The opening of the Haringvliet sluice is written in the Kierbesluit. Watch here whats involved in the implementation of this project. The opening of the sluice depends on the river discharge. The river discharge gives counter pressure to the salt water. This ensures that the water stays fresh at the freshwater intake points for agriculture and drinking water. What does it mean for the Predatortour in the coming years? Welcome to the European Predatortour. The European Predatortour is a predator fish competition which we fish in the Netherlands & Sweden. (Separate competitions)