Hydrography90m: a new high-resolution global hydrographic dataset

Abstract

Abstract. The geographic distribution of streams and rivers drives a multitude of patterns and processes in hydrology, geomorphology, geography, and ecology. Therefore, a hydrographic network that accurately delineates both small streams and large rivers, along with their topographic and topological properties, with equal precision would be indispensable in the earth sciences. Currently, available global hydrographies do not feature small headwater streams in great detail. However, these headwaters are vital because they are estimated to contribute to more than 70 % of overall stream length. We aimed to fill this gap by using the MERIT Hydro digital elevation model at 3 arcsec (∼90 m at the Equator) to derive a globally seamless, standardised hydrographic network, the “Hydrography90m”, with corresponding stream topographic and topological information. A central feature of the network is the minimal upstream contributing area, i.e. flow accumulation, of 0.05 km2 (or 5 ha) to initiate a stream channel, which allowed us to extract headwater stream channels in great detail. By employing a suite of GRASS GIS hydrological modules, we calculated the range-wide upstream flow accumulation and flow direction to delineate a total of 1.6 million drainage basins and extracted globally a total of 726 million unique stream segments with their corresponding sub-catchments. In addition, we computed stream topographic variables comprising stream slope, gradient, length, and curvature attributes as well as stream topological variables to allow for network routing and various stream order classifications. We validated the spatial accuracy and flow accumulation of Hydrography90m against NHDPlus HR, an independent, national high-resolution hydrographic network dataset of the United States. Our validation shows that the newly developed Hydrography90m has the highest spatial precision and contains more headwater stream channels compared to three other global hydrographic datasets. This comprehensive approach provides a vital and long-overdue baseline for assessing actual streamflow in headwaters and opens new research avenues for high-resolution studies of surface water worldwide. Hydrography90m thus offers significant potential to facilitate the assessment of freshwater quantity and quality, inundation risk, biodiversity, conservation, and resource management objectives in a globally comprehensive and standardised manner. The Hydrography90m layers are available at https://doi.org/10.18728/igb-fred-762.1 (Amatulli et al., 2022a), and while they can be used directly in standard GIS applications, we recommend the seamless integration with hydrological modules in open-source QGIS and GRASS GIS software to further customise the data and derive optimal utility from it.

Lake-TopoCat: A global lake drainage topology and catchment database

“…About 58 million river reaches were delineated, with a total length of ~75 million km. It is important to note that the point of MERIT Hydro-Vector was not to simply vectorize MERIT Hydro to the finest spatial detail (as something done by Hydrography90m (Amatulli et al, 2022)), but to simulate spatially variable river networks so that the vectorized channels resemble the actual densities of perennial and/or intermittent rivers in the world.…”

The global EPTO database: Worldwide occurrences of aquatic insects

“…Sixty-two percent of all occurrence records correspond to observations of Odonata, which is probably related to their being considered as charismatic, not least because their specimens are easily observable due to their size, colour patterns, and flying style (Vorster et al, 2020). The database includes more than 15 records for most genera of each order for which we have occurrence data Unique ID of the sub-catchment where the record is located, based on the Hydrography90m dataset (Amatulli et al, 2022) basin_ID Unique ID of the drainage basin where the record is located, based on the Hydrography90m dataset (Amatulli et al, 2022) elevation Elevation of the point of the record, in metres, based on the MERIT Hydro DEM (Yamazaki et al, 2019) WDPA_protection_status Status of the record's location based on the Protected Planet WDPA WD-OECM dataset, updated in November 2022 (UNEP-WCMC and IUCN, 2022). If "0", the record was not located in a protected area.…”

“…The Global EPTO Database includes 8,368,467 occurrence records, covering 1,505,302 unique locations worldwide and 39,584 out of 1.6 million drainage basins of the Hydrography90m dataset (Table 2; Amatulli et al, 2022). The records are spread across 417 out of 426 Freshwater Ecoregions of the World (FEOW, Abell et al, 2008), while 20% of them occur in protected areas.…”

AltiMaP: Altimetry Mapping Procedure for Hydrography Data

“…VSs must be assigned to river network pixels of the hydrodynamic model for accurate comparison of simulated and observed WSEs. The DEM-based river network can deviate from the cause of the actual river due to errors in DEM and low representability of the coarse-resolution of the river network (Amatulli et al, 2022;Paz et al, 2006;Yamazaki et al, 2009). 130 Moreover, the reported location of the VS provided in HydroWeb can be further away from the actual river because HydroWeb provides the center of the search region, within a range of a few kilometers (e.g., 5 km × 5 km).…”