Elsevier

Journal of Hydrology

Volume 237, Issues 1–2, 25 October 2000, Pages 17-39
Journal of Hydrology

Geomorphometric attributes of the global system of rivers at 30-minute spatial resolution

https://doi.org/10.1016/S0022-1694(00)00282-1Get rights and content

Abstract

In this paper we explore the geomorphometric characteristics and integrity of a 30′ (longitude×latitude) spatial resolution representation of the global system of potentially-flowing rivers. We quantify several geomorphometric attributes of digital, Simulated Topological Network (STN-30p) depicting potential flow pathways across the entire non-glacierized surface of the Earth. This data set was examined with respect to several metrics describing individual grid cells, river segments, and complete drainage systems. Nearly 60,000 grid cells constitute the global non-glacierized land mass. The cells are organized into more than 30,000 distinct river segments belonging to approximately 6200 drainage basins. STN-30p flow paths and drainage basins are classified as order one through six using the classification system of Strahler. STN-30p flow pathways depict rivers draining a global land area of 133.1×106km2. These pathways show a total length of 3.24×106km at 30′ spatial resolution. The relationships between STN-30p order and interior river segment numbers, accumulated sub-basin areas, and accumulated length within individual basins yield high correlation coefficients (average r2>0.96 for continents and globe). Mean values across individual continents and river orders for the bifurcation ratio (3.15 to 4.44), drainage area ratio (3.74 to 5.77), and basin length ratio (2.02 to 3.27) fall well within the ranges tabulated at finer spatial scales. A basin shape index, Sb=L/A0.5, defined as a function of potential mainstem length and drainage area, varies between 1.0 and 5.0 for basins >25,000 km2 and shows a global mean of 2.12. The structure of STN-30p potential river systems is consistent with those of rivers analyzed at finer spatial scales as demonstrated by the numerical similarity of the several geomorphometric indices analyzed. However, for a particular basin, indices from STN-30p will be based on a condensed set of river orders relative to those derived at finer scales. A first order STN-30p river is roughly equivalent to an order five-to-six river derived from 1:62,500 scale maps. While 30′ spatial resolution was found to represent well the 522 basins with areas >25,000 km2 that drain 82% of the land mass, it cannot be used with high confidence in characterizing the geomorphometry of the remaining smaller basins. For global climate and biogeochemical studies, a composite of the 30′ resolution and finer spatial resolutions appears to be necessary.

Introduction

The geomorphology of drainage basins and the organization of stream networks has been well-established for several decades (see Jarvis and Woldenburg, 1984). Quantitative tools emerged initially from field analysis of single, small catchments (e.g. Horton, 1945, Schumm, 1956) or of synthetic basins derived from statistical models (e.g. Shreve, 1966, Werner and Smart, 1973). Early regional-scale studies also exist, such as the summary of river network characteristics for the conterminous United States by Leopold et al. (1964). Recent research has focussed on scale-dependent extraction of drainage basin attributes (e.g. LaBarbera, 1989, Lammers and Band, 1990, Helminger et al., 1993, Band and Moore, 1995) as well as assessments of the influence such attributes have on hydrological response (e.g. Beven et al., 1988, Band et al., 1991, Band et al., 1995, Moore and Grayson, 1991, Famiglietti and Wood, 1994, Rodriguez-Iturbe, 1993, Sivapalan, 1993). However, these studies never progressed to the global scale and the generality of the statistics presented still requires testing as a precursor for use in global change studies.

We recently presented (Vörösmarty et al., 2000a) a gridded river networking scheme, global in domain and organized at 30′ spatial resolution and offered details on the construction and verification of this data base, its geographic co-registration to discharge and river chemistry monitoring stations, and an analysis of land-to-ocean linkages. We have applied versions of the STN-30p data set in water budget and river discharge studies at the regional (Vörösmarty et al., 1996a, Vörösmarty et al., 1991), continental (Lammers et al., 2000), and global scales (Fekete et al., 1999). It has also been used to study the impact of large reservoirs on continental runoff distortion and suspended sediment flux (Vörösmarty et al., 1997b, Vörösmarty et al., 1997c). The 1° to 30′ scale is developing as the focal point for continental and global-scale water and constituent transport modeling (e.g. Seitzinger and Kroeze, 1998, Oki and Sud, 1998, Ludwig et al., 1996, Ludwig and Probst, 1998, Vörösmarty et al., 1997a, Vörösmarty et al., 1997b, Vörösmarty et al., 1997c, Oki et al., 1995, Esser and Kolhmaier, 1991), which will require simulated river networks like STN-30p. The 30′ spatial resolution appears to be a sensible compromise between the necessary level of topological detail and computational requirements of finer-scale global data sets (e.g. Graham et al., 1999, USGS-EDC, 1998). Ongoing work is aimed at developing tools to create and analyze the nature of aggregated river networks using finer-scale data sets.

Section snippets

Methods

The steps and algorithms used in constructing the digital river network data set are summarized in Fig. 1. We developed the Simulated Topological Network for potential flow pathways (STN-30p) by spatially aggregating to 30′ (longitude×latitude) the ETOPO5 five to ten-minute digital elevation model (DEM) (Edwards, 1989), which was the best global data set available to us at the time we initiated this study. Because the data set is in geographic coordinates, individual cell areas change with

Results and discussion

In the following sections we present a set of geomorphometric attributes describing the STN-30p river networks and their associated drainage basins. We provide summaries for each of six continents and the globe, and use several individual river systems to highlight our major findings. The STN-30p river networks are shown in Fig. 3and the drainage basins in Fig. 4.

Conclusions

We have analyzed the spatial organization of the global land mass using a simulated topological network (STN-30p) representing potential flow pathways across the entire non-glacierized surface of the Earth at 30′ (longitude×latitude) spatial resolution. We derived from STN-30p a set of geomorphometric statistics on river segments defining sub-basins, complete drainage basins, individual continents, ocean basins, and the globe.

From both our study of individual stream segments reported here and

Acknowledgements

We wish to thank colleagues who assisted in the verification of STN-30p digital products (S. Kempe, University of Darmstadt, GERMANY; N. Fleming, CSIRO Division of Water Resources, Canberra AUSTRALIA; R. Wasson, Australian National University, Canberra AUSTRALIA). We also thank two anonymous reviewers and W. Ludwig for helpful reviews. We recognize important assistance on data base development and production of graphics, which were provided by S. Glidden and B. Tucker. Financial support came

References (65)

  • Bartholomew, J.C., Geelan, P.J.M., Lewis, H.A.G., Middleton, P., Winkleman, B., 1988. The Times Atlas of the World:...
  • Bartholomew, J.C., Geelan, P.J.M., Lewis, H.A.G., Middleton, P., Winkleman, B., 1994. The Times Atlas of the World:...
  • G. Billen et al.

    Nitrogen transfers through the Seine drainage network: a budget based on the application of the River Strahler Model

    Hydrobiologia

    (1999)
  • P.A. Burrough

    Principles of Geographical Information Systems for Land Resources Assessment

    (1986)
  • S.L. Dingman

    Physical Hydrology

    (1994)
  • M. Dynesius et al.

    Fragmentation and flow regulation in river systems in the northern third of the world

    Science

    (1994)
  • Edwards, M., 1989. Global Gridded Elevation and Bathymetry (ETOPO5), Digital Raster Data on a 5-minute Geographic Grid....
  • ESRI

    Arc/World 1:3 M Digital Data on CD-ROM: Users Guide and Data Reference

    (1992)
  • G. Esser et al.

    Modelling terrestrial sources of nitrogen, phosphorus, sulphur, and organic carbon in rivers

  • J.S. Famiglietti et al.

    Multi-scale modelling of spatially variable water and energy balance processes

    Water Resour. Res.

    (1994)
  • Fekete, B.M., Vörösmarty, C.J., Grabs, W., 1999. Global, Composite Runoff Fields Based on Observed River Discharge and...
  • Grabs, W., DeCouet, T., Pauler, J., 1996. Freshwater Fluxes from Continents into the World Oceans Bases on Data of the...
  • S.T. Graham et al.

    Five-minute and 1/2°, and 1° data sets of continental watersheds and river networks for use in regional and global hydrologic climate system modeling studies

    Water Resour. Res.

    (1999)
  • K.R. Helminger et al.

    On the use of digital elevation model data for Geographic Information System analysis

    Photogr. Engin. Remote Sens.

    (1993)
  • R.E. Horton

    Erosional development of streams and their drainage basins: Hydrophysical approach to quantitative morphology

    Bull. Geol. Soc. Am.

    (1945)
  • Jarvis, R.S., Woldenberg J.J., (Eds.), 1984. River Networks, Benchmark Papers in Geology #80. Hutchinson-Ross,...
  • Z. Kaczmarek

    Water resources management

  • G.W. Kite et al.

    Simulation of streamflow in a macroscale watershed using general circulation model data

    Water Resour. Res.

    (1994)
  • R. LaBarbera et al.

    On the fractal dimension of stream networks

    Water Resour. Res.

    (1989)
  • Lammers, R.B., Shiklomanov, A.I., Vörösmarty, C.J., Peterson, B.J., 2000. An assessment of the contemporary gauged...
  • L.B. Leopold et al.

    Fluvial Processes in Geomorphology

    (1964)
  • W. Ludwig et al.

    River sediment discharge to the oceans: present-day controls and global budgets

    Am. J. Sci.

    (1998)
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