Use of the non-invasive GPR method and remote sensing for determining groundwater vulnerability due to anthropogenic impacts

The degree of groundwater vulnerability to pollution depends on several factors. It is conditioned by natural hydrogeological settings and further exacerbated by anthropogenic impacts as one of the greatest burdens on the quality of groundwater comes from diffuse pollution in agriculture. In reducing groundwater pollution, spatial knowledge of the geological settings, soil properties and dynamics of hydrogeological processes is crucial. Currently, point data from the field (soil profiling, moisture probes, etc.) are used to determine groundwater vulnerability. However, due to the high heterogeneity of hydrogeological and soil conditions in nature, they often fail to reflect the actual state of the wider area. As a result, vulnerability assessments may over‐ or underestimate the actual state, which is not conducive to ensuring the sustainable use of agricultural land. International research shows that non‐invasive methods of ground penetrating radar (GPR) and remote sensing are increasingly used to obtain spatial data on hydrogeological soil features. Combining such methodological approaches would present a significant breakthrough in Slovenian hydrogeological studies on groundwater protection. Within the proposed project, we will therefore carry out a comprehensive 3D hydrogeological analysis on selected agricultural areas, combining spatial GPR and aerial imagery with the results of pedological soil analyses, and corroborate the obtained data through computer modeling. This will allow for a more accurate assessment of groundwater vulnerability and contribute to the preservation and improvement of drinking water quality. To this end, we will measure the pedological properties at selected points of agricultural fields, and use the obtained data to model the movement of water and nutrients in the soil. We will compare these data with the actual soil properties gained from sampling the soil solution in lysimeters. We will use standard analytical approaches (soil analysis, dielectric probes) as well as the SWAT and HYDRUS computer models. SWAT allows for examining short‐ and long‐term impacts of different agricultural practices and predicting the impact of land management on the amount of agriculture‐derived chemical substances, taking climate change into account. HYDRUS model determines the transport parameters of water and pollutants to the unsaturated zone. We will also test the suitability of non‐invasive methods for continuous spatial measurement of soil properties. We will use the GPR, which provides continuous data on soil composition and depth of groundwater, as well as data on the presence of discontinuities (cracks, karst features, etc.). With this method we will be able to create a 3D spatial model of the subsurface and determine the most representative location for soil profiling and installation of dielectric probes. In addition to GPR, we will also determine the soil properties by using an unmanned aerial vehicle, i.e. drone, equipped with different types of cameras. Remote sensing will enable us to track changes in soil and growth throughout the growth period without interfering with the agricultural surface. Combining spatial data obtained via these non‐invasive methods with the point data obtained through the already established approaches will enable a more accurate assessment of groundwater vulnerability. Through this integrated approach we will produce a final spatial model in the GIS system, which will include data on both natural properties and anthropogenic impacts on the transport of pollutants to the groundwater. They will contribute to the optimization of precision agriculture and thus help reduce the impact of agricultural activity on groundwater. Finally, integration of the mentioned methods will represent an important research innovation in hydrogeological research in the field of groundwater vulnerability.