L.D.W.F.
Takes Steps to Control Nantachie Lake Aquatic Vegetation
Posted:
7/7/06
The Louisiana
Department of Wildlife and Fisheries (LDWF) has proposed a
drawdown for Nantachie Lake in Grant Parish beginning July
17, 2006 and ending January 31, 2007. This will be the second
of three drawdowns recommended in an aquatic plant management
plan submitted by LDWF in August of 2005. The Grant Parish
Police Jury agreed to the drawdown at a meeting on June 27,
2006.
The drawdowns
were prompted by numerous calls concerning submergent aquatic
vegetation (SAV) received by fisheries personnel in the LDWF
District 3 office. In addition to native SAV, hydrilla, an
exotic noxious aquatic weed, has become established in the
lake and is hindering boating access and recreational opportunities
in many areas of the lake. Hydrilla was first located at the
public launch on the southeast end of the lake and has spread
throughout most of the southern half of the lake.
The July
17 start date is necessary due to the slower than normal ability
to dewater the lake. During the 2005/2006 drawdown it was
determined that the lake could only be lowered approximately
2 inches per day. Dewatering at a faster rate could cause
flooding of downstream property. The lake will be drawn down
approximately 7 feet below pool stage.
Hydrilla
requires water to survive; therefore, removing the water causes
the plants to die. This is more economically feasible than
using expensive herbicides. When possible, multi-year drawdowns
are preferable to reduce the numbers of reproductive structures
(tubers) deposited in the bottom substrate by hydrilla. Drying
the water bottom stimulates the majority of tubers to sprout.
This reduces the amount of existing tubers in the hydrosoil
the next year. The drawdowns are also timed to prevent the
production of tubers in the fall. The first drawdown must
be followed by
other drawdowns in following years to prevent the existing
plants from setting more tubers and to stimulate the remaining
tubers to sprout in each year of the project. With the combined
reduction of the tuber bank from each drawdown, tubers available
for re-infestation will be significantly depleted. Additionally,
having the drawdown last until January 31 could expose the
plants to frosts and freezing weather which would increase
the reduction of plants.
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