When it rains it pours. An old adage that is more than a metaphor in the Ozarks these days. The evidence is not just anecdotal.
Mark Owen, director of the Ozarks Environmental and Water Resources Institute, tells KSMU that “we've measured river stages and flow for over a hundred years at some stations in the Ozarks.”
He said that data shows an increase in the frequency and magnitude of floods. When it rains, it really does pour.
“This is not model data or something that somebody is trying to predict,” Owen explained. “This actually has occurred.”
He said rainfall records going back to the late 1800s show that total rainfall has changed little, but that rain is falling in fewer more intense events. This causes flash flooding for which our waterways haven’t been prepared.
“The size of a river, or the shape of the river is really a reflection of the hydrological processes in the watershed or that area that drains to that river," he explained. “It's in an equilibrium with the amount of rainfall, the amount of runoff that occurs."
Intense rains are pushing more water into the watershed, and our waterways and flood plains are responding. Owen said bedrock often prevents creeks and rivers from getting deeper, so they’re getting wider. He said he looks at historic aerial photography to measure how waterways have been shaped.
“Widths have changed maybe 30% all the way up to 100% change over those 80 years,” Owen said, with a noticeable increase in that rate over the last couple decades. "There's kind of a chain reaction as you go upstream from that river,” he said. “So, we might have tributaries or streams. Then once that river adjusts, then they have to adjust to that new flow as well. So, you end up getting erosion and sediment transport of gravels and other soil and sediment.”
This fresh erosion can reshape river and creek banks and leave debris, affecting property and property owners. It can also wreck public infrastructure, and bridges and roads that once rarely flooded may flood regularly now. It also increases turbidity, or the measure of cloudy sediment in water. This can make the water look dirty, which is unappealing in a region known for its beautiful nature, but it has real consequences as well. “You know, soil and sediment end up in reservoirs,” Owen explained. “It clogs up the channel bed where macroinvertebrates live or other aquatic species might live. It could carry, for instance, nutrients, and when nutrients get into our riverways, it creates algal blooms and drops in dissolved oxygen."
Water customers in Springfield are probably familiar with algal blooms. Will Sappington knows water quality. He is a lab analyst for Springfield’s City Utilities. We met up with him at Fellows Lake north of Springfield to follow that thread and see the impact of nutrient dumps in city waters and what is being done to address the issue.
“Seasonally, we get nutrient dumps like we've had here in the spring when we get a lot of rain and that rainwater runs off into our lakes and reservoirs," Sappington said. “The nutrients nitrogen and phosphorus are food essentially for harmful algal blooms.” These nutrients are also essential for fertilizing farms, gardens, lawns and golf courses, so there are plenty of them around.
“When we get a mix of nutrients, sunlight and warm temperatures,” Sappington explained, “it's just prime conditions for algal blooms to occur, and that negatively impacts the water quality on the source side, which makes it more difficult to treat on the plant side."
Treating water for public consumption is serious business. It is also complicated and expensive. “We actually can't fiscally treat Fellows Lake,” Sappington said. It is too big. The treatment necessary would cost more than their entire budget for lake treatments. “We want to be fiscally responsible with what we're given, and we understand that the customers are the ones that do end up funding these endeavors, so we want to be good stewards.” So, CU is hoping for a responsible way to manage algal blooms.
“We treat McDaniel twice a year," Sappington said, and getting that down to one treatment is a goal he thinks is attainable and exciting. One of the ways the city hopes to attain that goal is through partnering with the Missouri Department of Conservation to introduce floating artificial wetlands into the lakes Springfield uses for drinking water.
The manmade islands are made of aluminum and a recycled glass aggregate stuffed with plants that help filter nutrients out of water and create homes for insects and animals.
"There's not just one perfect plant," said Frank Nelson, a fisheries biologist with the Missouri Department of Conservation, as we boated around their floating wetland at Fellows.
“Each of these plants, their roots are slightly different. What they do with the nutrients is different," he said. "For example, pickerel weed. Recent research has just shown that pickerel weed is really good to take up nitrogen, whereas the bulrushes do a better job of taking up the phosphorus. Same thing with even some heavy metals. It's nice to have a mix of species because they all do something a little bit different."
It is a multifaceted project. The small island of plants cleans nutrients out of the water, but it also creates an ecosystem.
“We are seeing a diverse community building already on the wetland,” said Kara Tvedt, a wetland ecologist for MDC, “from mayflies, caddisfly larvae getting inside the rocks. We've had water snakes come out of the rocks. They've taken up residence there. They play a vital role. Fish are congregating underneath the wetland in the roots and stuff. We've got pictures of those coming in as the roots spin down in the water that provides habitat, but it's also little zooplankton attached to those roots, and that's what the fish are after. So, it's enhancing that part of the food chain for them. In terms of the bird community, we have seen everything from the Canada geese use them to blue herons, green herons, kingfishers."
It is a small island in a big lake, but these wetlands are having an impact at Fellows and other sites.
“There's never a silver bullet solution,” Nelson said. “You have to come at it from multiple angles. And so this is just one way in which we can kind of target and try to, if nothing else, try to reduce the extremes of algal blooms and, by providing this habitat, the plants and the microbes that are working on the nutrients itself try to reduce the harshness of algal blooms, kind of decouple those really big spikes that are so hazardous to, you know, human and wildlife health.”
The MDC has been piloting this project, using these floating wetlands on different bodies of water and developing a guide for how to use them. They hope to provide a tool to help communities and property owners keep their water clean while providing an attractive and productive ecosystem for native insects and animals.
“Missouri has a lot of manmade reservoirs,” Nelson said, “whether it's your big lakes or even your smaller ponds. We have a lot of open water that doesn't have a lot of wetland plants. And so, this is a way to kind of look at our changed landscape and try to increase and enhance the habitat quality."
Fewer, more intense rains will continue to cause flooding and reshape not just the breadth of our waterways, but their very makeup. The experiment with floating wetlands by MDC and CU is just one way our community is tackling the impacts that flooding and the changing climate have on water in the Ozarks.