Preventing salt intrusion through shipping locks: recent innovations and results from a pilot setup

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Otto Weiler, Arend Jan van de Kerk, Kees-Jan Meeuse

Thursday 2 july 2015

8:45 - 9:00h at Europe 2 (level 0)

Themes: (T) Water engineering, (ST) River and coastal engineering

Parallel session: 10K. Managing deltas - Saline

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At many locations, freshwater canals and reservoirs are connected to the sea or estuary by shipping locks. With every passage of a vessel, a lock transports saltwater into the freshwater area, affecting the water quality for consumption, agriculture or industrial application. As a result of climate change, with increased periods of drought, freshwater is becoming increasingly scarce while economic development increases the demand for fresh water. For this reason it is becoming more important to reduce salt intrusion through shipping locks. In the Netherlands there are 23 navigational locks at fresh/saltwater interfaces, of which at present only the Krammer locks have a fully operational salt intrusion prevention system. The current system however is complex, expensive to build and maintain, requires a lot of space and increases locking time significantly. For these reasons this technique is not suitable for implementation at existing locks. An alternative system is sought with a similar level of effectiveness, but without the demands in space, time and costs. One of the traditional ways of preventing salt intrusion is the application of air bubble screens, also known as pneumatic barriers, in the lock heads. Taking this as a starting point, a highly effective combination of measures has been developed, using lab experiments, numerical simulations and field experiments. The new system, referred to as the Delta Salt Barrier System, includes improved air bubble screens, combined with freshwater injection, sills and freshwater flushing of the lock. Also, a computational tool has been developed to predict the salt intrusion for the specific site, conditions and operation. The new system has recently been tested in prototype. For one of the recreational locks at the Krammer lock complex, a pilot installation has been designed and built which has been in operation during the summer of 2014. Measurements have been taken to establish the salt intrusion using different combinations of measures. In general the measures performed as expected, although some new insights were gained as well. Furthermore the pilot has provided important experience on the operational aspects. Supported by the results of the pilot project, it has been concluded that application of the Delta Salt Barrier System would be an attractive alternative for maintenance of the existing system on the Krammer locks.