Lake Water Quality Testing

 

Lake Water Quality Testing Methods

By Emily McGuckin, AmeriCorps Watershed Ambassador   6/17/20
 

Summary: Many factors contribute to the continued health of a freshwater body. Variations in these parameters will change the quality of the waterbody. There are tests that can be performed to determine the levels of certain parameters and how they are currently or might affect these bodies of water. Some tests can be done by association members based on experience level and availability of testing equipment, while others would need specialists and special equipment (listed below). Water quality testing kits are available for purchase, but can be quite expensive. Listed below are some parameters that can be tested with a brief summary of what they are, as well as how to perform these tests.

Parameters:

       1.  DO: dissolved oxygen - how much oxygen is available for living organisms in the water

       2.  pH: how acidic or alkaline the water is

       3.  Turbidity: how much suspended sediment is in the water column, how 'cloudy' the water is, usage of Secchi disc

       4.  Salinity:  how saline the water is

       5.  Temperature: how hot or cold the water is

       6.  Nitrogen: a nutrient that can promote the growth of undesirable aquatic plans and hurt other organisms

       7.  Phosphorus: another nutrient that can promote the growth of undesirable aquatic plants and hurt other organisms

 

 

1.  DO: how much oxygen is available for living organisms in the water

 

Summary:

This parameter is extremely important because it shows how capable a water body is at sustaining and supporting life. When oxygen levels are low, it can lead to declines in health or relocation of organisms or increased mortality of certain species within the water. Hypoxia is the term used to describe low levels of oxygen and anoxia is used to describe no oxygen levels. Hypoxia or anoxia can be a result of decomposition of large amounts of organic materials, such as algal blooms. This parameter is measured in milligrams per liter. It can be affected by temperature and salinity. Higher temperatures and/or salinity leads to a decrease in DO concentration.

Testing:

Dissolved oxygen can be tested using a water quality meter or colorimetry. Meters typically are more expensive, but easier to use and more accurate. Colorimetry uses colored chemicals, that when added to the water you wish to test, will change the color of the water and can be compared to a results sheet to show an approximation of the DO levels in that water body. These can be bought at a pet supply store. If using a meter, calibration is needed. It is straightforward and easy to use when following the given directions.

Results:  

Typically, when the DO level is below 3 mg/L it is concerning and when it is below 0.5 mg/L it is anoxic.  Low levels of DO can result in organisms in that area moving to new locations, while potential undesirable organisms move in. It can also result in mortality of organisms and is often seen via fish kills. Slow or stagnant water can increase DO as well.

Sources:

https://www.epa.gov/national-aquatic-resource-surveys/indicators-dissolved-oxygen

 

2.  pH: how acidic or alkaline the water body is

 

Summary:

This parameter is measured on a scale from 0 to 14 with 7 being neutral. Substances that have a pH measured at 0-6 are more acidic (like lemon juice) and substances that have a pH measured at 8-14 are more basic (increasing alkalinity). This is a logarithmic scale meaning that each whole value below 7 is 10 times more acidic than the whole number directly above it and each whole value above 7 is 10 times more alkaline than the whole number directly below it. Normal range of freshwater would be between 5.8 to 6.9.

Freshwater is not typically neutral (pH of 7). Salt water would be measured at a pH of 8 or 9, while rain water is typically found to be around 5 or 6. If the pH of your freshwater body is measured at 7.5 of higher, there might be an influx of salt and/or chemicals leading to increased alkalinity.

Testing:

With a kit: A typical pH testing kit will contain pH test strips, bottles of indicator drops and a meter to compare results to known pH levels. Simply collect a sample of water from the water body you wish to test and drop the specified amount of drops from the indicator bottles into the water. Then, compare the resulting color of the water to the meter to determine pH of the water. If you are using the test strips, dip the strip in the water and then remove. Compare the resulting color to the meter to determine pH of the water.

Without test kits: If you do not have a test kit, pH can be tested using a fresh red cabbage and distilled water. To do this, simply cut up the cabbage and place in a glass bowl. Boil the distilled water and then pour over the cabbage, just covering the top of the cabbage. Leave the cabbage in the water for about 30 minutes, stirring occasionally. After the 30 minutes is up, the water will be slightly red in color. This red water will be the pH indicator solution.

In a separate container, pour some of the water that you would like to test in. Then, put a couple drops of the indicator solution into the water. The mixture will change color to show either an acidic, neutral or alkaline result. Match the color of the tested water to a pH color chart to determine pH of your water body.

Results:

Freshwater with a pH of about 5.5 to 6.9 will indicate normal pH of that water. If the pH number is between 4 and 5, fish reproduction will be affected and if it is below 4 mortality rates will increase in mature fish. Additionally, aquatic plants might start invading that space and push out other desirable species. If the pH is above 8, mortality events will occur in fish species, as well as damage to the fish’s gills, eyes and skin. Higher pH might also increase the toxicity of other substances like ammonia. 

Sources

https://waterfiltercast.com/how-to-test-ph-of-water-without-a-kit/

https://www.lenntech.com/aquatic/acids-alkalis.htm

https://www.thoughtco.com/making-red-cabbage-ph-indicator-603650

 

3.  Turbidity: how much suspended sediment is in the water column, how 'cloudy' the water is, usage of Secchi disc

 

Summary:

Turbidity is the measure of clarity of the waterbody based on the amount of light that is reflecting off other objects in the water. It can also be used to describe how much suspended sediment might be in the water column. This could be from additional sediment like soil, silt or clay, actual pollution/litter, or plant material like algal blooms.

Testing:

With special equipment: Turbidity meters are available, often at high prices. It reads the turbidity of the water by shining a light from the instrument and reading how much of that light is reflected back. This parameter can be tested with kits from the Water World Monitoring Challenge listed below.

Without special equipment: To test turbidity, you can use a Secchi Disc. This is a circular plate that is divided into four quadrants with an alternating pattern of black and white quadrants. The disc is on a rope and ever meter or foot (depending on what your preference is) is marked. To use this device, simply lower the disc into the water until the line between the white and black quadrants is not distinguishable anymore. Mark the meter or feet mark on the rope and then pull up the disc and count the meters or feet on the rope. This will tell you how much light is being reflected back based on the amount of items the light has to reflect off of.

Results:

Turbidity is measured in Nephelometric Turbidity Units (NTU) and the higher the unit, the more turbid the water is. Extremely turbid water can be not only aesthetically displeasing, but also a health concern. Highly turbid water can promote pathogen growth which can lead to intestinal illnesses and might allow other pollutants to attach to these particles in the water. Particles in the water can also harm the local flora by clouding out the sunlight plants need to survive. In addition, it can clog organisms’ gills and make it hard for them to breathe, leading to increased mortality. It can also cause waterways or water bodies to fill up more quickly, due to the influx of particles.

Sources:

https://www.usgs.gov/special-topic/water-science-school/science/turbidity-and-water?qt-science_center_objects=0#qt-science_center_objects

     

4.  Salinity: how saline the water is

 

Summary:

This parameter is the measure of the concentration of dissolved salt in the water. It is an extremely important ecological factor. Changes in this parameter can alter almost every aspect of a water body, from abiotic to biotic factors. It is measured in parts per million (ppm). Freshwater has a low concentration of salinity while ocean water has a higher concentration of salinity.

Testing:

Without special equipment: A hydrometer is used to test this parameter. A swing arm hydrometer is extremely simple to use. Fill your hydrometer up to the designated line on the instrument; each type will have a different location of the line. Then, wait until the water settles and the arrow within the hydrometer will move showing the salinity levels of the water that was tested. The scale on the side of the meter shows results in ppm or specific gravity and clearly labels which side of the scale corresponds to which result. These are relatively cheap and can be bought at a pet supply store.

With special equipment: There is also a more expensive but more accurate tool to measure salinity called a refractometer. This tool needs to be calibrated using the instructions included with the item. Once it is calibrated, it is also fairly easy to use. Simply obtain a sample of the water you would like to test in a cup or bowl. Then, drop 1-2 drops of this water onto the surface of the refractometer’s test lens. Close the flap over the lens and look through the refractometer at a light (like a kaleidoscope). Inside you will see a scale on the left and a solid usually blue line that will move depending on how saline the water is. This will be measured in both ppm and specific gravity.

Results:

The salinity of freshwater ideally should be less than 1,000 ppm, but many things can influence this parameter. If salinity levels get too high within a freshwater body, many factors of the water will be thrown off. If the salinity is slightly higher, fish and other mobile organisms might be affected by differences in buoyancy. Certain plants might not thrive, while other less desirable vegetation might do better. If the salinity gets extremely high, most organisms normally found within this water body will either move out of the area to a less saline location or face mortality. Additionally, DO can be affected by increases in salinity. It might also cause upwelling within your lake because saltwater is more dense than freshwater.

Sources:

https://www.usgs.gov/special-topic/water-science-school/science/saline-water-and-salinity?qt-science_center_objects=0#qt-science_center_objects

     

5.  Temperature: how hot or cold the water is

 

Summary:

Temperature is simply how hot or cold the water is. Scientifically, this is measured in Celsius, but can also be measured in Fahrenheit.

Testing:

Measuring this parameter is straightforward. Simply collect a sample of the water that you would like to test and use a water thermometer to find the temperature.

Results:

All organisms found within a water body have an optimal range for every parameter talked about so far. Just like all the previous parameters, extreme changes in temperature can lead to organisms moving to different locations or dying off. Warmer water also promotes the growth of plants, potentially leading to HABs. Obviously, water temperature changes with seasonal changes. More often than not, you should worry about the water being too hot, rather than too cold. Cold water holds more dissolved oxygen than warm water does. Additionally, most of these organisms will be cold-blooded. With global warming, water will continue to get hotter, and will expand, bringing along a whole host of other problems with it. One way to combat warming waters is to create more shade via trees.

 

6.  Nitrogen: a nutrient that can promote the growth of undesirable aquatic plans and hurt other organisms

 

Summary:

This is a nutrient that can be natural within a waterbody and is needed for the growth of plants and animals. Overabundance of this nutrient can lead to problems for both the flora and fauna of a waterbody. Nitrogen can be found in three forms as nitrate, nitrite or ammonium. Typically, nitrogen can be introduced into an environment through runoff from agricultural locations as well as sewage.

Testing:

Nitrogen levels can be tested using test strips from a test kit. These can be bought at pet supply stores. They sometimes contain strips that will measure both nitrate and nitrite on the same strip. Collect a sample of water from the desired waterbody. Dip the test strip into water but do not let it soak. Follow the kits specific instructions for how long to wait for each test. After waiting the appropriate amount of time, match the color shown to the results paper. Results are shown in ppm.

Results:

Overabundance of nitrogen can lead to overstimulation of plant growth. This could lead to harmful algal blooms (HABs) which can release toxins that might harm humans, as well as clouding the water so plants on the bottom cannot grow and using too much oxygen resulting in hypoxic or anoxic conditions and fish kills. If excess nitrogen gets into shallow groundwater, it could be very dangerous for humans. Lots of nitrogen might lead to restrictions of oxygen transport in the body.

Sources:

https://www.usgs.gov/special-topic/water-science-school/science/nitrogen-and-water?qt-science_center_objects=0#qt-science_center_objects

 

7.  Phosphorus: another nutrient that can promote the growth of undesirable aquatic plants and hurt other organisms

 

Summary:

Phosphorus is another nutrient that is essential for plant and animal life and can come from fertilizers, manure or organic waste. Soil erosion is a big contributor to phosphorus that gets into streams. It attaches to the soil and then when it rains and the soil runs into the water, so does the phosphorus.

Testing:

Just like nitrogen which had multiple different types of nitrogen to test for, phosphorus also has multiple types; orthophosphate, condensed phosphate and organic phosphate. Only orthophosphate can be tested using the colorimetric method. Unfortunately, you will need to buy a testing kit for this parameter, but they can be bought at pet supply stores.

Results:

Too much phosphorus in the water can lead to an increase in eutrophication and HABs which can release toxins that might harm humans and a decrease in dissolved oxygen in the water. If lots of sediment is getting into the water, it can result in increased levels of phosphorus. One way to combat possible erosion is to plant trees on the banks. The roots will hold the ground in place, stabilizing the soil.

Sources:

https://www.usgs.gov/special-topic/water-science-school/science/phosphorus-and-water?qt-science_center_objects=0#qt-science_center_objects

TEST KITS:

https://www.monitorwater.org/order-kits

https://www.lamotte.com/en/education/water-monitoring

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