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Groundwater quality and contaminant hydrogeology 245

continuity considerations, there exists a small land-
ward flow in the saltwater wedge (Todd 1980).
Saline intrusion problems are known from around
the world with well-documented examples includ-
ing the Biscayne aquifer in Florida (Klein & Hull
1978), the Quaternary sand aquifers of Belgium and
The Netherlands (De Breuck 1991), the Chalk aquifer
of South Humberside (Howard & Lloyd 1983) and
the Llobregat delta confined aquifer of Spain (Iribar
et al. 1997) (Box 6.7).
Methods for controlling saline intrusion are des-
Fig. 6.27 Vertical cross-section showing flow patterns of cribed by Todd (1980) and include: (i) changing the
freshwater and saltwater in an unconfined coastal aquifer locations of pumping wells, typically by moving them
illustrating the development of a brackish transition zone and the inland; (ii) artificial recharge from a supplemental
cyclic flow of saline water to the sea. After Todd (1980).
water source to raise groundwater levels; (iii) an

BO X
Saltwater intrusion in the Llobregat delta aquifer system, Spain
6.7

The Lower Llobregat aquifer system is formed by the Lower Valley fans and beach deposits. The delta aquifer is formed by these
and deep delta aquifers located a few kilometres south-west deposits and the deep formation shown in Fig. 2. This formation
of Barcelona (Fig. 1). The Lower Valley aquifer is formed from extends seawards with decreasing thickness and outcrops on the
Quaternary sands and coarse gravels and extends over an area of sea floor at around 100 m depth and 4–5 km offshore. The deep
2
100 km . The aquifer formation continues below the present mor- delta aquifer is confined by wedge-shaped clay, silt and fine sand
phological delta towards the coast (Fig. 2). At the sides of the delta, sediments that act as an aquitard. Above this aquitard, the shallow
the aquifer materials change to sediments from local creek alluvial delta aquifer is formed by sands, gravels and silt.

Fig. 1 Location map of the lower valley
and delta of the River Llobregat, Spain.
After Iribar et al. (1997).