N. Geleynse1*, K. van der Laan1, M. Traas1, L. Perk1
1 WaterProof Marine Consultancy & Services
* Corresponding author: nathanael.geleynse@waterproofbv.nl
Introduction
Near the discharge locks at Kornwerderzand, a cut in the Afsluitdijk is realized for fish migration. At the Lake IJssel side, a meandering stream is planned: the fish migration river (VMR). Here, fish can adapt to the saline-fresh water transition. Our study focuses on two aspects: (1) expected changes in the morphology of the lake bed eastward of the VMR and adjacent to the existing scour holes at the discharge locks and (2) expected changes in the salinity distribution. This work focuses on the second aspect.
Objective and Methods
To determine the expected changes in salinity in Lake IJssel, the measured salinity response to various lock discharges was studied. Also, a 3-D Delft3D model was constructed to compute the salinity fields. Firstly, measured salinity levels were used to calibrate the model in terms of the influx of salt at the onset/stop of discharging and due to leakage through the lock complex. The calibrated model was then used to examine the changes in salinity levels due to various effects, including changes in layout, lock discharges and wind effects.
Results
The 3-D Delft3D model provides a useful tool to assess the salinity response to changes in the layout related to the construction of the VMR. The effects of future changes in the lock discharge regime or wind on the salinity distributionin Lake IJssel can also be assessed.
Figure 1: (A) Comparison between computed and measured salinity at different heights at the measurement location in Lake IJssel, south of Kornwerderzand for (B) a lock discharge time series in April-2021. (C) Computed spatial changes of salinity along a transect cross to the dike.
