Webster Lake Association


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Lake and Stream Monitoring Details

General Observation of Weather and Water Conditions

Weather Conditions include wind direction, wind speed, ambient temperature, and atmospheric conditions.
Water Conditions include color, odor, and amount of material floating and/or suspended in the water.

Equipment and Measurements

Secchi disk
The secchi disk is a black and white disk which is about 12 inches in diameter. It is suspended from a long tape measure and stays parallel to the surface when lowered into the water. The disk is used with an Aqua Scope which is an 8 inch diameter tube about three feet long. It is open at one end and closed with a clear plastic plate at the other. One tester lowers the disk into the water while a second tester watches through the Aqua Scope with the closed end in the water (somewhat like a glass-bottom boat). After the disk is no longer visible, it is gradually pulled up until it is again just visible. This depth is a relative measure of the turbidity (or clarity) of the water.

Van Dorn Water Sampler
The sampler used to gather samples from specific depths. It is a tube with a cap at either end. These caps can be latched open with a trigger mechanism. The sampler is lowered on a rope and, since both ends have been open, the water flows freely through the sampler. When the desired depth is reached, a weight is dropped down the rope to trip the trigger mechanism closing the two caps. The sampler is then brought to the surface with a sample from the selected depth.

The Troll 9500
The Troll 9500 is an electronic device which, when submerged, measures a number of levels and automatically records them in a small hand-held computer. The troll is lowered into the water in two foot increments from surface to bottom and measurements are recorded at each level. Thus, depending on the lake depth where the measurements are taken, somewhere between 10 and 20 sets of measurements are taken in each basin. See next section for more details on measurements recorded by the troll.

Measurements Recorded by the Troll
Conductivity of the Water
ORP (Oxygen Reduction Potential)
RDO (Rugged Dissolved Oxygen)
Water Temperature