ADDRESSING CLIMATE CHANGE UNCERTAINTIES IN THE INTERNATIONAL JOINT COMMISSION'S RIVER BASIN MANAGEMENT MANDATES: THE ST. CROIX RIVER CASE STUDY

Future changes in precipitation and temperature, as a result of climate change, can have a serious impact on a river basin organization’s ability to meet specific hydropower, recreational, environmental, and water supply requirements. The International Joint Commission’s (IJC’s) basin Boards have water management mandates in shared Canadian and US boundary waters across the North American continent. The IJC Climate Adaptation Working Group has developed a “Climate Change Guidance Framework” that can be used to assist IJC Boards to address climate change within the bounds of their mandates. The framework guides Boards to analyze and act on climate change issues in a logical manner through a four-step process: (1) organize, (2) analyze, (3) act, and (4) update.

This research implements this decision scaling assessment in the St. Croix basin in Northern Maine and New Brunswick – the easternmost land border between the United States and Canada. This work is the first implementation of the Climate Change Guidance Framework for the IJC. Several water level and flow requirements exist in the St. Croix basin: to meet hydropower, environmental, and recreational targets. By taking a bottom-up, decision scaling approach, we assessed how violations of these water level and flow mandates may change as a result of future climate change. We first defined the objectives and critical flow and level thresholds at various points in the basin. We then developed a coupled hydrology-water system model to analyze system performance under different future climate conditions, and implemented a “climate stress test” to assess violations to these critical thresholds. Results from the study was presented to the St. Croix Watershed Board and the IJC commissioners to provide quantitative information for decision making. Future applications of this framework can be useful for other watershed organizations to identify how climate change can uncover vulnerabilities in critical thresholds which affect basin level objectives.