The physical and chemical characteristics of the stream water are measured at least once each day the camp is in session. This method produces several data sets for averaging and increases the reliability of the final estimate of water quality. Tests are conducted either at the stream bank (dissolved oxygen and carbon dioxide) or 3 gallon water samples are taken to the lodge laboratory for immediate analysis.
Water tests are done by two students working together as a team. Each member checks on the other members procedure for quality control. Each team completes at least four different tests during the assigned class period. When each test is completed the test kit is returned to the storage area before another test is started. All results are reported to the instructor and are recorded by the instructor.
Water chemistry tests follow the procedures specified in the Hach methods manual, 13th edition (7). To teach these procedures, practice laboratories are done during the week prior to the field trip. Missouri river water is used for these practice laboratories. This practice data, when screened by the teacher for accuracy, also provides an estimate of the quality of the Missouri river at the St. Charles, Missouri water collection site. We feel that it is useful for the students to make the comparison between two water resources, one pristine and the other heavily used by man.
Air temperatures at the stream bank and water temperatures in the main channel are read with a hand held thermometer. Readings are taken at the test site and at a second site 1 mile downstream. Barometric pressure readings are also taken at the same time as the temperature readings.
Surface water velocity measurements are obtained from the flotation time of an orange over a distance of 10 meters. The measurement is made at three points across the channel to determine a representative velocity. This is done where the stream is fairly broad and shallow. Depth readings for the cross-sectional profile are taken at 30 centimeter intervals across the channel where the velocity readings are taken. The cross sectional area of the channel is computed by trapezoidal approximation. Stream volume is calculated from the velocity and cross-sectional values.
The total solid measurement includes both the suspended materials in the water and the dissolved materials. A procedure suggested by Mitchell and Stapp is used. Simply stated, the mass of suspended and dissolved material in 100 ml of water is found by the evaporation of the water in the sample. A good analytical balance is needed for this procedure as well as a clean and completely dry evaporating dish.
Chemical testing of the water involves either titration or
colorimetry methods. A modified azide Winkler method with drop
count titration is used for the dissolved oxygen tests. Carbon
dioxide levels are determined by titration to a phenolphthalein
end point with a standard solution of sodium hydroxide (0.0227N).
The total alkalinity level, as calcium carbonate, is determined
by sulfuric acid titration. Water hardness is found by titration
of the sample using ManVer 2 Hardness reagent. The cadmium reduction
method is used for determining the level of nitrogen-nitrate in
the water. When nitrate is present in the water a pink color appears
after the reagent is added to the sample. The intensity of the
pink color is read by a colorimeter. The concentration of total
phosphate in the water is also determined colorimetrically. This
test is time consuming and requires boiling of the sample following
the addition of reagents. Turbidity, color and pH are also found
using standard colorimetry procedures. Refer to the Hach manual
for complete descriptions of all tests.