Assessing Complex Water Quality Conditions Relevant to Ballast Water Operations in the Port of Hamburg

Sammanfattning

In estuarine ports, ballast water operations can be affected by short-term changes in water quality, especially when suspended sediment concentrations increase. This thesis assesses turbidity-related water-quality conditions relevant to ballast water operations in the Port of Hamburg, focusing on Seemannshöft during 2018–2024. Because direct total suspended solids (TSS) measurements were limited, a local turbidity–TSS relationship was developed and used to estimate daily TSS from the longer turbidity record. The estimated TSS series was analysed for temporal and seasonal variability, high-TSS events, and relationships with environmental drivers, while Sentinel-2-derived Normalized Difference Turbidity Index (NDTI) was evaluated as complementary spatial information. Results showed generally moderate TSS-related conditions, interrupted by rare elevated events. Only 16 daily observations exceeded the 80 mg/L screening threshold, representing 0.71% of the record. Air temperature, wind speed, water level, upstream discharge, rainfall, and electrical conductivity explained only part of the variability. Supplementary prediction tests showed that short-term turbidity prediction improved mainly when recent turbidity observations were included, indicating strong temporal persistence in the Hamburg estuarine system. Sentinel-2-derived NDTI provided useful complementary spatial information. A multi-year P95 hotspot-frequency analysis showed spatially heterogeneous elevated optical turbidity signals, although NDTI could not replace station-based TSS measurements. Overall, complex suspended-sediment conditions mainly occurred as short events, supporting local measurements, event-based screening, and operational awareness rather than reliance on average seasonal conditions or environmental variables alone.