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Home » LDWF Schedules Drawdown for Lake Bistineau

LDWF Schedules Drawdown for Lake Bistineau

by Minden Press-Herald

The Louisiana Department of Wildlife and Fisheries (LDWF) has scheduled a drawdown of Lake  Bistineau in Webster, Bossier and Bienville parishes for the purpose of reducing the further  expansion of giant salvinia. The drawdown will additionally benefit fisheries production by  improving aquatic habitat and reducing the amount of organic matter on the lake bottom. 

LDWF has requested the Department of Transportation and Development open the water  control structure on July 25. Once the water control structure is open, the lake should dewater  at a rate of 4 to 6 inches per day until it reaches a potential maximum drawdown level of 8 feet  below pool stage. This dewater rate could be impacted, however, by local rainfall in the  surrounding watershed. During the drawdown, the department will monitor aquatic habitat  conditions to determine the best time to conclude the drawdown and allow the lake to refill for  early spring recreational activities. 

Below are some frequently asked questions and related information regarding the upcoming  drawdown on Lake Bistineau. 

Why are drawdowns used to manage giant salvinia on Lake Bistineau? 

During the warmest parts of the summer, giant salvinia on Lake Bistineau can double its  coverage in less than three days. As the accessible parts of the lake are sprayed and the  dying salvinia sinks, the ever-growing salvinia mats in the forested areas of the lake  continue to push out new plant material. Due to the rate of plant growth, it is extremely  difficult to keep the plant coverage at manageable levels with only herbicide applications.  

Drawdowns strand and kill the plant material that is actively growing and reproducing in  the shallow areas of the lake, allowing the spray efforts to make greater strides in reducing salvinia coverage in areas that are accessible to boats.  

Relying on herbicides alone during the peak summer growing season would also carry a  very large price tag. It is more cost-effective to combine the benefits of a drawdown with  herbicide applications to make better use of available public funds. 

What factors do you consider when making a decision on a drawdown start date? We consider multiple factors such as: the amount of acreage covered by salvinia, the  amount of funding available to spray problematic areas, and the amount of public use  occurring on the lake. We attempt to balance the need to control salvinia expansion  through drawdowns with the desire by the public to use open areas of the lake during the  summer. An early summer drawdown would provide the best salvinia control, but that  would greatly impact use of the lake when the public desires it the most. Therefore, we  attempt to delay the drawdown as long as we can.

Will boaters still be able to access the lake during the drawdown? 

Yes. During the drawdown, more than 7,500 acres of water will remain in the lake. Boaters  can still access the lake during the drawdown from the following public boat launches: Port  of Bistineau Launch, Bossier Public Launch, Grice’s, and Bayou Dorcheat Public Launch.  Boaters are advised to use caution during the low water period, as boat lanes will not  provide normal clearance of underwater obstructions.  

Why does the drawdown need to be in the summer rather than winter?  One of the ways a drawdown works to control salvinia is to dry out the plant and the water  bottom. Giant salvinia is much more susceptible to drying during the summer than it is to  freezing during the winter. Additionally, exposed water bottoms do not dry out nearly as  well during the colder months (also some of the wetter months) of the year. If there is any  moisture left in the soil, the giant salvinia will be able to survive. The extreme hot and dry  conditions that we typically experience from June – September provide ample drying of the  water bottom and desiccation of the plant material. Also, this is the fastest growing time  of the year for giant salvinia. To have the lake at drawdown stage during this time provides  less water surface for the remaining salvinia to reproduce and thrive. Lake Bistineau also  has a very large watershed (draining nearly 1 million acres of land), which makes it difficult  to remove water from the lake or keep the lake lower during the wet winter season. 

I live on the southern part of the lake, where the giant salvinia doesn’t look too bad. Do we  really need to have a drawdown if the lake is still usable down here? 

Yes. The southern end of the lake contains more open-water habitat, which is less  conducive to the growth of floating aquatic vegetation such as giant salvinia. Therefore,  this portion of the lake will typically be the last area to experience problems. However,  with an exponential growth rate of salvinia in July and August, plant material will soon  begin to impact those open areas down the lake as well.  

Are drawdowns designed to improve the condition of the lake now, or to prevent worse  conditions next year? 

Both. A drawdown provides immediate benefits by reducing the amount of giant salvinia  coverage that currently exists on the lake. It is also a proactive management strategy used  to ensure a better situation on the lake the following year.  

Data from past years show a direct correlation between the number of acres of giant  salvinia on the lake before a drawdown is initiated, and the amount that will be present as  we approach the spring and summer of the next year. The longer we allow salvinia to grow  on the lake prior to initiating a drawdown this summer, the more salvinia will be present  next spring, and subsequently next summer. Herbicide application efforts and timing have  been consistent over the years. Therefore, the reduction in giant salvinia annually can be  mostly attributed to drawdown actions and their timing. We feel that it is critical to prevent salvinia from greatly expanding one year to prevent a worse situation next year. 

Are there other benefits from a drawdown? 

Yes. Drawdowns are beneficial to the fish population in flooded swamp lakes such as Lake  Bistineau. Drawdowns expose the bottom of the lake to drying action, which helps to  reduce the organic build-up such as dying salvinia, other vegetation and cypress tree leaf  litter. Without drawdowns, this material continues to build up on the bottom, reducing and  even preventing fish from spawning. Drawdowns offer opportunities to observe many  unique species of wading birds that are attracted to the lake, result in increased fish  catches during a time of year when fishing gets tougher on other area lakes, and gives shoreline property owners a chance to make repairs to docks and seawalls.  

Is Lake Bistineau the only lake with the salvinia challenge? 

No. LDWF Aquatic Plant Control Program is battling giant salvinia in more than 50 waterbodies around the state. Each waterbody is different, and all present a unique  challenge in managing the nuisance aquatic weed. 

With LDWF’s recent revenue increase, will Lake Bistineau be sprayed more often? Possibly. The increase in revenue through the recently-enacted license fee restructure will  provide more funding for control efforts on public water bodies statewide. However, there  are several factors that we use to determine how much herbicide spraying is conducted on  each – including the amount of plant material, its location on the lake and the availability  of herbicide application contractors and equipment.  

For additional information regarding the drawdown, contact Jeff Sibley, LDWF Biologist  Manager, at [email protected] or 318- 371-5294.

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