We’re observing a fundamental shift in seasonal precipitation patterns in Washtenaw County. Winters are increasingly characterized by rainfall rather than snowfall, even during colder periods. This shift reduces snowpack and leads to more rain-on-frozen-ground events, which significantly increases surface runoff and flash flooding. The reduced snowmelt also compromises springtime groundwater recharge and alters streamflow timing, with cascading impacts on infrastructure and ecological systems. This pattern has emerged more prominently over the past two decades and was particularly evident in the winter of 2024–2025.

Although total annual precipitation has increased, the distribution and timing of that precipitation are becoming less beneficial. Rainfall is now concentrated in fewer but more intense events, particularly in winter and spring. Meanwhile, summers are trending hotter and drier, increasing evapotranspiration and reducing soil moisture during critical growing periods. This seasonal imbalance complicates water management and presents substantial challenges for local agriculture.

Existing stormwater infrastructure across the county, particularly in urban areas like Ann Arbor and Ypsilanti, is not equipped to manage today’s precipitation extremes. Systems designed for mid-20th-century storm profiles are now frequently overwhelmed by high-intensity rainfall events, leading to localized flooding, sewer backups, and accelerated degradation of roads and bridges. These outcomes reflect a growing infrastructure resilience gap that demands both immediate and long-term investment.

Ecological systems in the region are also being disrupted. Sensitive wetland environments and tributaries, such as Paint Creek and Fleming Creek, are experiencing increased erosion, altered hydrology, and changes in seasonal flood patterns. These shifts undermine biodiversity, disrupt aquatic habitats, and threaten water quality—issues that are compounded by agricultural and urban runoff entering the Huron River, a critical drinking water source for the county.

Despite these challenges, Washtenaw County is well-positioned to respond with scientific and policy leadership. The region benefits from institutions like the University of Michigan’s School for Environment and Sustainability, where Dr. Drew Gronewold’s research focuses on hydrologic modeling, uncertainty propagation, and the application of climate data to water resource planning—critical areas for understanding and managing precipitation volatility.

The capacity to monitor and respond to these evolving climate dynamics has itself been constrained in recent years by reductions in federal research funding. During the Trump administration, proposed cuts to the National Oceanic and Atmospheric Administration (NOAA) jeopardized critical support for research initiatives based at the University of Michigan, including the Cooperative Institute for Great Lakes Research (CIGLR) and SEAS-affiliated projects. These cuts threatened work on invasive species, hydrologic forecasting, and algal bloom dynamics—issues directly relevant to the health of the Great Lakes and the watersheds that feed them. In response, the University launched internal support programs to preserve research continuity, but the gap in federal investment left lasting limitations on data collection and modeling capacity.

Transcription

David Fair: This is 89.1 WEMU, and I’m David Fair. And welcome to this week’s edition of Issues of the Environment. You may have noticed some changes in precipitation and weather patterns in Washtenaw County. Now, some of it is very subtle, but looking ahead, there could be some far-ranging implications. We wanted to learn more about what the changes have been and what the research indicates we may see down the line. And are we prepared? Well, here to help us navigate through these questions is Dr. Drew Gronewald. He is Associate Professor at the University of Michigan School for Environment and Sustainability. And thank you for the time today, Dr. Gronewald!

Dr. Drew Gronewald: Thank you! It’s good to be here!

David Fair: I just made an anecdotal observation that there are some changes in precipitation, both in levels and patterns. Would my rudimentary observations in any way align with the scientific data?

Dr. Drew Gronewald: Absolutely! You’re spot on! And there’s a couple key points in there. One is the last point made regarding being in line with the data, and we can talk about this later on. But it’s really important for our listeners to think about, as we talk about changes in precipitation, to also ask where is the information that we’re talking about coming from? Where is your original data? But if i move beyond that briefly, I’ll just reinforce what you’ve already hinted at, which is that there have been changes in rainfall and snowfall and the overall hydrological cycle throughout Washtenaw County and throughout Southeast Michigan and indeed the entire Great Lakes region. And they focus on two main themes. One is the transition of rainfall, especially in the winter, or precipitation, falling more as liquid rain rather than solid snow. And that has a big impact on the hydrologic cycle. The other big shift that we’ve seen over the past several decades is an overall increase in the amount of precipitation coming into Lake Michigan, the region, and including Washtenaw County. So, those are two big changes: a shift in the type of precipitation that falls and a shift and the total amount of precipitation on average is increasing.

David Fair: Most would attribute climate change as a primary source of why this is happening. Is there any way to determine how much is man-made climate change and how much is natural change in weather patterns that we’ve seen historically?

Dr. Drew Gronewald: There are ways. And so, there is a key point in your question there, which is, are there ways to figure that out? And there are. One of the primary ways that we look at is through using computer simulation models. So, a lot of folks, especially if you live in Washtenaw County, are familiar with the National Oceanic and Atmospheric Administration, including our local laboratory, or the local branch of that, the Great Lakes Environmental Research Laboratory. Groups like that are able to run very complicated computer models that can simulate a lot of the features of the atmosphere of the land surface over the past several decades and into the future. And what they can do is they can run those simulations and play around with different scenarios, including scenarios in which there either is or isn’t atmospheric or global warming. And they can see what the difference is in terms of the patterns that we see. The other way, of course, is just simply look at data from the historical record and take a look at when there have been abrupt changes in the historical record and test out hypotheses in those models about why they occurred.

David Fair: You mentioned it’s important we know where the data comes from. I assume NOAA is a part of that, but where are you basing your data from?

Dr. Drew Gronewald: Right. So, when it comes to precipitation, one of the main leaders in all of this is the National Oceanic and Atmospheric Administration. There’s also NASA, the United States Geological Survey, and even the Army Corps of Engineers. They’re just examples of the type of foundational organization or agency that are committed to collecting, processing, and communicating data on things like precipitation all throughout Michigan and all across the country. And they partner with agencies in other countries and other sovereign nations, like those in Canada, for example, to put together a clear picture or a clear mosaic of what’s happening at broader scales. So, for a lot of the findings that I’m talking about today, the information comes from rain gauges and satellites that are maintained by agencies like NASA and NOAA.

David Fair: Our Issues of the Environment conversation with Dr. Drew Gronewald continues on 89.1 WEMU. He is Associate Professor at the University of Michigan School for Environment and Sustainability. Let’s talk more impact. Given increased levels of precipitation, certainly more wet weather, is it fair to assess that, overall, we do not have sufficient stormwater infrastructure?

Dr. Drew Gronewald: That’s a good question! You know, when we assess overall, there’s questions at the Washtenaw County scale. There’s questions across the state of Michigan. But in general, most urban or even semi-urban environments have water management, stormwater management and wastewater management infrastructure that is multiple decades old. And that presents two problems. One is it just a natural aging process and a need for replacement from a basic maintenance perspective. And because of funding shortfalls and other limitations, some of that has fallen behind schedule. But the bigger problem that you’re hinting at here is that a lot of the design basis for some of the infrastructure was based on precipitation patterns from decades and decades ago. And it stands to reason that if those precipitation patterns are changing, the design bases for that infrastructure should change as well. So, another simple way to put it is that a lot our stormwater systems right now in cities across Michigan and around the world simply cannot keep up.

David Fair: And so, what are the impacts we’ll see on the ecology of Washtenaw County? Are we going to see different habitats and different wildlife?

Dr. Drew Gronewald: Yeah, great question! So, it’s a complicated question, and it’s a complicated thing to answer because our understanding of how the environment responds to these changes can be either based on historical records, sort of looking at how changes in hydrology in the past have affected wetlands, or by trying to put together predictive models that anticipate what those changes might be. But some of the changes that we’re seeing–some of these massive precipitation events or, for example, from 2016 to 2020, four to five years in a row of unprecedented cumulative precipitation, it’s very hard to look back in the historical record before then to find a relationship between ecological response and change in precipitation that matches what we’re seeing right now. And that makes predictions very, very tricky. So, most of the scientists that I work with believe that there are going to be important impacts on these changes, but it’s really hard to predict exactly what they’re going to be.

David Fair: The Huron River, of course, is a life source for the region. What challenges do we need to be prepared for with changing weather and precipitation patterns?

Dr. Drew Gronewald: Two big factors that I would think about here. One, which is not just for the Huron River, but all across Washtenaw County and all around the the state and the country, is that when you have increased precipitation, especially when you have it coming in these pulses and big storm events or even when you have rainfall rather than snowfall coming from the sky and landing on either impervious surfaces, which are increasing across the county or when they fall on frozen soil in the middle of winter, that can increase runoff, which can not only lead to flooding, but it could also exacerbate the transport of pollutants through the watershed. So, there may be legacy contaminants: things like PFAS and other contaminants in or on the soil. And the movement of those can be exacerbated into the river under those precipitation conditions. The other challenge that we face is there are a lot of dams along the Huron River, and operating those dams in a way that minimizes flooding can also be a big challenge as these precipitation patterns change.

David Fair: We’re talking with U of M School for Environment and Sustainability Associate Professor Dr. Drew Gronewald on 89.1 WEMU’s Issues of the Environment. I certainly don’t need to tell you there have been changes in environmental policy at the federal level over the past six months. Part of that includes reductions in research funding. What are you seeing at the School for Environment and Sustainability?

Dr. Drew Gronewald: So, there’s a couple different hats I’ll wear here. One is as a scientist and a scholar who works at the University of Michigan. Within the School for Environment and Sustainability, we have several sort of threads of connection to federal agencies and federal funding. Some of the more important ones include the Cooperative Institute for Great Lakes Research. That’s a partnership with NOAA. There’s also the Great Lakes Integrated Science and Assessment Center, or GLISA. And there’s also the Global Center for Transboundary Waters, where I served as a lead investigator. And all of those entities focus on digesting data about climate and the environment and helping people make better decisions with that information. And most importantly, they all rely heavily on federal funding sources, including those at NOAA and the National Science Foundation. So, one of the things that we’re seeing right now, as an academic researcher, is a look toward the future, in terms of how we’re going to continue getting information to public citizens about critical hydrological climate information in the face of some of the changes here. There’s another hat that I wear though as a public citizen, which is simply that I want to make sure that I talk to our congressional representatives and other politicians to make sure they understand how concerned I am as a citizen about some of these funding changes in shift in funding priorities to ensure that it’s the right information generated and it gets to people to make sound decisions about human and environmental health.

David Fair: If federal trends were to hold, what does it do to our ability to adapt to and accommodate changing precipitation patterns, not only in Washtenaw County, just about everywhere in the state and country?

Dr. Drew Gronewald: There’s two parts to that question. One is we, myself and others are continuously trying to assess what exactly is happening right now in Washington D.C., in terms of funding cuts. There are several stages of what’s happening, in terms of program evaluations, changes to funding, and they’re coming in phases. And there’s a lot of information coming in. It’s continuously assessed, and, quite frankly, there’s not really a clear trajectory forward right now, in terms of what’s going to happen. But there are scenarios that they can plan for. And so, what I can answer is that if a lot of funding cuts take place, it would definitely impact our ability to understand some of the changes that are happening in the environment, and it would impact our ability to plan moving forward for those changes in the future, including things like improving our infrastructure, keeping people safe, keeping commercial navigation waterways safe, and protecting the environment. So, that’s sort of the two-pronged answer I’d give you to that question.

David Fair: Well, thank you so much for the conversation and the information today! I appreciate it!

Dr. Drew Gronewald: Thank you! It was a pleasure!

David Fair: That is Dr. Drew Gronewald. He is Associate Professor at the University of Michigan School for Environment and Sustainability and our guest on Issues of the Environment. For more information, stop by our website at WEMU.org. I’m David Fair, and this is 89.1 WEMU-FM, Ypsilanti.

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