Rich north, poor south - Regionalization of European water retention: The landscape hydric potential concept

Natural water retention varies greatly across Europe. Understanding the key ecosystem factors that affect the quantity, quality, availability, and spatiotemporal distribution of water resources is essential for effective landscape management. This study presents the Landscape Hydric Potential (LHP) index of Europe, which serves as an indicator of the natural environment's ability to infiltrate and retain water. The LHP index was aggregated into 12 relatively homogeneous regions, each representing similar values of natural water retention. The main factors influencing the hydric potential, and thus the water resources of Europe, include climatic conditions, geomorphology, soil properties, and land cover and use, especially the proportion of urbanized areas. Northern Europe, in comparison to southern Europe, exhibits higher LHP index values, indicating greater retention capacities. The climatic water balance is the main factor determine poorer retention capacities in the southern part of Europe. In northern Europe positive values of climatic water balance and slope inclination promote to higher LHP value and thus higher retention capacity. The results also demonstrate that there are sufficient, freely available, and precise data to assess water retention potential - landscape hydric potential - even at a continental scale.