Seawater injection barrier recharge with advanced reclaimed water at Llobregat delta aquifer (Spain)

The main aquifer of the Llobregat delta (Barcelona, Spain) has been affected by seawater intrusion since the 1960s. The Catalan Water Agency (ACA) has sponsored the construction of a positive hydraulic barrier in order to stop the progress of seawater intrusion advance due to the intensive aquifer development. The hydraulic barrier consists of 15 wells into which highly treated reclaimed water from the waste water treatment plant of the Baix Llobregat is injected. Water is subjected, prior to the distribution to the injection wells, to secondary and tertiary treatments, and later to ultrafiltration, UV disinfection without chlorination, and salinity reduction through reverse osmosis. A preliminary pilot phase of the project was started in late 2007, with highly positive results, and the second phase started in mid 2010. Hydrogeological and hydrochemical monitoring data indicate an efficient performance and aquifer improvement. The evaluation of such efficiency and operational costs has been analyzed and discussed.

Aquifer recharge for securing water resources: the experience in Llobregat river

The Llobregat Delta Aquifer has historically been a strategic water supply resource to the Barcelona metropolitan area. The use of river water combined with the exploitation of groundwater resources during dry periods has enabled the demographic and economic growth of the Barcelona area during the last fifty years. The aquifer overexploitation has entailed the decrease of groundwater level and the penetration inland of seawater intrusion. The main consequences have been the salinization of several wells and the deterioration of the groundwater quality. In this context, aquifer recharge has been practiced during nearly 40 years with the following objectives: (i) storing excess of water for times of less water availability, (ii) introducing an additional barrier for purification of water for a specific use and (iii) preventing the degradation of groundwater resources due to overexploitation or seawater intrusion. These methods, jointly with an efficient management of well extractions, have enabled to recover groundwater quality and therefore to guarantee the sustainable exploitation of such a vulnerable aquifer.

An observational study of the 7 September 2005 Barcelona tornado outbreak

This paper presents an observational study of the tornado outbreak that took place on the 7 September 2005 in the Llobregat delta river, affecting a densely populated and urbanised area and the Barcelona International airport (NE Spain). The site survey confirmed at least five short-lived tornadoes. Four of them were weak (F0, F1) and the other one was significant (F2 on the Fujita scale). They started mostly as waterspouts and moved later inland causing extensive damage estimated in 9 million Euros, three injured people but fortunately no fatalities. Large scale forcing was provided by upper level diffluence and low level warm air advection. Satellite and weather radar images revealed the development of the cells that spawned the waterspouts along a mesoscale convergence line in a highly sheared and relatively low buoyant environment. Further analysis indicated characteristics that could be attributed indistinctively to non-supercell or to mini-supercell thunderstorms.