An estuary is a coastal, funnel-shaped mouth of a river and is influenced by the tide. The Ems estuary forms the lower course of the Ems, which is subject to the tidal influence of the North Sea (saltwater) and the headwater (freshwater) flowing from the inland. When freshwater and saltwater mix, it is called brackish water. 

The land between the dyke and the river is called the outer dyke, and land on the side where the river is averted is called the inner dyke.

Scouring is defined as the process of erosion at the bed of bodies of water, which turbulence swirls up into the current. The result: a deeper bed of the body of water, or a kolk. In natural bodies of water, for example, kolks can be caused by turbulence behind rocks on the land, collapse within the bed, or sharp river bends. With regard to the Master Plan Ems 2050, the planners for the low weir or tide control must address potential scouring upon technical encroachments on the tides.

Rivers and canals that serve national economic maritime traffic are often declared to be federal waterways. These include inland and marine waterways, whereby the latter may include fairways and coastal waters. In Germany they are managed and maintained by the Federal Ministry for Transportation and Digital Infrastructure's Federal Waterways and Shipping Administration (WSV), which guarantees accessibility and ease of transit.

This concerns the migration opportunities of fish and other small animals in flowing bodies of water which may be impeded by weirs or pumping stations, among other things. The goal is to improve the traversability of these migration inhibitors.

In order to be able to transport Meyer Werft's large cruise liners from Papenburg to the North Sea, the Ems is dammed. The Ems Barrier accumulates flood water for accumulation. Water at the Ems Barrier can also be pumped into the dam, as well as from the Leda via the pumping station there. The maximum target accumulation of 2.7 metres above sea level allows ships with a depth of up to 8.5 metres to pass. Such damming is only permitted outside of the breeding season of meadow birds, as the tracts of foreland are over-dammed at this water level. No more than 12 hours of damming are permitted during the summer months – a current legal level of 1.75 metres above sea level – so as not to harm the meadow birds. The damming allows for less dredging in the fairways. The Ems Barrier may be closed for a maximum of 104 hours per calendar year for damming.

The EU Fauna-Flora-Habitat Directive not only protects endangered species, but also typical habitats such as the Ems estuary and the homes of meadow birds. Such typical habitats should be interconnected and preserved, which is accomplished by designating Natura 2000 areas. Both EU directives have not been sufficiently implemented along the Ems. This is one of the reasons for the contract violation proceedings that were threatened and which initially impeded the Master Plan Ems 2050. The state of Lower Saxony must now regularly report to Brussels with progress on the implementation of the directives.

Naturally flowing waters in plains form loops. The river then winds through the plain. In many cases these loops were penetrated to create a straight waterway for ship transit. The loops first became oxbow lakes, and were then often cut off from the river. Many have silted up and vanished completely.

In order to prevent flooding of the hinterland, dykes are installed along rivers which also prevent high tide or storm floods from overflowing into the surrounding land. Many tidal rivers are also equipped with barriers which close during storm floods and prevent this water from flowing into the river system. The Ems is equipped with the Ems Barrier and the barrier at the mouth of the Leda.

Hydromorphology describes water structures and the flow of water into a body of water. It concerns the interaction between the two. Hydromorphology also examines the extent of human encroachment on the structure (straightening, dredging) and their effects on runoff characteristics. For example, the potential of tide control on the Ems was examined with a hydromorphological model.

Feasibility studies aim to determine whether a project or measure can be facilitated with the resources at hand. It is also ascertained – at least through theoretical calculations – whether the desired results can be achieved with the respective measure. Approaches to solutions are analysed, potential risks are identified, and the chances of success are estimated.

Through the Natura 2000 programme the EU aims to interconnect the protected areas within the European Union. Within these specially protected areas, the member states must take all necessary measures to ensure the preservation of habitats and prevent their deterioration and the disturbance of species. The respective countries are responsible for submitting reports on protected areas. The Ems has been reported to the Commission as a region of general significance. The natural protected areas of the Lower and Outer Ems are currently undergoing the protected area designation process.

Potential contract violation proceedings commenced by the European Commission against member states are always preceded by a so-called EU pilot process. This is an informal, structured dialogue between the European Commission and the respective member state. This allows for the majority of presumed EU violations to be clarified in advance and usually even eliminated without the need for formal contract violation proceedings.

State matters concerning water management and nature conservation in Lower Saxony were completely delegated to the Lower Saxony State Organisation for Water Management, Coast and Nature Conservation (NLWKN) in 2005. With the head office in the city of Norden (East Friesland) and eleven branch offices, the NLWKN is represented in 15 locations throughout all of Lower Saxony. These tasks include, among others, nature conservation, (storm) flood protection, coastal protection, and the implementation of the EU Water Framework Directive, which entails the improvement of quality of water and bodies of water, and prohibits deterioration thereof. The NLWKN is one of the most important authorities for the assessment, planning, and implementation of measures in the Master Plan Ems 2050.

The draining of low-lying areas in the northern German plains (and the watering thereof during a drought) is one of the most crucial fundamentals of agriculture and life in the lowlands. Sluices are sealable water outlets in a dyke that lock from the outside upon the exertion of flood pressure, thereby preventing flooding in the areas located within the inner dyke. The sluice doors open during low tide and the water can flow out from the interior bodies of water. Pumping stations are also located at many sluices now; when the water level is low the body of water in front of the dyke is passively drained, and when the water level is high the water is mechanically pumped out of the sluice from the dyke. However, in order to be able to manage as much of the draining as possible without consuming energy, impounding reservoirs are located in some areas behind the dyke, where water can accumulate during the flood so that it may be drained during the ebb. These impounding reservoirs are especially important during floods that last for a number of days.

During the construction of the Ems Barrier, the bed of the river was protected against washout from the strong current with a fleece and stone embankment (partially braced with concrete). Should the Barrier be used to control the tide, the protection has to be extended up- and downriver.

Ebb and flow.

In this context, tidal asymmetry means that the flow phase is considerably shorter than the ebb phase. Because of this, current speeds during the flow are much faster than during the ebb. This means that the flow current carries far more sediment into the tide than the ebb can carry back out.

More information: http://vzb.baw.de/publikationen/bawaktuell/0/BAWAktuell_03_2014.pdf

 Difference in water level between high and low tide.

Influencing tidal current and/or low tide level with the Ems Barrier.

Dyked or walled-in, man-made bodies of water or reservoirs connected to the Ems so that the tide can flow in and out. They either serve to improve habitats for flora and fauns, or to improve water quality in the Ems (tidal reservoirs).

The banks of many rivers with a strong current and/or deep fairways are reinforced. This is done with stone embankments, sheet piling, or a combination of the two. Bank reinforcements are supposed to slide down and prevent washout of the banks.

EU member states who, according to the European Commission, have violated a contract obligation give the respective state the opportunity to make a statement on the respective allegations. The Commission then releases a statement with justifications. Should the respective state not respond to this statement within the term set by the Commission, the Commission may call the European Court of Justice (ECJ). If this complaint is justified, the ECJ shall announce how the contract violation will be resolved. Otherwise a fine may be set. With regard to the Ems, the Commission commenced preliminary proceedings, but did not file a complaint after signing the contract for the Master Plan Ems 2050. The state must now regularly submit progress reports.

The European Water Framework Directive standardises the legal framework for water policy in EU member states and directs it toward sustainable and environmentally friendly water consumption more than ever before. In Germany it is implemented by the Federal Water Act. This law states that bodies of water must be protected by sustainable management as a component of the natural balance, as a necessity for mankind, as a habitat for animals and plants, and as a usable good. Protection and consumption are thus interconnected goals of the law, with neither having priority over the other. Conflicts between usage interests and conservation requirements, such as those present for the Ems, must be considered and decided upon individually by the authorities. The European Water Framework Directive has made the ecological aspects more significant. Deterioration of the ecological and chemical condition of the water is not permitted through usage, but rather the water must be kept - or achieved in the event that such condition is not present, as with the Ems - in good ecological and chemical condition. With regard to bodies of water heavily altered by human activity, the priority is achieving ecological potential - namely the best possible condition of the body of water given current human usage.