For years, the salt of the sea has been “devouring” the fresh water in Halkidiki – and no natural phenomenon is responsible for this. The region, which anyway has a problem with the water supply for various reasons, as became clear recently with the multi-day interruption of water supply in Pefkohori, is increasingly facing the “beast” of the so-called waterlogging.

This is a phenomenon related to the over-pumping of water in coastal areas to meet the needs of agriculture, but to a lesser extent tourism and residential development. The problem is multifactorial. The thousands of wells, legal and illegal, operate “at full capacity” during the summer months. At the same time, it is a common secret that the land of Halkidiki has been “ploughed” for decades by illegal networks, made by private individuals, which illegally transport water from wells up to kilometers away – while the law allows it to be transported up to a maximum distance of 800 meters. The irrational use of water, but also the climate crisis, which in many areas has dropped the level of the underground water table even by 10 meters, approximately as high as a four-story apartment building, also contributes to the phenomenon of waterlogging.

How is the drop in the groundwater level connected to the salinity? In very simple terms, fresh water acts as a sort of “barrier” for marine life. So when its level drops too much, seawater penetrates inland, as this dam “falls”, because the natural hydraulic gradient towards the sea is reversed. The problem is not new, but it has been getting worse in recent years.

“We have been dealing with waterlogging for years now. The very rapid development of intensive olive cultivation in our region, especially after the end of the 1990s, combined with the lack of rainfall and the prolonged heatwaves, which increase the need for irrigation, aggravate the problem” tells APE-MPE o mayor of Polygyros, Georgios Emmanuel and explains: “The city of Polygyros was supplied with water from the plain at Kalyves, which are located near the river Olynthios. However, in the last 20 years, olive cultivation has been growing more and more and thousands of new trees are planted every year, with the result that irrigation needs are also increasing. At the same time, water is irregularly transported from the boreholes over very long distances, even kilometers, to irrigate fields. A fixed borehole, with a yield of 10 cubic meters, can irrigate 100 acres, one of 100 cubic meters, 1000. So when the water is in excess, it is transferred elsewhere. Legally it can be transported up to 800 meters, but it is an open secret, a decades-old practice, that water often travels kilometers, transported through illegal networks, built by private individuals.”

If illegal drilling is a clearly reprehensible phenomenon (the exact number remains unknown), the continuation of olive cultivation in Halkidiki is certainly necessary. “We cannot put the farmers across the street and shoot them. On the contrary, serious investments are needed in smart agriculture, which can limit the unnecessary waste of water, but also a more rational use of water, e.g., drip irrigation instead of nozzles, with the use of which a large part of the water evaporates, but and irrigation according to the special needs of each crop and not horizontally” notes the mayor of Polygyros, pointing out that in the area of ​​his responsibility the agricultural sector currently absorbs 90% of the water, compared to a percentage of up to 10% for tourism and residents together (of course , tourism and citizens demand very high quality and potable water, unlike the primary sector).

According to Mr. Emmanuel, we need to look at the issue holistically, for example, instead of over-pumping through boreholes, “the water from the biological purifications can be used after treatment for irrigation, to create a water storage”, which to do so, of course, it is necessary to precede the necessary biological cleaning projects, many of which are still missing, but also to create the sewage networks that will be connected to the biological ones (which are also missing in many areas). There is also a need to modernize the water supply networks, which on the coastal front of Polygyros are in some cases over 50 years old, with the result that at least 40% of the water is lost due to leaks due to old age and moreover water theft is easy. In order for all of this to proceed, considerable funding is of course required, which is not always easy to obtain for various reasons.

The desired “peaceful rain” and water flows that Greece does not control

The problem of salt water in general is very extensive in Greece, due to the long length of its coasts, as Professor Emeritus of the Department of Civil Engineering of the Aristotle University of Thessaloniki (AUTH), Konstantinos Katsifarakis, tells APE-MPE. The problem, which is evident in almost all the islands, even in Crete, mainly concerns the underground water, but there is also salty intrusion in the estuaries. With the exception of areas such as Halkidiki, but also Pieria, where crops and tourism often coexist next to the sea, the problem of salt water is not particularly related to agriculture. “It has to do mainly with tourism – due to the temporal and spatial concentration of water consumption, four months a year, in specific areas – but also with the residential development of these areas. In some cases, such as in Northeast Halkidiki, mining activity also plays a role, which also requires a lot of water,” explains the professor.

How is waterlogging related to falling groundwater levels? “They are absolutely interconnected, because in order for seawater to penetrate inland, there needs to be no “dam” from fresh water. So if the water level drops, the sea “comes in”. And climate change is certainly affecting. We have long periods of drought, but also intense rains, which cause flooding – in Volos, last year, it poured in two days as much water as it pours in a year, but what to do with this water? – while what the water table needs to enriched is “peaceful rain”, gentle rain” notes. Today, in some areas of Northern Greece the water level has dropped by more than 10 meters, while in areas of Thessaly it is much higher, which is not unusual in recent years, observes the professor.

In the question of what volumes of water the annual water deficit in Northern Greece is calculated, Mr. Katsifarakis explains that we cannot talk about a deficit throughout the year, since the problem is localized in space (in specific areas with many tourist arrivals) and time (in the months of the high demand tourist season). Apart from the spatial and temporal concentration, the problem is also related to the fact that Greece does not fully “control” many of its water “pipelines”. With the exception of the Aoos, which originates in Greece and continues its waterway in Albania, all other transboundary rivers that cross Northern Greece originate from other countries. As a result, Greece is dependent on the management of its river waters by neighboring countries. Especially for Thessaloniki, Mr. Katsifarakis points out that, although the sea has penetrated long ago into the basements of buildings located near the sea (e.g., on Nikis Avenue), it does not make sense to talk about waterlogging in the urban fabric. Thessaloniki is supplied with water from Aliakmonas and Arabissos and boreholes exist only in a few stadiums in the city.

Natural decontamination requires months or even years

Salivation is considered pollution because when salt infiltrates fresh water, it can no longer be used by humans for most common uses. How easy is it to clean? “Natural decontamination is a time-consuming process, because it takes months or even years until the level of fresh water rises. In the case of desalination, the issue is not time, but energy expenditure. Even for decontamination with reverse osmosis, a lot of energy needs to be spent to get clean water.” points out Mr. Katsifarakis.

More appropriate, he estimates, are preventive measures, such as enriching the water table by storing underground water through small dams, “as the great Manolis Glezos did in Aperathos, Naxos”. Also, in coastal areas, where new tourist farms are being developed, some simple but important measures could be implemented, such as the installation of a double water circuit, to pump brackish or salty water for use especially in the toilets, which is already being successfully implemented in some other Countries. “The legislation also needs to be improved, in order to better define the responsibilities of agencies and organizations, because today there are many people responsible for the same issue, which does not work effectively,” concludes the professor.