Groundwater extraction data reveals major discrepancy

The hydrologist Marco Cremona has pointed out a “massive discrepancy” with past studies on Malta’s groundwater extraction which he says may reflect hundreds of unregistered boreholes.

Data released to MaltaToday shows that total groundwater extraction by the agricultural sector is expected to range between eight and 10 million cubic metres a year, a far cry from previous estimates that put groundwater extraction at 20 million cubic metres.

The figures show that water extracted from 2,874 agricultural boreholes amounted to just 1.44 million cubic metres.

Malta has over 8,000 registered boreholes, but metering of these boreholes was discontinued after 2,874 agricultural and 245 industrial boreholes were metered.

When the discrepancy of the new figures with past estimates of groundwater extraction was pointed out by MaltaToday, a government spokesperson replied that previous estimates provided an indicative “potential” water demand, based on estimates of land-use by the sector.

“The new volumetric data from borehole meters foregoes the need of land-use estimates being based on real data,” the spokesperson said.

But the spokesperson acknowledged that data from metered boreholes provides data only for “abstraction” from boreholes in the two mean sea level aquifer systems, and does not include abstraction from the perched aquifer systems (springs and ‘spieri’) as well as the “remaining unmetered boreholes and other groundwater abstraction sources”.

But when these omissions are taken in to account “the total groundwater use by the sector is expected to range between eight and 10 million cubic metres a year.”

This is in sharp contrast with previous estimates and does not take in consideration unregistered boreholes.

A study by the Food Agriculture Organisation (FAO) in 2006 had put demand for irrigated water in Malta at 21 million cubic metres. 

In 2008, a survey estimating the volume of water used for irrigation suggested 28.2 million cubic metres of water was used to irrigate 2,830 hectares of agricultural land in 2010: about 10,000 cubic metres per hectare. Groundwater accounts for most of irrigation in Malta. But that data was based on surveys and actual interviews with hundreds of farmers.

Then in 2011 the National Office of Statistics claimed that the amount of irrigation water used by the agricultural sector was 28 million cubic metres, “almost equalling the public water supply produced by the Water Services Corporation.” That figure was a massive increase from data submitted in parliament that said 19.5 million cubic metres was extracted by private boreholes in 2007, far higher than the 14 million cubic metres extracted by the WSC.

Irrigated land has increased exponentially in subsequent years even though the total amount of agricultural land in Malta has decreased. 2017 was a particularly bad year in terms of rainfall, forcing farmers to also use their boreholes in winter.

But hydrologist and water activist Marco Cremona has warned of a huge under-registration of extraction. “Whether these estimates are the result of the presence of numerous – hundreds, thousands? – unregistered boreholes, or deficiencies in the metering process I wouldn’t know.”

Cremona called for a more detailed investigation of the metered results “as the magnitude of discrepancy (with past studies) is way beyond acceptable” especially in view of “the substantial investment that went into metering” boreholes.

He pointed out that the actual data from the metering process (1.4 million cubic metres) amounts to only 5% of the figure the NSO had arrived at in 2011 in its detailed one-to-one questionnaire with more than 400 farmers.

Why is ground water important?

Groundwater is rainwater that permeates the ground and slowly seeps through porous rock until it reaches the aquifer. Since the only local source of groundwater recharge is rainwater, the amount available for human use is limited to the amount of rain recharging the aquifers. Past estimates placed current groundwater extraction at nearly 50 per cent higher than the safe limit. Over-extraction changes the shape of the aquifer, drawing saltwater and increasing salinity in the remaining groundwater. The government has recently embarked on a project of providing free treated sewage water to farmers as an alternative to ground water extraction.