A digital geospatial hydrographic dataset contains information about an area’s surface water, including its rivers, streams, canals, lakes, ponds, glaciers, dams, coastlines, and watershed boundaries. The United States and Canada each independently developed their own suite of hydrographic datasets using different standards and approaches. From the Canadian federal and provincial perspective, these fundamental hydrographic datasets translate to Canada’s National Hydrographic Network (NHN) and the working version of Canada’s Fundamental Drainage Areas (FDA). From the U.S. federal and state perspective, the geospatial datasets include the U.S. National Hydrography Dataset (NHD) for surface water and the U.S. Watershed Boundary Dataset (WBD) for drainage areas. These national datasets stopped at the border, thereby preventing a seamless transboundary exchange of data and water-related information. The mapped rivers, lakes, and watershed boundaries were often offset where they met the international border, leaving an area of uncertainty about how the water behaved. In addition, the scales of the data, the names of the waterbodies, as well as other information associated with them were inconsistent.
As a result of these hydrographic inconsistencies, federal, state, provincial, local, academic, and private users were developing their own interpretations of surface water maps in the transboundary region. In addition, differences in how each country presented the data made interpreting or connecting study results from each side of the border about environmental and ecological issues in transboundary watersheds complicated. For example, the word ‘basin’ does not mean the same thing in North Dakota as it does in Manitoba. This disconnect in the way hydrography is described and quantified was apparent along the entire boundary region.
One consequence of these disparities was that large portions of drainage areas were often overlooked. Drainage areas, or watersheds, represent the topographically-defined area of the landscape that drains to a common outlet or outlets. Without a uniform dataset, these areas could not be accurately defined, and they often stopped at the international border. These environmental systems do not know political boundaries, and a proper understanding of them is vital to assess issues like ecosystem health, flood and drought risk, as well as water resource management. It was clear that there needed to be a way to align the watersheds on each side of the border to enable a seamless interpretation of their water flow and physical characteristics between the United States and Canada by the agencies that oversee them.