A guide for water utilities, reservoir operators, and environmental engineers managing bird and wildlife activity on open water storage.
Why birds on reservoirs can be a compliance risk, not just a nuisance
Birds are drawn naturally to open water. For drinking water reservoirs, that can introduce a potential contamination pathway. When waterfowl roost and feed on a reservoir, they may introduce indicator bacteria such as fecal coliform bacteria, E. coli, along with other pathogens, directly into the source water.
Under the U.S. EPA’s Surface Water Treatment Rule and the Revised Total Coliform Rule (RTCR), utilities are required to monitor water quality and respond to detections of indicator organisms. While bird activity alone does not constitute a violation, it can contribute to water quality impacts that trigger Level 1 or Level 2 assessments, corrective actions, or increased scrutiny during sanitary surveys.
The relationship between waterfowl activity and reservoir water quality has been documented in multiple studies. For example, research at New York City’s Kensico Reservoir found that fecal coliform concentrations became significantly elevated during autumn and winter roosting periods for ring-billed gulls and Canada geese. Laboratory analysis showed that gull feces carry an average fecal coliform concentration on the order of 10⁸ CFU/g (colony-forming units per gram). Once the NYC Department of Environmental Protection implemented a formal waterfowl mitigation program, fecal coliform counts at the reservoir decreased measurably.
For utilities operating surface water systems, bird activity near reservoirs and intake structures is best understood as a manageable risk within a broader watershed control strategy.
How bird balls work as a wildlife deterrent
Bird balls are hollow HDPE spheres deployed across the water surface in sufficient density to form a floating layer. Their effectiveness is based on visual disruption as many waterfowl recognize open water visually. A surface covered by floating spheres no longer appears as water to waterfowl, making it less attractive as a landing, roosting, or feeding site. The birds move on.
Unlike netting or wire deterrent systems, bird balls do not create an overhead barrier above the water. Instead, they camouflage the water surface, allowing the system to self-adjust to water level changes; do not obstruct access to pumps, intake structures, or aeration equipment; and require no overhead infrastructure.
In addition to the bird deterrence, the floating layer also delivers secondary operational benefits by blocking sunlight, the floating layer can help limit algae growth and reduce evaporation, two problems that bird netting may not address.
Bird balls vs. pond netting
Water utilities often compare bird balls with pond netting when evaluating wildlife deterrence options. Both are passive systems that require no power and minimal ongoing management, but they differ in meaningful ways.
| Factor | Bird balls | Pond netting |
| Installation | ✓ Deploy directly onto water, no infrastructure | Requires scaffolding or frame above water |
| Water level changes | ✓ Self-adjusting, balls rise and fall with level | Fixed installation, does not adjust |
| Equipment access | ✓ Balls move aside for pumps, intakes, aerators | Net must be cut or removed for access |
| Algae control | ✓ Blocks sunlight, helps reduce algae growth | No sunlight blocking, algae can still grow |
| Evaporation reduction | ✓ Reduces evaporation as secondary benefit | No evaporation benefit |
| Wildlife deterrence | ✓ Surface camouflage deters attraction to water | Physical barrier, does not camouflage water |
| Maintenance | ✓ Replace individual balls as needed | Repair or replace net sections when damaged |
Pond netting remains appropriate in certain applications, particularly where physical exclusion of all wildlife is the objective. Bird balls offer greater operational flexibility and may deliver additional water quality benefits beyond netting.
Regulatory context: what utilities should consider
Surface water systems are required to evaluate and manage potential contamination pathways as part of watershed control and sanitary survey processes. Bird and wildlife activity is commonly recognized in practice as a potential contamination pathway.
During sanitary surveys, state primacy agencies assess watershed control programs, including how utilities identify and manage sources of contamination. Reservoirs with documented wildlife activity but no mitigation strategy may be noted during sanitary surveys, while systems with documented control measures can demonstrate proactive risk management.
Under the RTCR, total coliform or E. Coli detections require utilities to perform assessments to identify potential causes and implement corrective actions where needed. If bird activity is identified as a contributing factor, mitigation measures may be incorporated into the utility’s response.
Bird balls can serve as a passive, physical control measure that reduces wildlife access to the water surface. When used as part of a broader management approach, they can support documentation of actions taken to address identified risks.
Applications beyond drinking water reservoirs
Wastewater and stormwater facilities
Wastewater treatment lagoons and stormwater retention ponds attract the same species of birds as water reservoirs. Bird balls can be used as a wildlife deterrent in both applications without requiring additional infrastructure.
Mining and industrial process water
Open process water ponds in mining and industrial applications attract birds, which creates concerns with potential wildlife exposure risk water may contain tailings or chemicals. Wildlife ingestion of tailings water and chemical laden water may lead to wildlife exposure and, in some cases, fatalities. A covered pond surface removes the visual attractant that draws birds and wildlife, reducing the potential for wildlife exposure.
Recycled water storage
Recycled water storage facilities operate under water quality requirements for reuse applications. Bird activity introduces contamination that can cause unwanted water quality changes. Bird balls provide passive, continuous deterrence without requiring active management.
EnviroBalls™ for reservoir wildlife control
EnviroBalls™ are manufactured in the United States from UV-stabilized HDPE, designed for long-term deployment on drinking water reservoirs, lagoons, and industrial basins. Each EnviroBall™ is a hollow sphere that floats naturally on the water surface, self-organizes into a continuous protective layer and adjusts with changing water levels.
For utilities and infrastructure operators, U.S. manufacturing ensures compliance with Buy America requirements. If you are managing bird or wildlife activity on a reservoir, lagoon, or industrial water basin, contact the GES team to discuss the right configuration for your facility.
Request Information on EnviroBalls™
GES provides coverage calculations, product sizing, and project cost estimates for reservoir wildlife control applications. Contact Global Environmental Solutions to get started.
