The Great Lakes hold about 20 percent of the world's available surface freshwater, and 84 percent of North America's surface freshwater. As a resource, the lakes and their tributaries are invaluable -- providing drinking water for 40 million people and serving as the region's economic and recreational lifeblood. Yet, the sheer vastness of the lakes belies a fragility that policy-makers, scientists and other experts have struggled to address for more than a century . With less than 1 percent of the waters of the Great Lakes renewed annually through rainfall and snowmelt, the lakes are vulnerable to misuse and depletion. Congress unanimously approved and President Bush signed the Great Lakes-St. Lawrence River Basin Water Resources Compact into law in October 2008. The eight-state water management pact is a first-of-its kind model for a consensus-based, basin-wide approach to decisions about how much and how far away Great Lakes water can be used. The eight Great Lakes governors who collectively wrote and unanimously endorsed the pact deliberately left it to the states to devise their own rules of implementation for in-state water use. Since the compact's adoption, the Great Lakes states have developed water use standards that are much improved from what existed before, though many lack proactive policies designed to protect and nurture water sustainability. Meanwhile, the Great Lakes-St. Lawrence River Basin Water Resources Council -- the body established by the compact to make decisions about water diversions outside the basin -- has not rendered binding rules for its review of diversion applications, leaving a void that may expose the pact to legal challenge and put Great Lakes water at risk. The compact will soon face its first regional test from Waukesha, Wis., a community eligible to apply to divert Great Lakes water beyond the basin because of its location within a county straddling the Great Lakes and Mississippi River divide. The compact allows for straddling communities and communities within straddling counties not currently using Great Lakes water to be granted an exception to its ban on diversions -- but only if the community can prove no reasonable alternative water source exists and that the water will be returned to the basin. Absent water-tight regional implementation rules, however, this precedent-setting application could reveal deficiencies in the application process that, if unaddressed, leave the compact vulnerable to legal challenges . Waukesha is only the first of a number of communities that may line up for Great Lakes water in the coming decades. We encourage the Great Lakes governors to consider not only the implications of reviewing the Waukesha application under current guidance, but how the decisions made during this review will inevitably shape the basis for future decisions. The first section of this report identifies a number of communities -- some similarly situated in straddling counties, others themselves straddling the border of the Great Lakes Basin -- that may face the need for an alternative water supply soon and could find requesting Great Lakes water a sensible prospect in the coming decade. The second component of the report seeks to take advantage of a narrowing window of opportunity to fix shortcomings in the Compact Council review process; a window that will shut with the arrival of the first diversion request on its doorstep. The report analyzes Compact Council implementation deficiencies which, if not addressed, leave the application review process vulnerable to legal challenges that could reshape parts of the compact.