Resumen de Bases geológicas e hidrogeológicas para la naturalización de una zona fluviolitoral: Las Madrigueras de la Riera de La Bisbal (El Vendrell), Tarragona

Narcís Carulla Gratacós, David Albalat Vàzquez, Jorge Jodar Bermúdez

• español

  Gracias al ordenamiento urbanístico en el litoral alterado de la desembocadura de la Riera de La Bisbal, en el extremo meridional de la comarca del Penedès, se efectúa un plan de reconocimientos para un proyecto de naturalización de acuerdo con los medios paleogeográficos antiguos que pudieran hallarse. El plan consta de 38 catas mecánicas, 10 sondeos mecánicos de hasta 15 m, 2 SEVs y seguimientos químicos y piezométricos. Posteriormente se construyen 9 balsas a diversas profundidades y en diferentes fondos litológicos para prever el funcionamiento hidrogeológico futuro. La naturalización ocupa 23 Ha y configura lagunas fluviales (con fondos de gravas predominantes), lagunas litorales (con arenas litorales) y ámbitos de marismas (con presencia de lodos con materia orgánica), todo ello según la reconstrucción paleogeografica hallada. Los reconocimientos hidrogeológicos denotan mezclas de aguas, profundas y superficiales, que condicionan contrastes marcados en el espacio.

• English

  The degraded mouth of the Riera de La Bisbal (190 km2) is the application area of a restoration project, performed in the framework of the urban planning of the neighbouring zones. The restoration takes into account the ancient paleogeografic distribution characterised by mean of 38 trial pits, 10 exploration boreholes ranging in depth from 10 to 15 m, 2 SEVs, and finally chemical and piezometric controlsof the ground water which flows through the underlying aquifer. As a result of the soil heterogeneity and also of the aquifer discharge scheme, ground water from deeper aquifers flow upwards and is mixed with the upper ground water, giving a spatial distribution of ground water quality in the aquifer. To take advantage of this ground water quality spatial distribution, the projected natural setting will be surrounded by coastal lagoons (presenting gravel as dominant lithology at the bottom), coastal wetlands (with litoral sand) and finally wetlands or marshland (with abundant organic mud). For this purpose an important volume of ground will be excavated and spatially redistributed. In order to assess the evolution of the ground water quality for the different accounted settings, 9 small ponds (pools) have been excavated, having different depths and different lithological bottoms. Pond water quality evolution is measured taking into account the pond head level, and also their geographical and lithological emplacement.