Because of the use of the Sea Lock, an extra amount of salt water enters the North Sea Canal. Rijkswaterstaat has deliberately chosen this time of year because then there is (normally) more water discharge and the salt intrusion is then less of a problem. In addition, in this period there is less use of water by farmers etc. This allows them to be a little more flexible with the salt levels.

In order to keep the salt levels as low as possible from the outset, it has been decided to make optimum use of the sea lock by clustered locking as much as possible, with a maximum waiting time of about 2 hours. In addition, during this time the rule of order time equals departure time will apply. This involves a maximum number of 49 sea lock passages per week (in relation to 84 passages through the Noordersluis). This is expected to be more than sufficient to handle all shipping traffic.

If you want to know more about the salt levels go to the website of Rijkswaterstaat.

Rijkswaterstaat has also taken a number of measures to get through this period as well as possible:
-RWS will increase the water discharge via the North Sea Canal
-The restriction on the Middensluis has been lifted during this period (so ships up to max 145 meters can pass through the Middensluis). 
-There has been a deliberate choice for a maximum number of locks per week so that the quantities may fluctuate per day.