Winter Draw Downs – Lake Bistineau
Not to argue the merits of a lake draw down. Simply put, drawing down Lake Bistineau is something that is here to stay. But taking exception to what has been done in the last few years of drawing the lake down from mid-summer or early fall until the end of November is a plan that isn’t working.
Winter draw downs on this lake are nothing new:
There have been 18 winter drawdowns from 1966 through 2012 that have all had one thing in common. The gates were closed in mid January or at the end of January. [1] [4]
Why leave the lake down until the end of January?
(Whether you agree with them or not – a few reasons are as follows.)
*It allows more drying time for vegetation that is stranded on the exposed lake bed.
*Greater opportunity for days with freezing temperatures.
*Moves salvinia from the cover and protection of the cypress canopy out to areas of open water which achieves better results from freezing temperatures.
* A 7-ft drawdown reduces the water acreage to approximately 50% of the lake’s normal size therefore making it easier to treat chemically.
Let’s assume that we are trying to expose the maximum amount of salvinia to colder temperatures, then closing the gates at the end of November defeats this purpose. Each year since 1960 thru 2006 (most current data), Northwest Louisiana averages only 36.5 days where the lowest temperature drops down to or below 32 degrees. 30.7 of those days are in Dec., Jan., and Feb. November’s average is 3 days. With January having the most, at 12.7 days. Closing the gates in Nov. takes away the two months (Dec. & Jan.) that produce the most freeze days.See [5] Freezing Temperatures – Northwest Louisiana
Quotes from LDWF reports of successful freezes:
Jan. 2008 – “Plants in the more open areas of the lake were most affected. Little effect was observed on salvinia protected by tree canopy”[2]
Jan. 2010 – “Unusually cold temperatures the first two weeks in January, 2010, resulted in most of the salvinia on Lake Bistineau being encapsulated in frozen mats of vegetation as approximately 50% of the north end of the lake froze and most areas under the cypress trees froze”[2]
What about drying time?
Well, there is no definite climate dry spell. Every month or season is just about as good as the other. See Chart [6] Each season has just about the same amount of rainfall so trying to dry out salvinia that is stranded on the lake bank in the winter is pretty futile. Without the heat of the summer sun very little salvinia dries during the winter.
Chemical Treatment:
Very little chemical spraying done during a winter drawdown.
[5]
Freezing Temperatures – Northwest Louisiana
The average date of the first freeze in Northwest Louisiana is November 15, while the last is March 10. However, freezing temperatures have been recorded as early as October 19 and as late as April 11.
Since 1960 thru 2006 (most current data). The following list the number of days of each month where the lowest temperature was at or below 32 degrees regardless of duration.
Nov. Averages 3 days
Dec. Averages 10.8 days
Jan. Averages 12.7 days
Feb. Averages 7.2 days
March Averages 2.4 days
April Averages 0.2 days
October Averages 0.2 days
Remaining Months – 0 days
Each year since 1960, Northwest Louisiana averages only 36.5 days where the lowest temperature drops down to or below 32 degrees. 30.7 of those days are in Dec., Jan., and Feb.
[6]
Sources and/or References
CLIMATE OF SHREVEPORT, LOUISIANA
Glenn Carrin
Jim DeBerry
Jason Hansford
National Weather Service Office
Shreveport, LA
National Oceanic and Atmospheric Administration
[1]
History of Lake Bistineau Drawdowns
http://www.lakebistineau.com/drawdowns.htm
[2]
LOUISIANA DEPARTMENT OF WILDLIFE & FISHERIES
OFFICE OF FISHERIES
INLAND FISHERIES SECTION PART VI-B
WATERBODY MANAGEMENT PLAN SERIES
LAKE BISTINEAU
LAKE HISTORY & MANAGEMENT ISSUES
[3]
CLIMATE OF SHREVEPORT, LOUISIANA
Glenn Carrin
Jim DeBerry
Jason Hansford
National Weather Service Office Shreveport, LA.
and
National Oceanic and Atmospheric Administration
[4]
LOUISIANA DEPARTMENT OF WILDLIFE & FISHERIES
OFFICE OF FISHERIES
INLAND FISHERIES SECTION PART VI-A
WATERBODY MANAGEMENT PLAN SERIES
LAKE BISTINEAU
LAKE HISTORY & MANAGEMENT ISSUES