The lower part of the Llobregat River (ca. 120 km2) is a catchment located near Barcelona (NE Spain) which includes numerous wells for abstraction of groundwater and two important surface water collection points for drinking water production. The waterworks situated in San Joan Despí supplies drinking water to approximately half of the population of the Barcelona’s metropolitan area and uses water from the Llobregat River on regular basis mixed with groundwater from the lower valley and Llobregat delta aquifers when the quality or quantity of the river water is low. The hydraulic regime of the river is of the Mediterranean type with low flows during normal conditions (around 5 m3/s) and peak events of either absolute dryness or flooding (up to 2000 m3/s).
This catchment holds both intense agricultural activities typical of Mediterranean areas (mainly crops of fruits and vegetables spread over multiple small extension properties) as well as urban and industrial activities.
Despite several successful mitigation measures, numerous contaminants (including nitrates, ammonium, pesticides and a large variety of emerging contaminants) are stillfound to pollute the water of the river and its aquifers..