A web-based watershed delineation tool and its application to delineate 24,000 watersheds across Canada

Watershed delineation is the identification of the boundary of a drainage basin, representing the contributing area for a specific outlet. This application of hydrography is essential in the analysis of watershed behaviour and has historically been performed manually. The automation of delineation provides faster and more consistent results which can be more accurate and reproducible definitions of borders compared to the results of the manual delineation. There is a wide range of software and tools capable of performing watershed delineation automatically; all generally following the same steps – utilizing conditioned DEMs to create flow direction and accumulation rasters used in addition to a specified pour point that defines the extent of contributing area desired. These different tools and their results have been explored, addressing their similarities, contrasts, and complications. Using this analysis, selected methods have been included in a web application for watershed delineation for users to either delineate individual points selected on a web map or upload lists of points of interest The automatically delineated watersheds are then made available for download. One tool has been deemed most applicable and has been used to delineate more than 24,000 watersheds across Canada successfully. The presentation will include (1) the results of the comparison of the various tools tested, (2) a demonstration of the webtool as well as (3) the presenting the results of the large scale delineation task across Canada.