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Coastal groundwater stresses

Coastal groundwater stresses

There are a number of stressors impacting coastal aquifers worldwide, such as sea level rise, overexploitation (leading to land subsidence), coastal flooding, and reduced recharge due to decreasing rates of precipitation and anthropogenic sealing of potential infiltration surfaces, as shown in the figure below. All of these stresses jeopardize the precious fresh coastal groundwater resources which are utilized for domestic, agricultural and industrial purposes.

Rising of saline groundwater

Since one third of the world’s population lives within ~100 km of the coast, it is critical to have a good understanding of the hydrological system (both surface water and groundwater). Increasing water demands from growing populations can threaten otherwise reliable sources of clean drinking water. For example, overexploitation of groundwater can lead to rising saline groundwater and saltwater intrusion, contaminating fresh groundwater sources (see figure below).

Near-coastal water system

Ref: Bocanegra, E., Da Silva, G.C., Custodio, E. et al. Hydrogeol J (2010) 18: 261. https://doi.org/10.1007/s10040-009-0520-5

What information is needed?

Sustainable aquifer management is essential in order to ensure water security in these vulnerable coastal areas. This requires knowledge about:

  1. where groundwater is already an important source of drinking water (due to its quantity and quality);
  2. which areas are threatened in a changing urbanized environment and may be temporarily affected due to natural disasters, such as flooding (requiring additional measures to ensure safe access to drinking water);
  3. where there are possibilities to safeguard groundwater resources (so that they can be preserved and can still be accessed post-disaster); and
  4. where groundwater is already saline (in which case, these areas should not be prioritized or accessed in disaster situations, but measures could be taken in some areas to prevent an increase in saltwater intrusion).