Восстановление водных ресурсов: борьба с вредоносными водорослями в бассейне реки Херон

About Ric Lawson Ric is primarily responsible for coordinating the development and implementation of several watershed management plans in the upper, middle and lower sections of the watershed. He also runs the Chemistry and Flow Program, and is facilitating Green Infrastructure planning for stormwater. Ric earned joint Masters Degrees in Environmental Management and Public Policy at Duke University. He joined HRWC in 2006 and lives in the Allens Creekshed. Resources Huron River Watershed Council (HWRC) Washtenaw County Health Department: Harmful Algal Blooms Transcription Rebekah Warren: This is 891 WEMU. Summer is when many of us head to the Huron River or our local lakes to kayak, fish, paddleboard, or simply cool off. But warmer temperatures and increasingly intense rainstorms are creating conditions that allow harmful cyanobacteria, often called harmful algal blooms, to flourish. These blooms threaten recreation, wildlife, drinking water, and public health. They're also becoming more common as our climate changes. Joining us today is Ric Lawson, Director of Programs at the Huron River Watershed Council. Ric, welcome back to Issues of the Environment! Ric Lawson: Glad to be here, Rebekah! Rebekah Warren: We just experienced an extended stretch of extreme heat across this county in southeast Michigan. As someone who monitors the health of the watershed, what does a heat wave like that do to our Huron River system, and what should local residents be paying attention to now? Ric Lawson: Yeah, thanks! Yeah, that was quite a heat wave we had! And I would expect that these are going to become more common over the coming years with the effects of climate change, at least that's what's projected in the models. How that affects the water is it's a combination really of the rainfall and the heat. So, if we have heat and if we had hot, dry conditions, that's the recipe for algae blooms, those cyanobacteria blooms that you referenced in the intro. And what happens is the water starts to stagnate in lakes, it can separate, and then, a whole bunch of phosphorus can come out of the sediments or nutrients can come out of the sediments. And then the algae just go crazy and eat that all up. And they bloom like crazy. And then, you get this sort of really, really green water. And then, sometimes, you will also get the cyanobacteria along with it. Rebekah Warren: One of the things that surprised me in doing research for our conversation today was that officials advise people not to boil water that's contaminated with these cyanotoxins. Why is that? And what does that tell us about the serious nature of these toxins? Ric Lawson: Yeah. So, the cyanobacteria contain the toxins within them, so boiling the water, while it will kill the bacteria itself, it won't remove the toxins from the water. So, that's why they don't recommend it. That's not a treatment mechanism for reducing the water. Plus, drinking water is monitored and treated. If you're on a city or municipal water, and most everybody else if you're not on municipal water, will be on deep water wells, which are not exposed to cyanobacteria. So, there shouldn't be a risk there. We're really talking about a surface water contact risk, so think about if you fall in and you're canoeing or you go swimming or any of those kinds of body contact risks. Rebekah Warren: I feel like a lot of people hear the phrase harmful algae blooms and they imagine ponds covered in green slime. But you've talked a lot here about what might be happening actually below the surface. What more can you tell us about internal loading and what makes solving this problem so challenging? Ric Lawson: It is challenging, Rebekah. Yeah, it does start long before we have the blooms. So, the blooms, as I mentioned before, are caused by elevated nutrients in the in the waters. And this is coming from upstream of any inputs to lakes. And where we see the kind of the biggest, broadest problems are in two of our impoundments: Ford Lake and Belleville Lake, which are really close to where your studios are. And those are impoundments formed by dams on the Huron River. And so, those nutrients have come into the lake in two ways. They've come from upstream in the watershed from all the things that we do on the surface of the land: fertilizer application, the leaves that fall from the trees in the fall, soil that gets eroded out from places, and then agricultural inputs as well. Those are all direct sources of nutrients into the lakes. But the lakes also have nutrients in their sediments at the bottom and inside the lake, internal to the lake and bottom of the lake. You know, phosphorus, or soils in Michigan, in southeast Michigan in particular, are high in nutrients. They're high in phosphorus already. So, when you impound the river, you're already starting from a pretty high load of nutrients into the river. And then, you add the runoff from upstream, and it just exacerbates the situation. So, over years, since these improvements were formed, we've been adding all those nutrients. And then, they can be released. They're stored in the sediments, and they can released from the sediments when we have the conditions that drive that process. And that's called "internal lake loading," as opposed to external loading, which is coming from upstream in the watershed. Rebekah Warren: This is Issues of the Environment on 89.1 WEMU. I'm Rebekah Warren. And today, we're talking with Ric Lawson of the Huron River Watershed Council about harmful algae blooms, water quality, and protecting one of Southeast Michigan's most valuable natural resources. Ric, communities throughout the watershed have worked hard to reduce that external loading, the phosphorus entering the rivers and lakes through fertilizer restrictions and better stormwater management. But we do continue to see these algae blooms, like you said, in places such as Ford Lake and Belleville Lake. Some of it sounds like our communities today might still be dealing with pollution that settled into lake sediments decade ago. Is that a fair way to think about it? Ric Lawson: Yeah, it is. While we have had some significant reductions in our data, we have data that we collect from upstream waters in the river every year over the summer months. And we're seeing significant declines in those sources coming into those impoundments. But unfortunately, all that has come before that, since the lakes have been in existence, has been stored in the lake. It doesn't go away. So, it is fair to say that what we're seeing in the blooms today is mostly coming from sentiments at the bottom of the lake. But I should point out that we still have, coming to the lakes, were still above the targets that we're seeking to reach. But the policies and the practices that we have in place from fertilizer ordinances to millions of dollars of investments by wastewater treatment plants has significantly reduced those inputs. Rebekah Warren: Are there engineering solutions that can reduce that legacy phosphorus and legacy pollution that we're dealing with? Or is this something that only nature can gradually correct over time? Ric Lawson: Yeah, it is both. It certainly is a time issue. The new sediments that get added to the lakes, if they're lower in nutrients, then they'll cover over the existing, higher nutrients in the sediment currently today. But there are also some engineering solutions that can be effective and that are being used in at least one of the lakes. So, at Ford Lake, Ford Lake has a dam that has the ability to open up gates at the bottom of the dam, rather than just at the top. Whereas, Belleville Lake does not have that capacity. And what we have learned over time is that what happens with the mechanism is that when we have those conditions when it's hot and dry and the lake separates into two different levels, the dissolved oxygen in the bottom level of the water drops to zero. And then, there's a chemical process that occurs that creates the release of nutrients, mostly phosphorus, from those bottom sediments that causes the algae bloom. And so, what they have found at Ford Lake, when they see them starting to fall toward zero, they open up those bottom gates, and that mixes the lake water again and causes the oxygen level to go back up and keeps those sediments locked into place. Rebekah Warren: Ric, many of us think about lawn fertilizer when we talk about phosphorus pollution. There's also some studies that show that failing septic systems can have an impact, particularly locally. What can you share with our listeners about what impact septic systems have on algae blooms? Ric Lawson: Septic systems are another source of nutrients. Obviously, that's coming from human waste. It's high in nutrients. When septic systems are not properly maintained and cleaned out periodically, those systems can be overrun. And so, they start to fail. And then, those nutrients are then entering into our surface waters. And then, they will go downstream. So, they come through the groundwater and then into surface waters. And they go downstream into the lake. So, that is another source of nutrients that needs to be controlled. Rebekah Warren: Ric, thank you so much for joining us today and for helping us better understand both the science behind harmful algal blooms and practical steps communities and individuals can take to protect the Huron River Watershed! For more information on our conversation today, visit our website at WEMU.org. Issues of the Environment is produced in partnership with the Office of the Washtenaw County Water Resources Commissioner, and you hear it here every Wednesday. I'm Rebekah Warren, and this is your community NPR Station, 89.1 WEMU, Ypsilanti. Non-commercial, fact based reporting is made possible by your financial support. Make your donation to WEMU today to keep your community NPR station thriving. Like 89.1 WEMU on Facebook and follow us on X (Twitter) Contact WEMU News at 734.487.3363 or email us at [email protected]