Authority proposes ‘no-go areas’ for borehole drilling
Boreholes used to cool houses are a threat to Malta’s groundwater supply
James Debono The Malta Resources Authority has warned that the use of boreholes for cooling house temperatures can pose a new threat to Malta’s already threatened groundwater supply.
The MRA is proposing new guidelines on using boreholes to cool buildings, a system that works through the process of heat exchange: exchanging higher surface temperatures, for cooler subterranean ones.
Since groundwater temperature is equal to the average surface annual temperature and remains the same all year round, heat exchange can provide warmer temperatures in winter and cooler temperatures in summer.
But the MRA warns this system poses new threats to the Malta’s threatened groundwater supply, already over-extracted by a staggering 43% over sustainable extraction (see box).
The authority said it wants to demarcate no-go areas where boreholes cannot be drilled to cool buildings.
Heat exchange can help in reducing carbon emissions from the heavy use of associated with air-conditioners. But the greatest risk is posed by ‘open-loop systems’ – a one-directional flow of water, commonly used for large-scale developments which draw water from greater distances.
On the other hand, closed-loop systems do not contribute to over-abstraction, as they rely on the circulation of fluid through a heat pump at the surface.
An MRA report says that open-loop systems “will undoubtedly increase the demand for groundwater abstraction, exposing the aquifer to additional pressures.”
It also notes that due to the relatively warmer temperature in groundwater in Malta – 20ºC compared to 12ºC in northern Europe – heat exchange will rely on high pumping rates, which would entail drilling deep into the aquifer, the underground reservoir.
In turn, pumping of more water up to the surface reduces the pressure inside the aquifer, which would be faster replenished by sea water. This could lead to a sharp rise in salinity affecting irrigation boreholes and those used by the Water Services Corporation.
The MRA is recommending that open-loop systems are only considered in coastal areas. Closed-loop system will not be allowed within a 300-metre radius of protected drinking water sources.
Developers will also be required to conduct an assessment of the effect of this development on the aquifer and third parties.
An estimated 19.5 million cubic metres of water were extracted from private boreholes in 2007, far higher than the 14 million cubic metres of water that the Water Services Corporation extracted. This shows the degree of extraction by private citizens with both legal, and illegally drilled boreholes.
Even worse is the fact that while annual rainfall refills the underground aquifers with just 23 million cubic metres, Malta is extracting 35 million cubic metres from both private and public boreholes – 12 million cubic metres more than it should. Extraction by the WSC decreased from 15 million cubic metres in 2003 to 13 million cubic meters in 2006. But it increased to 14 million cubic metres in 2007.
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