Innovative saltwater intrusion prevention at the Krammer locks


© Rijkswaterstaat, Kees-Jan Meeuse

Saltwater intrusion prevention steps up a gear with big benefits to shipping operators and the environment

The Krammer locks, located in the Philips Dam in the Netherland’s southwest region, enable ships to move inland from the Oosterschelde to the freshwater of the Volkerak. A set of recreational and commercial locks, each 280 metres long and 24 metres wide make up the Krammer system.

For more than 25 years, the locks have used a system of salt water intrusion prevention, replacing the saltwater content in each lock with fresh water when ships move inland and vice versa. This is an effective process, but it relies on pumps and hundreds of sliding gates in the lock walls and is therefore time-consuming, energy intensive and expensive.

New benefits from existing ideas
In 2010, discussions began between the governing water authority Rijkswaterstaat and other parties to look at ways in which costs, energy and passage time could be reduced. As a result research institute Deltares, Rijkswaterstaat and Royal HaskoningDHV developed the innovative concept of air bubble screens to create a barrier that could be used to quickly and effectively separate fresh and saltwater.

Kees-Jan Meeuwse, projectmanager at Rijkswaterstaat explains: “The air screen works in combination with a water screen, flush flow or moveable sill depending on the characteristics of the lock. A pilot test earlier this year on the recreational Krammer lock proved to be highly effective in significantly reducing energy use and speeding up the passage of ships by about 40%.

“In fact,” adds Kees-Jan, “improvements were so good that discussions are now underway to approve installation on larger commercial locks. Further learning since pilot phase has also helped us identify ways in which energy use can be even further reduced.”

Environmental and ecological benefits
“And reduced energy isn’t the only benefit,” continues Wiel Tilmans from Deltares, “operational and maintenance costs are much lower too. But perhaps more importantly, under the existing system 2 – 5% of saltwater will leak from the lock during transfer. Results from the pilot study show the air screen system significantly improving on this with minimal leakage. Saltwater that intrudes on our freshwater systems can negatively impact agriculture and drinking water, so this is an important improvement.” In addition, early results show improved fish migration which will benefit the ecology of the freshwater Volkerak-Zoommeer Lake.

Cooperating for today and tomorrow
Taking innovative ideas and moving them a step further isn’t the only fascination. Huib van der Kolk from Royal HaskoningDHV, says, “One of the most important aspects of this pilot project has been the way all those involved have cooperated to help realise the air screen innovation. Generating collaboration and understanding has produced excellent results set to benefit the environment and those we have a responsibility towards in future generations.”

This pilot scheme is considered by the Dutch government to be among the most important water innovation projects taking place in the Netherlands this year. An easily retro-fitted system with quick investment returns, the air screen could be used to great benefit on 23 similar locks in the Netherlands and countless locks around the globe.

To find out more, please contact Huib van der Kolk, huib.van.der.kolk@rhdhv.com