A.W. Research Laboratories, Inc.

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Winter Sampling Program

The cornerstone of winter sampling is to assess water quality when the lake is somewhat buffered from thermal influences of rain and wind, thereby providing stable and easily comparable results from year to year.   In addition, the concentration of total phosphorus at the bottom water of the lake should approach its maximum level during the winter months as algae and other aquatic vegetation dies and settles to the bottom.   In other words, winter samples collected on the bottom of a lake should provide a "worst case" record of nutrient levels in a lake.   In many respects winter sampling can also be viewed as a measure of historic water quality, since benthic sediments can serve as either a reservoir or a sink for nutrients in the lake.

A winter sampling program can also be used to compliment summer Trophic Status Index (TSI) and nutrient mass balance programs.   The TSI program provides a measure of existing conditions in a lake, and the mass balance program measures the concentration and flows entering and leaving a lake.   These programs traditionally serve as the basis for recommendations on pollution reduction and best management programs for watershed improvements.   However, if a lake has served as a nutrient sink then the "best laid plans" may take time to show results.   Winter sampling can help identify if a reservoir of nutrients have accumulated on the lake bottom, and therefore help establish realistic expectations for the speed and effectiveness of lake recovery.

A typical winter sampling program records total phosphorous, conductivity, pH, temperature, dissolved oxygen and secchi disk measurements.  However other parameters are often tested including, but not limited to, chloride, sulfates, nitrite, nitrate nitrogen and total nitrogen.

After sampling is completed, a final analysis including conclusions and recommendations is produced.  Based on the laboratory analysis, the total pounds of each parameter is calculated per depth layer and graphed.  The following example shows a graphical analysis included in the report.

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winter sampling program