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Design Monitoring Network Fresh Groundwater Resources Zeeland -  Technical and geohydrological research

Clients: Province of Zeeland and Water Board Scheldestromen 

Understanding the dynamics of fresh groundwater resources in the Zeeland subsurface is important for sustainable use of these resources. Many new agricultural withdrawals have been added over the past 10 years, but there is no monitoring of whether and what effect this is having on the freshwater lenses. In this project, a monitoring network was designed to monitor fresh groundwater resources. The measurement technique was been worked out based on a so-called 'automatic salt keeper'. This consists of a cable on which there are several electrodes, and a measuring instrument consisting of a sensor/switching module and telemetry.  Also a  geohydrological survey of potential measurement sites has been conducted. These locations were assessed based on available data of the subsurface, groundwater system and fresh-salt groundwater situation. On top, 53 conductivity probes were conducted as input for the design of the monitoring network. These locations will be equipped with a monitoring well for monitoring the phreatic groundwater level and a salinity probe for measuring at the fresh-salt distribution in the groundwater. The appropriate placement depth of the salinity monitor cable was determined for each location, using a fixed electrode section with as much as 24 electrodes over a total length of 11.5 m (electrode spacing of 0.5 m).

Report: Kaandorp, V. P., & Hopman, V. (2024). Ontwerp Meetnet Zoetwatervoorkomens Zeeland - Technisch en geohydrologisch onderzoek. In Deltares report 11207005-002-BGS-0001.

Lock Facility

Deltares can test lock designs in the Lock Facility. It features brine storage and salt mixing tanks, as well as underground reservoirs for storage of salt- and freshwater. The Lock Facility was used to study the flow patterns around the salt screen used to selectively withdraw salt water near the new sea lock in IJmuiden.

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Computational Fluid Dynamics (CFD)

Computational Fluid Dynamics analyses in salinisation projects are often carried out using Simcenter STAR-CCM+, a commercial CFD based simulation software. STAR-CCM+'s description of the buoyancy-term in the Navier-Stokes equations and k-epsilon turbulence models has been validated by Deltares.

Other CFD software packages include D-HYDRO and OpenFOAM but these are used less frequently in salinisation projects

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iMOD

iMOD is freely available and open source software for a wide range of ground water modelling tasks. iMOD consists of user interfaces, pre- and postprocessing software and computational cores based on USGS MODFLOW source code to support analysis of groundwater flow.

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Airborne Electromagnetic (AEM) geophysical methods

Met deze meettechniek wordt met een actief elektromagnetisch (EM) systeem de elektrische geleidbaarheid van de ondergrond bepaald. De uitvoerig vindt plaats vanuit het vliegtuig of de helikopter. Door gebruik te maken van verschillende frequenties kan op verschillende diepten worden gemeten en een geleidbaarheidsprofiel van de bodem worden opgebouwd. Twee specifieke toepassingen zijn HEM (ontwikkeld door BGR, Duitsland) en Sky-Tem (ontwikkeld door Universiteit Aarhus, Denemarken).

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Sea Lock Formulation

Quick assessment tool to calculate the influence of salt intrusion through shipping locks on the salinity of fresh water, which can for example be used to calculate the salinity at drinking water abstraction points or the salinity of irrigation water.

The Sea Lock Formulation is the successor of WANDA-Locks and the Zoutlekmodel (literally: 'salt leakage' model). Previous box-models also included SWINLOCKS.

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