Investigation of the Spatio-Temporal Behaviour of SubmarineGroundwater Discharge Using a Low-CostMulti-Sensor-Platform

Christoph Tholen, Iain Parnum, Robin Rofallski, Lars Nolle, Oliver Zielinski

In: Journal of Marine Science and Engineering (MDPI) 9 802 Seiten 1-26 MDPI Journals Basel 7/2021.


Submarine groundwater discharge (SGD) is an important pathway of nutrients into coastalareas. During the last decades, interest of researchers in SGDs has grown continuously. However,methods applied for SGD research usually focus on the aquifer or on the mixing processes onlarger scales. The distribution of discharged water within the water column is not well investigated.Small remotely operated vehicles (ROV) equipped with environmental sensors can be used toinvestigate the spatial distribution of environmental parameters in the water column. Herein, alow-cost multi-sensor platform designed to investigate the spatial distribution of water qualityproperties is presented. The platform is based on an off-the-shelf underwater vehicle carrying variousenvironmental sensors and a short-baseline localisation system. This contribution presents the resultsof SGD investigations in the area of Woodman Point (Western Australia). Various potential SGDplumes were detected using a skiff equipped with a recreational echo sounder. It was demonstratedthat this inexpensive equipment could be used to detect and investigate SGDs in coastal areas. Inaddition, the low-cost multi-sensor platform was deployed to investigate the spatial distribution ofenvironmental parameters including temperature (T), electric conductivity (EC), dissolved oxygen(DO), oxidation-reduction potential (ORP), pH, and dissolved organic matter fluorescence (FDOM).Three ROV surveys were conducted from different skiff locations. Analyses of the spatial distributionof the environmental parameters allowed the identification of nine potential SGD plumes. At thesame locations, plumes were identified during the sonar surveys. In addition, fuzzy logic was usedfor the fusion of salinity, DO, and FDOM readings in order to enhance SGD detection capability of thedesigned multi-sensor system. The fuzzy logic approach identified 293 data points as potential withina SGD plume. Average minimum-distance between these points and the identified SGD plumes was0.5 m and 0.42 m smaller than the minimum-distance average of the remaining data points of surveyone and three respectively. It was shown that low-cost ROVs, equipped with environmental sensors,could be an important tool for the investigation of the spatio-temporal behaviour of SGD sites. Thismethod allows continuous mapping of environmental parameters with a high spatial and temporalresolution. However, to obtain deeper insights into the influence of SGDs on the nearshore areas, thismethod should be combined with other well-established methods for SGD investigation, such aspore water sampling, remote sensing, or groundwater monitoring

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Investigation_of_the_Spatio-Temporal_Behaviour_of_Submarine_Groundwater_Discharge_Using_a_Low-Cost_Multi-Sensor-Platform_-_jmse-09-00802.pdf (pdf, 2 MB )

Deutsches Forschungszentrum für Künstliche Intelligenz
German Research Center for Artificial Intelligence