The Dollart (German name, ) or Dollard (Dutch name, ) is a bay in the southâÂÂeastern Wadden Sea at the GermanyâÂÂNetherlands border, west of the Ems estuary. It forms the innermost part of the EmsâÂÂDollart estuarine system and is characterised by extensive intertidal flats, salt marshes and shallow channels. A large proportion of the surface falls dry at low tide, creating internationally important feeding grounds for migratory shorebirds and waterfowl. The remaining unembanked forelands belong to the transnational Wadden Sea World Heritage Site.
The toponym appears in lateâÂÂfifteenthâÂÂcentury sources as Dollard/Dullert. A contemporary dossier from the Aduard monastery (c. 1485) and a notice by the Groningen rector Wilhelmus Frederici (1498/99) are among the earliest mentions. The origin of the name is uncertain. A plausible explanation derives it from Middle Dutch dole/dole in the sense of a "large pit, pool" (hence "deep, excavated water"), alternatively "grave/pit of the dead"; popular earlyâÂÂmodern writers instead connected it with the "furious nature" (Dutch: dolle aard) of the sea in this area, a view paraphrased by Ubbo Emmius around 1600 as "from the rage of its waves" (a fluctuum rabie). The related form Dullaert/Dollaert is also attested historically for other sea inlets, such as the Braakman in Zeeland.
The Dollart lies south of the seaport city of Emden (Germany) and northâÂÂeast of Delfzijl and Eemshaven (Netherlands). Its mouth, the Dollartmond, opens to the northâÂÂwest between the Dutch headland Punt van Reide and the tidal flat known as the Geise that separates the Dollart's channel system from the Emden fairway of the Ems. From north to south the bay is about 9 km wide. Its presentâÂÂday surface area is about 100 km<sup>2</sup>, of which the larger share is intertidal; on the Dutch side alone, c.à9,100àha is open tidal area and c.à1,050àha consists of saltâÂÂmarsh forelands. The German portion is partly included in the Lower Saxony Wadden Sea National Park.
Freshwater enters principally from the Westerwoldse Aa, which debouches at Nieuwe Statenzijl through the BuitenâÂÂAa and Schanskerdiep into the main channel, the Groote Gat; another important channel is the Kerkeriet. The tidal range in the bay averages around 3àm, with values rising seaward from c.2.6àm near the Eemshaven. The water is brackish, with strong spatial and seasonal salinity gradients.
To stabilise the Emden fairway and prevent a southward shift of the Ems, German authorities from 1872 onward built a system of groynes, separation and guiding works along the Geise (Geise Leitdamm). These training structures concentrated the tidal flow near the north shore and deepened the Emden channel; as a consequence, most tidal exchange between the bay and the Ems takes place through the narrow Dollart mouth west of Punt van Reide.
The Dollart originated gradually during the later Middle Ages through a combination of peat excavation and oxidation, soil subsidence, bank erosion and repeated storm surges that progressively converted a lowâÂÂlying peat and clay landscape into an estuarine basin. Earlier scholarship placed the catastrophe in 1277 or connected it with the Marcellus flood of 1362, but historical and geological studies indicate a much more protracted process with stepwise enlargements. Archaeology shows that freshwater conditions persisted inland near Bad Nieuweschans, Vriescheloo and Scheemda into the fifteenth century, whereas saltâÂÂtolerant vegetation already characterised the Pogum area on the German side in the thirteenth century.
A decisive enlargement occurred during the Cosmas and Damian flood of 1509, which drove the sea far inland. Contemporary and earlyâÂÂmodern sources speak of more than thirty settlements lost; the East Frisian chronicler Eggerik Beninga reported twentyâÂÂfour, likely closer to the truth. By around 1520 the bay had reached its maximum extent, commonly estimated at 340âÂÂ350 km<sup>2</sup>. WellâÂÂknown drowned places include Oosterreide and Westerreide, Fletum, Torum and the Premonstratensian monastery of Palmar (Porta Sanctae Mariae).
From the sixteenth century onward, both shores undertook extensive land reclamation. By means of dikes and polders roughly twoâÂÂthirds of the inundated area was recovered between the sixteenth and twentieth centuries. On the German side the last major enclosure was the Kanalpolder (1877); on the Dutch side, the Johannes Kerkhovenpolder (1878), the Carel Coenraadpolder (1924) and the Polder Breebaart (completed 1979). Polder Breebaart was ultimately developed as a nature reserve and, upon opening in 2001, became the first managed inland tidal area in the Netherlands.
The Dollart's extensive intertidal flats and salt marshes support rich benthic microphytobenthos and invertebrate communities that feed large numbers of waders and waterfowl along the East Atlantic Flyway. The Dutch sector alone comprises c.à9,057àha of open tidal area and 1,057àha of salt marshes; the forelands on the German shore add several hundred hectares. The area is designated as a Ramsar site as part of the 121,620âÂÂha Wattenmeer, Ostfriesisches Wattenmeer & Dollart (listed 1976; on the Montreux Record since 1990), as Birds Directive and Habitats Directive sites, andâÂÂon the German shoreâÂÂwithin the core zones of the Lower Saxony Wadden Sea National Park. In 2009 the transboundary Wadden Sea was inscribed on the World Heritage List for its outstanding biodiversity and geomorphological processes.
High suspendedâÂÂsediment concentrations and persistent turbidity are longâÂÂrecognised ecological pressures in the EmsâÂÂDollart system. Following construction and commissioning of the Emssperrwerk (Ems Barrier) at Gandersum in 2002âÂÂbuilt for stormâÂÂsurge protection and to facilitate ship transfers from the Meyer Werft yardâÂÂGermany and the Netherlands agreed to develop a joint "ecological strategy for sediment management" to reduce the silt surplus, improve ecological status and increase climate resilience. On the Dutch shore, the Brede Groene Dijk (Broad Green Dike) pilot near Nieuwe Statenzijl demonstrates climateâÂÂresilient dike reinforcement using clay produced from locally harvested estuarine silt; in 2022 some 70,000àm<sup>3</sup> of matured clay was applied to strengthen a 750âÂÂm dike section, with further rollâÂÂout planned after 2025.
Large parts of the Dutch intertidal area are owned by Natuurmonumenten and managed by Het Groninger Landschap; the latter also manages the Dollard foreland marshes, the Punt van Reide headland and Polder Breebaart. On the German side the coastline belongs to the Landkreis Leer and the municipality of Jemgum; nature conservation is framed by the National Park and EU designations. Ports at Emden, Delfzijl and Eemshaven handle sea and inland shipping. The historical protection of the Emden fairway by the Geise training works continues to shape navigation. A seasonal passenger ferry Dollard connects Ditzum, Emden and Delfzijl and forms the keystone of the crossâÂÂborder cycling route Internationale Dollard Route.
The precise maritime boundary through the Dollart and the outer Ems has never been definitively delimited. Both states maintain conflicting legal positions but have preferred pragmatic cooperation to adjudication. On 8ÃÂ AprilÃÂ 1960 the Netherlands and the Federal Republic of Germany concluded the Ems-Dollart Treaty, which organised navigation, fisheries and administrative cooperation in the estuary while leaving sovereignty claims unaffected.
In 2011 the issue gained practical prominence when Germany issued permits for the Riffgat offshore wind farm within the 12âÂÂnauticalâÂÂmile zone, an area affected by the differing claims. A second bilateral agreement was signed on 24àOctoberà2014 to regulate "use and management" of the territorial sea between 3 and 12ànautical miles by reference to a functional line; the treaty expressly states that it is not a boundary settlement and preserves both parties' positions. Media reports at the time described the dispute as "ended", but the agreement does not demarcate sovereignty.
SeventeenthâÂÂcentury maps by Ubbo Emmius (1630, after Jacob van der Meersch, 1574) depict the drowned villages of the Dollart. The loss of Reiderland in particular entered regional memory; folklore speaks of bells still ringing beneath the waves. In the twentieth century, the neverâÂÂbuilt Dollarthafen deepâÂÂwater port proposed for Emden (1970sâÂÂ1980s) became a focus of crossâÂÂborder environmental activism and intergovernmental negotiation; the project was abandoned in 1988 on economic grounds. Today the area is a centre for natureâÂÂbased recreation; the Kiekkaaste bird hide near Nieuwe StatenzijlâÂÂstanding outside the sea dike on the borderâÂÂis a wellâÂÂknown vantage point over the marshes and tidal flats.
Ems Dollart Region (EDR), a DutchâÂÂGerman euroregion founded in 1977