Here is a list of commonly asked questions about sampling compiled by the project team. If you have any questions, please feel free to contact us via email.
- What is water quality sampling and why is it important to do?
- How are samples collected and how often are they collected?
- What is done with the samples once collected?
- How will the analytical data be used?
- The water is tested for what parameters (nutrients, bacteria, etc.)?
- Why are both Dry-weather and Wet-weather Monitoring Important in a Watershed Assessment?
- Why does water quality shift naturally?
- How were the sampling sites selected?
- Where are the sampling sites located?
- Where can I find the definitions for technical terms I do not know?
- Can I access the raw sampling results?
1. What is water quality sampling and why is it important to do?
Water quality sampling in the Alcovy involved manually collecting water samples at predetermined locations throughout the watershed. Once collected, samples were analyzed to estimate the water quality conditions at particular locations. By sampling various sites in the watershed and studying the analytical data from those locations, one can gain an understanding of the general "health" of the Alcovy. In addition, the analytical data are being used in BASINS, the water quality computer model selected for this project.
2. How are samples collected and how often are they collected?
A team of trained environmental scientists and engineers collected the water samples. The samplers wade carefully into the Alcovy, trying to stir up as little sediment as possible. In order to collect an undisturbed sample, the samplers stand downstream of the point of collection. Strict sampling procedures are followed to ensure sample integrity. Examples of such procedures include wearing latex gloves and packing the samples in ice for shipment to the laboratory and collection of duplicate and blank samples.
Samples were collected over a period of eight months from fall of 1999 through spring of 2000. Eight samples were collected during dry weather, also known as baseflow conditions and four samples were collected during storm events.
3. What is done with the samples once collected?
Once collected, properly labeled and packed in ice, the samples are shipped to an environmental laboratory for analysis. Samples must be collected, received and analyzed by the lab within a certain period of time known as a holding time. Accompanying the samples to the laboratory is a Chain-of-Custody form, sometimes referred to as a COC, which assures samples are routed correctly within holding times. The COC is a document completed by the samplers listing each individual sample, the date and time it was collected, sample preservatives, parameters to be analyzed, the sampler's name, etc. Once the laboratory has analyzed the samples, a laboratory report is generated and returned to the scientists for evaluation.
4. How will the analytical data be used?
Once the laboratory report has been generated, the samplers thoroughly study and validate the analytical data using a procedure called data QA/QC (quality assurance/quality control). The data are compared to water quality standards and known levels of impairment to assess current water quality conditions. Results are then compared across sites and time so that any extreme fluctuations can be detected, studied, and ultimately explained. The analytical data help to identify potential contaminant sources in the watershed and are used in calibrating the water quality computer model.
5. The water is tested for what parameters (nutrients, bacteria, etc.)?
During the eight dry weather sampling events and the four storm events, the Alcovy River is sampled for the following water quality parameters.
- Hardness, as CaCO3 (calcium carbonate)
- Total Phosphorus
- Soluble Reactive Phosphorous
- Total Kjeldahl Nitrogen
- Ammonia
- Nitrate + Nitrite
- Total Nitrogen
- Total Suspended Solids
- Total Dissolved Solids
- Total Organic Carbon
- Dissolved Organic Carbon
- Biological Oxygen Demand
- Chemical Oxygen Demand
- Fecal Coliform
- E. coli bacteria
In addition to the above water quality parameters, all sites were sampled for EPA's priority pollutants during one dry weather and one wet weather sampling event, which are listed below. Trace metals were also analyzed using clean sampling techniques.
- Total Metals
- Phenols
- Pesticides/PCBs (polychlorinated biphenyls)
- Herbicides
- Volatiles
- Semi-volatiles
- Hexavalent Chromium
Although the Alcovy River has been sampled for many water quality parameters, the four key parameters that are being considered for computer modeling are:
- Total Phosphorus
- Total Suspended Solids
- Fecal Coliform
- Total Nitrogen
6. Why are both Dry-weather and Wet-weather Monitoring Important in a Watershed Assessment?
Both dry-weather and wet-weather monitoring are critical in a watershed study in order to determine the varying pollutant loadings to streams/rivers and the variation in flow during diverse weather conditions. During dry-weather conditions, otherwise known as "base flow," the velocity of river/stream flows is usually slower and pollutant loading concentrations are more sustained. Conversely, during wet-weather, otherwise known as "storm flow," river/stream velocities are higher and polluting loadings are temporarily elevated and continually fluctuating.
Typically, in wet-weather, streams and rivers receive more runoff and therefore have higher flow velocities. Also, in wet-weather streams and rivers receive more runoff, which in turn carries higher concentrations of non-point source pollutants. Water quality sampling during wet-weather conditions frequently involves taking grab samples at various points throughout the hydrograph. This type of wet-weather sampling is known as "full-hydrograph sampling." Typically, the highest concentration of pollutants can be found in the "first-flush" grab sample. The first flush is the first grab sample to be taken once a stream/river shows an increase in surface water level, usually 0.30 ft, from storm runoff. Subsequent grab samples are taken as the water surface level continues to rise, peaks, begins falling, and then returns to base flow conditions. By taking samples and monitoring flow velocities at these various points in the hydrograph, scientists can better understand the functions of the watershed and computer models can better predict pollutant loading rates.
Another noteworthy product of wet-weather events in watershed science is the re-suspension and reactivation of contaminants contained in the stream sediment. Contaminants that reach the stream are adsorbed by the sediment and can be trapped in streams by rocks and plants. A storm event can cause these contaminated sediments to come loose and be re-suspended in the water column, ultimately affecting the health of many aquatic species. It is important to understand that varying rainfall and overall storm intensity causes fluctuations in the amount of in-stream contaminants re-suspended, runoff reaching the stream/river and the flow rate of the stream.
The state standards for water quality concentrations do not distinguish between dry and wet weather. In other words, the regulations the state EPD sets for what the concentration for a particular water quality parameter must be give no regard to whether the sample is taken during base flow or storm flow. Thus, many state water quality standards are frequently exceeded during storm flow.
7. Why does water quality shift naturally?
Water quality shifts naturally due to a wide range of environmental factors, including weather conditions, seasonal variations, and stream physical characteristics, such as slope and topography. As explained above, dry-weather conditions promote more sustained pollutant concentrations and flow rates, whereas wet-weather generally promotes temporarily elevated pollutant concentrations and higher flow rates. Seasonal variations can also be a significant source of water quality variation. For instance, during the spring and summer seasons there is less natural nutrient release in streams because evapotranspration rates are elevated. Plants in the stream uptake more nutrients and release water back into the atmosphere during spring and summer. Stream physical characteristics, such as flood plain area, slope and topography can greatly affect water quality. For instance, a stream with a wide buffer area will most likely have higher water quality than a stream with a small buffer area. This can be attributed to the fact that buffer areas serve as natural filter areas where contaminants are filtered out of the runoff reaching the stream.
8. How were the sampling sites selected?
A total of fifteen sampling sites were carefully planned and mapped along the Alcovy River. The sites were selected, in part, on land use and accessibility. For example, a sampling site may be located downstream of a known point-source discharge (point-source pollution is water pollution coming from a single point, such as a sewage-outflow pipe). On the other hand, a sampling site may be in the vicinity of a drinking water intake or in a predominantly agricultural area. The samples collected at the fifteen chosen sampling locations help indicate to us the overall "health" of the Alcovy River.
9. Where are the sampling sites located?
Click here to display a map with all the sampling sites. Click on a site to pull up sampling data for that location. (The map is rather large in size and may take a second to load)
10. Where can I find the definitions for technical terms I do not know?
Click here for our glossary.
11. Can I access the raw sampling results?
Yes, however, we recommend that you first review the data by sampling location as this includes definitions of terms and explanations of results. This aids in putting the data into context and offers a summary of the raw data results in a more meaningful format. To review the data by sampling site, click here. To review the raw data, click here. Please note, the raw data file is quite large (607K) and may take a few minutes to load.
