What Are We Testing For?

There are a number of water quality measurements that can be documented that help us learn about the health of the river. The things that we measure for are called parameters; they can be indicators that something has polluted the water.  The main parameters that GTC tests for are temperature, pH, dissolved oxygen (DO), and turbidity.  Continue on for a description of each of these parameters.  Turbidity is identified by looking at the water, whereas the rest are determined with the use of a YSI 556 water meter.


Turbidity is caused by suspended particles which scatters light passing through the water.  The more particles, the muddier and cloudier the water becomes, thus reducing its clarity and making it more turbid. 

Why we test

An increase in suspended solids in the water affects water quality in many ways - the particles absorb heat from sunlight, increasing water temperature and thus causes oxygen levels to fall.  Photosynthesis decreases because less light can penetrate the water, further decreasing oxygen.  Suspended solids can also clog fish gills, and smother the eggs of fish when they settle.  Some activities that can increase turbidity are runoff from construction, logging activities, and discharges.


pH is a measurement of how acidic or basic the water in the river is - the pH scale ranges from 0 (strongly acidic) to 14 (strongly basic).  Aquatic organisms have a optimal range of pH 6.5 to 8.2 where they thrive. Generally speaking, the quality of life diminishes as the pH becomes more than 9.0 or less than 5.0.  Most organisms have adapted to life in water of a specific pH and may die if it changes.   

Why we test

Most aquatic plants and animals are used to life in water with a specific pH. Changes in pH may reduce reproduction, and could be deadly.  Mining and the discharge of industrial or residential pollutants directly into waters are examples of activities that can have a negative impact on a water’s pH level.  Mining may expose rocks to rain water and produce acidic runoff, thereby decreasing its pH and making the water more acidic.  As you can see in the pH scale in the previous article, as pH levels decrease, dangers to a variety of aquatic organisms increase.


temperature may be one of the easier of the indicators to understand, and it is also one of the most important parameters to test because of how it affects the rates of chemical and biological reactions in the water.

According to Alaska Water Quality Standards:

May not exceed 20oC at any time. The following maximum temperatures may not be exceeded, where applicable: 

     ▪     Migration routes 15o C 

     ▪     Spawning areas 13o C 

     ▪     Rearing areas 15o C 

     ▪     Egg & fry incubation 13o C 

Why we test

Thermal pollution is an increase in water temperature caused by adding relatively warm water to cooler water.  Measurement of temperature change can help detect the cause of thermal pollution.  High water temperatures can stress aquatic ecosystems by reducing the ability of water to hold essential dissolved gasses like oxygen.  

Dissolved Oxygen (DO)

 is just what it sounds like - oxygen dissolved in water.  Dissolved oxygen is a result of diffusion from surrounding air, aeration of water tumbling over falls or rapids, and as a waste product from photosynthesis.  It is essential for the basic metabolic processes of plants and animals living in the river.   How much DO an aquatic organism needs can vary depending on its physical state, its species, water temperature, and more.  The Alaska Water Quality standards state that in waters used by anadromous or resident fish, DO must be greater than 7 mg/l, and in no case may it be lower than 5 mg/l or greater than 17 mg/l.

Why we test

Dissolved Oxygen is essential for aquatic life.  The presence of aquatic plants, the temperature of the water, the amount of suspended solids in the water are all examples of factors that affect the amount of DO in the water.  Removal of riparian vegetation decreases DO, and human activities causing runoff decrease DO by increasing the amount of suspended and dissolved solids in the water.   


Conductivity is a measure of how well water can pass an electrical current.  It is an indirect measurement of the presence of inorganic dissolved solids.  These dissolved solids are essential for aquatic life, but sometimes there is such thing as "too much of a good thing”.  A high concentration of dissolved solids can cause water balance problems and decreased oxygen levels.  The conductivity of a water source is often determined by the surrounding bedrock and soil types.  It can also be impacted by human influences.  

Total Dissolved Solids (TDS)

Total Dissolved Solids (TDS) is a measurement of inorganic salts, organic matter and other dissolved materials in the water.  Dissolved solids can come from organic sources like leaves, silt or plankton or runoff from urban areas.  They can also come from inorganic materials like rocks containing calcium carbonate, nitrogen or other minerals.  Similar to salinity, changes in TDS can have differing impacts, depending on the species.  TDS can cause toxicity through increases in salinity, changes in the overall ionic composition of the water, or changes to individual ions.  


Salinity is a measure of the concentration of dissolved salts in fresh water, and is measured in parts per thousand (ppt).   Salinity influences the kinds of plants and organisms that live not only in a body of water, but also the kind of plants that will grow on land that is fed by that water source. In elevated concentrations, prolonged exposure can result in profound ecological impacts.  The impact varies from species to species.

What We Test

Why do we analyze the water data?

As part of our IGAP grant, one of GTC's goals is to establish a water quality baseline to ensure the continued health of the Kuskokwim River alongside responsible development.   Having a reliable and consistent set of data to establish what is called baseline data, allows us to address changes to the quality of the water that may occur due to various external influences such as human activities on the river, mining operations, etc.  Parameters such as pH, conductivity, temperature, and dissolved oxygen (DO) are used to measure the quality of the water on site.