• The Evolution of Binational GWS Governance

As far back as the 1794 Jay Treaty, aimed at maintaining Great Lakes' levels for international navigation during the Napoleonic wars, binational governance of GLB water uses prioritized maintaining surface water quantities [63]. Modern governance began with the 1909 Boundary Waters Treaty (1909 BWT) that banned large diversions of surface waters straddling the international border. Aiming to ensure equitable "domestic and sanitary uses, navigation uses, and uses for power and irrigation", it established the International Joint Commission (IJC). The IJC did not have a major GWS governance role until the 1988 Cabin Creek Coal Mine case, when its Water Use Reference was updated allowing investigation of GWS issues as a matter of practice [64].

The next significant binational agreement was the 1956 Great Lakes Basin Compact that created the Great Lakes Commission (GLC) to promote "orderly, integrated, and comprehensive development, use, and conservation" of GLB water resources. It was the first agreement to adopt a whole-of-basin approach to governance, explicitly considering the range of water uses: "industrial, commercial, agricultural, water supply, residential, recreational, and other." However, its mandate was limited to the Great Lakes and all connected "rivers, ponds, lakes, streams and other watercourses.", reflecting the original interpretation of the Public Trust Doctrine by excluding groundwater from its purview.

Another important update was the 1985 Great Lakes Charter (1985 Charter). Established as a good faith agreement between the GLB governors and premiers, it is significant as it introduced many of the key standards and policies for the uses of "all GLB waters" still in place in today. It expanded GLC membership to include Canadian premiers, introduced the regional review process for making decisions on bulk water use and diversions, and most significantly, was the first binational agreement to include groundwater in its purview as a public trust responsibility [65]. Improving science–policy alignment, the 1985 Charter introduced volumetric limits to GLB water use to safeguard "nonrenewable" GLB water resources. It required regional review of bulk water uses, defined as any withdrawal exceeding 380,000 L/day in any 30-day average, and any new or increased diversion or consumption of GLB water exceeding 19 million liters per day in any 30-day period. It also initiated the Great Lakes St. Lawrence River Regional Water Use Database that was eventually established in 1988.

Despite these milestones, the 1985 Charter did not appear to consider sustainable aquifer yield in recommending policies and standards to govern groundwater use. Notwithstanding well-documented knowledge that aquifers can be depleted due to over-pumping since 1910 [62], the 1985 Charter did not reflect on groundwater's relative scarcity and lower replenishment rates compared with surface waters as it provided identical volumetric definitions and controls for bulk groundwater and surface water use. By stating its overall aim was to safeguard GLB surface waters, it invoked the Underground Stream Doctrine, considering groundwater flow systems as merely tributaries to surface water bodies, and interrelating the policies governing the uses of both resources. In so doing, it failed to keep pace with groundwater science that had advanced considerably from the 19th century in North America. By 1903, key hydrogeological concepts relevant to sustainable

aquifer yield had been developed, including that environmental flows provided by groundwater were not just limited to surface water bodies, as well as the relationship between groundwater budgets and sustainable limits for consumptive uses and aquifer geometry and geological media [62]. Though the Regional Water Use Database has been providing yearly reports on GLB water withdrawals, consumption, and diversions, since its inception it has not had a specific data field for tracking water use from aquifers. This has made it difficult to garner consistent groundwater use data, an essential input for determining sustainable aquifer yield.

Since the 1985 Charter's original policy prescriptions remained largely unchanged in the intervening years, many of its original GWS governance gaps have carried through to the present day. As the 1985 Charter was set up as a non-legally-binding agreement, it did not include enforcing mechanisms. Thus, the GLC later agreed to the 2001 Great Lakes Charter Annex, committing the GLB states/provinces to agree on policies to be included in laws within the next three (3) years. This was fulfilled when the 2005 GLSWRA was passed and subsequently integrated into current state/provincial laws governing GLB water use.

Sustainable aquifer yield considerations have also been absent from binational economic policies affecting GWS. Though they can be traced back to the 1855 Reciprocity Treaty, it was not until 1987 that the first such policy was established that had direct impact on maintaining GWS when both countries established the Canada–United States Free Trade Agreement. Superseded by the 1994 North American Free Trade Agreement that admitted Mexico to the free trade zone, these agreements followed the General Agreement on Tariffs and Trade of the World Trade Organization. Herein, GLB groundwater and surface water were allowed to be exported when "captured whether in bottles, tankers or pipelines." Successive trade agreements have ignored the cumulative impacts the virtual groundwater trade can have over time on source aquifers and the environmental safeguards for maintaining GWS. Instead, these agreements have always included settlement mechanisms for trade disputes, opening the door to growing competition and conflicts between conservationists and industries drawn to the Basin by its cheap, clean, and abundant groundwater supply [66].
