Development of a 3D geological model of the island of La Palma (Canary Islands) to improve the management of the groundwater resources

Sustainable management of water resources in insular aquifers is a major challenge due to the special vulnerability of these territories to climate change. Therefore, it is very important to develop tools that help to understand the water resources of these regions. Currently, 3D geological models provide data on the geometric properties of geological bodies, allowing the inference of volumes and the availability of their water resources for exploitation. Additionally, 3D models allow the development of numerical groundwater flow models, providing valuable geoscientific information. This work has developed the first 3D geological model of the volcanic island of La Palma (Canary Islands, Spain) using the GeoModeller software. The code uses surface and subsurface geological data and then applies a geostatistical interpolation algorithm, cokriging to obtain the 3D model. ArcGIS has also been used for geographic information management. The information sources used have been the Digital Terrain Model of the island, surface geological maps, geological cross-sections, and lithological data from hydraulic works. In order to obtain a coherent 3D model, it was necessary to define the formations of the model, reclassifying and unifying the aforementioned information. The data were distributed in different geological maps and databases, encoded in different formats and transcribed in various geological classification schemes. This is relevant because the calculation by cokriging requires the coherent definition of the formations involved in it, as well as a hierarchy between them. The geological model obtained covers the entire island of La Palma, both the emerged surface and the underwater zone, down to a depth of 3km below sea level. The model includes a hydrogeological sequence of nine formations that represent the main volcanic edifices and the most important geological and hydrogeological structures of the island, including rifts, giant landslides, and perched and semi-confined aquifers. This 3D geological model will allow the development of the first hydrogeological and geothermal model of the island. This methodology can be exported to the rest of the Canary Islands, being key to improving knowledge of the island's aquifers and developing management strategies for different climate change scenarios.