summer day at the beach in Iowa
Water Quality Monitoring

Routine water quality monitoring is conducted at all of the State Park beaches and many locally managed beaches in Iowa. In order to help protect the health of those wishing to recreate at the beaches, the Iowa Department of Natural Resources works with various public health and management agencies throughout the state to inform the public of the most current water quality conditions.

Outdoor recreation at beaches in Iowa is typically limited to the time period between Memorial Day and Labor Day. Therefore, most beach monitoring is conducted and standard swimming advisories are issued during this time frame. Results for specific beaches are published as soon as they become available.

Coralville Reservoir, Red Rock and Saylorville Beach Monitoring Results

For information regarding beach advisories and conditions, please contact the Natural Resource Specialist or Park Ranger at the following lakes:

  • Saylorville Lake - (515) 276-4656 
  • Lake Red Rock - (641) 828-7522 
  • Coralville Lake - (319) 338-3543 

Water Monitoring FAQ

Swimming in lakes or any other natural body of water involves risks. By far, the greatest risk is drowning caused in part by cloudy water, fast currents, submerged objects, or the lack of lifeguards. Water at Iowa’s state-owned swimming beaches is monitored to assess the public health risk from waterborne diseases that may result from immersion in the water.

Water samples from the beaches are analyzed for microorganisms, known as bacteria and cyanobacteria toxins. These indicator bacteria are one-celled organisms visible only under a microscope. High levels of these bacteria indicate that the water has come into contact with fecal material. Indicator bacteria (Bacteria that normally are not pathogenic [disease causing] but serve as indicators of certain types of pollution such as sewage or manure runoff) are commonly used by state environmental agencies and by the U.S. EPA to determine the suitability of beaches for swimming-type uses.

Cyanobacteria, which are often referred to as blue-green algae, are microscopic organisms that are naturally present in all aquatic ecosystems, ranging from hypersaline to freshwater environments, and are important components of food webs and the nitrogen cycle. Cyanobacteria can form blooms that sometime produce toxins. The Iowa Department of Natural Resources analyzes for cyanotoxins called microcystins which is the most widespread and frequently occurring cyanobacterial toxins produced by blooms found in Iowa’s surface waters.

The indicator bacteria for which we monitor do not themselves make you sick. These bacteria are easy to collect and analyze and are relatively safe to handle. They are very common in the environment, including lakes and rivers. High levels of these bacteria indicate that the water has come into contact with fecal material and that pathogens or disease-causing microorganisms may be present.  Levels of indicator bacteria above the water quality standard indicate a greater risk of becoming sick for people recreating in the water.

Disease-causing organisms, known as pathogens, exist as bacteria, viruses or parasites. Monitoring for these pathogens is expensive and difficult. Large volumes of water are needed to monitor for pathogens because they are present in such small numbers. Many different types of pathogens exist and testing for a single pathogen may not accurately assess the health risk present due to other pathogens. Because indicator bacteria occur in greater numbers than pathogens and are easier to isolate in a laboratory, monitoring for them is more cost-effective.

Fecal bacteria, and sometimes pathogens, are present in the intestines of warm-blooded animals, including humans. They are carried into the water with fecal material. Fecal contamination can occur due to improperly constructed and operated septic systems and sewage treatment plants, manure spills, storm water runoff from lands with wildlife and pet droppings, or direct contamination from waterfowl, livestock, or small children in the water.  

Samples are collected weekly at 39 state owned beaches from the week prior to Memorial Day through Labor Day.   Water samples are taken at three locations along the beach and at three water depths (ankle-, knee- and chest-deep).The water from these locations is mixed to form one sample, which is placed in a sterilized bottle and taken to a laboratory for analysis.

The United States Environmental Protection Agency (EPA) has guidelines for the amount of bacteria acceptable in water bodies designated for primary body contact recreation, including swimming and water skiing. In Iowa, these waters are called "Class A waters". The bacteria level in the water is acceptable if the “geometric mean” is not greater than 126 colonies per 100 milliliters of water for E. coli bacteria. According to U.S. EPA guidelines, the “geometric mean” is calculated using at least five consecutive samples collected during a 30-day period. Additionally, Iowa also has a "one-time" standard for E. coli bacteria of 235 colony forming units per 100 milliliters of water.

Fecal contamination of beach water occurs due to improperly constructed and operated septic systems and sewage treatment plants, manure spills, storm water runoff from lands with wildlife and pet droppings, or direct contamination from waterfowl, livestock, or small children in the water. In Iowa, rain appears to be one of the most important factors in generating high levels of bacteria. Surface runoff after a heavy rainfall may transport high levels of fecal bacteria to the water at the beach. The rain also increases the sediment in the water causing it to be murky. Since bacteria are destroyed by sunlight, murky water aids in their survival.

Thousands of people swim at Iowa's beaches every year and most of them do not get sick. However, children, the elderly and people with weakened immune systems have an increased risk of becoming ill when in contact with contaminated water. A variety of diarrheal diseases, and other infections such as skin, ear and respiratory infections, are associated with swimming in contaminated water. Diarrhea is one of the most common illnesses associated with swimming. Diarrhea is spread when disease- causing microorganisms from human or animal feces get into the water. You can get diarrhea by accidentally swallowing small amounts of water that contains these microorganisms.

Avoid swimming after a heavy rainfall when indicator bacteria levels are generally higher and the water is murky. Avoid swallowing the water. Young children swimming at the beach can leak fecal bacteria and associated pathogens from their diapers, so change your child’s diapers often and visit bathrooms frequently. If you or your child has diarrhea, please stay out of the water because you may contaminate the water with fecal material. Although swimmers with diarrhea do not mean to contaminate the water, this is often how disease is spread.

High levels of indicator bacteria or pathogens have no influence on the quality of fish for human consumption. While alive, the fish is protected from water-borne contaminants by the skin, scales and mucus covering its body. Proper fish cleaning, rinsing, refrigeration and cooking should always be used.

Beach Monitoring

For current beach advisory, call the DNR Beach Monitoring Hotline: (515) 725-3434

The DNR Beach Monitoring Website and Hotline are updated on Fridays during the monitoring season.

If you have any questions or concerns, contact us by email.

DNR Beach Monitoring and Advisory Implementation Plan
State Standard

The bacteria standard for Iowa’s recreational waters consists of two components:

  • A geometric mean standard based on 5 samples in a 30-day period (126 colony-forming units of E. coli bacteria per 100 mL of water).
  • A one-time maximum standard based on a single sample (235 colony forming units of E. coli bacteria per 100 mL of water).

State advisory threshold for Cyanobacteria Toxins (Blue-Green Algae Toxins)

The Iowa Department of Natural Resources, in partnership with the Iowa Department of Public Health (DPH), follows guidelines recommended by the US EPA in 2019 for monitoring cyanotoxins in recreational waters in order to safeguard public health.

  • 8 µg/L total microcystins from any composite beach sample.
Posting of Signs/Advisories

All State monitored beaches are posted with Information Signs on indicator bacteria and blue-green algae toxins that provide general information regarding ways to reduce the potential health risk associated with swimming at public beaches. These signs will also inform the public of current monitoring efforts and ways to obtain the data.

Posting will only occur between Memorial Day and Labor Day (recreational monitoring season). Advisories are generally updated on Fridays of each week during the recreational monitoring season, but may be earlier or later in the week depending on the timing of holidays, sampling schedules and availability of laboratory results. All monitored beaches will be signed to “Watch / General Information” when an advisory is not in effect or when monitoring is not occurring.

Beaches that exceed Iowa’s geometric mean water quality standard for indicator bacteria (the geometric mean of 5 samples in a 30-day period exceeds 126 colony forming units of E. coli bacteria per 100 ml of water) will be posted with a warning sign that state, “Swimming is Not Recommended”.

Vulnerable and Transitional Beaches that exceed the one-time sample maximum water quality standard for indicator bacteria (235 CFU/100ml) will be posted with a warning sign that states,“Swimming is Not Recommended”.

Beaches that exceed Iowa’s advisory threshold level for cyanobacteria toxins (8 µg/L total microcystins) will be posted with a warning sign that state, “Swimming is Not Recommended”.

Advisories will remain in effect until the geomean for indicator bacteria drops below the water quality standard, the one-time sample maximum for indicator bacteria drops below the water quality standard, and the one-time sample maximum for Cyanobacteria toxins drops below the advisory threshold.

Beach Classes

Beaches are placed on “vulnerable” list if they have exceeded the geomean standard for indicator bacteria two or more times in the previous five years. The list is reviewed annually to update the beaches classified as “vulnerable”.

Beaches are placed on the “transitional” list if improvements have been observed with respect to indicator bacteria levels. Beaches in the transitional classification will be eligible to be reclassified to “non-vulnerable” if they do not exceed the geometric mean standard for one year.

Beaches that have not exceeded the geometric mean indicator bacteria standard or only exceeded the standard once during the most recent five years are classified as being “less vulnerable” to experiencing prolonged or chronic problems with elevated levels of indicator bacteria.

Swimming Registration at State Parks

People wishing to swim outside the designated swimming beach areas at Iowa state parks, for example to train for a triathlon, must obtain special permission by completing a registration form and communicating with local park staff.

For information and guidelines:
Swimming Registration Form