Delineation and Evaluation of Hydrologic-Landscape Regions in the United States Using Geographic Information System Tools and Multivariate Statistical Analyses

Abstract

Hydrologic-landscape regions in the United States were delineated by using geographic information system (GIS) tools combined with principal components and cluster analyses. The GIS and statistical analyses were applied to land-surface form, geologic texture (permeability of the soil and bedrock), and climate variables that describe the physical and climatic setting of 43,931 small (approximately 200 km2) watersheds in the United States. (The term "watersheds" is defined in this paper as the drainage areas of tributary streams, headwater streams, and stream segments lying between two confluences.) The analyses grouped the watersheds into 20 noncontiguous regions based on similarities in land-surface form, geologic texture, and climate characteristics. The percentage of explained variance (R-squared value) in an analysis of variance was used to compare the hydrologic-landscape regions to 19 square geometric regions and the 21 U.S. Environmental Protection Agency level-II ecoregions. Hydrologic-landscape regions generally were better than ecoregions at delineating regions of distinct land-surface form and geologic texture. Hydrologic-landscape regions and ecoregions were equally effective at defining regions in terms of climate, land cover, and water-quality characteristics. For about half of the landscape, climate, and water-quality characteristics, the R-squared values of square geometric regions were as high as hydrologic-landscape regions or ecoregions.

Willamette River Basin surface water isoscape (δ18O and δ2H): temporal changes of source water within the river

“…We tested the model on isotope data from 58 independent sites within the Willamette Basin that were part of a different study (Fig. 1 To apply the selected water isotope model basinwide to create the isoscape, we generated hydrologic assessment units for the entire Willamette Basin using the NED and methods similar to those described by Wolock et al (2004). We extracted a linear stream network from the DEM using a 25 km 2 minimum drainage area threshold for initiating the synthetic stream network.…”

Hydrological landscape classification: investigating the performance of HAND based landscape classifications in a central European meso-scale catchment

“…For example, Winter (2001) classified the catchment into hydrological landscape units (upland, valley side and lowland) exploiting the combination of topographic, geological and climatic conditions. Based on this concept Wolock et al (2004) classified hydrological units for the entire United States of America using GIS data. Topography, land use and geology have also been used to directly infer dominant runoff processes within a catchment (Flügel, 1995;Naef et al, 2002;Schmocker-Fackel et al, 2007;Hellebrand and van den Bos, 2008;Müller et al, 2009).…”

Scaling down hyporheic exchange flows: from catchments to reaches

“…The topographic slope defines the direction of flow by creating discontinuities and localized groundwater flow paths (Toth, 1963; 15 Wolock et al, 2004;Devito and Smerdon, 2005;Mitchell-Bruker and Haitjema, 2005). Spectral analysis has demonstrated the fractal nature of land topography and the associated fractal distribution of recharge and discharge areas and of subsurface flows (Wörman et al, 2006.…”