Limitations in the Hydrologic Applications of C-Band SRTM DEMs in Low-Relief Settings

The shuttle radar topography mission (SRTM) data represent a major breakthrough in terms of providing accurate and consistent elevation data on a worldwide basis. These data are being used in many scientific applications, hydrology in particular. This letter examines the feasibility of using SRTM data for hydrologic characterizations, particularly in a region of low relief exemplified by the Otter Tail basin in Minnesota. The Version 2 SRTM data product provides a useful starting place for estimating the stage for larger lakes. Indications for Minnesota are that these estimates are accurate to several meters but are biased toward underestimation. Over land, the inherent noise in the data makes watershed boundary and stream network extraction problematic. We found large errors in estimated basin shape and area, and in the geometry of extracted stream networks, as compared to more traditional U.S. Geological Survey data products.