MERIT Hydro: A High‐Resolution Global Hydrography Map Based on Latest Topography Dataset

TLDR

High‑resolution raster hydrography maps are a fundamental data source for many geoscience applications. The study introduces MERIT Hydro, a new global flow‑direction map at 3‑arc‑second resolution derived from the latest elevation and water‑body datasets. An algorithm was developed to automatically extract river networks by distinguishing true inland basins from dummy depressions caused by elevation data errors. MERIT Hydro, after minimal hand editing, shows high agreement with existing river network datasets, achieving <5% relative error for 90% of GRDC gauges, expanding coverage to N90–S60 and better representing small streams, and providing new flow‑direction, accumulation, elevation, and channel‑width layers that will enhance global and local river hydrology studies.

Abstract

Abstract High‐resolution raster hydrography maps are a fundamental data source for many geoscience applications. Here we introduce MERIT Hydro, a new global flow direction map at 3‐arc sec resolution (~90 m at the equator) derived from the latest elevation data (MERIT DEM) and water body data sets (G1WBM, Global Surface Water Occurrence, and OpenStreetMap). We developed a new algorithm to extract river networks near automatically by separating actual inland basins from dummy depressions caused by the errors in input elevation data. After a minimum amount of hand editing, the constructed hydrography map shows good agreement with existing quality‐controlled river network data sets in terms of flow accumulation area and river basin shape. The location of river streamlines was realistically aligned with existing satellite‐based global river channel data. Relative error in the drainage area was &lt;0.05 for 90% of Global Runoff Data Center (GRDC) gauges, confirming the accuracy of the delineated global river networks. Discrepancies in flow accumulation area were found mostly in arid river basins containing depressions that are occasionally connected at high water levels and thus resulting in uncertain watershed boundaries. MERIT Hydro improves on existing global hydrography data sets in terms of spatial coverage (between N90 and S60) and representation of small streams, mainly due to increased availability of high‐quality baseline geospatial data sets. The new flow direction and flow accumulation maps, along with accompanying supplementary layers on hydrologically adjusted elevation and channel width, will advance geoscience studies related to river hydrology at both global and local scales.