EGU General Assembly 2021
© Author(s) 2023. This work is distributed under
the Creative Commons Attribution 4.0 License.

Ephemeral Streams: An overlooked permanent source of groundwater and Nutrients to the Mediterranean Sea

Marc Diego-Feliu1, Valentí Rodellas1, Aaron Alorda-Kleinglass1, Júlia Domínguez-Gabarró1, Maarten Saaltink2,3, Albert Folch2,3, and Jordi Garcia-Orellana1,4
Marc Diego-Feliu et al.
  • 1Institut de Ciència i Tecnologia Ambientals, UAB, Bellaterra, E-08193, Spain
  • 2Department of Civil and Environmental Engineering, UPC, Barcelona, E-08034, Spain
  • 3Hydrogeology Group, UPC-CSIC, Barcelona, E-08034, Spain
  • 4Departament de Física, UAB, Bellaterra, E-08193, Spain
Fluxes of nutrients, metals, contaminants, among others dissolved compounds transported from land to oceans have a direct impact on coastal biogeochemical cycles. One of these land-ocean interaction mechanisms, recently recognized as an important source of these compounds, is the flow of groundwater from continental margins to the coastal ocean, commonly known as Submarine Groundwater Discharge (SGD). The Mediterranean coastline is characterized by the presence of ephemeral streams, geomorphological settings that act as preferential flow paths for both runoff and groundwater towards the sea. The Mediterranean Basin is highly influenced by strong precipitation events (>50 mm) that commonly occur during fall and spring seasons such as isolated depression at high levels events, locally named ‘gota-freda’. In such situations, runoff causes several social and environmental impacts along ephemeral streams that have been long recognized. However, when the surface water flow ceases, the subterranean part of ephemeral streams may continue supplying water and solutes to the coastal ocean via SGD. This process and its effects for coastal ecosystems have been largely overlooked. In this study, we evaluated the influence of a ‘gota-freda’ event on both the role of ephemeral streams as preferential areas for groundwater discharge and on the magnitude of SGD and SGD-derived nutrient fluxes. To do so, three seawater sampling campaigns were performed in a Mediterranean coastal region dominated by ephemeral streams (Maresme, Catalunya) after heavy rainfall events (~50 mm) and in baseflow conditions. Results of this study indicate that SGD flows are between 5 and 7 times higher after a strong precipitation event than in baseflow conditions indicating that the supply of nutrients and other dissolved compounds to the Mediterranean Sea is highly dependent on these events. This study highlights that this mechanism is a relevant process for coastal biogeochemical cycles of semi-arid regions such as the Mediterranean basin.

How to cite: Diego-Feliu, M., Rodellas, V., Alorda-Kleinglass, A., Domínguez-Gabarró, J., Saaltink, M., Folch, A., and Garcia-Orellana, J.: Ephemeral Streams: An overlooked permanent source of groundwater and Nutrients to the Mediterranean Sea, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-15871,, 2021.