Watershed
The Home | New Map | Specialty | Watershed command or the 
button can be used to create a watershed map from a grid file. The Home | Add to Map | Layer | Watershed or Map Tools | Add to Map | Layer | Watershed command adds a watershed map layer to the selected map.
Key Concepts
Understanding the following terms is helpful when working with watershed maps:
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Catchment Basins: A basin (or catchment area) is a region where all water flows downhill across the surface to a common stream outlet.
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Threshold (cells): To understand stream creation thresholds, it helps to know how Surfer defines a "cell." While a grid node is a single point, a cell in watershed calculations is a square or rectangular area centered on that grid node.
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Depressions: Depressions are local pits or low points in the grid where water naturally accumulates because there is no downhill path to an outlet.
Watershed Properties
The watershed properties contains the following pages:
Map Properties
The map properties contains the following pages:
Watershed References
Many of the parameters for the watershed map are technical in origin, and a detailed development is beyond the scope of this document. For additional information, see the following resources:
O'Callaghan JF, Mark DM. (1984) "The Extraction of Drainage Networks from Digital Elevation Data.” Computer vision, Graphics and Image Processing, Vol. 28, 323-344.
Wang, L. & H. Liu (2006) “An Efficient Method for Identifying and Filling Surface Depressions in Digital Elevation Models for Hydrologic Analysis and Modelling.” International Journal of Geographical Information Science, Vol. 20, No. 2: 193-213.
Garbrecht, J. and Martz, L.W. (1997) “The assignment of drainage direction over flat surfaces in raster digital elevation models.” Journal of Hydrology, Vol. 193, 204-213.
Welsh, D. J. A.; Powell, M. B. (1967), "An upper bound for the chromatic number of a graph and its application to timetabling problems." The Computer Journal, Vol. 10 (1): 85–86.
Jenson S. K. and J. O. Domingue. 1988. "Extracting Topographic Structure from Digital Elevation Data for Geographic Information System Analysis." Photogrammetric Engineering and Remote Sensing, Vol. 54 (11): 1593-1600.
Pierre Soille, Jurgen Vogt, and Roberto Colombo, 2003, "Carving and adaptive drainage enforcement of grid digital elevation models." Water Resources Research, Vol. 39, NO. 12, 1366.