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