PREVENTING SALT INTRUSION
THROUGH SHIPPING LOCKS:
RECENT INNOVATIONS AND
RESULTS FROM A PILOT SETUP
6 juli 2015
A brief history of the area
South west of the Netherlands:
• a delta tamed by dams,
• basins with fresh or salt water,
• basins connected by
shipping locks
A brief history of the area
6 juli 2015
Volkerak – Zoommeer:
- freshwater for agriculture
- shipping route between
Rotterdam and Antwerp
without tide;
- Volkerak locks to the North
- Kreekrak locks to the South
- Krammer locks to the West
- salt and tide vs. fresh
Krammer locks
6 juli 2015
• two lock chambers of 225 x 24 m;
• two smaller locks of 80 x 9 m;
• separation of salt and fresh water
Krammer locks
6 juli 2015
• two lock chambers of 225 x 24 m;
• two smaller locks of 80 x 9 m;
• separation of salt and fresh water
Delta Salt Barrier System
6 juli 2015
- air bubble screens on both lock heads,
- fresh water injection on salt water side,
- flush flow of fresh water through the lock.
Locking cycle for pilot set-up
6 juli 2015
salt fresh salt fresh
Levelling HW 1 Levelling LW 1
fresh fresh
water injection air bubble screen flush flow
water injection air bubble screen
HW 2 LW 2
salt fresh salt fresh
levelling
Levelling HW 3 LW 3
salt salt
air bubble screen air bubble screen
flush flow HW 4 flush flow LW 4
around low wateraround high water
Lock head on salt water side
6 juli 2015
water supply
water distribution box
water injection slot
air supply
air injectors
Lock head on salt water side
6 juli 2015
Measurement locations
6 juli 2015
Measurement set-up
Measured signals:
• waterlevel gauges in lock chamber and approach harbour
• 3 vertical arrays of 6 CTD-Divers in lock chamber
• 2 vertical arrays of 3 or 4 CTD-Divers in each approach harbour
• CTD-Diver in culvert
Locking process recorded by the control system:
• water levels in lock chamber and approach harbour
• positions of lock gates and valves
• pump speeds
• flow of water towards the water screen
• airflow and pressure
6 juli 2015
Post-processing
‘Book keeping’ of the transportation of salt:
• with flow of water:
• for levelling
• for flushing
• through the open lock head:
• difference between total salt content in the lock chamber
between two moments:
• just before opening of the gate
• just after closing of the gate
difference between two large number:
• result sensitive to limitations in accuracy in large numbers
6 juli 2015
Basics of salt transportation
regular lockage cycles over night;
evolution of salinity in lock chamber
• up and down with lock cycle
• higher average salinity near HW,
and larger ‘amplitude’
6 juli 2015
Based on this we expect:
• salt transport to decrease during ebb
• salt transport to increase during flood
Salt Load Model
Basically ‘book keeping’ of the transportation of salt:
• with flow of water:
• for levelling
• for flushing
plus:
• density driven transport through the opened lock gate,
computed from:
• undisturbed lock exchange flow (dimensions, density difference)
• reduction factor: Salt-Leak Ratio (flow in air bubble screen and
water screen, waterlevel in the lock head, density difference)
• time during which lock gate is open
Computation for recorded lock cycles as recorded
6 juli 2015
Results of measurements (example)
Recorded and computed salt transport:
• for each cycle: time averaged salt
transport through lock head
• some mismatches ….
6 juli 2015
• calculations not so well initiated;
• measurements show low value of salt
transportation around HW
under study …..
Conclusions from the Pilot
• Despite some questions from these measurements:
• high level of confidence in the Delta Salt Barrier System,
and the predictions from the Salt Load Model;
• decision to prepare implementation of this system on the
commercial locks of the same complex;
• selection and designing of the components is now underway;
• Delta Salt Barrier System is versatile and effective:
• components can be selected to suit local needs and conditions
• Lock operation is crucial:
• time during which the lock gates are open must be limited;
• crucial role for the lock keeper
6 juli 2015
Questions ?
6 juli 2015
Thank you !
Kees-Jan Meeuse
Arend Jan van de Kerk
Otto Weiler
and many others …
6 juli 2015