or spring fed streams that are normally cool. Warmwater stream temperatures should not exceed 89° (Fahrenheit). Cold water streams should not exceed 68° (Fahrenheit). Visit our Water Temperature Testing page for instructions on testing water temperature. But, you must first register for the World Water Monitoring Day event and get your water test kit.
- Dissolved Oxygen (DO): Dissolved Oxygen is a measurement of how many molecules of oxygen are in the water. Oxygen gets into water by diffusion from the surrounding air, by aeration (rapid movement), and as a waste product of photosynthesis. Adequate dissolved oxygen is necessary for good water quality. Oxygen is a necessary element to all forms of life, including people. Fish, invertebrates, plants, and aerobic bacteria all require oxygen for respiration.
Several factors can affect the dissolved oxygen levels of a body of water, including:
- Volume and velocity of water flowing in the water body
- Climate/season
- The type and number of organisms in the water body
- Altitude
- Dissolved or suspended solids
- Amount of nutrients in the water
- Amount of organic waste in the water
- Amount of riparian vegetation bordering the water body.
Changes to any of these factors will either increase or decrease the dissolved oxygen levels of a water body. Depletions in dissolved oxygen can cause major shifts in the kinds of aquatic organisms found in water bodies. As dissolved oxygen levels in water drop below 5.0 mg/L, aquatic life is put under stress. The lower the concentration, the greater the resulting stress. Oxygen levels that remain below 1-2 mg/l for a few hours can result in the death of many species of aquatic life.
DO levels of:
- Less than 5 mg/L are considered bad.
- 5 - 10 mg/L are considered good.
- More than 10 mg/L are considered excellent.
Find out how healthy the water is in your areas. Register for the World Water Monitoring Day event and get your water test kit.
- % Saturation: % Saturation is a shortened term for Dissolved Oxygen (DO) Percent Saturation, the percent of the potential capacity of the water to hold oxygen that is present. It is the amount of oxygen dissolved in the water sample compared to the maximum amount that could be present at the same temperature. If the water is determined to contain the maximum amount of oxygen at that temperature, it is considered to be 100% saturated. If the water sample is 50% saturated, it only has half the amunt of oxygen that it could potentially hold at that temperature. % Saturation values of 80% to 120% are considered to be excellent and values less than 60% or over 125% are considered to be poor.
The sample Dissolved Oxygen Percent Saturation level reading from Percent Saturation page of our Water Monitoring Testing instructions indicates that the body of water tested only has 41% of the amount of oxygen that it could potentially hold at that temperature because it is only 41% saturated. If you're interested in testing the water quality in your area, you will need to register for the World Water Monitoring Day event and get your water test kit.
Three factors affect the percent saturation (the highest DO level possible even in well aerated water):
- Salinity: Fresh water holds more oxygen than salt water.
- Temperature: Cold water holds more oxygen than warm water.
- Atmospheric Pressure (Altitude): The greater the atmospheric pressure the more oxygen the water will hold.
But, when salinity, temperature, and altitude increase oxygen at saturation decreases. Critically low oxygen levels often occur during the warm summer months when decreased capacity and increased oxygen demand, caused by respiring algae or decaying organic material, coincide.
| Maximum dissolved oxygen concentrates vary with temperature, as shown by this table from the Environmental Protection Agency (EPA). You'll see that warmer water becomes "saturated" more easily with oxygen. As water becomes warmer it can hold less and less DO. |
| Temperature (°C) |
DO (mg/l) |
Temperature (°C) |
DO (mg/l) |
| 0 |
14.60 |
23 |
8.56 |
| 1 |
14.19 |
24 |
8.40 |
| 2 |
13.81 |
25 |
8.24 |
| 3 |
13.44 |
26 |
8.09 |
| 4 |
13.09 |
27 |
7.95 |
| 5 |
12.75 |
28 |
7.81 |
| 6 |
12.43 |
29 |
7.67 |
| 7 |
12.12 |
30 |
7.54 |
| 8 |
11.83 |
31 |
7.41 |
| 9 |
11.55 |
32 |
7.28 |
| 10 |
11.27 |
33 |
7.16 |
| 11 |
11.01 |
34 |
7.16 |
| 12 |
10.76 |
35 |
6.93 |
| 13 |
10.52 |
36 |
6.82 |
| 14 |
10.29 |
37 |
6.71 |
| 15 |
10.07 |
38 |
6.61 |
| 16 |
9.85 |
39 |
6.51 |
| 17 |
9.65 |
40 |
6.41 |
| 18 |
9.45 |
41 |
6.41 |
| 19 |
9.26 |
42 |
6.22 |
| 20 |
9.07 |
43 |
6.13 |
| 21 |
8.90 |
44 |
6.04 |
| 22 |
8.72 |
45 |
5.95 |
What is the % saturation in the water near you? Register for the World Water Monitoring Day event and get your water test kit to find out.
- pH (Acidity): pH levels are measurements of how acidic or basic a liquid is. Water (H20) contains both H+ (hydrogen) ions and OH- (hydroxyl) ions. The pH test measures the H+ ion concentration of liquids and substances. The pH level is measured on a scale from 0-14, where 0 is most acidic, 14 is most basic, and a value of 7 is neutral. Natural waters with conditions favorable for supporting life usually have a pH reading between 6.5 and 8.5.
On a more technical level, pH is actually a measure of the relative amount of free hydrogen and hydroxyl ions in the water. Water that has more free hydrogen ions is acidic, whereas water that has more free hydroxyl ions is basic. Since pH can be affected by chemicals in the water, pH is an important indicator of water that is changing chemically.
For example, water dissolves mineral substances it contacts, picks up aerosols and dust from the air, receives man-made wastes, and supports photosynthetic organisms, all of which affect the pH levels. And, we can't forget that pollution also changes a water's pH, which in turn can harm animals and plants living in the water.
A pH level of:
- Less than 6.5 is low, so the water would be acidic.
- 6.5 - 8.5 is normal, so the water would be considered to have a good pH level.
- More than 8.5 is high, so the water would be considered basic.
What is the pH level of the water near you? Register for the World Water Monitoring Day event and get your water test kit to find out.
- Turbity (Clarity): Turbitity is an indication of how clear or cloudy the water is. Light's ability to pass through water depends on how much suspended material is in the water.
Clear water has a low turbidity level and cloudy or muddy water has a high turbidity level. High levels of turbidity can be caused by soil erosion, waste discharge, urban runoff, bottom feeders like carp that stir up sediments, household pets playing in the water, and algal growth. Turbid waters become warmer as suspended particles absorb heat from sunlight, causing oxygen levels to fall—warm water holds less oxygen than cooler water.
Turbidity impacts the aquatic ecosystem by affecting photosynthesis, respiration, and reproduction of aquatic life. For example, suspended solids in turbid water can clog fish gills, reduce growth rates, decrease resistance to disease, and prevent egg and larval development. Settled particles smother eggs of fish and aquatic insects. Suspended particles may also provide a place for harmful microorganisms to lodge, and some suspended particles could provide a breeding ground for bacteria.
The turbidity level is measured in Jackson Turbidity Units (JTU). A turbidity reading of 0-10 JTU is considered normal. Register for the World Water Monitoring Day event and get your water test kit to find out how turbid or clear the water near you is.
- Macro-invertebrate (Benthic) Counts: Otherwise known as a "bug" counts, this test provides a living indicator of the health of the water by counting the "bugs" that are found in aquatic environments. Benthic macroinvertebrates include insects such as larval damselflies, dragonflies, and midges, as well as crustaceans, mollusks, etc. that live in the streambeds of fresh water rivers. Macroinvertebrates, or "macros" for short, are an important part of the ecology of watersheds. They can also be used as an indicator of water quality based on their preferences and tolerances because macroinvertebrates have different levels of tolerance for pollutants and other factors that impact the health of the water.
For example, certain macros such as mayfly larvae can only thrive in waters with relatively high dissolved oxygen. Therefore, the presence of mayfly larvae in a river segment is an indicator of high dissolved oxygen. However, if that river segment only contained macros that can tolerate low dissolved oxygen (such as damselfly larvae), it is logical to conclude that the dissolved oxygen levels are too low to support a diverse range of macros.
By observing the benthic population and classifying more or less tolerant species, a general observation about the quality of the water can be made. These findings can often be compared to the chemical/physical indicators to determine overall health of the water at the sampling site.
Find out the bug count in your area. Register for the World Water Monitoring Day event.
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