In hydrologic terms, a “gaining stream” is a surface stream augmented by groundwater flow. In a more conventional sense of the term, legal and policy disputes surrounding groundwater are also “gaining” in importance, though localized groundwater-related issues have perplexed the courts for generations. In a 1903 opinion, at the end of a lengthy discourse summarizing various authorities on the subject of groundwater withdrawals, Justice John B. Winslow of the Wisconsin Supreme Court admitted that “[p]erhaps more time has been spent in reviewing these decisions than is profitable, but the subject is interesting, and . . . should be given serious consideration.”[1] Winslow’s comments came during the latter part of a long period of judicial unfamiliarity with the science of groundwater. Nineteenth century jurists characterized its movement and sometimes its very existence as “unknown”[2] or even “occult.”[3]

About two-thirds of Wisconsinites draw their drinking water from the ground. Still, both in this state and elsewhere, groundwater lacks the intuitive familiarity of surface water. Perhaps as a result, many states still don’t have well-developed jurisprudence or legal management systems for groundwater even though hydrogeology has become a well-developed and well-accepted science. Judicially-created groundwater doctrines vary widely from state to state. This legal dissonance is of increasing concern in light of a surge of groundwater problems and disputes involving water quality concerns, the viability of the public trust doctrine as a tool for groundwater regulation, and transboundary management issues, among many others. This societal and legal evolution proves Justice Winslow correct: The law of groundwater is indeed “interesting,” and courts are giving it ever more “serious consideration.” Consider the following examples:

In recent years, it has become relatively common knowledge that the Great Lakes Compact generally bans diversions of Great Lakes water outside the Great Lakes basin but offers limited exceptions. A community that straddles the basin line, or that lies within a county that straddles the basin line, may apply for a diversion subject to certain stringent technical conditions. I have previously written in this space that the Compact has been successful at least insofar as the party states were able to agree on and subsequently enforce a common decision-making process to consider such requests. In October 2018, Compact supporters will celebrate its 10-year anniversary.

But the Compact’s first decade has not passed without controversy, much of it centered on the diversion provisions generally and on southeastern Wisconsin in particular. In fact, during a recent conference keynote address here at the Law School’s Lubar Center, Compact expert Peter Annin noted that our area has more “diversion hotspots” than the other Compact party states combined. Consider that in 2009, the City of New Berlin (a straddling community) became the first community to successfully apply for a diversion, and in 2016, the City of Waukesha became the first community within a straddling county to successfully apply for a diversion.

Just last week, the region made Compact history for yet another reason. For the first time, opponents to an approved diversion have filed a legal action to challenge the approval in a state administrative hearing, potentially as a precursor to an appeal to Wisconsin circuit court. The proceedings to follow will provide important and novel insights on how to interpret the Compact.