The map “Hydrographic overview” at 1:750 000 in the “Atlas of the GDR”

Summary

This article explains the conception, compilation, cartographic methodology, and geographical interpretation of the map “Hydrographic Overview” at 1:750,000, published as Sheet 10 of the Atlas of the German Democratic Republic and coordinated with the companion “Hydrological Overview.” The map depicts surface-water divides and drainage basins down to the fourth order, subject to thresholds for basin area, mean discharge, and flood-peak discharge. Its river network was derived from the 1:200,000 national overview map and supplemented to include perennial natural, regulated, or relocated watercourses longer than two kilometres, together with selected shorter streams, navigation canals, interbasin transfers, standing waters, reservoirs, and flood-retention basins. Fifteen inset examples compare the atlas representation with 1:25,000 topographic maps and demonstrate the effects of cartographic generalization. A major methodological innovation is the areal portrayal of drainage density in seven classes. Values were measured or estimated for 10 km² cells, calibrated through statistical analysis, regional comparison, and control measurements, and subsequently adjusted from rectangular sampling units to boundaries reflecting hydrological, geological, geomorphological, and natural-regional conditions. The article emphasizes that the form and density of the drainage network are governed less directly by runoff volume than by relief history, substrate, geological structure, groundwater storage, and inherited palaeodrainage routes. Subsurface flow through Quaternary and Tertiary gravels, glaciofluvial deposits, karst systems, and fault zones may therefore produce substantial differences between surface and underground catchments. Genetically, the GDR is divided into a normally hierarchical network southwest of the Baruth glacial valley and a complex young-moraine drainage system to the northeast, characterized by lakes, internally drained areas, and incomplete surface connections. The regional patterns arose through crustal movements, cuesta development, salt dissolution, headward erosion, river capture, valley incision, and repeated Pleistocene glaciation. Ice sheets blocked existing rivers, created proglacial and subglacial drainage forms, established glacial valleys, and forced networks to adapt to newly formed relief. These inherited structures are examined across the principal natural regions, including uplands, forelands, old- and young-moraine lowlands, and coastal areas. The study also stresses extensive human modification. Mining water systems, mill dams, canals, river engineering, lake lowering, drainage, lignite extraction, and land-improvement projects enlarged, redirected, or locally reconstructed the network. Examples from the Havel and Jäglitz systems, the Magdeburg glacial valley, the Schraden, the Wische, and the Friedländer Große Wiese illustrate the historical shift toward managed hydrological landscapes. Modern schemes combine rapid spring drainage with irrigation during the growing season and reversible groundwater regulation. Overall, the map is presented not merely as an inventory of water bodies but as a synthetic representation of the interaction among geological evolution, glacial history, contemporary water balance, and anthropogenic water management.