 All right. Good afternoon, everybody. My name is Megan Lowry. I am a media officer with the National Academies of Sciences, Engineering and Medicine. Thank you for joining us today for a webinar on the report that was just released this morning titled, The Future of Water Quality in Coeur d'Alene Lake. You can now download a copy of the report and other supporting materials at www.nap.edu and we'll also chat that link out to you. And a recording of this webinar will be available on our website in the coming weeks. For those of you who are not familiar with National Academies of Sciences, Engineering and Medicine, we are non-profit private institutions that provide independent objective analysis and advice to the U.S. to solve complex problems and inform public policy decisions related to science, technology and medicine. For each requested study, panel members are chosen for their expertise and experience and they serve pro bono to carry out the study statement of task. The reports that result from the study represent the consensus view of the entire committee and must undergo external peer review as did this report. Before I introduce the chair of the committee joining us today, I want to go over a few reminders. Please note that this webinar is scheduled to last one hour, so we'll start off with a presentation summarizing the report by the committee and then we'll open it up to any questions you might have after their presentation finishes. And to ask a question, you can just click the Q&A button at the bottom of your screen and you can submit a question at any time during the presentation and we'll just go through them at the end. So with that, I will turn it over to Sam Luloma, chair of the committee and research ecologist at the John Muir Institute of the Environment at the University of California, Davis. Thank you, Megan. Appreciate it very much. As Megan said, I'm Sam Luloma. I'm the chair of the committee appointed by the National Academies of Sciences, Engineering and Medicine to assess the future of water quality in Coeur d'Alene Lake. The committee is composed of 12 members, all of whom are distinguished scientists and experts in various disciplines associated with lake science and relevant to the issues that we see in Coeur d'Alene Lake. Before I begin, I would like to thank the financial sponsors of the study, the Idaho Department of Environmental Quality, Kootenai County, and the U.S. Environmental Protection Agency. And I'd especially like to thank the staffs of those agencies, as well as the staff of the Coeur d'Alene Tribe, the U.S. Geological Survey, and others who have helped us tremendously with presentations and with access to resources, including reports and data. We really appreciate the openness and the professionalism of all the people that were involved in helping us get the materials we need for this work. Well, Coeur d'Alene Lake is an immensely valuable natural asset to Idaho, to the region, and nationally. It's an economic asset in terms of tourism, real estate development. It's aesthetically beautiful. It's a lake with low plant nutrients, sufficient oxygen to provide ecosystem services that include recreation opportunities, fisheries, wildlife, biodiversity, and others. But it also sits at the nexus of a variety of modern and historic issues. It's the homeland of the Coeur d'Alene Tribe from time immemorial. Water quality has affected the cultural, spiritual, subsistence, and recreational benefits that it provides to the tribe and has always provided to the tribe. It was part of the mineral exploitation that occurred throughout the western U.S. from the period of 1850 through the 1960s. The Bunker Hill mining complex is within the watershed of the South Fork of the Coeur d'Alene River. Over that approximately 100-year period, lead, silver, zinc, cadmium, and other metals were extracted at great profit from the lands in the South Fork. But in the process, metal contamination, waste containing a contamination of toxic metals, including lead, zinc, cadmium, arsenic, were spread across the landscape. The landscape was disturbed to a great degree. Floods came every year, washed those wastes downstream into the lower basin of the Coeur d'Alene and ultimately into the Coeur d'Alene Lake, which lies right here. A really interesting aspect of this is there's only 60 kilometers, about 30 miles from the mining complex to the lake. Very little room for dilution, very little time for dilution, so the waste that ended up depositing in the lake were tremendously concentrated, right, out of the mining complex. A fairly unique aspect, in fact, of this problem. In 1983, the Bunker Hill complex was designated a superfund site, and repairing the damage in the watershed began. The lake is not included in the superfund site. The lake management of the lake process, or the lake, I'm sorry, the lake watershed has been left the lake management plant and the local entities, the tribe and the state. On top of the historic mining issues is a much more modern or much more recent issue in modern times, growing populations. Population in Kootenay County has been growing about 2.5% per year, much higher than anywhere else in Idaho. With population growth, growth comes the release of nutrients in wastes and in landscape disturbance. Too much nutrients flowing into a lake, or too many nutrients flowing into a lake, can result in nuisance algal blooms and can result ultimately in growth of phytoplankton in the lake to the point of what we call eutrophication, which just means ultimately that loss of oxygen, bottom waters, and changes in geochemistry that might actually affect the mining issues. Although this is not necessarily the state of the lake at this point in time, growing population is also of concern in this scenic area. Finally, another issue involved is multiple jurisdictions. The superfund site is under the jurisdiction of U.S. Environmental Protection Agency, the Southern Lake under the jurisdiction of the Cardolan tribe, and the Northern Lake under the jurisdiction of the state, making management of the issue much more complex. Sponsors recognize these issues when they set the task for this committee. I have to say that our conclusions about these, as Megan said, are consensus conclusions, but they asked us to evaluate not only water quality in the lake at present, but trends in nutrient metals loading, our changes in the future, and things like temperature precipitation and stream flow might affect those trends. Then some specific questions about summertime inoxia, reducing metal contaminants in the lake, how would that affect the affected nutrients, affected metals in lake sediments, and the relevance of metals to human and ecological health. Let's just take a second and establish a setting, and then I'm going to go on and present seven conclusions from the report. It's a long report. It's 500 pages, so there's a lot in there, but I'm going to kind of condense it down for this short talk into seven conclusions. I'll then talk about the future and how we have evaluated the future and provide some recommendations. So first of all, the setting. Now, this just blows up the map that you saw previously of Cardolan Lake. The major inputs to the lake are the Cardolan River to the east. This is the home of the mining complex and the source of the metal inputs, and the St. Joe River to the south. In the springtime, during high river flows, the waters flow from north to south in the lake. As high discharge recedes, post-fall falls down, which is at the exit of the lake. Post-fall falls down, closes. Hydrodynamics become much more complex, and the outcome of that has been over the century of waste discharge in the lake that metal-contaminated sediments have been spread throughout the deeper waters of the lake. So we have monitoring stations, C6 and SJ1 in the southern lake. Those stations are shallow water stations, and in fact, sediments are much less contaminated than water does not contain the contamination of the rest of the lake. Monitoring sites, C5 is the tribal monitoring station in the southern lake. Monitoring stations, C4 and C1 in the northern lake are places that we use to evaluate data again to look at both water quality metal concentrations and nutrient concentrations. At present, most of the lake is in violation of Idaho and Coeur d'Alene tribe water quality standards. Zinc concentrations in the waters of the lake are 20 to 85 micrograms per liter in summer, and through most months of the year, exceed the 35 microgram per limit lake management plan target for the lake and the state water quality standard. At station C6 and SJ1, as I mentioned before, there's less contamination, and zinc concentrations less than five micrograms per liter. Just for perspective, in almost all the lakes in the United States, zinc concentrations are less than two micrograms per liter, and the vast majority of those zinc concentrations are less than one. So it gives you a sense of still the mining legacy that remains for the lake, although as we'll see, there are encouraging trends. The lake is not currently listed as nutrient impaired. It is in violation of mercury water quality standards based on fish tissue concentrations, and we consider those in the report. We have a section describing those, but I won't go into those further. So what are the trends and inputs to the lake, and how is the lake responding to those trends? First, I'm going to talk about metals, and then I'll talk about nutrients. These slides show on the x-axis the time that data is available from 1993 through 2020. The slide on the left shows lead inputs to the lake. The slide on the right shows zinc inputs to the lake. The red line represents inputs at Harrison, which is at the mouth of the Cardylane River in the lower basin of the Cardylane River. It shows a complicated trend of lead inputs to the lake. Inputs increased between 2000 and 2010, then declined from 2010 to 2020. So for the last decade, lead inputs to the lake have been declining in a statistically significant fashion. The difference between the red line and the green line, the green line represents inputs from the south fork of the Cardylane River. You can see at least on this scale that those inputs are very low from the south fork into the main stem of the Cardylane River. The south fork is where most of the remediation activities have occurred, and so there's been great success in reducing lead inputs during that time. The difference reflects a huge body of particulate lead that's located in the lower basin of the lake. Most of the lead coming into the lake comes in from the lower basin. This contains a massive reservoir of metal waste poised to enter into the lake. The difference between the red line and the blue line represents the difference between the outflow of the lake and the blue line and the inflow of the lake, which is the red line. The difference between the two represents lead that is deposited in the lake. In contrast to lead, zinc inputs are relatively straightforward. They're declining through time. Zinc inputs are primarily from groundwater inputs in the rivers. Entering the zinc enters the rivers through acidic groundwater below the flood plains. There's been a great success in cleaning up some of those inputs from the south fork. The green line shows a consistent downward trend in zinc inputs. Part of this is the success in cleaning up zinc from the central treatment plant. Again, the difference between the two shows that about half the zinc coming into the lake is coming from the flood plains in the lower basin, probably mostly in the form of groundwater. The difference between the red line and the blue line again shows that zinc is still being deposited in the bottom of the lake. Despite the downward trend, there is still deposition of the lake, continuing net deposition of zinc in the bottom of the lake. In other words, more zinc is coming into the lake, but it's going up. Well, how's the lake responding to these inputs? We see again two slides showing lead trends in the lake at the mouth of the Coeur d'Alene River, C4, and zinc trends in the lake at the mouth of the river, C4. The lead trends in the lake reflect the complexity of lead inputs. They show that, although muted to some degree, they show the increased inputs occurring during the up to the 2010 period and the downward trend since 2010. The difference between the red dots and the blue dots in this slide are important. As high discharge recedes in the spring in a deep water lake like this, surface waters warm, bottom waters stay cool, and the lake separates something called stratification. The lake separates into two layers, two separate layers. What we see in the red dots here are the lead concentrations in bottom waters. The blue dots represent lead concentrations in surface waters. You can see bottom waters and surface waters are important, I'm sorry, are both about the same concentration at most times in the lake. What this says is that there probably is very little release of lead from bottom waters in this time when bottom waters are isolating, very little release of lead. It stays with the particles that entered into the lake from the watershed and does not accumulate in bottom waters. Zinc is a slightly different story. Zinc concentrations as in the inputs are progressively downward, but zinc concentrations in bottom waters during the summertime as when the lake stratifies become higher than zinc concentrations in surface waters. That's either because as plants grow in the surface waters and decay and settle to the bottom waters that are releasing their zinc, or because of release from the sediments. We didn't have the data to separate the difference between those two, but it is important to understand that zinc flux is not only from the river, but also comes from the particles that grow in the lake and are already deposited in the lake unlike lead over time. This however does not seem to have greatly slowed the improvement in zinc concentrations in the lake over time. In other words, generally there are downward trends in zinc cadmium and lead in the lake, but we also need to note that in 2020 concentrations are still very high. As you can see zinc concentrations, as I mentioned before, most of them exceed the 36 microgram per liter ambient water quality standard for the standard for the lake as well as for the nation actually for this kind of water body. So concentrations are still high and there is a long way to go in terms of complete full recovery of the lake. What about nutrients? This slide shows phosphorus inputs to the lake between the period of 1995 and 2010. The red line again represents phosphorus inputs to the lake at Harrison. At the mouth of the Cardilane River, the orange line represents phosphorus inputs from the St. Joe River. So while metals are coming primarily or entirely almost from the from the Cardilane basin, phosphorus, the nutrient that we worry about with plant growth is coming from both the St. Joe and the Cardilane River in about equal amounts and discharge from these two rivers is very similar. But you can see over the last decade that there has been a decline in phosphorus inputs. Early studies showed that between 1993 and 2000, around 2012, I think was the end of that study that that study concluded that phosphorus inputs were increasing the lake. Now that we've added more recent data, we can see that there's in recent years a more encouraging decline in phosphorus inputs. The committee we have to have to say the committee is not sure what was driving it's unclear what was driving these phosphorus inputs and these trends in phosphorus inputs. If we're going to try to better understand and control phosphorus inputs and nutrient inputs in the future, it's really important to get a better understanding of these processes that determine these fluctuations that occurred over time. The difference between the red line here and the orange line and the blue line represents both inputs versus output from the lake. Again, phosphorus is still being deposited in the sediments of the lake. There's a net deposition because inputs exceed outputs. How is the lake response? What is the lake response to this change in phosphorus input? This represents total phosphorus concentrations in the lake at C4 near the mouth of the Cardylane River. Again, the difference between the red dots and the blue dots is surface water versus bottom water. There's not a great difference between this, suggesting not a lot of phosphorus release from the bottom. However, between 2010 and 2020, we're seeing what looks like a declining trend in phosphorus concentrations in the lake. For the most recent decade, the data indicate declines in total phosphorus concentration. Now this trend is not statistically significant at C4 between 2010 and 2020, but the data indicate that there is a decline. So good news for phosphorus in the deepest part of the lake, but something to be very aware of is that when nutrient conditions start to deteriorate in a lake, and this is what we've learned from lakes elsewhere, lakes elsewhere, that in shore bays, we begin to see in inshore bays, and the drill just means shallow waters, we begin to see nuisance algor growth, filamentous algae in the beginning signs of beautification. So the inshore bays and shallow waters are not being monitored, that's not unusual, they're challenging to do that, but they're not being monitored in the lake. So those are places where caution needs to be, we need to be careful about monitoring those and looking for signs of increased nuisance algae and beautification of the lake as we move ahead into the future. Here's the same phosphorus concentrations in C5 is the southern part of the lake, in this case the decline in lake concentrations of phosphorus are more obvious, more simplistic, a statistically significant decline, just to show that those declines are occurring. Again, we're not sure what is driving the decline in inputs, but the decline in inputs seems to be driving declines in the lake. The importance of this is that even though population has been growing 2.5% per year, we don't yet see population overwhelming these greater tendencies of phosphorus that are going within the lake. Well, why are we worried about phosphorus in a lake? Partly because I said before, if you get too much algor growth from too much phosphorus input, one result can be depletion of oxygen in bottom water and that can be harmful to the ecosystem of the lake, as well as have influences on what happens in the sediments where all that metal is deposited. This just shows two, for two places, Station C4 at the mouth of the Coeur d'Alene river and Station C5 in the southern part, the deep water southern part of the lake. What we see here for each dot is the average from 1995 to 2021 for each month across all those years, the average concentration of dissolved oxygen within the lake. This is dissolved oxygen milligrams per liter, the red represents the surface water, blue represents deep water, and we can see as is not unusual in a deep water lake like this, after stratification occurs as we get into the summer, we begin to see a little bit of erosion of oxygen in the bottom water as plants growing in the surface water all to the bottom and begin to decay. Excuse me. Same thing happens at C5. Again, this is not unusual in lakes. When it becomes problematic is when if those milligrams per liter of oxygen should reach this orange line down here, which is what's called hypoxia, between two and four milligrams per liter, some organisms in a lake will be affected, will be adversely affected. And if we reach the point of anoxia, which is zero oxygen in a lake, both the geochemistry, the lake sediment changes, and many organisms are affected by the lack of oxygen. So right now, in the deeper part of the lake, we do not see that degree of oxygen depletion within the sites in the deeper water places at C6, where there is shallow water, those are the place that is not contaminated with metal. We do see anoxia all the way down to anoxia happen for a month or sometimes two months as we get into the late summer. So the question is, is anoxia getting, or is I'm sorry, is the depletion of oxygen getting any worse as time has gone on? So for each one of these points, the committee used a sophisticated statistical approach called seasonal candle analysis in which for each one of these points trends were analyzed between 1995 and 2021. The next slide is a little bit complicated, but I'm going to show it to you anyway. It just shows the slope of the relationship for February for each month. In this case, let's just look at, let's go over here and look at September, the slope of the relationship between over time in terms of concentrations of oxygen in the deep waters of the lake at C1, C4, C5, and C6. When the number represents the slope of the relationship, when a box is clear, it represents a trend that is not statistically significant. When a box is slightly colored in in blue, it means a slight upward trend, when it's dark blue, I'm sorry, it means a statistically significant upward trend. So we can see that through the summer months, which are most important from June through October, almost all the boxes are clear or blue for the deep water sections of the lake, C1, C4, and C5. This just means there has been no trend over time, or perhaps even an upward trend over time in oxygen concentrations in the bottom water. Again, this is good news. Trend analysis do not show depletion of oxygen over time. The biggest concern that we would have in terms of unification. We do see at C6 two negative slopes, one of them not significant, one of them slightly significant, but very shallow slope. So there might be some change at C6 over time in terms of worsening conditions, but it's extremely slow if there is. So in general, we conclude that there is not worsening, and there are not worsening conditions at present in terms of oxygen depletion. Well, one of the interesting questions has to do with the interaction between mining waste inputs and nutrient input in phytoplankton growth. A hypothesis raised in studies done in the 1990s and the early 2000 by the US Geological Survey, that study showed that zinc at the concentrations that occurred in the lake at that time, which are higher than they are now, of course, that zinc at those concentrations could inhibit the growth of some kinds of phytoplankton. And so the question was raised whether the high concentrations of zinc in the lake were holding down algal production and perhaps preventing the eutrophication or the worsening of algal conditions in the lake. And so if we clean up the zinc, does the result going to be making it more difficult to control the response to nutrients? Kind of an interaction of these two problems. And when we first looked at this line, the gold triangles here represent a global set of lakes. And it just shows the relationship, the dotted line here shows the relationship that we know lake scientists know from looking at many different lakes like this, that in general, total phosphorus controls the amount of plant growth, which is on the y-axis represented by chlorophyll over time. But when we looked at the blue dots, the black dots, and the white dots, these are all data from Lake Coeur d'Alene annual summer means, we can see they pretty much all fall below that global line. That's suggested to us, well, maybe perhaps something is inhibiting production of the algal in this lake and perhaps at zinc. So we used a bunch of different techniques to look at this, but the most obvious one was that the fact that at C6 and SJ1, two stations with low zinc concentrations in the water column, we still saw what appeared to be suppression of the phytoplankton growth compared to the global line. So that suggested, well, maybe it's something else other than zinc. We then used several other different techniques, the statistical technique, multiple regression analysis. We used something called limiting factor analysis. We looked at, in the report, we talked about several other things that are involved in the response of phytoplankton to changing concentrations, and it talks in such a thing. Although there's still, the data remains still somewhat equivocal, our general conclusion was that the weight of evidence suggests that zinc suppression does not seem to be the reason that it does not seem to be holding down zinc concentrations in the lake. And indeed, at these phosphorus concentrations, if there was a suppression to below the line, if these concentrations rose to the line, it wouldn't make the lake eutrophied. It would make it a kind of middle-level condition called mesotrophic. But we do think that we do encourage other analyses with other data sets. We think more monitoring as time as zinc concentrations come down, keeping track of this is really important and suggests some further experiments that could further clarify this very important hypothesis. What about these concentrations of metals that are deposited in the bottom of the lake? Immense concentrations of metal were deposited during and still are being deposited as a result of the mine waste inputs. The slide below shows the degree to which and the severity of the metal contamination in the sediments. The brown line here in the slide shows the something called sediment quality criteria, which are the range of concentrations of cadmium, lead, and zinc that are toxic in hundreds of experiments that have been conducted with sediments from all over the world to kind of get an idea of the range of under different sediment conditions concentrations. For example, lead that would cause toxicity, 110 to 530 micrograms per liter. Usually toxicity starts to occur somewhere in there. My apologies again. The lead concentrations in the sediments of Lake Cardelaine are 1,800 to 38 micrograms per gram compared to 110 to 530 toxic range. You can see tremendously high concentrations of lead in the sediments, at least in experiments. Those cause toxicity to the organisms that live within the sediments. One of our concerns and we review the few studies that have been done on lead in the toxicity to bottom organisms living in the lake, but one of our concerns has to do with the food web that depends upon the bottom of the lake. There has not been a lot of study of the benthic food web within the lake nor of food webs in general. That's one of the things that we encourage as further study along those lines. In terms of geochemistry, we use geochemical models and also analysis of the few sediment cores that are available from the lake. To come to the conclusion that inoxia in the lake sediments should it occur and inoxia is not occurring anywhere with contaminated sediments right now, at least in the deep waters that are being monitored, should it occur that the release of arsenic and phosphorus are the greatest risks. Again, that's not occurring in the deep water, but that's something that should be kept in mind even in shallow water, for example, should nuisance algal blooms result. If that turns out to be a drinking water location, then potential release of arsenic and phosphorus from those sediments must be considered again. In some studies, there was a concern about release of zinc and lead. Should anoxia occur in bottom sediments, we concluded based on the models that's not likely. However, the lower pH, the lower acidity in bottom waters, which occurs when respiration occurs in those isolated bottom waters, that will release zinc. And so some of the higher zinc we see in bottom waters could be result of the result of slightly acidic conditions releasing zinc from settling particles or releasing zinc from the surface sediments. So what about the future? We can say that Cardylane Lake is beginning to recover from a century of mining waste inputs, but we did some projections of just projecting current trends, some of the trends I showed you before, into the future. And we found that full recovery, if we just project current trends, would take one to multiple decades in some places, even as much as a century, depending upon the location and depth of the water. So while their progress has been made in terms of the mining waste input, there's no question about it. Progress has been impressive. In fact, there's still a long way to go in terms of a full recovery of the lake. This is a problem that took a century to develop. It's a complicated problem and it will take time to clear it up. But the future is not necessarily going to be a projection of the past. In fact, the most, the thing that we can expect most about the future, or as most uncertain or most certain about the future probably, is that there will be surprises. And some of the things that we do see coming possibly with changing climate and the changing setting could slow or reverse the progress that has been made in the lake. Committee considered four aspects of the future in a qualitative way that we think could affect the existing trends that we talked about before. Increasing lake temperature, forward shift in the timing of river flow into the lake, that just means earlier inflows and an earlier end to inflows. An increase in the magnitude and frequency of high flow events. Again, as we know, severe events are increasing in many locations. Fires and population growth. One of the examples of a change that is occurring within the lake that we've identified from past trends is that air temperatures are warming by as much as 2.5 to 3 degrees centigrade. It's projected air temperatures will warm on average by 2050. Surface water temperatures at C4 are following this and are increasing. The trends are increasing through time and most significantly in August. There has been a decrease in snow water equivalent in the past 30 years associated with these increasing temperatures. That could all affect inputs of metals and nutrients to the lake. Precipitation flow and flood trends are more ambiguous in the Carta Lane region. We don't see significant trends of those in the past, but we do know from climate projections for the Pacific Northwest as a whole, for example, that extreme precipitation events could become 5 to 34 percent more intense by 2080. We can't discount the possibility that those kinds of trends are going to move into the Carta Lane basin eventually, but we don't see those trends right now. The future will be challenging. There's no question about that. We can't project trends from the past with much confidence. These trends that are happening are these changes in climate that are happening throughout the country have their implications for the Carta Lane basin. Being aware of that uncertain future is a very important part of successfully coping with the future. So how do we prepare for an uncertain future? These are recommendations from the committee. First of all, one of the things we recommend is better understanding the processes that control nutrient flux, flux from the sediment within the lake, and cycling within the lake of metals and nutrients. We have a general understanding of some of these processes, but important details are missing, and understanding those processes is really key to being able to anticipate when some of these changes in climate are upon us, being able to anticipate how they might affect the lake. We suggest increasing frequency and locations where inputs to the lake are being monitored. We suggest expanding lake monitoring to selected bays and inshore locations. Better understanding food webs the lake so that we understand metal effects and the interaction of metal effects and production in the lake, and also in ecosystem services. To do that, I think we need to better understand zooplankton fisheries and the food web connected to the bottom of the lake. As communities grow, waste inputs to a lake can increase greatly. One of the factors that has been most successful in dealing with these in the past has been expanding advanced wastewater treatment, both to the number of homes that are subject to such treatment and to the capabilities of the treatment facilities. Finally, I think a really important recommendation is the crucial data sets and synthesis, especially of those data sets need to be made widely available. So in summary, inputs of nutrients and metals to the lake, especially metals to the lake, are declining. Nutrients seem to be declining and the lake is responding. CDA or Cartoline Lake is beginning to recover from the effects of mining and so far is maintaining against the pressures of population growth. The caution about the future is certainly warranted. There are uncertainties about the future. The best preparation for an uncertain future is fortification and expansion of monitoring to provide early warning of deteriorating conditions and regular synthesis of data and targeted studies and all coordinated amongst interest groups and jurisdictions and then applied to managing the lake. So that's it for our report and we'll be glad to answer questions. Thank you very much for your attention. All right. Well, thank you so much for that presentation. As Sam said, we're going to open up to questions now. So as a reminder to ask a question, just click the Q&A button at the bottom of your screen and type it in there. And we also have a few more members of the committee joining us for the Q&A. So I will ask them to turn on their video if they wish and then introduce themselves just the first time they answer a question so the audience knows who you are. Okay. Our first question today is the phosphorus levels that you presented were largely measured at C5. So they represent trends in the Coeur d'Alene River. What do you see in the northern parts of the lake where the water is more mixed and potentially more affected by population growth? Well, I think I presented inputs from both rivers and I'm not clear from the question. Really, I presented inputs from both the St. Joe River and the Coeur d'Alene River both from both inputs of both where are pretty equal. Maybe in terms of inputs, Bob Hirsch can help us understand the nature of the trends in the two locations which I think is the question. Yeah. This I'm Bob Hirsch, a member of the committee. Both the Coeur d'Alene River and the St. Joe River have been showing declines over about the last decade in terms of their phosphorus inputs. We really, they're really at this point are no data on inputs from the areas that are very near the shores of the lake. And that means that many of the areas that are undergoing some population growth are not monitored. Since we started our study, there has been a monitoring program that has begun and we think that's a great move forward. But it's going to be very challenging to interpret those data and try to understand what the effects of the increased development are because they're very diffuse as opposed to something we can measure on the larger rivers that are easier to get a handle on. Great. Well, thank you both very much for addressing that. Our next question is, you mentioned that shallow waters and bays aren't being monitored and that is challenging to do. How confident is the committee in the overall lake health and progress considering we aren't monitoring the waters where eutrophication is more likely? What would it take to put shallow water monitoring in place? I think the committee is pretty confident about our analysis of the deeper water stations. The shallow water stations are of course more of a challenge because there are many bays and many inlets. A great deal of shallow water to look at. And I don't think that it's, I think the shallow waters are where we would see the early signs. So that's an early warning indicator. But maybe Mike Brett can help us understand a little more about that question if Mike or Jim, whichever one I'd say, let's start with Mike. Okay. But yeah, I think the main issue is it would be time and money to monitor those shallow areas because there are many of them and each one is different. It would just require a fairly substantial increase in sampling effort. But there are indications that some lakes in the West United States are having more problems with benthic algal blooms and that could be the type of response that you might expect if there's more nutrients coming in from people's septic systems and those more sheltered areas, those more constrained areas. Jim, do you want to say something? No, I don't have anything beyond that. Yeah, it's groundwater inputs and if there's septic leachate would cause those kind of problems or localized nutrient losses coming in and small tributaries that aren't monitored. Just very challenging to get after those kind of processes. And because there are so many of them, Rob, Anir also had a comment. Rob, did you have something you wanted to add? I just wanted to say we have another member of our committee who's not here today works as responsible for a lot of monitoring in Lake Tahoe and I think Tahoe is a great example to use as another very high quality lake in the West which has seen a lot of population growth and they carry out a standard regular monitoring program of those bays and side areas to look for some of these kind of problems, the development of these kind of problems in addition to doing the kind of monitoring out in the middle of the lake as well as monitoring the rivers coming in. So there's good examples of people who have sort of paved the way for how to do those kind of monitoring programs. So I think they're not overwhelmingly difficult. Any additional comment, Rob? You were going to say something about it. Yeah, I was just going to say that I agree with all the comments. I think it would be really instructive to have some of these in-bainment areas sampled. It would be a good indicator of where perhaps there's increases in nutrient loading that need to be reduced. It might help drive on the watershed side of things if they have that understanding. Thank you. Thanks. Great, thank you all. What impact might increased flooding and river flows have on the inflow of toxins from the quarterly basin as climate changes? You mentioned it could slow or reverse progress. What might that look like? Well, I think the biggest risk comes with increased floods because we know that particulate material which contains lead and phosphorus as well as some zinc, we see big pulses come in in the spring with floods. So I think that's one of the big things. Bob, any further thoughts about that? Yeah, just in general, I think we know that there's a very nonlinear relationship between the amount of both of phosphorus and of lead that comes in with high flows. That is to say, a modest increase in flow can result in a large increase in these particularly phosphorus and lead because those are the two contaminants of interest that are very much attached to sediment and sediment moves at these very higher flows. We have a lot of uncertainty, however, about what the future of high flows may be. And it's really a couple of contrasting trends that are going on. On the one hand, many of the largest floods in the history of this basin have been from what we call rain on snow events where there's a large snowpack, a relatively warm storm. And so you get all that runoff occurring and those have carried huge amounts of contaminants into the lake. What we're seeing now is we have less snowpack and so that decreases the tendency towards very large rain on snow events. On the flip side, we all know that as the climate changes, we are getting more intense precipitation as time progresses, as the greenhouse effect increases. So we may get bigger storms, but they wouldn't be coming on top of as much snow as we saw. So we can construct arguments for a growing problem of this kind or perhaps a decreasing problem we don't know. And I think it really points to the need for monitoring particularly at the upstream and downstream end of the lower basin. That is below the superfund site and above the lake. It's a very dynamic area and things are going to continue to change enormously in the coming decades and we need to particularly be able to monitor accurately during these high flow events to understand those dynamics and how they're changing over time. Thank you. Thank you. Can you provide further explanation as to what specific recommendations for advanced wastewater treatment should be implemented? Well, actually solutions are outside of the scope of our committee. So the specifics of these things I think are something that we did not spend a lot of time on. This is again, our scope is limited to the future and but maybe Mike can provide some specifics about what we were thinking in general about this. Yeah, what I could say is that they have instituted advanced phosphorus removal in all the wastewater treatment plants that are downstream of the lake in the Spokane River basin and that region has some of the best advanced phosphorus removal wastewater treatment plants in the entire country. And you can get the phosphorus concentrations and the phosphorus loading from the wastewater treatment plants down by a factor of 10 with fairly moderate intervention using biological phosphorus removal. And you can go quite a bit lower than that using chemical phosphorus removal with either aluminum or iron salts. And like I say, that's been done very successfully. I think there is one system already in the Port Elaine basin that is using advanced phosphorus removal. But that is potentially a fairly important source of phosphorus because the phosphorus coming out of wastewater treatment plants tends to be much more bioavailable than the phosphorus is transported during peak storm events when much of it is associated with sediments and maybe in mineral complexes. So that's I think low hanging fruit in terms of protecting the long term health of the lake would be to institute advanced phosphorus removal wherever possible. Great, thank you. Our next question is, Sam mentioned that it might take a century or a long time to clean up the lake. What does that mean? Is that through natural attenuation or some method of cleanup? Well, I think the trends that we're looking at in the past were heavily influenced by the remediation activities. Remediation has been successful in the in the Superfund site, has clearly been successful in reducing zinc and lead inputs. It's just the problem is massive. It took 100 years to accumulate this problem throughout the flood plain. There are great challenges in remediating the lower basin. There are huge deposits of metals in the bottom of the river. And so I think it just is it would I think if it were left to natural processes, there would be a cleanup of some sort where that's been studied. It literally takes centuries those natural processes to occur. But we don't know. I mean, there are certain certain there are uncertainties about this. On the other hand, persistence with remediation is really important. And I think that's that's always a challenge. But persistence with continuing this remediation, even though there's a long time ahead to do it, is very important. Maybe Lynn, do you have any more comments about the past and the remediation? And what could be done? Yeah, sorry, I am at a wastewater treatment plant today. But so I would I would concur exactly with what Sam said. And I think I think Bob would agree that you know, the remediation has done a significant amount of work to slow the release of metals into the lake. But I'd also say that there's still issues down in the lower portion of the river. And I think there's still work on going there that needs to be continued. And it needs to keep going. I think that as we, you know, with increased monitoring, both in those regions, but also in the sediments to look at what's happening within the sediments, are those changing? And what are the geochemical conditions in there, such as anoxia and changes in pH, as Sam mentioned earlier, all those things will be important. But the, you know, the just the massive contamination that's been there will take time. And so I would just agree that remediation efforts are key to continued effort, but it will still take time for the sediments in the lake to, you know, to well, to be covered or essentially not be exposed to the like water bottles. Yeah, it took 100 years of irresponsible waste discharge. That's not that's no local criticism. It's just what happened across the waste, across the West. I mean, and so I think we can't expect to clean this up in a couple of decades. It's going to take a considerable time and considerable effort to do this, Bob. Sam, if I could just add to that, when we talk about remediation in the process, and particularly with respect to lead, the focus in the future really needs to be not so much on the area that was mined because we've seen that the what's coming out of the mined area has decreased enormously. And what's going into the lake, the amount that's coming in from the mined area is really miniscule now compared to what's coming out. So the lower court of lane watershed and particularly the floodplain and the channel are a very large source, particularly of lead, but also phosphorus and zinc and cadmium. And right now there's no engineering, significant engineering action being taken there. And it's going to be is a complicated process to come up with what those solutions are. But the focus for further improvement will have to be quite strongly on this lower portion of the basin where they've really had this, I think a great success, really upstream on the South Fork. Rob, addition to that. Yeah, I was just going to echo those comments. This is as as Bob was saying earlier, this is the really dynamic area. And this is the area that tends to back up in the summertime when they raise the water level in the lake. And then it tends to flush out when they lower the water level in the fall. So this is a very dynamic area. And as Bob was saying, the, you know, the phosphorus and the lead attached to these sediment particles are becoming more highly mobilized in this area. So that's where the focus of effort should be. Everything that we look at suggests that the lower basin is critical to is critical to recovery. And it's the most challenging, of course, as well. So there are tremendous challenges into resolving this as as US EPA has pointed out, but that means persistence is essential. Megan. Thanks. Do you have any thoughts on why the change in the lake's phosphorus levels are lagging the river declines? The CDA river decline started in 2010, the same June 2005, but the lake didn't start declining until after 2018. We did. We don't go into that in detail. I'll let Mike and Jim address that here in a minute. But I do think that, you know, seeing a lag in a complicated system like this before before the response is reaches full scale is is not actually too surprising. But Mike and Jim are the limnology experts here. So maybe they can make, Jim, you want to take a shot at what you might think be involved here? Well, the lake does have a short residence time, which suggests that, you know, it's going to respond quickly to changes in inputs. On the other hand, it's not instantaneous either. So it's not surprising that it takes a few years to respond to a changing load. Then there's internal processes as well that are going to buffer those changes. You know, if there's lower amounts of phosphorus building up on surface sediments, and then they'll slowly stop returning so much phosphorus into the water column by whatever processes are underway, they're also going to slow things down. So it's not surprising to me to see the lag. It's not that long. So it didn't it didn't necessarily surprise me, but because of the size of the system and the inherent times timescales you're likely to have any other comments? Yeah, I could. Bob, do you want to go first? Go ahead, Mike. Oh, what I would say too is that when you're comparing the inputs to the lake concentration trends, one important distinction is that the inputs are very dominated by the particulate fraction. And the particulate fraction doesn't tend to persist in the water column very much because it settles out very easily. And so the lake is what's in the water column is dominated by dissolved phosphorus and phosphorus sits in biotic material like algae and other sorts of plankton. So there's somewhat different fractions. You could get a big pulse of particulate phosphorus into the lake with a storm event, but that might not obviously manifest as a big change in concentration in the lake because that particulate phosphorus has a tendency to be captured by the sediments pretty quickly. So there's a bit of a difference there. I would just add that the rising phosphorus in the previous decade of what was coming into the lake and what was present in the lake, followed by the decline in the committee, we spent a lot of time thinking about and trying to understand what was going on and what we're driving those changes. And we have a variety of hot prophecies that are described in the report, but we still think there's a tremendous amount of uncertainty as to why these things have been happening. Both the rises early on and the declines, and the fact that the declines seem to be true both in the mined parts of the watershed, mined and remediated parts of the watershed, and in other parts that were not heavily mined and did not subject to remediation. And I think the going forward and Sam talked about synthesis and the need for ongoing improvement of understanding is any efforts to control phosphorus into the future are really going to depend on a much improved understanding of what's driving phosphorus in this system. It may have to do with forest practices. It may have something to do with climate. It may have to do with the former air pollution effects of the mining activity having gone away. There's a whole lot of possibilities. And we frankly are were fairly stumped as to the causes of the patterns that we saw in phosphorus. And Lynn, you had to come in. Yeah, I was just going to mention that this is a really important area where monitoring continued, but not just monitoring, but monitoring the speciation of phosphorus. So what form is the phosphorus in? Is it in this particulate? Is it organic? Is it orthophosphate? And I think that's also will help to unravel some of this lack of understanding or complexity. Thanks. So I think we have time for probably about two more questions. The first I'll ask is all note from the University of Idaho Bay Watchers. They say we have been measuring multiple parameters in the lake for the last five years. The major change we have seen at Beauty Bay and Blue Creek Bay is an acid pH in the lower depths about five meters above the bottom and below. We have measured pH is in 6.6 and 6.7 ranges. Is this enough to increase dissolution of heavy metal? I'll part with the rest of this and Lynn could be prepared to help too. But small changes in pH have a large influence on zinc, how tightly zinc sticks to particulate materials. And so changes in the 6 to 7 period, 6 to 7 range could be very important, specifically for zinc, less so for lead. But Lynn, you did some of the geochemical modeling. Maybe you can expand on that. Yeah, that's exactly right, Sam. What we noted was that, you know, once we get into this pH 6 range in that area, we will, you would expect to see some release of zinc due to its option to the solid. So most of the sediment, there's a large fraction of iron in those sediments. And the iron hydroxides that are there, that mineral phase that's there, is really good at absorbing zinc, lead, and even arsenic. And so you have a lot of association of these metals with that iron. Lead absorbs much more strongly to the iron than zinc. So with the small changes in pH that you're looking at, we would not expect lead to release but zinc could. And I think we discussed that and show sort of a range of pH where we see that, you know, predict that that could be happening. I think one other aspect, this is really a neat idea for the Baywatch Group to be monitoring pH that's really insightful. Because over time, if we do get more eutrophication, that means more decay or more respiration of decaying plant material than perhaps a change in pH. So monitoring this at sufficient intervals and over time is a good idea in bottom waters. It's a simple measure and it could be very important to keep track of. So that's an important question. Great. And it looks like we have time for probably one more question today. We've got about two minutes left. And that is, you know, you've mentioned quite a few of these already during your presentation and during the Q&A. But what opportunities do you think are presented by improving or changing the way that we monitor the lake? What more can we learn and what can do to benefit the lakes community? Well, monitoring in general, I mean, monitoring has the benefit of keeping track of the past and that helps to anticipate the future, of course. But monitoring key metrics is probably again, the most effective way of anticipating surprises or recognizing surprises when they occur and reacting to them. And the future is going to be full of surprises. So I think monitoring is, and process studies are really important too. A good scientific base includes both process studies and monitoring. But I think we've suggested some specifics. But I'd be curious what other people think about this general question about monitoring. I'll take part of that. As we've mentioned several times, this reach of the river between the bottom end of the South Fork and the river where it enters the lake around Harrison is very dynamic. And monitoring of the channel itself, that is to say, what is the shape and slope and size of that channel could be very important. And there's no systematic effort underway to continually describe that and particularly how it changes when a big high flow event occurs. So that would be an important area. Another is to be able to try to use some real-time capabilities. And again, since sediment is so important to what's happening is the measurement of turbidity, which is simply the ability of light to pass through the water. One can set up instruments and measure that every few minutes and using that to learn a lot about the amounts and timing of sediment movement. So those are some innovations that could come and really help the understanding through improved monitoring. Mike? I just wanted to reinforce what Lynn's already said about improved monitoring of the forms of phosphorus that are being loaded to the lake. There's a lot of uncertainty as far as that is concerned and there's a lot of variability in the potential impact of different phosphorus fractions on eutrophication in the lake. And so that's an area where we could greatly improve our understanding with probably a modest amount of effort. And I would also like to emphasize one of our most important conclusions and that is data monitoring is data collection. Data isn't useful unless synthesis occurs. And so synthesis and collaboration and synthesis are the real secret and challenging both institutional and physical and biological environment like this. So I think that's a big emphasis of something we discussed a lot as a committee is the importance of regular collaborative synthesis of what data you're collecting. Let me and just let me add to that. If you look at other water bodies where there are major efforts to make improvements and I'm particularly familiar with the Chesapeake Bay watershed. The data sets there every two years a complete reanalysis of the trends of all the major things moving down the river. Those analyses are run, they're made public and they're discussed in terms of trying to understand what's going on and the trends within the water body itself. This is an ever-changing system and one needs to repetitively as in every couple of years relook at the numbers and say what is there a new story that's being told here? You really have to stay on top of it. Okay, great. Well, thank you all so much for those closing thoughts. Unfortunately, we're out of time for questions today. I'll note a recording of this session will be available on our website in the coming weeks so you'll be able to see it there and again the full report and a few other communications resources are available for free and then full on our website at www.nap.edu. Once you exit this webinar, you'll be redirected to that page. So with that, I'd like to thank our speakers and thank you all again for joining us today.