A Micro Controller Based Sensor System for Autonomous Measurements of Submarine Groundwater Discharge

Michael.Schlueter [ at ] awi.de


An instrument for volumetric measurements of groundwater discharge was improved and tested with coastal groundwater springs, which can be found close to Sahlenburg, Cuxhaven. A new measurement procedure is applied. The procedure is based on the injection of sodium chloride and the determination of the variation of conductivity with flow of discharging groundwater. Hardware was revised and a microcontroller unit was set-up, to automate the measurement procedure. Mean residence time (MRT) of sodium chloride was measured with a program on the microcontroller, that simultaneously controls actuators and logs data. Volumetric flow is calibrated with MRT-measurements at constant flow in a laboratory. A feature is the detection of flow direction additionally to measurement of volumetric flow. Auxiliary sensors were integrated, to measure conductivity temperature and depth, when the device is inundated. The device was three times successfully tested at the field site. Two operations included inundation and measurements during high tide. Progresses of logged volumetric flow rates showed distinctively, that positive and negative trends coincided well with periodic variations of the water level due to tides. Maxima occurred, when inundation with seawater started, followed by decreases. Lowest flow rates were measured at high tide. With decreasing water levels, intensities of discharge were rising passing a second maximum at the time, when the location fell dry.

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Thesis (Bachelor)
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Maier, P. (2016): A Micro Controller Based Sensor System for Autonomous Measurements of Submarine Groundwater Discharge , Bachelor thesis, Hochschule Bremerhaven & AWI.

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