High Resolution Watersheds for Lake Superior

High resolution watersheds for Lake Superior

We used ArcHydro, a data model developed by ESRI, designed to manage and process watershed delineations and watershed summary information. Using flow direction and flow accumulation grids derived from elevation maps, stream networks were identified based on a minimum flow accumulation threshold. This allows for selectively delineating streams at either broad scales or very fine scales. Once the stream networks were delineated, flow direction was used to delineate the contributing area or sub-catchment for each stream reach between stream confluences (Hollenhorst et al. 2007).

The watershed delineation was based on a 10 m Digital Elevation Model (DEM) for the U.S. side of the Lake Superior basin, and 20 m DEMs on the Canadian side. Drainage enforcement, the process of removing spurious ‘sink’ data points from the DEM, was done using stream data from the National Hydrologic Data (NHD) for the U.S. portion of the basin and the Water Virtual Flow Seamless Provincial Data Set for the Canadian basin.

The ArcHydro model maintains hydrologic continuity, by assigning a unique “Hydro-ID” to each subcatchment, and identifying a downstream hydro-id for the next downstream catchment. These attributes are also transferred to the corresponding stream reach and pour points. Because of this “nextdown” id, it is possible, to accumulate information as the streams flow down the drainage network. For example, area-weighted means of relative values associated with each catchment (i.e. proportion or density) can be accumulated down the network. NextDownID

The ArcHydro procedure resulted in the delineation of approximately 131,000 subcatchments in the Lake Superior basin (below). The average size of each subcatchment was 93 ha (230 ac). Subcatchments were combined based on their Hydro-IDs to identify watersheds emptying into into Lake Superior. Approximately 7,000 Lake Superior tributary watersheds (hereafter referred to as simply ‘watersheds’) and the adjacent coastal areas that drain directly into the lake (interfluves) were identified.

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Additional Info

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Last Updated May 2, 2017, 13:05
Created September 16, 2015, 19:28