3D Geological model of the Medina del Campo GWB

Description

The Medina del Campo groundwater body is a large detrital aquifer in the Duero basin whose water levels fell by tens of metres over four decades of irrigation abstraction. Understanding what happened requires a three-dimensional picture of the geological formations that hold and transmit the water — not a map of the surface.

The 3D model was built from the datasets held by the Duero River Basin Authority (CHD), the litostratigraphic maps and borehole records of the Spanish Geological Survey (IGME), the isohypses of the National Plan for Groundwater Research, and lithostratigraphic columns from the TRAGSA reports, combined with the expert knowledge of IGME and UPCT hydrogeologists. It represents the aquifer in two layers: the upper 50 metres, which contain the shallow processes that matter most for the wetlands and for shallow pumping, and the remainder of the sequence down to the hydrogeological basement. The top of the model follows the digital elevation model; the base was defined from basement depth information and more than fifty borehole logs. Cells are 500 by 500 metres.

The model provides the geological framework within which the regional groundwater flow model (iMOD) and the local-scale artificial recharge models were subsequently built, and it is what makes it possible to state how much water is available, where, and at what depth.

Applications to decision making in the insurance sector

Drought exposure in a detrital aquifer is a function of storage, and storage is a geological property. The 3D model establishes how much of the abstraction can be replaced by recharge and how quickly levels respond — which is the physical basis for treating recharge as a risk-reduction measure rather than as an environmental improvement.

Added value of this modelling approach

It converts scattered records from several institutions and decades of drilling into one consistent object that can be interrogated. That is what allows a water management option to be tested against the aquifer's real geometry instead of against a conceptual sketch.

What decision can be improved with this modelling approach

Where artificial recharge would be most effective; how deep wells can be drilled before the productive layers are exhausted; and what the sustainable abstraction level of the body actually is.