Piet's Notes on Deep Creek Lake Science
Sensible Technologies - The Science of Deep Creek Lake
Managing Submerged Aquatic Vegetation
Submerged Aquatic Vegetation (SAV) at Deep Creek Lake is a concerning problem. Over the years there is ample evidence that it is taking over large areas of the lake in the late summer.
One of the suggested remedies is to lower the lake level during the winter time and expose the bare bottom of the lake to the freezing temperatures of the air.
This note collects a few references that address this problem and extracts from them some relevant quotes that could be useful in developing a plan for treatment. The search term in Google used to extract the below references was “exposing subaquatic vegetation to freezing temperatures”
- Taming Aquatic Vegetation - 4/9/2020
Weeds can be controlled using a variety of methods, which are usually categorized as physical, mechanical, biological, and chemical.
Physical manipulation, such as a winter drawdown, is one way to control unwanted plants. During the fall, water should be released to expose the pond bottom where the problem vegetation grows. The drawdown should be completed by November and continue through February. This practice air-dries the exist-ing plants and exposes the roots to freezing temperatures.
- Low Temperature Limits of Waterhyacinth - J. Aquat. Plant Manage. 33: 63-68, 1995
Waterhyacinth withstood near-freezing temperature (<5C) for a limited period of time, but exhibited a steady decline in regrowth potential. Rooted plants appeared to resist the effects of cold temperature longer than free-floating plants.
Lowering the lake in the winter to expose the plants to freezing temperatures is a popular way to keep it under control…
Historically, the deeper the drawdown, the less milfoil the following summer because more plants are exposed and killed by the winter’s deep freeze.
In those tests, the plant died when temperatures were at -5 degrees Celsius, or about 23 degrees Fahrenheit for 24 to 48 straight hours. He said that happened in ideal conditions in a lab and generally takes longer in the real world.
Lake drawdown, or water withdrawal, is used to control invasive submerged aquatic vegetation (SAV) and has been used in New Zealand (Clayton 1996), France (Barrat-Segretain and Cellot 2007), North America (Manning and Sanders 1975, Cooke et al. 1993), South America (Thomaz et al. 2006, Silveira et al. 2009), and Australia. It is used in artificial or managed lakes such as reservoirs, where water levels remain relatively stable and thus facilitate the accumulation of weeds, and where water levels can be actively managed, for example in irrigation and hydroelectric dams. The objective of a drawdown is to expose plants to hot and dry or freezing and dry conditions for a period sufficient to kill the plants (Cooke et al. 1993).
- Identifying and Managing Aquatic Vegetation - 11/3/2009
Drawing down the water level over the winter also can be an effective option. Exposing sediments in the shallow areas to freezing and thawing kills the underground structures of many aquatic plants, but its effectiveness depends on the severity of the winter. This method has been successful at controlling Eurasian watermilfoil and waterlily populations.
Coontail sometimes called “Hornwort” is a common, dark green, submerged perennial aquatic plant (Fig. 1). While it lacks true roots, Coontail may be loosely anchored to the bottom by specialized, finely divided, buried or free-floating stems (rhizoids). The fanshaped leaves are relatively stiff and best observed in the water.
Coontail has no roots to obtain nutrients from the sediment. It absorbs nutrients directly from the water, so reducing nutrients from the water will ultimately suppress growth.
Lake water lowering is sometimes used to control aquatic vegetation. In this method, the lake water surface is lowered by several feet exposing the bottom sediments, along with nuisance Coontail plants. Plants are exposed to either freezing or desiccation, depending on time of year (NHDES 2010).
- CHAPTER 4 - FROST DAMAGE: PHYSIOLOGY AND CRITICAL TEMPERATURES - From the book “Frost Protection: fundamentals, practice and economics volume 1 and 2” - 2005
Low temperature (e.g. chilling and freezing) injury can occur in all plants, but the mechanisms and types of damage vary considerably.
In this chapter, a short discussion of the mechanisms, types and symptoms of freeze injury is presented.
- Aquatic Vegetation Control in Arkansas - date unknown
Lake drawdown, or water withdrawal, is often used to control invasive submerged macrophytes; however, regrowth of the target species often occurs rapidly. A mechanism proposed to explain such unsatisfactory results is that as water recedes and submerged aquatic weeds become exposed to the air, mounds of stranded vegetation form on the dewatered lakebed. These mounds may insulate underlying weeds, creating an environment protected from desiccation and frost.
The results confirm that, although the drawdown of Lake Mulwala was effective in killing exposed stems of E. densa, it was much less effective in killing bottom stems and crowns. A 22 day exposure to local winter conditions, with- out significant frost, was enough to kill all E. densa stem material exposed to those conditions (i.e., stems on top of the mounds).
- Plants and Their Environment - August 2007
During rest, dormant buds can withstand low temperatures, but after the rest period, buds become more susceptible to weather conditions and can be damaged easily by cold temperatures or frost.
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Impacts of climate change on submerged and emergent wetland plants - 6/10/2016
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How do plants survive ice - Annals of Botany 78: 529–536, 1996
Plant species have had to adapt to freezing and the presence of ice in many climatic zones. Annual plants avoid ice by seed dispersal but, for biennials and perennials to survive they must cope with ice in various forms
And many more. These should provide a good overview of what might happen.
PLV
First Published: 11/9/2021