Entergy Arkansas Inc. announced last week that it had changed the refill dates for lakes Hamilton and Catherine to accommodate construction-related work at Blakely Mountain Dam's powerhouse.
The new refill dates for lakes Hamilton and Catherine call for raising both lakes beginning March 10 and for completing the refill March 16.
Bobby Pharr, manager of Entergy's Hydro Operations Support, said the lakes were originally scheduled to be allowed to return to normal summertime levels beginning Tuesday.
Pharr said the request came from the U.S. Army Corps of Engineers to allow time for the construction-related work to be completed.
Blakely Mountain Dam, which forms Lake Ouachita above Lake Hamilton, is managed by the Corps of Engineers. Lake Hamilton, which forms behind Carpenter Dam above Lake Catherine, and Lake Catherine, which forms behind Remmel Dam above the Ouachita River, are managed by Entergy.
Lakes Hamilton and Catherine were each drawn down 3 feet in November as part of Entergy's annual wintertime drawdown plan.
The lakes are drawn down each winter to facilitate shoreline maintenance and inspections and to help control nuisance aquatic vegetation.
Pharr said all of the implications for all of the stakeholders in the lake, including lakefront property owners, the Corps of Engineers, the Arkansas Game and Fish Commission, and Entergy's hydro generation operation, were debated after the request for the delay was made.
"We talked to the Arkansas Game and Fish Commission, and they didn't think it was going to affect their walleye program," Pharr said.
The Game and Fish Commission conducts a walleye egg harvest program below Carpenter Dam each year as the lake refills. The annual harvest has taken place for about 20 years, and the goal is to harvest about 1.2 million walleye eggs.
Entergy and the stakeholders also decided the delay will actually help contractors who work on sea walls and docks, because they lost several work days as a result of the recent inclement winter weather, Pharr said.
Also, the longer the lakes are drawn down, the bigger the effect on nuisance vegetation, which is part of the reasoning behind the drawdowns. The drawdowns affect the vegetation in part by exposing the plants to dry, freezing conditions.
Entergy's Nuisance Aquatic Vegetation Management Plan, developed in 1997, identified lake level drawdowns and grass carp as the primary methods of attacking the problem of nuisance vegetation, primarily in Lake Hamilton.
Entergy said in a statement released last year that there had been some decrease in many species of nuisance vegetation, except algae, since the previous winter.
Two problem plants, southern naiad and Eurasian water milfoil, declined after being exposed to colder temperatures the previous winter, and because lake water was less clear as a result of higher-than-normal rainfall.
While some species of vegetation are more sensitive to freezing temperatures and drying of the lake bed during drawdowns, Entergy said algae remained as problematic as ever, particularly in shallow areas where the light still penetrates to the lake bed.
Filamentous algae, a long, stringy, mossy type, begins its growth on the lake bottom or water's edge and can form floating mats. Chara grows more like a weed and is also known as "muskgrass" because of its musky smell.
The Game and Fish Commission released about 1,900 young grass carp into Lake Hamilton last summer to help the situation.
Metro on 03/02/2015