Florida LAKEWATCH Data -
What does it all mean?
This handout is your guide to the LAKEWATCH data packet. "-"- ,
We'd prefer to look at this material with you in-person, especially if
you're seeing it for the first time. However, a one-on-one review
isn't always possible. So we're sending along this basic explanation
in our place and relying on you to call us if you have questions or
want to talk with us about it.
What are data?
Data are measurements, or numbers, generated from samples that
Florida LAKEWATCH volunteers diligently provide each month The
samples are analyzed in the water chemistry laboratory at the University
of Florida, and the measurements are recorded in a computerized data
base. Every year we provide these data to our volunteers, in the form of
tables and bar graphs.
It's true that data are generally collected and intended for use by
professionals who have the training necessary for interpreting the
numbers. However, lay people willing to invest a little time can learn the
story behind the numbers too. So read on to find out how you can use
LAKEWATCH data in a variety of applications. By reading this handout
you can learn:
* how LAKEWATCH data can be useful to you;
* how to read LAKEWATCH data tables; and
* how to read LAKEWATCH bar graphs.
How LAKEWATCH Data Can Be Useful To You
* LAKEWATCH data can be used to establish a baseline a
long-term record that provides a basis for comparison with
In nature, change is the rule. Your waterbody will change
naturally over the course of its lifetime. It may even change with
the seasons or in response to natural environmental conditions.
Only by knowing what changes have been normal in the past, can
you determine those that are abnormal and possible cause for
In addition to documenting individual events, the bar graphs
provided in your data packet make it easy to spot whether baseline
values themselves have changed significantly over time.
Changes in baseline values may indicate a change in the basic
ecology of the waterbody, perhaps even a change in its trophic
state. For example, baseline changes have been observed when a
significant amount of aquatic vegetation has been removed from
waterbodies; or when a major source of nutrients (such as sewage
treatment plant effluent) has been removed.
+ LAKEWATCH data provide an "insurance policy" in that it can
be taken to different experts for their opinions. Because you have
the data in hand, you won't have to rely on the judgement of an
individual but can use these numbers to get multiple opinions -
as you may do with your medical records.
LAKEWATCH data are trusted by the scientific community
and can be used to document conditions credibly. You will not
have to rely on anecdotal observations that are often viewed with
skepticism by the regulatory and governmental communities.
LAKEWATCH data can be used to red flag potentially
alarming situations in the early stages when they may be
corrected more readily and economically.
LAKEWATCH data can be helpful in obtaining funding for
restoration or preservation efforts.
LAKEWATCH data can be used to monitor restoration or
preservation efforts to see if your management strategies are
LAKEWATCH data can be : UNIVERSITY OF
used to establish water FLORIDA
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Continued t bottom ojpg 4) Depariment of Fisheries and Aquatic Sciences
The first section of your data packet contains tables, which display your data in full detail.
These tables might not be as interesting to look at as the graphs in this packet, but they provide
data in its most basic and useful form rows and columns of numbers.
Not interested in studying all those numbers? No problem. File these tables away and feel
good that you have them if you should ever need them in the future. Want more information
about your packet? Read on
The second section of your data packet contains bar graphs one of each for the four
parameters that LAKEWATCH monitors. Graphs are among the most valuable tools we
have for telling a waterbody's story. When several year's worth of bars are shown together
in one graph, they compress reams of data into a visual image that can reveal patterns and
trends at a glance.
Anatomy of a Table
Every table in your data packet
is presented in the same format:
(A) The heading at the top of the
page tells you the name of the lake
or waterbody and the county in
which it's located.
(B) There should be a separate table for
each of the four LAKEWATCH param-
eters. This heading tells you which one \
is being presented:
* Total Phosphorus is a combination of the
many forms of phosphorus found in sedi-
ments and dissolved in the water.
* TotalNitrogenis acombinationofthe many
forms of nitrogen found in the water.
*Total Chlorophyll is measured by LAKE-
WATCH. You will see"Chlorophyll a" inyour
* Secchi Depth represents water clarity
(not water depth).
(C) Sampling dates (month-day-year) are
listed in the column with the "Date" heading.
(D) Columns with a "Station #" heading display the
actual measurements forthat station onthe particular
-C4H date to its left. (in the date column).
S\(E) The column with the heading "Lake Average"
displays the average of all the individual stations
4a monitored for a particular sampling date. These
4 5 lake averagenumbers ae representedasindividual
S\ \ bars in the LAKEWATCH bar graphs.
Black Dots -Sometimes a black dot is printed
4 \ \ instead of a number. This means that LAKE-
S\ WATCH data were not available on the com-
^ 4 \ puter at the time the data packet was printed.
Whenadotappearsforanindividual station, no
values usedfromthat stationinthe calculation
of the lake average for that date.
t Secchi Depth Averages- If theSecchi
,4pt diskwasvisible onthebottom(neverdisap-
peared) or disappeared into the weeds, the
value entered for that particular station was
not used to calculate the Lake Average for
that date. Inthis way, we use only values that give anindica-
tion of water clarity.
(F) The footer includes the date the report was printed as well as the
page number. If you have more than one page for each table, it simply
means that your lake has been monitored for many years and has more
data than one page will hold.
Anatomy of A Graph
Every graph in this data packet is
presented in the same format:
(A) The heading at the top of the graphtells
you the name ofthe lake orwaterbody and FLORID
the county in which its located. I ce/
(B) The name of the parameter being ph"..
illustrated is shown in the long rectan- 6-
gular box at the top of the graph.
(C) The symbol pg/L means
"micrograms perliter," and is a unit of
measure indicating the weight of a
substance in one liter of water.
A microgram per liter is the same as
"parts perbillion" (abbreviated" ppb").
(D) Terms in this box refer to the
Trophic State* of the waterbody.
(E) The scale of numbers up the left
side shows the value of the height
of each bar in the graph (use this as
(F) Dates when the samples were taken are listed horizontally along the
bottom of the graph (month-day-year).
* See the LAKEWATCH handout" Trophic State: A Waterbody's Ability To Support Plants, Fish, and Wildlife."
Check Uniformity. Look to see if one station has higher or lower numbers than others sampled on
the same date. For example, as you review your Chlorophyll a table, you may see one sampling
station has a higher number than the others.
If you do spot a difference, the next step is to ty to explainit Inthis instance, the higher chlorophyllmeasure-
ment may have been caused by algae being wind blownto the downwind side of awaterbody. You can look at
your LAKEWATCH data sheet enty for wind direction for that day to see if this explanation checks out
Look for consistency. Check to see if the numbers for one station are consistently higher or lower
than at the other stations.
Proofread the data report. Checkthe Secchi depthmeasurements fromyour original data sheets to
see if they match those numbers shown in the table. (We do recommend that volunteers keep copies of
every data sheet for this reason)
Identify Patterns. Canyou see patterns inthe bar graphs? The heights of the bars may indicate patterns suchas a repeating cycle of
highs and lows, a steady increase, a steady decrease, an abrupt change, etc. If you've spotted a recurring pattern, consider whether
the cycles correspond to something like seasonal changes, periods of heavy rainfall, drought, or other recurring events.
Compare Total Phosphorus with Total Nitrogen. Do the bars rise and fall atthe same time? at opposite times? Apattem may
tell give you a clue about the source of nutrients in your wateibody.
Compare Ch lorophyll with Nutrients. Do the bars rise and fall at the same time? If they are synchronized, it may indicate that
nitrogen and phosphorus are fertilizing the growth of algae in your waterbody.
Compare Secchi Depth with Chlorophyll Graphs. Dothebarsonthese two graphsfluctuate oppositely fromoneanother? If
they do, it probably means that the algae content in the water is a major influence on your water clarity. If they don't, it indicates that
otherfactors are influencing yourwater clarity more than algae do. (Remember: Ashort bar means that the Secchi diskvanishedfrom
view only a short distance down in the water.)
P Diving Into Data
Match bar graphs A through F with the six trends listed below the graphs.
Write your answers in the spaces provided and check them
with the answer key in the right margin of this page.
Total Nitrogenbargrap for Total Phosphorus bal gah forI
Total Nitrogen bar graph for
Lake Lawsona in Orange County
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Total Phosphorus bar graph for
Lake Bennett in Orange County
Total Phosphorus bar graph for
Lake Estella East in Orange County
Chlorophyll a bar graph for
Lake Little Bear in Seminole County
Total Phosphorus bar graph for
Lake Redwater in Putnam County
Secchi Depth bar graph for
Lake Isleworth in Orange County
1 A slight gradual increase
2 An unusual event (sometimes called a "spike")
3 A steady decrease
4 Minimal overall change
5 Seasonal cycling
6 An abrupt increase followed by a gradual decrease
How LAKEWATCH Data Can Be Useful to You (continued from page 1)
quality standards that may be applied to present or future
discharges into your waterbody.
* LAKEWATCH bar graphs create a visual picture
of the data and what patterns, trends, cycles, or abrupt
changes have occurred over time.
* LAKEWATCH data can provide clues to understanding
the cause-and-effect relationships between water quality and
When you see a big change in your data, the real
detective work begins. What was happening during that
period that might possibly account for the change? If you
are the LAKEWATCH volunteer, you can look back at copies of the
LAKEWATCH data sheets for clues. Potential causes of change
might include large numbers of birds roosting on the shore, boating
activity, changes in stormwater runoff, unusual weather conditions,
fires or massive land clearing in the watershed. Ifyou can find out
what factors affect your water quality, you have discovered a
powerful tool that can be used for effective management
For more information call:
appreciate your comments, questions,
and suggestions anytime.
7922 NW 71st Street Gainesville, FL 32653-3071 Phone: (352) 392-9617 ext 228 Fax: (352) 846-1088
E-mail: firstname.lastname@example.org Web site: http://www.ifas.ufl.edu/~lakewatch/index.htm
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