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Water Quality Program Page 2

 Methodology

 

Volunteers are provided with instructions about sample collection procedures prior to their first sample collection day. Instruction through hands-on experience is provided by a VWIN coordinator, and a training manual is given to each volunteer to read.

Lake Glenville stream samples are collected on the fourth Saturday of each month. Collecting coincident samples from all the sites in the monitoring area greatly reduces meteorological variability between sites. Therefore, the volunteers are asked to collect samples from the assigned site as close to noon as possible. Water samples are collected in six 250 mL polyethylene bottles. In order to assure consistent sampling techniques, each bottle is labeled with the site number and the parameter for which the water from that particular bottle will be analyzed. Stream water level is used as a surrogate measure of stream flow and is recorded using bridge markings or bridge-to-water measurements. Other information recorded by the volunteer can be found in Appendix A which is a copy of the data sheet used by the volunteer.

After collection, the volunteer takes the samples and data sheet to a designated drop point where the samples are refrigerated. It is the job of the volunteer coordinator to pick up the samples from the drop point and deliver them to the EQI laboratory for analysis Monday morning. Various statistical analyses are performed on the data and are intended to:

1) Characterize the water quality of each stream site relative to accepted or established water quality standards;

2) Compare water quality of each stream site relative to all other sites in the VWIN program;

3) Identify effects of precipitation, stream water level, and seasonality and temporal trends on water quality, after sufficient data has been collected.

 

Long Term Evaluation of Pollutant Sources to Lake Glenville: Year One (2000-2001) Report

 

Acidity (pH) and Alkalinity: pH is used to measure acidity. The pH is a measure of the concentration of hydrogen ions in a solution. If the value of the measurement is less than 7.0, the solution is acidic. If the value is greater than 7.0, the solution is alkaline (more commonly referred to as basic). The ambient water quality standard is between 6.0 and 9.0.  Natural pH values in area streams are generally in the range of 6.5 ‑ 7.2.  Values below 6.5 may indicate the effects of acid rain or other acidic inputs, and values above 7.5 may be indicative of an industrial discharge.

Because organisms in aquatic environments have adapted to the pH conditions of natural waters, even small pH fluctuations can interfere with the reproduction of those organisms or can even kill them outright. The pH is an important water quality parameter because it has the potential to seriously affect aquatic ecosystems. It can also be a useful indicator of specific types of discharges.

Alkalinity is the measure of the acid neutralizing capacity of a water or soil. Waters with high alkalinity are considered to be protected (well buffered) against acidic inputs. Streams that are supplied with a buffer are able to absorb and neutralize hydrogen ions introduced by acidic sources such as acid rain, decomposing organic matter and industrial effluent. For example, water can leach calcium carbonate (a natural buffer) from limestone soils or bedrock and then move into a stream, providing that stream with a buffer. As a result, pH levels in the stream are held constant despite acidic inputs. Unfortunately, natural buffering materials can become depleted due to excessive acidification. In that case, further acidic inputs can cause severe decreases in stream pH. Potential future stream acidification problems can be anticipated by alkalinity measurement. There is no legal standard for alkalinity, but waters with an alkalinity below 30 mg/l are considered to have low alkalinity. Western NC streams tend to have low alkalinity because the granite bedrock does not contain many acid-neutralizing compounds such as calcium carbonate.

These graphs show median pH and alkalinity levels compared with the average median for the eight-county VWIN region.  Median pH and alkalinity levels at all of the sites monitored are relatively low compared with median values for the region. In fact, the average median for the Lake Glenville sites for both pH and alkalinity are the lowest of any county analyzed in the VWIN program.  The county with the next lowest median levels is neighboring Transylvania County. Factors such as rock and soil type, rainfall levels, and elevation can all be important in determination of pH and alkalinity of streams.  The state Division of Water Quality has reported low pH levels in Jackson County that are related to rock formations.  The Glenville area also receives greater annual rainfall amounts than much of the rest of the VWIN monitoring region.  Lake Glenville is also at a higher elevation than most of the VWIN stream sites monitored in the rest of Western North Carolina, and higher elevation streams generally have lower pH and alkalinity levels.

In spite of the generally low pH and alkalinity levels, only two sites, upper Norton Creek and the spring control site (both times monitored at this site), exhibited pH levels below 6.0 during the year. Some sampling in the past year occurred shortly after rains, but the past year in general has been relatively dry. In more normal years it seems likely that the very low alkalinity levels at several sites, particularly Norton Creek, Hurricane Creek, and Glenville Creek, would make them highly vulnerable to pH extremes during heavy rains.                                                                                                   

 

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