Groundwater is one of the main sources of freshwater for agriculture, domestic and industrial uses all over the world. However, this resource is in a critical situation due to its massive exploitation and the still uncertain consequences of climate change.
Nowadays there exists a wide consensus about the fact that climate change will have a main impact in water resources including groundwater and natural disasters related to water, like floods and droughts.
This impact could get even worse because of anthropic actions like the increase of groundwater pumping due to longer drought seasons.
Connection between climate change and saltwater intrusion
Sea level rise would be one of the most evident effects of climate change along with the prolongation of drought seasons in some areas.
Then, saltwater intrusion phenomena in coastal aquifers as a consequence of sea level rise, would be a major risk for coastal communities. It is because of this reason that the phenomena has been specially studied among the scientific community in the last years.
To better understand this, we must consider that coastal aquifers have a strong hydraulic bond with seawater. This bond sets a freshwater/saltwater interface of over 40 times the depth of freshwater upper bound over sea level.
Hence, If there is a landward encroachment of saltwater, freshwater volume in the aquifer will be reduced affecting the amount of freshwater supply.
The above, along with a sustained population and water demand increase, tend to raise groundwater vulnerability to saltwater intrusion.
Impact magnitude
According to an ocean’s report from the Intergovernmental Panel on Climate Change (IPCC) presented to the United Nations (UN), sea level could rise on average about one meter in 80 years if greenhouse gases emission do not reduce.
Based on this, there are several models and scenarios that had been made up to quantify the impact extent of climate change and how it will influence the boundary saltwater/freshwater in coastal aquifers.
Those models usually quantify saltwater lanward flow considering:
- Sea level rise scenarios.
- Increase of freshwater demand.
- Natural aquifer’s recharge reduction due to drought seasons.
According to mathematical simulations made by Carretero in 2012 for a coastal aquifer located in Buenos Aires, in a smooth topographic zone with low elevations and in a sea level and water demand rising context, there is a quantification of saltwater landward flow of over 200 meters using a constant hydraulic charge model (figure 1). As a result, the simulation shows us that one of the main consequences would be the resource’s deterioration and decrease on the supply.
The importance of an effective management
To avoid this future scenario that could lead to a sea level rise as a cause of global warming it will be necessary to boost an efficient water resource management
This management should incorporate a global perspective of water systems in a way that their allocation and use guarantee surface water as much as groundwater sustainability in the long term.
Are we all ready to face this change?
Sources: Carretero et al., 2012; Ghyben and Herzberg, 1901; Carretero, 2012.
