Summary: The hyporeic zone is the transition zone located below the river channels (sediments) in which they converge and there are exchanges between surface waters and groundwaters. Doctoral thesis of Rubén Rasines Ladero.

The hyporeic zone is the transition zone located below the river channels (sediments) in which they converge and there are exchanges between surface waters and groundwaters. This area is considered as one of the most threatened aquatic environments, especially in Mediterranean regions, because it is strongly influenced by the climatic variations typical of these regions that affect river flows; and also by the impact of human activity that causes water and sediment contamination, changes in the channels morphology, variations in flow rates and impacts derived from extractive activities (gravel). The fauna of the hyporeal zone is a clear indicator of the water quality, which is threatened by the habitats degradation or loss, in which it is established.

In the Mediterranean region, the special environmental conditions determine the importance of the hyporheic zone, since it acts as a hydraulic connector between surface and groundwater ecosystems (ecotone). Furthermore, it also behaves as a buffer zone and refugee for benthic fauna, especially in the presence of extreme conditions. This region is characterised by its vast diversity of organisms (biodiversity hotspot), which favours the highly diverse community and endemism occurrence in the hyporheic ecotone.

In this context, Ruben Rasines Ladero, predoctoral researcher at IMDEA Water Institute, has developed his doctoral thesis “The ecology of the hyporetic zone associated with the rivers Henares and Tajuña (Jarama River Basin, Spain)”, directed by Dr. Sanda Iepure, principal researcher of Groundwater Ecology Group of IMDEA Water. His thesis, frammed in the PhD Program in Hydrology and Water Resources Management, was defended on July 6, 2017 at the Rey Juan Carlos University.

This thesis aims to characterise both, biotic and abiotic environmental properties associated to the hyporheic zone of Henares River (nine sampling points) and Tajuña River (eleven sampling points). The characterization has been developed through a semiquantitative sampling, in which a total of 44 environmental variables related to the sedimentological, physical chemical characteristics of the water, biological and of ecological quality have been analyzed.

The focus will be mainly on the distribution and dynamics of the cyclopoids copepods group (micro-crustaceans) and their relationship to environmental conditions, so as the basis to establish a future biological index applied to the hyporheic ecotone.

In the same way, the possibility of using surface water bodies as “research units” for the hyporheic zone studies, together to its integration in the processes related to surface water ecological status assessment.

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