Serene lake beach with geese and subtle bacteria visualizations

Beach Bacteria Blues: Can We Fix Our Favorite Swimming Spots?

Nico Varela in Climate & Environment December 2025 • 4 min read.

"Uncover the hidden sources of bacteria at your local swimming hole and learn about new modeling approaches that could help clean up our beaches."

Imagine a hot summer day, the sun is blazing, and all you want to do is take a dip in the cool, refreshing waters of your local lake or beach. But what if that water isn't as clean as it looks? Inland lake beaches are a major source of recreation, and when these areas are impaired due to poor water quality major economic losses can occur in local communities. Pathogens are the primary cause of surface water impairments in the United States.

Every year, countless beaches are closed or face warnings due to high levels of bacteria, making what should be a fun outing a potential health hazard. The U.S. Environmental Protection Agency (USEPA) has developed stringent water quality standards to protect humans from exposure to pathogen contaminated waters. Fecal indicator bacteria (FIB) such as the fecal coliforms, enterococci, and Escherichia coli are primarily used to detect fecal contamination as they are the preferred indicators of pathogens in waters. But where does all this bacteria come from, and what can be done to fix the problem?

A recent study focused on Hickory Grove Lake in Iowa offers some insight, exploring a novel approach to pinpoint bacteria sources and set Total Maximum Daily Loads (TMDLs) – essentially, pollution cleanup targets – for beaches. The goal is to determine all the factors affecting the bacteria movement, decay, and growth in lake waters needed to develop reliable bacteria TMDLs for inland lake beaches.

Decoding the Bacteria Mystery: Where Does It Come From?

Serene lake beach with geese and subtle bacteria visualizations

Traditionally, identifying the sources of bacteria in a lake or beach is a complex task. It involves considering everything from agricultural runoff to failing septic systems. In the case of Hickory Grove Lake, researchers identified a few key culprits:

The watershed area that drains into Hickory Grove Lake is dominated by cultivated land cropped in corn and soybean rotations. The use of subsurface tile drains to remove excess water from subsurface soils to improve crop productivity. The subsurface tile drainage system and other drainage infrastructure are managed within the context of the drainage district per regulations established in Iowa Law.

Unpermitted septic systems leaching into the water
Manure applications in the surrounding watershed
Livestock with direct access to streams
A surprising amount from waterfowl and wildlife

While all these factors play a role, the study highlighted waterfowl – specifically geese – as a major source of contamination at the Hickory Grove Lake beach. It was also found that there are approximately 50 resident geese present at the lake during the recreation season (Memorial Day to Labor Day) and that migrating geese through Iowa during each Spring and Fall range from 1,500 to 2,000.

Cleaning Up Our Act: Future Steps for Healthy Beaches

The approach used at Hickory Grove Lake offers a promising alternative for setting beach bacteria TMDLs, particularly when the primary source is localized. Identifying the sources of contamination and the degree of contaminant loads received by the waterbody are the first steps in the TMDL development process. The near shore beach volume model approach proposed here is a viable alternative for setting load reductions at bacteria impaired beaches, where the predominant source of E. coli is waterfowl. Future research should focus on improving our understanding of how bacteria interact with beach sediments and refining models to better predict bacteria levels in complex environments. The NBSV approach would allow Clean Water Act Section 319 implementation funds to target the localized contributions from geese and increase the likelihood of achieving water quality improvements.

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Everything You Need To Know

Why are beaches sometimes closed or have warnings issued?

Beaches often face closures or warnings due to high levels of bacteria. The U.S. Environmental Protection Agency (USEPA) has established water quality standards to protect people from exposure to pathogen-contaminated waters. Fecal indicator bacteria (FIB), such as fecal coliforms, enterococci, and Escherichia coli, are used to detect fecal contamination. When these FIB levels exceed safe limits, it indicates a potential health hazard, leading to beach closures or warnings.

What are Total Maximum Daily Loads (TMDLs) and why are they important for beach water quality?

Total Maximum Daily Loads (TMDLs) are pollution cleanup targets set for impaired water bodies, including beaches. They determine the maximum amount of a pollutant, such as bacteria, that a water body can receive and still meet water quality standards. In the context of beaches, TMDLs aim to identify all the factors affecting bacteria movement, decay, and growth in lake waters. Setting effective TMDLs is crucial for developing strategies to reduce bacteria levels and ensure that beaches are safe for recreation. A near shore beach volume model approach is a viable alternative for setting load reductions at bacteria impaired beaches.

What sources of bacteria were identified at Hickory Grove Lake?

At Hickory Grove Lake, several key sources of bacteria contamination were identified. These included unpermitted septic systems leaching into the water, manure applications in the surrounding watershed, livestock with direct access to streams, and a significant amount of contamination from waterfowl and wildlife, particularly geese. The watershed area that drains into Hickory Grove Lake is dominated by cultivated land cropped in corn and soybean rotations. The use of subsurface tile drains to remove excess water from subsurface soils to improve crop productivity. The subsurface tile drainage system and other drainage infrastructure are managed within the context of the drainage district per regulations established in Iowa Law.

How can near-shore modeling help in cleaning up beaches?

Near-shore modeling is a novel approach to pinpoint bacteria sources and set Total Maximum Daily Loads (TMDLs) for beaches. Identifying the sources of contamination and the degree of contaminant loads received by the waterbody are the first steps in the TMDL development process. The near shore beach volume model (NBSV) approach proposed here is a viable alternative for setting load reductions at bacteria impaired beaches, where the predominant source of E. coli is waterfowl. This would allow Clean Water Act Section 319 implementation funds to target the localized contributions from geese and increase the likelihood of achieving water quality improvements.

What role do waterfowl, like geese, play in beach bacteria contamination, and how can this be managed?

Waterfowl, particularly geese, can be a major source of bacteria contamination at beaches. At Hickory Grove Lake, approximately 50 resident geese are present during the recreation season, with 1,500 to 2,000 migrating geese passing through Iowa each Spring and Fall. Their presence contributes significantly to the bacteria levels. Managing this involves strategies to reduce waterfowl presence near beaches, such as habitat modification or deterrents. The NBSV approach would allow Clean Water Act Section 319 implementation funds to target the localized contributions from geese and increase the likelihood of achieving water quality improvements.