Dollart in the context of "Dortmund-Ems canal"

The Dortmund–Ems Canal is a 269-kilometre (167 mi) long canal in Germany between the inland port of the city of Dortmund (51°31′30″N 7°26′40″E / 51.52500°N 7.44444°E / 51.52500; 7.44444) and the seaport of Emden. The artificial southern part of the canal ends after 215 kilometres (134 mi) at Herbrum lock near Meppen. The route then takes the river Ems for 45 kilometres (28 mi) to Oldersum lock. From there, the canal continues along a second artificial segment of 9 kilometres (6 mi). This latter section was built because inland ships at the time of the construction of the canal were not built for the open sea, which they would have faced at the Dollart and the entry to the sea port of Emden. It is connected to the Ems-Jade Canal from Emden to Wilhelmshaven.

The Germany–Netherlands border (German: Grenze zwischen Deutschland und den Niederlanden; Dutch: Grens Duitsland-Nederland) consists of a 570-kilometre (350 mi) land and maritime border across the Dollart through the Frisian Islands into the North Sea.

The Ems (German: Ems [ɛms] ; Dutch: Eems [eːms] ) is a river in northwestern Germany. It runs through the states of North Rhine-Westphalia and Lower Saxony, and discharges into the Dollart Bay which is part of the Wadden Sea. Its total length is 362.4 kilometres (225.2 mi). The state border between the Lower Saxon area of East Friesland (Germany) and the province of Groningen (Netherlands), whose exact course was the subject of a border dispute between Germany and the Netherlands (settled in 2014), runs through the Ems estuary.

East Frisia (German: Ost-Friesland; East Frisian Low Saxon: Oost-Freesland) is a collective term for all traditionally Frisian areas in Lower Saxony, Germany, which are primarily located on a peninsula between the Dollart and the Jade Bight. Along with West Frisia and North Frisia, it is one of the most commonly used subdivisions of Frisia.

It is distinct from Ostfriesland – also translated to English as "East Frisia" – which refers to a historic region that occupies the western half of the peninsula (Aurich, Leer, Wittmund and Emden). Besides Ostfriesland, East Frisia includes Landkreis Friesland and Wilhelmshaven (Oldenburger Friesland), and in a broader sense also Saterland, the Butjadingen peninsula (Rüstringen) and Land Wursten.

West Frisia (/ˈfriːʒə/; Latin: Frisia Occidentalis; West Frisian: West-Fryslân) is a term that, when used in an international context, refers to the traditionally Frisian areas that are located west of the Dollart (i.e. in the present-day Netherlands). Along with East Frisia and North Frisia, it is one of the most commonly used subdivisions of Frisia. In its narrowest sense, the term is synonymous with the province of Friesland. Within the Netherlands, however, it is mostly used to refer to the region of West Friesland, located west of Friesland.