Davenport, Iowa has a unique relationship with the Mississippi River. It’s one of the only major cities along the Mississippi that has never built a permanent flood wall or levee system. The city made a deliberate choice decades ago to maintain open access to its riverfront — and that decision means Davenport lives with flooding in a way that most river cities don’t.
The floods of 2019 were a stark reminder. When a temporary barrier failed in April of that year, the Mississippi surged into downtown, inundating streets and buildings. But flooding’s effects on Davenport go beyond property damage. They affect the water that comes out of residents’ taps — and the infrastructure that delivers it.
The Flooding Problem
Davenport (population roughly 100,000) is part of the Quad Cities metro area that straddles the Iowa-Illinois border. The Mississippi River is the lifeblood of the region, but it also poses a recurring threat.
Major flood events affecting Davenport have occurred in 1965, 1993, 2001, 2008, 2019, and at various other intervals. Climate patterns suggest that the frequency and intensity of Mississippi River flooding may be increasing. The Upper Mississippi River Basin has seen more frequent heavy precipitation events, and changes in land use and drainage patterns upstream have reduced the landscape’s ability to absorb and slow runoff.
When the Mississippi floods, several water quality concerns emerge:
Overwhelmed sewer systems — Davenport, like many Midwest cities, has areas with combined sewer systems that carry both sanitary sewage and stormwater. During flooding, these systems can be overwhelmed, resulting in combined sewer overflows (CSOs) that discharge untreated sewage into the river and local waterways.
Contamination mixing — Floodwaters pick up everything in their path: agricultural chemicals, petroleum products from flooded facilities, raw sewage from overwhelmed systems, industrial chemicals, household hazardous materials, and sediment. This contaminated cocktail can infiltrate groundwater, contaminate private wells, and challenge water treatment facilities.
Infrastructure damage — Flooding can damage water mains, service connections, and the water treatment plant itself. Physical damage to the distribution system can allow contaminated floodwater to enter the drinking water supply through breaks and joints.
Davenport’s Drinking Water Source
The Davenport Water Works sources its drinking water from the Mississippi River and from an alluvial well field adjacent to the river. The treatment plant, located along the riverfront, processes raw water through a multi-step treatment process including coagulation, sedimentation, filtration, and disinfection.
Drawing from the Mississippi means that everything upstream affects Davenport’s raw water quality. The river at this point has already passed through Minneapolis-St. Paul, industrial cities, and vast stretches of agricultural land. It carries:
- Agricultural runoff — nitrates, phosphorus, atrazine, and other pesticides from Iowa, Minnesota, Wisconsin, and Illinois cropland. The Upper Mississippi watershed is some of the most intensively farmed land in the world.
- Urban and industrial discharges — treated wastewater, stormwater, and permitted industrial discharges from upstream communities.
- Sediment — the Mississippi carries enormous sediment loads, particularly during high-water events.
- Emerging contaminants — pharmaceuticals, personal care products, and PFAS that pass through upstream wastewater treatment plants.
During flood events, the raw water quality deteriorates significantly. Turbidity spikes, contaminant concentrations change, and the treatment plant must adapt its processes in real time to maintain water quality.
What Flooding Does to Water Quality
The 2019 flooding was particularly instructive. When the temporary HESCO barriers failed on April 30, 2019, floodwater inundated several blocks of downtown Davenport. But the water quality implications extended well beyond the flooded area:
Well contamination — Private wells in flood-affected areas are vulnerable to contamination when floodwater reaches the wellhead or when saturated soil allows surface contaminants to reach the aquifer. The Iowa Department of Natural Resources (DNR) recommends that any well that has been submerged or surrounded by floodwater be tested before use and potentially shock-chlorinated.
Boil advisories — Flooding events can trigger boil water advisories for portions of the water system if pressure is lost or contamination is suspected. Even brief pressure drops can allow infiltration of untreated water through cracks in aging pipes.
Sediment and turbidity challenges — High river levels and fast currents increase the sediment load in raw water, which challenges the treatment plant’s filtration capacity. Extreme turbidity can reduce the effectiveness of disinfection if particles shield microorganisms from chlorine contact.
Nutrient loading — Flood events mobilize nutrients from agricultural fields, increasing nitrogen and phosphorus concentrations in the river. While these nutrients are primarily an environmental concern (contributing to the Gulf of Mexico’s hypoxic “dead zone”), elevated nitrate levels in raw water require attention at the treatment plant.
Infrastructure Vulnerabilities
Davenport’s water infrastructure faces the same age-related challenges as many Midwest cities, compounded by the added stress of periodic flooding:
Aging pipes — portions of the distribution system date back to the early 1900s. Older cast iron and lead-jointed pipes are more vulnerable to damage from ground movement associated with flooding and the freeze-thaw cycles of Iowa winters.
Lead service lines — as with many cities built in the early-to-mid 1900s, some homes in Davenport may be served by lead service connections. The Iowa DNR oversees compliance with the Lead and Copper Rule, and the water utility has been working on its service line inventory.
Treatment plant vulnerability — the water treatment facility’s riverfront location, while logistically necessary for its intake, means the plant itself is at risk during major flood events. Protecting critical treatment infrastructure during flooding is an ongoing operational challenge.
The Iowa DNR and the city have been investing in infrastructure improvements, but the scope of needed upgrades across the system is substantial. The Bipartisan Infrastructure Law has provided additional funding opportunities for water system improvements in Iowa.
Agricultural Chemical Concerns
Iowa is the nation’s leading corn producer and a top soybean state. The intensive agriculture surrounding Davenport means that agricultural chemicals are a persistent water quality factor:
Nitrates are the most significant agricultural contaminant for drinking water. Nitrogen fertilizer applied to cornfields can leach into groundwater and wash into surface water. The EPA’s MCL for nitrates is 10 mg/L, and Iowa river systems frequently approach or exceed that level during spring application season and after heavy rains.
Davenport’s water treatment plant monitors nitrate levels continuously and has the capability to blend water sources or adjust treatment to manage elevated nitrate concentrations. But high nitrate events require the plant to work harder and sometimes limit certain operations.
Atrazine and other herbicides are commonly detected in Midwest surface waters during the growing season. Atrazine, one of the most widely used herbicides in US agriculture, has an EPA MCL of 3 ppb (measured as a running annual average). Iowa water systems regularly detect atrazine, though levels typically remain within the regulatory standard when averaged over time.
Emerging contaminants including neonicotinoid pesticides, glyphosate, and various metabolites of agricultural chemicals are increasingly being studied in Midwest waterways. Many of these compounds don’t yet have EPA drinking water standards.
What Residents Can Do
If you’re on Davenport public water:
- Review the annual Consumer Confidence Report from Davenport Water Works. Pay attention to nitrate results and disinfection byproduct levels.
- During and after flood events, follow any boil advisories or water quality advisories issued by the utility. These aren’t optional — they exist to protect you.
- If you’re in an older home, check on your service line material and household plumbing. Lead is a concern in pre-1986 construction.
If you’re on a private well:
- Never use well water after flooding without testing it first. The Iowa DNR recommends testing for bacteria and nitrates at minimum after any flooding event.
- If your wellhead was submerged, the well should be shock chlorinated before testing and use. Contact the county health department or Iowa DNR for guidance.
- Annual testing for bacteria and nitrates is recommended for all private well owners in Iowa.
- Wells in agricultural areas should also be tested for pesticides periodically.
After any flood event:
- Don’t wade in or allow children to play in floodwater. It commonly contains sewage, chemicals, and debris.
- Discard any food that has contacted floodwater.
- If your home was flooded, have your plumbing inspected before assuming your water service is intact.
Water Treatment Options
For nitrates: Reverse osmosis is the most effective residential treatment. Ion exchange systems designed for nitrate removal are another option. Standard carbon filters do not remove nitrates.
For agricultural chemicals (atrazine, herbicides): Activated carbon filtration effectively removes most common agricultural chemicals. Look for NSF/ANSI 53 certification for VOC and herbicide reduction.
For lead: Point-of-use RO systems or NSF/ANSI 53-certified filters reduce lead at the drinking water tap.
For well owners post-flooding: UV disinfection provides continuous protection against bacteria and viruses. Combined with sediment and carbon filtration, it creates a robust treatment train for private wells.
Davenport chose to live with its river rather than wall it off. There’s something admirable about that — but it means residents need to be especially aware of how the Mississippi’s cycles affect their water. Testing, treatment, and staying informed aren’t just good practice in Davenport. They’re essential.
If you’re concerned about your water quality, a certified water treatment professional can test your water and advise on solutions.