L.D.W.F. RELEASES IVAN LAKE
VEGETATION CONTROL PLAN
Ivan Lake, a 520-acre waterbody in Bossier Parish created in 1954 by the
United States Army Corps of Engineers, was recently surveyed by the
Louisiana Department of Wildlife and Fisheries (LDWF) Aquatic Plant
Research and Control Section. Submerged vegetation was present in severe
to moderate amounts in a fringe around the lake out to six feet in depth.
The area of the lake approaching the Highway 529 bridge is most severely
impacted, with boating access restricted to the creek channel. All
submerged species combined cover approximately 25 to 35 percent of the
waterbody, with the most problematic species being hydrilla.
Hydrilla is an exotic species that is difficult to control and nearly
impossible to eradicate. Hydrilla can usually out-compete native
vegetation and when left unchecked, will form monotypic stands of dense
vegetation. Hydrilla produces reproductive structures, turions and
subterranean turions, from which it can regenerate after control efforts.
The subterranean turions, called tubers, are produced up to a foot deep in
the hydrosoil where they can remain viable for up to five years. These
tubers are resistant to drying especially in heavy clay, organic soils.
Dewatering the water bottom stimulates the sprouting of approximately 85
to 90 percent of the existing supply of tubers. The main production of
tubers is triggered when periods of daylight fall below 13
hours.Consecutive drawdowns will not only prevent the plants from
producing tubers but will also deplete the population of tubers in the
water bottom. Several years of drawdowns are necessary to achieve some
measure of control on a hydrilla infestation.
Due to the infestation of submerged aquatic vegetation and lack of funding
for expensive aquatic herbicides, LDWF is recommending that five
consecutive fall/winter drawdowns be considered. Upon acceptance of this
recommendation by the Bossier Parish Police Jury and the U.S. Army Corps
of Engineers, the gates will be opened September 15, 2003 allowing the
lake to fall at the rate of three to four inches per day until it is six
feet below pool state. The department will survey the lake after the lake
reaches the desired level to assure dewatering of the majority of the
vegetation. This six-foot drawdown should continue until January 19, 2004
when the gates should be closed to allow the lake to refill. The
department will conduct yearly surveys to monitor vegetation levels and
adjust the management plan as necessary.
For additional information, please contact Scott Longman at 337/948-0255
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