Applied Geophysics to Create Insight and Reduce Uncertainties
Water scarcity due to climate changes and over abstraction make it very important to establish groundwater sustainability plans based on accurate hydraulic flow models. Often scattered and uneven spatially distributed boreholes and general geological maps are the only information available knowledges of subsurface conditions. Geophysical data, including TDEM, are therefore used in order to minimize model uncertainties.
TDEM is a non-intrusive, effective and cost-efficient method for obtaining information about the subsurface to 400m and sometimes even deeper. With the TDEM method, the hydrogeology can be described as variations in electrical resistivity. By comparing the resistivity with information from boreholes, the distribution of the different sediments can be described and thus create a valuable base for defining the basin boundaries or setting up flow models.
Due to high contrast in conductivity of fresh and brackish groundwater, the TDEM method is particularly suitable for mapping the mixing zone between fresh and saline water, which is important when sustainably managing groundwater abstraction in coastal areas or well fields influenced by saltwater intrusion.
When designing Aquifer Storage and Recovery (ASR) solutions, the TDEM method can be used for delineating areas having hydraulic conditions suitable for infiltration of surface water or treated waste water. In same way, data can help minimizing uncertainties when designing where to extract recharged resources.
The presentation will showcase different case studies where the TDEM method has played a key role in creating insight in the hydrogeological conditions. The method has been applied since the early 90’s and is the basis for the development of airborne systems for large scale mapping purposes.