Remote sensing and integrated hydrological models in hydrogeology

Integrated hydrological models (IHMs), have become nowadays a standard method in hydrogeology. The advantages of IHMs will be discussed based on their comparison with standalone groundwater models, the two models set up and calibrated within exactly the same study area (Lubczynski and Gurwin 2005; Hassan et al. 2014). Among the differences between the two modelling methods, the main is that in the standalone groundwater models, the driving forces are represented by recharge and groundwater evapotranspiration which are typically uncertain or unavailable due to the lack of data, while in the IHMs, by rainfall and potential evapotranspiration, which are much easier to acquire in the field and besides, they can be derived by remote sensing (RS). A constant increase of IHM's popularity and easy access to readily-available RS-products (freely available, web-based, RS data), created an avenue for enhancement of RS-applications in hydrogeology. Besides, with rapid earth observation technology development, also the quality and versatility of RS products continuously increases, providing data at successively improved spatial and temporal resolutions. Three IHM studies with RS applications in three different areas will be discussed: 1) Sardon Catchment (Spain) based on: a) Hydrogeophysics and remote sensing for the design of hydrogeological conceptual models (Journal of Applied Geophysics, 2014(110)); and b) Surface groundwater interactions in hard rocks: an integrated modeling approach (Journal of Hydrology, 2014(517)); 2) Lake Turawa (Poland) based on Interactions of artificial lakes with groundwater applying an integrated MODFLOW solution (Hydrogeology Journal, 2018(26)); 3) Central Kalahari Basin (Botswana and Namibia)based on: a) Hydrogeological conceptual model of large and complex sedimentary aquifer systems (Physics and Chemistry of the Earth, 2018, doi.org/10.1016/j.pce.2018.05.006); b) Use of remote sensing and long-term in-situ time-series data in an integrated hydrological model of the Central Kalahari Basin, Southern Africa (Hydrogeology Journal, 2019, doi.org/10.1007/s10040-01901954-9). The review of the 3 study cases will be followed by a discussion on state of art (including limitations) of RS applications in IHMs and finally concluded with a vision for future developments in that field