SEAWATER INTRUSION BARRIER IN THE DELTAIC LLOBREGAT AQUIFER (BARCELONA, SPAIN)

F. Ortuño1, J. Molinero2,3, E. Custodio3, I. Juárez2, T. Garrido1 and J. Fraile1 
1 AGENCIA CATALANA DE L´AIGUA. C/ Provenza 204-208, 08036 Barcelona, Spain.
 2 AMPHOS XXI Consulting S.L., Passeig de García i Faria 49-51, E08019- Barcelona, Spain.
3 Departament of Geotechnical Engineering and Geosciences, Technical University of Catalonia (UPC). Jordi Girona, 1-3. 08034 Barcelona. Spain

ABSTRACT

The main aquifer of the Llobregat Delta (Barcelona, Spain) is affected by seawater intrusion processes since 1970. The Catalan Water Agency is currently promoting several actions of enhanced aquifer recharge, including the construction of a positive hydraulic barrier in order to stop the advance of the seawater intrusion. Such a positive hydraulic barrier works by injecting reclaimed water in 14 wells. This is the first time that a project of this type is performed in Spain, and it is also pioneer in Europe. The positive hydraulic barrier produces the rise of the groundwater head near the coast and avoids seawater penetration inland. The injected reclaimed water comes from the WWTP of the Baix Llobregat after passing through several treatments (ultrafiltration, osmosis and disinfection). The pilot phase of the project has been working during the last 2 years. Hydrogeochemical analyses and modeling reflects that the pilot phase of the project is showing highly positive results and effectively reversing the salt water intrusion process. Substantial improvement of the groundwater quality has been observed in wells surrounding the injection points and no clogging has been appeared. A second phase for the whole planned project is already under operation.

Keywords: Llobregat aquifer, reclaimed water, hydraulic barrier, seawater intrusion, artificial recharge.