Looking back at 2025 Developments in Wisconsin Water Law and Policy

2025 was a momentous year for water law and policy issues, both in Wisconsin and nationally. In this post, I focus mainly on some Wisconsin-specific developments and then summarize a few national-level issues.

Water use at data centers. The past year saw the emergence of widespread public concern over the environmental impacts of data centers—facilities that store and share vast amounts of data for the internet, artificial intelligence, cloud storage, and related applications and services, resulting in community opposition in some places. By most counts, Wisconsin is already home to more than 40 data centers, with several more in development. Data centers have become controversial because of their effects on the environment; perhaps most prominently, some use significant amounts of water for cooling their sensitive equipment (reportedly millions of gallons per day, in extreme cases). Other data centers have “closed loop” recycled water systems that use much less water but require increased electricity to operate. Of course, water and energy are closely connected – water is required to produce energy, and energy is required to treat and deliver clean water. This means that even those data centers that use recycled water systems have a sizable water footprint, considering the water used at the energy generating facility. Complicating the matter further, some data center developers have required host municipalities to sign nondisclosure agreements that purport to treat water use as a trade secret. Several proposed sites are facing backlash from surrounding communities.

PFAS rulemakings. The Wisconsin Department of Natural Resources (WDNR) is engaged in several rulemaking efforts related to per- and polyfluoroalkyl substances (PFAS). The term “PFAS” encompasses a broad range of chemical compounds, not a single substance.  Since the 1950s, PFAS have been manufactured around the world and widely used in a broad array of products including food packaging, cosmetics, non-stick cookware, and firefighting foam.  Prized for their durability and propensity to repel both oil and water, PFAS do not break down easily in the environment and have been tied to serious risks to human health. PFAS are commonly called “forever chemicals” because of the lack of degradation pathways. 

WDNR’s ongoing regulatory efforts include setting limits for PFAS in groundwater (updates to Wisconsin Administrative Code Chapter NR 140), management of firefighting foam containing PFAS (updates to Chapter NR 159), and bringing Wisconsin drinking water rules for PFAS in line with federal standards (updates to Chapter NR 809). More information about these efforts can be found here on WDNR’s website.

Spills Law. The Wisconsin Supreme Court sided with the WDNR in a dispute over the extent of the agency’s authority to require responsible parties to clean up releases of PFAS and other emerging contaminants under the state’s “Spills Law,” Wis. Stat. s. 292.11. At its core, the Spills Law requires a person who causes the discharge of a “hazardous substance” (or who possesses or controls a hazardous substance that has been discharged) to notify WDNR of the spill and then to “take the actions necessary to restore the environment”—a potentially time-consuming and expensive process.

The central question in the case decided in June, Wisconsin Manufacturers and Commerce, Inc. et al. v. Wisconsin Natural Resources Board, et al., arose over whether WDNR could continue its historical practice of identifying “hazardous substances” on a case-by-case basis, or whether it had to engage in administrative rulemaking to create a list identifying which substances it considered hazardous, and at what quantities or concentrations in the environment. The rulemaking process is lengthy and often controversial, so a decision against DNR would have posed substantial challenges for it, potentially eliminating its ability to respond in real time to spills of emerging contaminants. On the other hand, a list of hazardous substances would provide predictability and certainty to parties responsible for cleanups under the Spills Law.

The supreme court held in DNR’s favor that the agency could continue its practice of determining whether a release involved a “hazardous substance” based on the individual circumstances of each case. The court held that the statute’s “broad and open-ended” definition of “hazardous substance” is cabined by the requirement that the substance significantly increase mortality or contribute to serious illness in humans, or that it may pose a substantial hazard to human health or the environment.

In considering how the Spills Law works, context is important, the court observed: “a gallon of milk spilled into Lake Michigan may not ‘pose a substantial present or potential hazard to human health or the environment,’ but a 500-gallon tank of beer or milk discharged into a trout stream might well pose [such a hazard] to the stream’s fish and environment.” Thus, the court thought it was critical for DNR to retain some flexibility in interpreting the statute.

Climate litigation and Wisconsin water resources. From constitutional claims that seek to reform the implementation of energy law in the state, to litigation over the federal government’s efforts to claw back funding for the development of renewable energy resources, Wisconsin has become increasingly involved with legal battles over the climate. Interestingly, one of the cases prominently invokes a constitutional doctrine connected to the state’s water resources – the public trust doctrine. Read more about these developments in one of my previous blog posts.

Aftermath of Evers v. Marklein II. This summer the Wisconsin Supreme Court issued its opinion in Evers v. Marklein II, striking down the authority to pause, object to, or suspend administrative rules held by the powerful legislative Joint Committee for Review of Administrative Rules (JCRAR). The basis for the ruling was a rather technical matter: the court held that JCRAR’s authority to block, suspend, and object to administrative rules was tantamount to legislative action, and therefore failed the constitutional requirements of bicameralism (a bill must pass both houses) and presentment (the bill must be provided to the governor for signature). Technical grounds notwithstanding, Evers v. Marklein II appeared to significantly reduce the legislature’s power to check agency action, although it also touched off a new round of political squabbling ultimately leading to Governor Evers suing the legislature all over again.

Ten years of Wisconsin water use data. The WDNR released its annual Report on Water Withdrawals, which gives an overview of the past decade of water withdrawals throughout Wisconsin. In an era of uncertainty over the reliability of information, the report provides very valuable data about water use in Wisconsin.

The DNR summarized the main takeaways from its report as follows:

  • “The largest water withdrawals were for power production, municipal water supply and crop irrigation.
  • In 2024, Wisconsin cities, agricultural operations, businesses, industry and power generation facilities withdrew almost 1.7 trillion gallons from groundwater and surface water sources – the equivalent of just over 1% of the volume of Lake Michigan.
  • Power production was the largest water use category at 73% of the total water in 2024, with municipal supply following at 11%.”

Developments at the federal level have been largely driven by the second Trump administration. Some of these were expected, such as the administration’s proposed rule to narrow the regulatory definition of “waters of the United States” (WOTUS) to better conform with the Supreme Court’s 2023 decision in Sackett v. EPA. The issue is important because it dictates whether a federal permit is required to fill wetlands. Obtaining the permit can be a time consuming and expensive process – but also one that protects a critical environmental resource. Sackett narrowed the class of qualifying waters to traditional waters that are navigable in fact, such as rivers and lakes, and all other waters that have a continuous surface connection to waters in the first category, such that the boundary between them is indistinguishable.

Other developments were mildly surprising, such as the administration’s apparent decision to defend the Biden administration’s lead and copper rule, which had been challenged by water utilities as unreasonable given its establishment of a ten-year deadline for public water systems to replace all lead pipes within their jurisdiction.

Still other developments occurred in the judicial branch, perhaps the most important being the Supreme Court’s opinion in San Francisco v. Environmental Protection Agency. The Clean Water Act generally prohibits the discharge of a pollutant to surface waters, unless the discharger holds a permit issued under the Act. In San Francisco, the U.S. Supreme Court held that EPA lacked the authority to issue what the Court termed “end-result” conditions in those wastewater discharge permits. Those conditions are sometimes known as “narrative” limitations that take the form of a water quality goal when numeric standards are too difficult to quantify. For example, such a condition may prohibit a permittee from “creating pollution, contamination, or nuisance,” or from “causing or contributing to the violation of water quality standards.” The City argued that these standards were too vague to enable compliance. The Court held that “end result” provisions exceeded EPA’s authority because they condition a single discharger’s compliance on whether the receiving waters meet applicable standards. The holding is likely to change permit drafting processes and enforcement actions nationally.  Permits will have to be more detailed and provide more clarity on specific (numeric) effluent standards necessary to avoid impacts to receiving water quality.

Continue ReadingLooking back at 2025 Developments in Wisconsin Water Law and Policy

Where Americans Choose to Move and Where They Leave: Domestic Migration from 2020 to 2024

Patterns of domestic migration—where people who already live in America choose to move—reveals a lot about where people do or don’t want to live. Or, framed differently, where they can and can’t afford to. This map shows the cumulative domestic migration of each US county, from 2020 to 2024.

The darkest green color shows places where the (net) number of people who’ve moved in since 2020 is equal to 10% or more of the population in 2020. The darkest purple color shows the reverse. In those counties the net number of people who’ve moved out is equal to 10% of the 2020 population. This only includes people who moved from one place in the United States to another, not people who moved into or out of the country.

Because this map shows net migration, a place where a roughly equal number of people move in and out—like a college town—won’t feature prominently.

map showing US counties shaded corresponding to their net domestic migration from 2020 to 2024

There are six times as many dark green counties as dark purple ones. A few counties are experiencing intense in-migration, while a lot of counties are seeing a small out-migration.

Some of the patterns seem to follow state boundaries, but more commonly they reflect urban agglomerations or ecological regions.

In fact, I was surprised by the extent to which certain ecological regions correspond to the patterns on this map. The next version of the map shows a few of the patterns that most stood out to me. I highlighted certain regions, like the Ozarks, by identifying the counties included in specific EPA Level III ecoregions. (Follow that link to see official maps of Level I, II, III, and IV ecoregions. They are fascinating).

I placed a county into one of these regions if its mean population weighted center in the 2020 census fell inside the region.

map, with regions outlined and annotated, showing US counties shaded corresponding to their net domestic migration from 2020 to 2024

Rural Northern Tier Winners

Three pockets of growth dot the northern perimeter of the lower 48. Each is in a very different rural area.

The Upper Rockies

These are the 41 counties lying mostly inside of the following ecoregions: Northern Rockies, Canadian Rockies, Middle Rockies, and Idaho Batholith. Mostly, these are in Idaho and western Montana, but some stretch into northeastern Washington and a few disconnected pockets stretch all the way to extreme western South Dakota. Since 2020, these counties have gained about 99,000 net new residents who previously lived elsewhere in the country. That’s equal to 6.0% of the region’s total population in 2020.

The Northwoods

The “Laurentian Mixed Forest Province” (as it is also known) is a single ecoregion stretching from Minnesota’s iron range, through northern Wisconsin, across the entire Upper Peninsula, and into the northern half of Michigan’s lower peninsula. This whole area is scarcely populated: Duluth is the largest city. But since 2020, 56,000 more people have moved in than out of these 65 counties, equal to 3.3% of the population in the last census. This sets the Northwoods apart from pretty much everywhere else in the rural Midwest.

Rural New England

I’m using “rural” in an expansive sense. These are the 46 counties in New England’s six counties which lie outside of a combined statistical area. Since 2020, they’ve added 86,000 residents thanks to domestic migration, equal to 2.0% of their starting population. Notice that the New England counties located inside CSAs have fared less well. Nor have migrants flocked to nearby rural upstate New York.

Perhaps rural New England, the Northwoods of the Upper Midwest, and the northern Rockies are all benefiting from increased access to remote work in recent years. The absolute numbers of people moving to these regions are small, compared with some of the other regions we’ll discuss shortly. But because their populations were so low to begin with, the influx of new residents is enough to make a big different proportionally.

The Sunbelt is Still Hot

The biggest hotspots for domestic movers are in the American South. Many of these cross state lines in ways that follow ecoregions.

The Piedmont / Southern Appalachia

One such region covers portions of the Carolinas, Georgia, Alabama, Kentucky, and nearly all of Tennessee. The sprawling area (340 counties) basically corresponds to the ecoregion comprising Appalachia south of Virginia (the Blue Ridge Mountains, Southwestern Appalachians, Ridge and Valley) along with the plateaus to their east (the Piedmont) and west (the Interior Plateau). 974,000 more Americans moved into this region than out of it from 2020 to 2024, equal to 3.3% of the 2020 population.

Notice that I do make an artificial alteration to the ecoregion boundaries: cutting several off at the southern border of Virginia. Virginia displays its own pattern of migration growth, concentrated on the DC metro.

The Southern Coastal Plain

Florida’s appeal to domestic movers is legendary, and that’s most of what is happening in this region. But it turns out the counties attracting the most growth correspond even more closely to the boundaries of the Southern Coastal Plain ecoregion than they do to the state lines. Notice how the southern tip of Florida (a different ecoregion) had negative net migration, while Florida’s growth regions extend seamlessly along the Georgia and South Carolina coasts which are part of the same ecoregion. The 76 counties in the Southern Coastal Plain region added 1.17 million residents, equal to 7.1% of the 2020 population.

The Texas Triangle

The Texas Triangle isn’t any kind of official region, so you can define it different ways. I drew a concave hull around the combined statistical areas for Dallas, Houston, and San Antonio. Basically, it contains the biggest metros in Texas and everything in between them. All told, these 103 counties gained 804,000 net domestic movers, equal to 3.5% of the population.

The Greater Ozarks

This one surprised me the most. As a kid, I often visited my grandparents in Yellville, Arkansas, deep in the Ozark Mountains. The whole region seemed beautiful but sleepy. Evidently, that has changed. The Ozarks, and their surrounding ecoregions, grew considerably. This region of growth extends across several states. It includes the Ozark Highlands, Boston Mountains, Arkansas Valley, and Ouachita Mountains. From 2020 to 2024, these 92 counties gained 143,000 people from net domestic migration, worth 3.5% of the 2020 population.

Some Losers

Most of the places with more out-movers than in-movers only lost a very small fraction of their population. But a few regions stand out with more serious losses.

The Lower Mississippi

The Mississippi Alluvial Plain extends from the river’s confluence with the Ohio in southern Illinois all the way to its mouth in the Gulf of Mexico. Nearly all of these 58 counties lose more movers than they gain. In total, the region lost 116,000 people, or 5.0% of its population to net domestic migration from 2020 to 2024. Losses were even more severe (proportionally speaking) in the core of the region, the Mississippi Delta.

The 100th Meridian West

The 100th Meridian is notorious on the Great Plains as the location beyond which, it is often said, growing crops becomes impractical without irrigation. While making this map, I was struck by the vertical streak of population loss corresponding to the area immediately west of this line. The vertical region I’ve drawn is simply those counties lying mostly within the 100th and 103rd meridians (and outside of the Texas Triangle or Upper Rockies). This is basically the width of Oklahoma panhandle, extended north  to Canada and south to Mexico. Collectively, the region’s 166 scarcely populated counties have only lost 45,000 people to domestic migration (1.9% of the population), but it includes counties with losses of 10% or more.

California

Finally, any discussion of net migration has to mention the county’s most populous state: California. From 2020 to 2024, 1.47 million more people moved from California to elsewhere in the United States than from a different state into California. That outflow is equal to 3.7% of the state’s 2020 population.

Continue ReadingWhere Americans Choose to Move and Where They Leave: Domestic Migration from 2020 to 2024

Milwaukee’s Baby Bust Hit New Lows in 2025

The fewest babies on record were born to Milwaukee mothers in 2025, according to preliminary vital statistics records.

As of January 5th, the state’s vital statistics database shows 7,343 Milwaukee births in 2025. Based on the reporting pattern in previous years, I estimate that the total number of 2025 births will stand at about 7,386 after the last records trickle in.[i]

This is a 5.0% decline from 2024, when 7,774 babies were born to Milwaukee moms. It is a 15.0% decline since 2020 and a 28.7% decline since 2010.

line graph showing the number of babies born to Milwaukee mothers, 1990 to 2025

Births are only one component of population puzzle. Each year, people of all ages move both in and out of Milwaukee. But the number of births is the first ingredient of our future population, and the number of babies born has ripple effects in every following year. For example, in a response (at least partly) to declining demand, one large Milwaukee hospital stopped delivering babies altogether in 2022.

The drop in births throughout the 2010s also explains why Milwaukee’s population loss in the 2020 census was so surprising. The 2020 census came in well below what projections based on administrative data predicted. Those projections used birth and death records collected at the county level, and they estimated the county’s overall population accurately. The problem was that the Census Bureau model allocated births to each municipality based on patterns from the 2010 census, when, in fact, the share of babies born in the suburbs grew, relative to the city: a fact independently confirmed by both the 2020 census and local vital statistics.[ii]

Birth counts quickly affect school enrollments. Milwaukee’s births actually remained steady—even growing a bit—between the late 1990s and the late 2000s. This had a stabilizing effect on school enrollments, benefiting each sector of the city’s fragmented school system. There were actually more first graders attending a Milwaukee school in the 2014-15 school year than in 2005-06.

Then enrollment began to fall. The Great Recession, accompanied by an extreme mortgage foreclosure crisis in Milwaukee, coincided with a sharp drop in births. Newborn counts fell from 11,457 in 2007 to 9,213 in 2018. By 2023-24, there were 1,500 fewer first graders attending a Milwaukee school than in 2014-15.

During the COVID-19 pandemic, births dropped by 14.5% from 2019 to 2022. This was nearly three times the statewide decline of 5.1% over this period, so the drop in Milwaukee likely reflects prospective parents leaving the city in addition to couples putting off having a kid. Supporting this, census data shows a net outflow of 15,800 people leaving Milwaukee in the year ending July 1, 2021. Things improved after that, and net migration actually turned slightly positive in the year ending July 1, 2024, when the city gained about 500 residents in this way.

Mirroring this net migration pattern, births fell most sharply in the calendar years 2020 and 2021, before remaining more stable in 2023 and 2024. The renewed sharp drop in 2025 may indicate a resumption of negative net migration for the city or changes to the age profile and childbearing preferences of existing residents. Some hints might be gleaned from the map of where births have fallen in Milwaukee.

These three maps show, from left to right, the total number of babies born in each City of Milwaukee zip code during 2025, the change from 2024 to 2025, and the change from 2019 to 2025.

maps showing the number of babies born in each zip code and comparing this with 2024 and 2019.

The cumulative effect of Milwaukee’s years-long run of declining births is large. As we begin 2026, 39,210 babies were born in Milwaukee over the past 5 years. At the beginning of 2020, that number was 46,345. Here are some final thoughts:

  • There is no sign that Milwaukee’s baby bust has bottomed out. Two years ago, I thought it might have, but the latest data points toward continued declines of several hundred babies each year.
  • Schools across all sectors will face declining enrollment for the foreseeable future, with each cohort likely being smaller than the last.
  • While it is true that fertility rates are declining nearly everywhere, I think the rapidity (and location) of Milwaukee’s baby bust points to out-migration of prospective parents as a large factor. Much of this could be solved if more young couples felt Milwaukee was a good place to raise a family. In general, in Milwaukee’s healthiest and safest neighborhoods, the baby bust is either small or not happening at all.

[i] In the last couple years, a little over half of one percent of birth records were still outstanding by the following January 5th.

[ii] The Census Bureau Population Estimates Program uses vital statistics and modeled migration data to estimate county-level population. It then allocated the county-level population into municipalities based on the number of housing units in each (another tracked metric) and the average household size in the previous decennial census. In Milwaukee, the city’s average household size actually fell from 2.5 in 2010 to 2.39 in 2020, while in the Milwaukee County suburbs, the average household size stayed about the same.

Continue ReadingMilwaukee’s Baby Bust Hit New Lows in 2025
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