Impacts of Climate Change on Groundwater

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The impacts of climate change on groundwater systems are conceptually known; however, in the context of climate change impact assessment there has been little research conducted on groundwater compared to surface water resources. Nevertheless, from a qualitative point of view, it is known that aquifers respond to precipitation variability and climate fluctuations much more slowly than surface water. Aquifers act as a more resilient buffer during droughts, especially when they have a large capacity [2]. Furthermore, it is expected that predicted global changes in temperature and precipitation will alter groundwater recharge to aquifers, causing shifts in water table levels in unconfined aquifers as a first response to climate trends. Therefore, determining the change in groundwater recharge is the key to estimate climate change impacts on groundwater. The effect of changing precipitation patterns on groundwater recharge rates depends on whether the region of interest has humid or arid climate characteristics besides other factors such as the magnitude, intensity and the period of precipitation [3].

Increased variability in rainfall may decrease groundwater recharge in humid areas because more frequent heavy rain will result in the infiltration capacity of the soil being exceeded, thereby increasing surface runoff. In semi-arid and arid areas, however, increased rainfall variability may increase recharge, because only high-intensity rainfalls are able to infiltrate fast enough before evaporating, and alluvial aquifers are recharged mainly by inundations during floods [1]. In the case where an aquifer is hydraulically connected to surface water, the groundwater levels are expected to be affected by any hydrological alteration. This type of interaction is relatively complicated to quantify compared to groundwater recharge change driven impacts on groundwater levels.

There are other indirect impacts of climate change on groundwater that can be considered in impact assessment studies. One of them is the deterioration of groundwater quality in coastal aquifers due to increased saltwater intrusion driven by sea level rise. Also, elevated evapotranspiration rates cause changes in soil moisture and in particular increases in groundwater salinity. Another indirect implication of higher temperatures and less precipitation is the exacerbation of water demand, which in turn triggers more groundwater withdrawal from the aquifers.

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