Winter Drawdowns in Ponds: A Comprehensive Guide to Aquatic Weed and Fishery Management
Summary:
- Scott Jones, a specialist at UAPB, advocates deliberate winter pond water reduction for aquatic weed and fishery management.
- Different pond plants respond uniquely to drawdowns, impacting growth, control measures, and subsequent seasons.
- Drawdowns expose forage fish to predators, aiding predator efficiency and accelerating growth, but caution is advised in summer due to potential water quality issues.
Scott Jones, a dedicated Small Impoundment Extension Specialist at the University of Arkansas at Pine Bluff (UAPB), advocates for a strategic practise known as winter drawdowns in managing ponds. This intentional reduction in pond water levels during winter provides multifaceted benefits, encompassing aquatic weed control, fishery management, and shoreline maintenance in specific scenarios.
Jones’s recommended practise involves a carefully orchestrated process that entails draining a substantial percentage—typically between 30% and 50%—of a pond’s normal water volume. This deliberate reduction starts in November and is maintained until around February, allowing the pond to replenish naturally as spring heralds the fish spawning season, courtesy of natural rainfall and runoff.
For ponds equipped with efficient and operational drainage systems, executing this controlled drawdown is relatively straightforward. The process merely involves regulating the pond’s water levels by simply opening and manipulating the drain. However, for ponds lacking functional drainage systems, alternate approaches are suggested, such as employing makeshift syphon drains or utilising rented trash pumps to achieve the desired reduction in water levels.
Crucially, the types of plants present in a pond play a pivotal role when considering a winter drawdown for effective aquatic weed management. Emergent plants, those rooted at or near the water’s edge, exhibit distinct behaviour during drawdowns. These plants, which include species like alligatorweed, water primrose, rushes, and cattails, thrive when exposed to increased sunlight due to the absence of water depth limitations. While the drawdown period facilitates easier access for herbicide application or physical removal, it simultaneously fosters a conducive environment for these emergent plants to proliferate.
In contrast, submersed plants, characterised by their predominantly submerged nature beneath the water surface, react differently to drawdowns. Species like milfoils, fanwort, coontail, and hydrilla, amongst others, are susceptible to desiccation and freezing during drawdowns, often resulting in diminished abundance in subsequent warm seasons. However, certain species, such as coontail and hydrilla, exhibit remarkable reproductive adaptations that enable them to endure exposure, ensuring their persistence and healthy resurgence post-drawdown.
Jones advises that for certain species, alternative control measures such as employing grass carp might prove more effective than a drawdown in most situations. Furthermore, some rooted floating plants, like spatterdock and fragrant waterlilies (distinct from drawdown-resistant American lotus), are also susceptible to the effects of drawdowns.
To offer comprehensive guidance on plant responses to winter drawdowns and effective aquatic weed control strategies, Jones highlights Extension publication FSA9628 as a valuable resource.
However, Jones stresses that weather conditions during the drawdown phase significantly influence the efficacy of aquatic plant control. Ideal conditions encompass prolonged exposure to drying, preferably six to eight weeks, complemented by at least two weeks of sub-freezing temperatures. These optimal conditions are conducive to effective aquatic plant management and curbing their proliferation.
Moving beyond aquatic plant management, Jones underscores the manifold benefits of drawdowns on the fishery within ponds. He explains that drawdowns offer a unique advantage by exposing smaller forage fish to predation. This exposure enhances predator efficiency and potentially accelerates the growth of remaining forage, a vital aspect of enhancing spawning seasons.
Additionally, Jones advocates for thinning fish populations during drawdowns, suggesting that reducing fish numbers can lead to accelerated growth among the remaining forage. This practise often translates into healthier and more robust fish populations, fostering a balanced ecosystem within the pond.
However, Jones offers a word of caution against implementing drawdowns during the summer in Arkansas. The summer season already witnesses natural water level declines due to increased evaporation and reduced rainfall and runoff. Moreover, the unpredictability of precipitation during the summer adds uncertainty about when depleted water supplies will be replenished adequately. Most significantly, water quality concerns escalate during the summer as shallow waters experience elevated temperatures and reduced surface area interaction with air, leading to lower dissolved oxygen concentrations.
These environmental conditions, exacerbated by shallower waters, heighten stress on fish populations and create a conducive environment for potentially harmful algal blooms to thrive. While certain submersed plants may succumb to extremely hot and dry conditions during summer drawdowns, the risks posed to fish health often outweigh the anticipated benefits.
Jones recommends seeking further information and guidance on winter drawdowns by contacting him directly at (870) 575-8185 or through email at [email protected].
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