Average Annual Lake Levels  High resolution chart in PDF format
This chart summarizes the average, high and low elevations of Lake Conway from 1952 to present.  The annual average elevation is actually the average of the monthly averages.  Each high and low elevation for the year is actually the elevation of the average high month and average low month respectively.

There are some points of interest on the chart.  In 1960 the high peak corresponds to hurricane Donna which passed through Orlando in mid September of that year.  You will notice that the average lake level for 1959 and 1960 were high which would indicate the hurricane was preceded by two wet years.  The resulting high water table was a major contributor to the flooding created by the hurricane.

It was right after Donna when it was decided to install an outflow for Lake Conway in the south pool at Daetwyler Drive.

From 1968 to 1973 deep wells were installed with pumps and the lake level was artificially maintained at a fairly high level.  The energy crunch in the mid 70's brought that to an end and the pumps stood idle.  Eventually the pumps were removed.  In 2004 one of those wells (I believe the last) was capped.  It is highly unlikely the lake will ever be level controlled by pumps again as that process is environmentally unfriendly.

2001 brought the historic low water elevation.  Many of you may recall having your dock completely landlocked.  fortunately, that only lasted about a year.  It is interesting to note that each severe drought comes on quickly and recovers quickly.  Generally, it can be seen that the flood - drought cycles occur on an approximately 10 year interval. 
 

In 2008 we have added a linear curve fit of the average annual lake level. For statistics buffs it is a least squares best fit of the historic data. It is clear that the average level is going down. This appears to be related to the lowering of the water table through human consumption. While there has not been a substantial change in the long term rainfall the water level in the USGS 282051081183401 Boggy Creek Road Well at County Line near Taft, FL has dropped 5 feet since 1961.

1975-2005 Monthly Levels Histogram High resolution chart in PDF format
A histogram is a bar graph where each bar indicates a range of data and the height of the bar indicates how many data points are within that data range.  If you have heard the term "bell curve" that usually refers to data displayed in a histogram.  Generally, the bulk of the data is grouped near the top of the bell and represents "normal" events.

The Lake Conway average elevations for each month were divided into 0.1 foot intervals and each month with a common average elevation was put into that data range.  The vertical axis shows how many months in the last 30 years fell within each elevation range.  The result has a vague resemblance to a bell curve.  Since the resemblance is vague it shows the data is relatively random.  That is to say we cannot easily predict what the next value will be as would be expected with natural phenomena.

Superimposed on the chart is a line showing the Lake Stage.  That is the percent of data points (months) which are at a lower elevation than the current elevation.  As might be expected, 100% indicates that all the months are lower the current one.  That occurs at elevation 87.3.  At elevation 86.4 it can be seen that about 85% of the months are below this elevation.  This histogram forms the basis of the Lake Stage information.

30 Year Lake Stage 1976-2005  High resolution chart in PDF format
This table numerically shows the Lake Stage as derived from the histogram discussed above.  The elevations in the green are considered the NORMAL elevation range of the lake and the elevations in the red are considered unusual conditions.

30 Year Lake Stage Comparison  High resolution chart in PDF format
This is a comparison of Lake Stage calculations from three 30 year periods and one from the entire recorded history.  The red line is the Lake Stage calculation for the 30 years ending in 2005 and the blue lines are for 30 year periods ending in 2000 and 1995.  Finally the lightest blue line is for the entire recorded history.

Of note is the shift of the lines from the right to left as the time progresses.  The shift is more pronounced at the mid and lower Lake Stages but is relatively steady at the upper Lake Stages.  This indicates that in recent history the lake is spending more time at the lower levels while maintaining substantially similar high level conditions.  The high level conditions maintain similarity because of the relief provided by the weir during wet seasons.  The shift in the low water conditions could be indicating we may be seeing more drought conditions in the future.

Monthly Level Changes High resolution chart in PDF format
The lake level can change substantially in a single month.  This chart shows seven different pieces of information about how the level can change each month.  The data is compiled from the entire recorded history of the lake since 1952.  It is this information which makes it possible to provide projections on the daily lake level charts which are published every month.

First the AVERAGE change in level is shown by the red line without markers.  This is the average of all the increases and decreases in the level within that month.

Second the NORMAL RISE is the average of all the raises in level for each month.  It is shown by the blue line with discs.  This is used to predict the upper end of the projected lake level.

Third the NORMAL DROP is the average of all the drops in level for each month.  It is shown by the red line with discs.  This is used to predict the lower end of the projected lake level.

Fourth the MAXIMUM is the most the level has ever increased in that month.  It is shown by the blue bars.

Fifth the MINIMUM is the most the level has ever decreased in that month.  It is shown by the red bars.

Sixth the UP COUNT shows the number of months the level has increased historically.  It is shown by the blue triangles with the apex pointed upward and is read from the right scale.

Finally the seventh item is the DOWN COUNT shows the number of months the level has decreased historically.  It is shown by the red triangles with the apex pointed downward and is read from the right scale.