The Fond du Lac Office of Water
protection conducts its monitoring program through site-specific
designs and sampling locations that we believe are most appropriate
for each waterbody. Our monitoring program is tailored to specific
waterbody types and their designated uses, which include fisheries
lakes, wild rice lakes, five primary streams, and a large river. We
use fixed stations for our ongoing lake and stream monitoring
Water Quality Parameters
Protecting human health requires
monitoring for indicators that assess the safety of eating fish or
other aquatic wildlife, or of swimming and boating. Protecting
ecosystems requires monitoring for indicators of diverse, healthy
aquatic plant and animal communities; indicators are also needed to
assure that water quality and sediment conditions are capable of
maintaining those biological communities. The parameters chosen for
our monitoring program are commonly used by state and federal
agencies and other monitoring groups, and our methods for collection
and analysis are standard.
Physical Parameters: Field
measurements of physical parameters are performed using a Hydrolab
Minisonde and Surveyor datalogger.
Total Suspended Solids: a
measurement similar to turbidity that indicates how much particulate
matter is in the water. Total Suspended Solids (TSS) are solids in
water that can be trapped by a filter. TSS can include a wide
variety of material, such as silt, decaying plant and animal matter,
industrial wastes, and sewage. High concentrations of suspended
solids can cause many problems for stream health and aquatic life.
Temperature: a measure of how
cool or warm the water is. Lake and stream temperatures change with
the seasons and with depth. Cool water temperatures are critical for
maintaining healthy trout populations in Otter Creek.
Dissolved Oxygen (DO): a
measure of the amount of oxygen dissolved in the water and available
to aquatic organisms. Slow moving water has a lower DO concentration
than turbulent water because it does not mix as frequently with the
atmosphere. Low DO concentrations can also be attributed to warm
water temperature and increased nutrient inputs, because algae
blooms can form and draw down the oxygen supply. When less dissolved
oxygen is available for aquatic organisms, it leads to stress,
increased susceptibility to disease, and population decline.
Specific Conductivity: a
measure of the resistance of the water to electrical flow. When high
concentrations of ions are dissolved in the water, the resistance of
the water to electrical flow is reduced.
pH: pH is a measure of the
acidity of the water. A lower pH indicates more acidic water. Most
lakes have a neutral pH, though bog lakes tend to have a low pH due
to dissolved tannic acids in the water.
Turbidity: Turbidity is
defined as the clarity of the water. Murky water caused by too much
sediment prevents aquatic plants from getting enough sunlight;
sediment clogs fish gills; and pollutants often adhere to sediment
particles. The EPA lists suspended sediment as the number one
impairment to water quality in streams and rivers.
Secchi Disk Transparency: a
measure of water clarity. A weighted white disk that is 20 cm in
diameter is lowered into the water on the shaded side of a boat
until the disk disappears from view. An average is taken from the
measured depth where the disk disappears from view and the depth
where it reappears into view. Clear water will have a larger Secchi
depth measurement than murky water. Secchi measurements are part of
the calculated Trophic State Index for a lake.
Chemical Parameters: We test
for a suite of chemical components in lake and stream water to make
sure they are within acceptable parameters.
Alkalinity: a measure of the
dissolved compounds in water that shift the pH to the alkaline side
of neutrality. High alkalinity usually indicates the presence of
exposed bedrock in a lake.
Hardness: a measure of the
concentration of dissolved ions in the water, including calcium and
magnesium salts. If alkalinity is high in a lake, hardness is also
Apparent Color: a measure of
the amount of light absorbed by suspended particles in the water.
Lakes that contain a high concentration of organic particles such as
algae will appear murky and can indicate problematic algae blooms.
True Color: a measure of the
amount of light absorbed by dissolved organic carbon after particles
in the water have been filtered out. Some of our bog lakes are
naturally tea-colored because of dissolved tannic acids in the
Chloride: a measure of the
concentration of chloride ion concentrations in the water. High
chloride salt concentrations indicate a water quality problem, often
because of a direct pollution source.
Ammonia, Nitrite +
Nitrate, TKN, Orthophosphorus, and Total Phosphorus: a measure
of the amount of nutrients present in the water. Nutrients are
needed to drive the food chain whereby algae use these nutrients and
energy from the sun to grow. The algae are consumed by zooplankton
that are in turn eaten by fish. When too many nutrients get in the
water from sources like fertilized lawns and farm fields, and animal
and human waste, problematic algae blooms can occur. Algae blooms
cause water quality problems, such as when algae use up enough
oxygen in a lake that it causes fish kills.
Sulfate: if sulfate
concentrations in a lake are too high, it can inhibit wild rice
growth. We monitor sulfate to make sure it stays within acceptable
levels for wild rice growth.
Trophic State Index (TSI): a
mathematical way of determining the condition of a lake. The concept
of trophic status is based on the fact that changes in nutrient
levels (measured by total phosphorus) causes changes in algal
biomass (measured by chlorophyll a) which in turn causes changes in
lake clarity (measured by Secchi disk transparency). A lake with a
low TSI value is considered oligotrophic, a lake with a high TSI
value is considered eutrophic, and lakes in the zone between
eutrophic and oligotrophic are considered mesotrophic.
Biological indicators include algae in lakes (chlorophyll a),
periphyton in streams (chlorophyll a), zooplankton in lakes, and
benthic macroinvertebrates. Only chlorophyll a and fish data are
included in the table.
Chlorophyll a: a measure of a
component of chlorophyll that is present in algae cells. When a lake
has a high chlorophyll a concentration, it could possibly indicate a
problem algae bloom due to excessive nutrients in the water.
Chlorophyll a is used in conjunction with total phosphorus and
Secchi depth to calculate the Trophic State Index (discussed above).
Fish species: we conduct an
annual survey of fish populations in all streams, and check for
presence of trout in our designated trout streams. Fish surveys for
lakes and the St. Louis River are conducted less frequently, and
some of these data are included in the table.
Lakes & Streams Water Quality
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