Thursday, May 18, 2006

HydroSHEDS: Hydrologic Watershed Data for the World

As seen on the CAA: Cartography Blog this morning, the World Wild Life Fund is partnering with the U.S. Geological Survey (USGS), the International Centre for Tropical Agriculture (CIAT), The Nature Conservancy (TNC), and the Center for Environmental Systems Research (CESR) of the University of Kassel, Germany to make available HydroSHEDS, a world wide watershed based hydrologic database.

As of now, only data for South America is available, but I would imagine this is the first time such data is made available in a consistent format for such a broad area. The data, served by the USGS, is downloadable in ESRI Shapefile format for vector data and ESRI GRID format for raster data.

“HydroSHEDS is a mapping product that provides hydrographic information for regional and global-scale applications in a consistent format. It offers a suite of geo-referenced data sets (vector and raster) at various scales, including river networks, watershed boundaries, drainage directions, and flow accumulations. HydroSHEDS is based on high-resolution elevation data obtained during a Space Shuttle flight for NASA’s Shuttle Radar Topography Mission (SRTM).”

Archaeologists, at least in the US, often use watershed boundaries as a base unit of analysis, especially in constructing settlement models. Interestingly, I was once told (please help me out if this is dead wrong) that in US archaeology, watershed studies focus on the river and the watershed is the boundary, whereas in European archaeology, the topographic divide is the focus and the rivers are the boundary. This thought opens up a number of avenues for discussion. Does this relate to the types of archaeology, ie. Roman outlooks vs. Late Woodland Villages, or the types of analysis. Chances are, it is a bit of both and everything in between.

Watersheds, as with environmental studies, offer the archaeologists a non-political boundary for which to contextualize there data. It can, and has, been argued that such thinking is just archaeological environmental determinism. Seen as, a way of stripping Native Americans of social creations and complexities that would extend their influence and accessibility beyond a topographic divide. And I agree, it does at times limit our analysis to say this watershed is one way and this one is another, but especially in the Eastern United States, most of the time this is all out data resolution will allow. The watershed of a major river is a large chunk of land, but the great thing about sheds is that they are conglomerations of smaller sheds and build into larger sheds. Although an imperfect unit of analysis for socially active agents of any time period, the natural fractal nature of watershed boundaries works well. This is not to mention the ethnographic data, both from contact America and elsewhere that show that watersheds boundaries were quite important.

Back to the topic at hand, this data set should be helpful not only to hydrologists, ecologists, and other environmental studies, but to archaeologists as well.

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