Understanding salt intrusion in a salt wedge estuary under extreme drought conditions using data from a unique field campaign

Salt intrusion is a growing problem in deltas worldwide, and under climate change it is predicted to become an even greater problem. During extreme events like droughts salt intrusion can intrude far inland. To understand salt intrusion in urbanising deltas and come with solutions the research program SALTISolutions was carried out. One of the key elements of SALTISolutions was to understand what happens during a drought. To achieve this a dedicated field campaign was designed and conducted around the mouth of the Port of Rotterdam. Here we present some results from these unique measurements recorded during the major drought of 2022. We investigate the changes in ROFI dynamics during the drought using velocity, salinity and temperature data from various field campaigns near the mouth of the Rotterdam Waterway and within the delta. We describe the changes in the near field plume dynamics during the drought using the data from the moorings deployed around the mouth of the estuary. We show the importance of wind conditions for the connection between the near-field plume dynamics and salt intrusion, and how this changes for an extremely low discharge and shrinking river plume.