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Napa County Resource Conservation District |
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Napa County Resource Conservation District |
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Through the Water Quality Monitoring Program, volunteers use wet chemistry kits and field meters to measure the temperature, pH, dissolved oxygen, and electrical conductivity of various streams. Measurements are taken on a biweekly basis in the summer and monthly during the winter. Data is entered and stored in a database at the RCD office.
This set of data serves two important purposes. It acts as a screening mechanism for detrimental changes in water quality. Volunteers check to make sure the readings obtained at their site are within acceptable parameters defined by the California Department of Fish and Game. If readings are outside of the acceptable ranges, volunteers notify the RCD to initiate additional testing by RCD or Fish and Game staff. In addition, this data set is important in establishing a base of information to look at long-term trends. The longer data is collected, the more valuable it becomes.
The Water Quality Monitoring Program always needs additional volunteers who are willing to spend about an hour a week on a local creek. Contact the RCD to sign up for training. For more information on the parameters being monitored, connect to the links below.
Site Selection
Site selection is coordinated between a member of the Napa County Resource Conservation District (RCD) staff and the volunteer monitor. The monitor may select a tributary or a reach of the Napa River in which he or she has interest, or may take on a site that is recommended by the RCD.
Once a general region for the monitoring site has been designated, the volunteer monitor and a RCD staff member go to the region and determine an appropriate location for water quality monitoring. The preferred location for the testing is in a run habitat. A run is characterized by swiftly flowing reaches with little surface agitation and no major flow obstructions. If a run is not available, a site may be chosen in a glide or pool. However, during the dry season, as sites dry up, testing typically occurs in the nearest residual pool.
A physical site assessment must be carried out at every site. The site assessment is done with the guidelines laid out in the RCD Site Survey Field Data Sheet. This survey can be conducted by the volunteer with assistance from a RCD staff member.
Water Quality Parameter:
Temperature
Fish and aquatic organisms usually have a specific temperature range in which they survive. For steelhead trout and their primary food source (benthic macroinvertebrates), cool water is an essential component of good habitat. Water temperature has a direct effect on dissolved oxygen levels. Cold water can hold more dissolved oxygen than warm water, and as temperature increases, dissolved oxygen decreases.
The acceptable temperature range for water in the Napa watershed is 2-23 degrees Celsius (36- 73 degrees Fahrenheit). However, steelhead typically need temperatures below 20 degrees Celsius (68 degrees Fahrenheit) to thrive.
Both air and water temperature are measured by volunteer monitors using a calibrated, waterproof thermometer.
Water Quality Parameter:
Dissolved Oxygen
Dissolved oxygen (DO) is critical for fish and other aquatic species in lakes, ponds and streams. Water with consistently high dissolved oxygen, 90% saturation or more, can support a greater diversity of aquatic organisms and a more stable ecosystem. Dissolved oxygen data, in conjunction with biological inventories and other water quality data, can be used to determine the capacity of the stream to support fish and other aquatic species. Low levels of dissolved oxygen may signal the presence of pollution in the water and indicate the need for further investigation. Temperature affects how much dissolved oxygen water can hold. The cooler the temperature, the higher the levels of dissolved oxygen in the water.
Dissolved oxygen is measured by volunteer monitors using a series of chemicals that "fix", or stabilize, the level in the sample. Once the sample is "fixed", a technique called titration is used to determine the level of dissolved oxygen in parts per million.
Water Quality Parameter:
Electrical Conductivity
Conductivity is the ability of water to conduct an electrical current. Dissolved ions (or dissolved salts) in the water are conductors. By determining the flow of electricity through a water sample, the amount of dissolved ions in the sample can be detected.
Conductivity is measured by volunteer monitors using an electronic meter. The conductivity meter measures the electrical current (carried by the dissolved ions) flowing between two electrodes. A sample with a higher conductivity reading would have more dissolved ions, and vice versa.
Conductivities of 100-1000 uS/cm are considered acceptable for the Napa River system.
Water Quality Parameter:
pH
pH is a measure of how acidic or basic (alkaline) the water is. As the pH decreases, water becomes more acidic, and as the pH increases, water becomes more basic. Fish and other aquatic life can only tolerate a limited pH range.
The acceptable range for pH is 6 to 9. A pH of 7 is neutral, and a pH of 7-8 is best for most fish. Fish can not survive at a pH lower than 3.5 or higher than 9.5. Some fish, like trout are more sensitive than others. Trout begin to die if the pH goes down to 5.5 or up to 9.5.
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