Only 23 million cubic meters of groundwater are sustainably available for extraction, but it is conservatively estimated that 34 million cubic meters are being extracted. This over-extraction is of serious concern as it lowers the quality of the remaining groundwater.
Groundwater is a lens-like body of freshwater floating on seawater, stored deep underground in porous rocks. It is only replenished by rainwater which gets absorbed into the ground and slowly, over a period of decades, percolates into groundwater bodies. Since only a fixed amount of rainwater is making its way into groundwater bodies every year, that is the amount that is sustainably available for extraction.
Extracting more however, decreases the volume of freshwater within the aquifer, displacing it with increasing amounts of seawater. The result is that the remaining groundwater increases in salinity. This has already happened to several of Malta aquifers. Furthermore, over-extraction is not the only threat facing Malta’s groundwater. Trends in fertilizing agricultural land over the past few decades have led to excessive nitrates coming into contact with rainwater. Rainwater dissolves these nitrates and carries them down into the aquifers. Since nitrates are a cancerous substance, the amount of nitrates which can be considered safe in drinking water is fixed at 50 ppm.
Between excessive nitrates and excessive salinity due to over-extraction, the water produced by 90% of Malta’s aquifers no longer meets the Maltese and EU standards for safe drinking water.
To restore Malta’s groundwater to a good status it is important to balance extraction with recharge. A key element in this is reducing wasteful consumption by increasing the efficiency with which we consume water.