Introduction
The Terneuzen lock Complex in the Dutch city of Terneuzen gives access to the Ghent-Terneuzen Canal and thus to the port of Ghent (Belgium) from the Western Scheldt. Currently, the construction of a new lock is being prepared, which is expected to be operational in 2022.
In the context of the licensing process of the new lock, how to deal with the available (fresh)water in the most optimal way was examined. The quality values for water (mostly focusing on salt intrusion and taking into account the directions from the WFD ) must be met, while respecting at the same time the shipping requests.
As a result of these questions, combined with the daily water management issues of the canal, the decision has been made to prepare for a Decision Support System for the Ghent-Terneuzen Canal, in a joint Flemish-Dutch collaboration.
The extended paper will give an overview and further detail on both the process that led towards the definition of the DSS, as well as the content of the DSS and the technical aspects of the implementation.
The Ghent-Terneuzen Canal & the Terneuzen Locks
The Ghent-Terneuzen canal is situated on Belgian and Dutch territory and was constructed between 1823 and 1825 and ended in the Western Scheldt, thus linking the hHarbour of Ghent to the sea.
At the Western Scheldt side, originally two locks were built at Terneuzen (Netherlands). Since the original construction, the locks have been enlarged several times, evolving towards the current complex. In the near future, a new lock will be operational. The new lock will be 427 meters long, 55 meters wide and 16 meters deep and is expected to be suitable for large seagoing vessels up to 366 meters long, 49 meters wide and 15 meters deep. In Ghent (Belgium) the canal is bordered by the locking complex in Evergem, which regulates most of the freshwater supply towards the canal.
The functions of the canal are shipping and water management : shipping for access to the harbours of Ghent and Terneuzen, water management as the canal provides a discharge capacity for water coming from the upstream rivers Leie (Lys) and Schelde (Scheldt) that join in Ghent.
A treaty between Belgium and the Netherlands (1960, revised in 1985) regulates the obligations and responsibilities, focusing on the canal level and the salinity management in the canal. The treaty defines the water level in the Canal and the minimal supply of freshwater on the upstream side and the minimal discharge capacity on the downstream side, as well as the obligation to minimize the salt water intrusion on the downstream side. The freshwater supply is important both for the water levels in the canal and for limiting the salt intrusion in the canal. The limits for the salinity in the canal are defined in the context of the Water Framework Directive (WFD).
The decision support system : background
During the permitting process for the new lock in Terneuzen, the Dutch Government issued a set of conditions to ensure that the finished project would comply with the WFD , and more specifically the salinity concentrations in the canal. One of those conditions was that a group of experts would draw up an advice on the optimal use of the lock, so that the salinity in the canal remains within the standards defined in the WFD, with minimal disruption to shipping.
The expert group, including representatives from both countries, from the water management, the lock management as well as the port authorities, considered the management of the salinity in the broader picture of water and shipping management and issued a set of practical management measures and guidelines for regular situations, situations with high freshwater discharges, situations with low freshwater discharges and situations with high salinity, as well as possible combinations of those four. Those measures and rules were defined for the entire lock complex (not only the new lock ) and kept within the framework of the existing treaty. The underlying idea in the conclusions of the expert group was to provide longer-term gradual measures, with minimal disruption to shipping; and as such avoid that lock operations should experience an acute shut down because e.g. the salinity levels in the canal were too high or the water level in the canal too low.
The expert group also stated that a Decision Supporting System for the Ghent Terneuzen Canal could be an important tool in optimizing water management on the Canal with as little as possible disruption to shipping. A joint Dutch-Flemish collaboration was then set up to further define the content and technical specifications of the decision support system
The decision support system : features and applications
The DSS is designed to objectively process all relevant available information from the Netherlands and Flanders : shipping traffic information and planning, water levels, freshwater discharges, salinity, wind speed, … . Direct links and information streams are provided for the DSS with the existing tools for ship planning (both maritime and inland waterway transport), operational forecast models and in –situ measurements. With the operational forecast models, two-way information exchange is foreseen.
The first goal of the DSS will be to provide the lock operator with an awareness of the current scenario and then to provide him with a standardized, uniform overview of all relevant parameters for that scenario : discharge quantities, water levels, forecasted discharges, shipping traffic,…
The DSS will provide the operator with a proposal for the use of the lock complex over different time scales ; in addition to the proposal the DSS will, when requested, provide the operator with all the underlying relevant information. The final decision on how to operate the lock complex stays with the operator, the DSS offers advice and feedback on the decisions.
The final content and technical aspects for the decision support system are currently being completed and the implementation will start shortly. The goal is to have the DSS in service before the newly constructed lock is operational, in 2021.