WILL
BRATISLAVA CEMENT ITS DRINKING WATER SOURCES?
Ján Madarás
Simplicity wins in nature. The chemical
compound of hydrogen, the simplest element in the universe, with another simple
element, oxygen, is called water. Thanks to our knowledge, we know that water
is a common compound in the universe and has been discovered even on
neighboring planets and their moons. In exists on asteroids and comets. We know
from the Earth that there is life or that life may exist where there is water. Because
water is the elementary condition for the existence of life on Earth. So far,
we do not know if this also applies elsewhere. No matter how hard we try, we
have not discovered life anywhere but on Earth. Perhaps life also exists on a different
basis than water somewhere in the universe, but we cannot confirm this.
Therefore, we have to stay “close to the ground.” Water is an elementary
component of the food chain necessary for the survival and development of all
species of organisms on our planet. Water enables the transfer of organic
substances and energy through various species of living creatures which
comprise a biological community, or ecosystem. Humans and most terrestrial
organisms (plants and animals) need fresh water, i.e. water with a minimum degree
of other soluble chemical substances and elements. Marine life does not need
fresh water, but humans cannot survive without it. The many sailors, who despite
the fact that they were swimming in an ocean of water, suffered and died
without fresh water, could tell horror stories about it.
Since mankind uses the noble term civilization for itself, this civilization is able to wage wars because of fresh drinking water. It was no accident that developed ancient civilizations were born at the mouths of large rivers which provided them everything they needed to survive. A sufficient amount of fresh water meant prosperity. Shortage meant famine, disease, suffering, wars for survival, and the migration of entire nations. No matter what we try to tell ourselves, this is how it is even today. Drinking water is fundamental for survival. Can we treat it with respect and can we protect it? We want to try to answer this based on the example of Bratislava.
Development of the City on the Danube
Bratislava is a city on the Danube, without any exaggeration, because this river used to flow and, in some places, it still flows under the city. The successful efforts of human striving in form of settlements were not accidental. Bratislava was predestined for long-term successful development thanks to its location at the foothills of the Little Carpathians Mountain range running into the plains of Vienna and the Danube (Pannonian) basin, through which a huge river full of water flows. Archeologists have confirmed the settlement in Mlynská dolina from the Stone Age where hunters’ dwellings and even mammoth bones were found by the Vydrica stream near the zoo. Celts built their stone structures according to Roman models on Castle Hill and other dwellings and workshops on the territory of today’s Old Town. Slavs further developed these sites until medieval Bratislava was created. The city developed for centuries in intimate contact with the Danube and Morava rivers which provided food in the form of fish, and which during annual high waters and occasional floods also brought necessary organic admixtures for the fertilization of fields. Something like the Nile in ancient Egypt...
The development of the city depended on the important life-sustaining offerings from the river, but also its strategic location and protection by surrounding watercourses. The Morava River, which coiled in many meanders before it ran into the Danube, also created dead branches; the Danube does the same when entering through Devín Gate to the area of Bratislava. Thus, the city was protected from attack from the lowland side thanks to the tangle of river branches, islands and wetlands. Did someone ever think about why, for example, during the battles between the Ottoman Empire and Hungary the Turkish armies never made it to Bratislava but attacked Vienna? Why Bratislava became the capital and coronation city during the Turkish occupation of a large portion of Hungary? Thanks to rivers and their multiple branches, the city at the foothills of the Little Carpathians was protected from the west, the south and the east. And in times of danger, its population found shelter in the forests of the Little Carpathians to the north... For centuries the communication routes did not run on the lowlands along rivers, as today, but on mountain foothills. The low-lying routes were limited by rivers and particularly by their size during high water and floods. The character of the city did not begin to change swiftly until in the second half of the 19th century thanks to the Italian engineer Lanfranconi (Enea Grazioso Lanfranconi, 1850 - 1895) and firm stone banks began to define the Danube River flow. Further industrial growth brought along the river’s regulation and the burying of river branches; and thus water “disappeared” figuratively from Mlynské Nivy, the location of today’s modern bus station... The left side of the river was the first to be regulated, while the right side resisted radical changes until the 20th century.
Underground Bratislava: Drinking Water and Industrial Pollution
After this detour into history, let’s take another look at the Danube from the perspective of its development and geology. Thanks to its water yield and the fact that it carries a large amount of gravel and sand, particularly from the Alps (Morava is meaningless in this respect) the Danube began to create an inland delta when entering our territory. Through gravel and sand before Bratislava, the Danube supplies gravel at the Sihoť water-supply island and gravel under Petržalka (Ostrovné lúčky water source) with pure filtered water. There is no problem with ground water even for drinking, but the thickness of the gravel (up to a few dozen meters) is not as massive as downstream.
The inland delta in the form of Žitný ostrov begins below Bratislava (approximately from the Apollo bridge and Prístavný bridge) where the thickness of the gravel rapidly grows and near Gabčíkovo it reaches a thickness of 400 to 600 m. Think of a huge tub filled with gravel and sand with water between those materials. The subsoil of the “tub” is loamy, and thus impervious. While Bratislava was still just a small town or before it existed, the Danube waters created a complicated network of branches and smaller islands and the unregulated river flooded annually allowing water to soak into the gravel, permanently replenishing the ground water. However, over time, the regulation of the Danube increased; its banks were reenforced, branches were filled up, and water was drained. In the late 19th century and especially in the mid-20th century, industrial complexes were built completely illogically at the entry of groundwater infiltration: the former Apollo refinery, at the location of today’s tall buildings in the area of the port and Mlynské Nivy; Dynamitka (the former CHZJD chemical plant, later Istrochem) a bit further from the river, but still on top of permeable gravel and the former Apollo refinery which was moved to the location of today’s Slovnaft refinery. Perhaps by turning a blind eye to it and considering the knowledge at the time, the building of factories of more than 100 years ago can be still justified, but, the construction of Slovnaft, which began in 1956, cannot be pardoned from the perspective of a geologist. On the other hand, even the Schwechat refinery in Vienna is in the same situation. In case of CHZJD - Istrochem, and the Matador factory in Petržalka, these factories leaked toxic substances. At first, no continuous concrete tub (only in certain spots) was built under Slovnaft, and petroleum products could leak undisturbed into the subsoil. This was a big issue from the very beginning as petroleum products replaced a former source of drinking water in Podunajské Biskupice in the early 1970s. The factory was already built, it could not be demolished and its subsoil could not be cleaned up. As a result, the only effective method was to build a hydraulic shield around the entire Slovnaft premises. There are numerous boreholes from which groundwater, which is polluted by petroleum products even from the past, is constantly pumped out, cleaned and returned to the Danube. This drawing of water has created a cone of depression, making the groundwater lower than it would be under normal circumstances. This prevents pollution from moving further to the Žitný ostrov.
However, the Istrochem chemical factory is a huge problem. Toxic chemical waste dumps which are not sealed were created on its grounds, and so the pollution is slowly moving to the southeast with the groundwater. And if that was not enough, the former dead branch of the Little Danube in Vrakuňa was drained and filled with toxic waste. The groundwater almost did not reach the dump until the completion of the Gabčíkovo water dam – specifically the Hrušov reservoir; however, then its level rose under the influence of water in the reservoir and it also reached the dump. Pollution also comes from there. Cleaning is possible and it is being addressed, but the waste will remain in the same place. In order to prevent the contamination of the groundwater, it will be necessary to build impermeable walls, up to 30 meters deep at certain spots into impermeable subsoil, around the entire waste dump in order to prevent the ingress of water. Any water which leaks into it as well as the rainwater, will have to be drained and cleaned just as in the case of Slovnaft. The same needs to be done on the grounds of the Istrochem factory, but that is a much larger area. The cleaning costs will be huge and leaks will have to be drained and cleaned forever. Today this is the only option for preventing the overall pollution of the groundwater in Žitný ostrov.
Since mankind uses the noble term civilization for itself, this civilization is able to wage wars because of fresh drinking water. It was no accident that developed ancient civilizations were born at the mouths of large rivers which provided them everything they needed to survive. A sufficient amount of fresh water meant prosperity. Shortage meant famine, disease, suffering, wars for survival, and the migration of entire nations. No matter what we try to tell ourselves, this is how it is even today. Drinking water is fundamental for survival. Can we treat it with respect and can we protect it? We want to try to answer this based on the example of Bratislava.
Development of the City on the Danube
Bratislava is a city on the Danube, without any exaggeration, because this river used to flow and, in some places, it still flows under the city. The successful efforts of human striving in form of settlements were not accidental. Bratislava was predestined for long-term successful development thanks to its location at the foothills of the Little Carpathians Mountain range running into the plains of Vienna and the Danube (Pannonian) basin, through which a huge river full of water flows. Archeologists have confirmed the settlement in Mlynská dolina from the Stone Age where hunters’ dwellings and even mammoth bones were found by the Vydrica stream near the zoo. Celts built their stone structures according to Roman models on Castle Hill and other dwellings and workshops on the territory of today’s Old Town. Slavs further developed these sites until medieval Bratislava was created. The city developed for centuries in intimate contact with the Danube and Morava rivers which provided food in the form of fish, and which during annual high waters and occasional floods also brought necessary organic admixtures for the fertilization of fields. Something like the Nile in ancient Egypt...
The development of the city depended on the important life-sustaining offerings from the river, but also its strategic location and protection by surrounding watercourses. The Morava River, which coiled in many meanders before it ran into the Danube, also created dead branches; the Danube does the same when entering through Devín Gate to the area of Bratislava. Thus, the city was protected from attack from the lowland side thanks to the tangle of river branches, islands and wetlands. Did someone ever think about why, for example, during the battles between the Ottoman Empire and Hungary the Turkish armies never made it to Bratislava but attacked Vienna? Why Bratislava became the capital and coronation city during the Turkish occupation of a large portion of Hungary? Thanks to rivers and their multiple branches, the city at the foothills of the Little Carpathians was protected from the west, the south and the east. And in times of danger, its population found shelter in the forests of the Little Carpathians to the north... For centuries the communication routes did not run on the lowlands along rivers, as today, but on mountain foothills. The low-lying routes were limited by rivers and particularly by their size during high water and floods. The character of the city did not begin to change swiftly until in the second half of the 19th century thanks to the Italian engineer Lanfranconi (Enea Grazioso Lanfranconi, 1850 - 1895) and firm stone banks began to define the Danube River flow. Further industrial growth brought along the river’s regulation and the burying of river branches; and thus water “disappeared” figuratively from Mlynské Nivy, the location of today’s modern bus station... The left side of the river was the first to be regulated, while the right side resisted radical changes until the 20th century.
Underground Bratislava: Drinking Water and Industrial Pollution
After this detour into history, let’s take another look at the Danube from the perspective of its development and geology. Thanks to its water yield and the fact that it carries a large amount of gravel and sand, particularly from the Alps (Morava is meaningless in this respect) the Danube began to create an inland delta when entering our territory. Through gravel and sand before Bratislava, the Danube supplies gravel at the Sihoť water-supply island and gravel under Petržalka (Ostrovné lúčky water source) with pure filtered water. There is no problem with ground water even for drinking, but the thickness of the gravel (up to a few dozen meters) is not as massive as downstream.
The inland delta in the form of Žitný ostrov begins below Bratislava (approximately from the Apollo bridge and Prístavný bridge) where the thickness of the gravel rapidly grows and near Gabčíkovo it reaches a thickness of 400 to 600 m. Think of a huge tub filled with gravel and sand with water between those materials. The subsoil of the “tub” is loamy, and thus impervious. While Bratislava was still just a small town or before it existed, the Danube waters created a complicated network of branches and smaller islands and the unregulated river flooded annually allowing water to soak into the gravel, permanently replenishing the ground water. However, over time, the regulation of the Danube increased; its banks were reenforced, branches were filled up, and water was drained. In the late 19th century and especially in the mid-20th century, industrial complexes were built completely illogically at the entry of groundwater infiltration: the former Apollo refinery, at the location of today’s tall buildings in the area of the port and Mlynské Nivy; Dynamitka (the former CHZJD chemical plant, later Istrochem) a bit further from the river, but still on top of permeable gravel and the former Apollo refinery which was moved to the location of today’s Slovnaft refinery. Perhaps by turning a blind eye to it and considering the knowledge at the time, the building of factories of more than 100 years ago can be still justified, but, the construction of Slovnaft, which began in 1956, cannot be pardoned from the perspective of a geologist. On the other hand, even the Schwechat refinery in Vienna is in the same situation. In case of CHZJD - Istrochem, and the Matador factory in Petržalka, these factories leaked toxic substances. At first, no continuous concrete tub (only in certain spots) was built under Slovnaft, and petroleum products could leak undisturbed into the subsoil. This was a big issue from the very beginning as petroleum products replaced a former source of drinking water in Podunajské Biskupice in the early 1970s. The factory was already built, it could not be demolished and its subsoil could not be cleaned up. As a result, the only effective method was to build a hydraulic shield around the entire Slovnaft premises. There are numerous boreholes from which groundwater, which is polluted by petroleum products even from the past, is constantly pumped out, cleaned and returned to the Danube. This drawing of water has created a cone of depression, making the groundwater lower than it would be under normal circumstances. This prevents pollution from moving further to the Žitný ostrov.
However, the Istrochem chemical factory is a huge problem. Toxic chemical waste dumps which are not sealed were created on its grounds, and so the pollution is slowly moving to the southeast with the groundwater. And if that was not enough, the former dead branch of the Little Danube in Vrakuňa was drained and filled with toxic waste. The groundwater almost did not reach the dump until the completion of the Gabčíkovo water dam – specifically the Hrušov reservoir; however, then its level rose under the influence of water in the reservoir and it also reached the dump. Pollution also comes from there. Cleaning is possible and it is being addressed, but the waste will remain in the same place. In order to prevent the contamination of the groundwater, it will be necessary to build impermeable walls, up to 30 meters deep at certain spots into impermeable subsoil, around the entire waste dump in order to prevent the ingress of water. Any water which leaks into it as well as the rainwater, will have to be drained and cleaned just as in the case of Slovnaft. The same needs to be done on the grounds of the Istrochem factory, but that is a much larger area. The cleaning costs will be huge and leaks will have to be drained and cleaned forever. Today this is the only option for preventing the overall pollution of the groundwater in Žitný ostrov.
This is how the drinking water under Bratislava
has been polluted or seriously endangered due to industrial activities. However,
this is not all of the bad news. Up to now, we just mentioned the past events. We
can analyze them negatively, but these are the facts which have already
happened. Equipped with more knowledge, it is our duty to address them, but we
also have here the recent past, present-day reality and the near future...
Urban Development and Draining of Precipitations in Underground Layers
As we have already mentioned, figuratively speaking, Žitný ostrov is a huge tub with water flowing between rocks – gravel and sand. It is permanently replenished by water from the Danube, but not as much as before. Water may percolate from Hrušov reservoir and the old Danube river bed, but the vast majority of water is drained in an impermeable asphalt navigation derivation channel all the way to the electric power plant in Gabčíkovo. More than two thirds of the Danube flow cannot partially percolate into the subsoil due to building of this dam. The infiltration area of Bratislava is still there: but some of the water flows under Slovnaft and Istrochem. Here the water is contaminated or may be contaminated, as we have mentioned above.
Bratislava is a megalomanic. This city wants to transform itself into a modern metropolis, if not on a global standard, at least in relation to Central Europe - although it lacks a metro, but that’s a different story. Developers like to offer model constructions with views of the city or its surroundings. And where is the best place to build such structures if not with a view of the Castle, the Danube... The construction of the Sky Park buildings near Mlynské Nivy and other high-rise buildings near the river - past Euroveoa towards Apollo bridge, where the tallest building in Bratislava is in the process of construction, is accomplished by digging deep foundations, mostly all the way to impermeable subsoils. Let’s imagine it as an impermeable encapsulation of the toxic waste dump in Vrakuňa. We do not create pollution, but we build a barrier for penetrating groundwater from the Danube in the huge reservoir of drinking water under Žitný ostrov. This again diminishes the capacity of percolation of water on the left bank of the Danube.
Only a small section on the right Petržalka side has remained... If the construction of high rise structures would be permitted there, deep foundations which would obstruct the percolation of water, would be really bad. Plans for the construction of Nove Lido are underway on the location of one of the last remnants of the original alluvial forest by the Danube. From a geological and hydrological perspective, it is one of the few original natural percolation sites of Danube water into the Žitný ostrov reservoir. It is also a unique location for developers, offering a beautiful view of the high-rise section around Eurovea with the Castle and the Little Carpathians on the horizon. Well, don’t go for it. The view alone will cost hundreds of thousands. But, the underground Danube once flowed in the area below the third underground floor of the projected location of the parking garage for ecological electric cars.
Even though we will clean the groundwater under Istrochem and Slovnaft, the supply of the Danube water into Žitný ostrov is necessary. Žitný ostrov is an agricultural region and its groundwater is constantly polluted by nitrogen and phosphate fertilizers. Today the fertilizer contamination of shallow groundwater (20 to 40 m) is so bad that it may only be used for irrigation and not for drinking. That is why the wells must be much deeper in order to eliminate contamination. New groundwater from the Danube (an amount that is decreasing by the day) can at least dilute the shallow pollution. If this is not impossible, the entire Žitný ostrov will become contaminated land.
Drinking water, either without treatment or after hygienic treatment, designated for the network of public water pipes in Slovakia, comes from multiple sources. The best quality water is drawn from wells with a maximum depth of several dozen meters down to the gravel and sand layers, where filtered river water is cumulated. We emphasize again that we have the best quality sources and the largest drinking water supplies at the gravel sand locations of the Danube alluvial deposits at Žitný ostrov. After the construction of the infrastructure, the Šamorín water source alone will be capable of supplying more than 2 million people in Slovakia with drinking water. Thus, the entire Žitný ostrov could do the same for all of Slovakia and even parts of surrounding countries. Since the circulation of river water within its percolation into the gravel and sand subsoil lasts for no more than several years, the drinking water does not have enough time to mineralize, i.e. become enriched by soluble and insoluble mineral components and elements, to an increased extent in comparison with surface river water. River water or rainwater quite easily soaks into porous layers of sedimentary rock, where it is properly filtered mechanically and biologically, and cleansed of slight natural inorganic and organic contamination; however, this water is vulnerable to artificial pollution from agricultural activities (inorganic and organic fertilizers), industrial activities and road traffic (chemical compounds and petroleum products). Therefore, protective hygienic zones of the third degree should be built around water sources in order to partially or completely eliminate the risk of the pollution of the groundwater. This also applies to all drinking water sources, sources of mineral and thermal water for drinking, and therapeutic and spa purposes.
Instant Profit vs Strategic Protection of Natural Resources
If you’ve made it all the way to this point, you understand that this is a recipe for big problems, a bleak inheritance, joyless reality and the same future if something is not radically changed. The fact is that the amount and acceleration of the natural flow of surface Danube water into the groundwater still supplying our largest drinking water reservoir is growing smaller. Most probably, the speed of groundwater movement will not grow due to additional restrictions, in fact the opposite is more likely. Further, the change in the direction of the flow of underground water is also questionable. In certain places the speed will drop, in other places the underground flows will create new “channels” (please, take this image with a grain of salt; it is not a free space, rather it is filled with gravel and sand), through which groundwater will reach those sections of waste dump pollution, which up to now were relatively dry (safe). Gravel and sand subsoil is not homogenous. In certain places it is more permeable, and less so in other places. In some places only gravel is found, in others there is just sand, clayey sand or loam in the former river branches. It is a complicated system and so is the modeling, but changing conditions can be approximately presented. Modeling is based on available data from construction pits, profiles of exhausted gravel pits, and hydrogeological and civil engineering geological drills.
In any case, further construction activities in the form of high-rise buildings near the Danube will not contribute to the quality of groundwater under Bratislava. The impact of any extensive construction activity near the Danube will affect the groundwater and its dynamics. The river and gravel and sand sediments of the Danube are interconnected vessels and although changes happen with a certain delay, they will happen eventually.
It is up to us to take facts from experts seriously. There are no doubts about the fact that the city needs to be further developed, but it must be sensible. If we don’t protect drinking water sources and non-contaminated agricultural soil for future generations, we will face disaster. Modern development in the Mlynské Nivy area where the Apollo refinery once stood is proof that smart solutions can be found even for large construction activities. Although its construction partially cemented the directions of groundwater flows, the removal of petroleum pollution under the old refinery was good news. Such development would also be possible on the Istrochem grounds. The costs connected with the cleaning of contaminated subsoil would be high, but very beneficial from the perspective of the environment. If we don’t want future generations to look at our present-day activities with disdain, this is our chance to show them a change.
So, what to do with future Lido? Naturally, leaving this territory as it would be the best solution. Perhaps it is a deeply naïve idea, but even here there is a compromise solution: the sensitive harmonization of new development and natural heritage. It failed in the case of Petržalka. The original plans to create a modern city borough, a kind of Bratislavian Venice or Amsterdam with sensitively placed architecture in contact with flowing branches of the Danube, water channels and alluvial forests preserved to a great extent. We already know, how this ended up. There is still a chance for Nove Lido.
RNDr. Ján Madarás, PhD.
Scientist, geologist, general director of the Earth Science Institute of the Slovak Academy of Sciences
Urban Development and Draining of Precipitations in Underground Layers
As we have already mentioned, figuratively speaking, Žitný ostrov is a huge tub with water flowing between rocks – gravel and sand. It is permanently replenished by water from the Danube, but not as much as before. Water may percolate from Hrušov reservoir and the old Danube river bed, but the vast majority of water is drained in an impermeable asphalt navigation derivation channel all the way to the electric power plant in Gabčíkovo. More than two thirds of the Danube flow cannot partially percolate into the subsoil due to building of this dam. The infiltration area of Bratislava is still there: but some of the water flows under Slovnaft and Istrochem. Here the water is contaminated or may be contaminated, as we have mentioned above.
Bratislava is a megalomanic. This city wants to transform itself into a modern metropolis, if not on a global standard, at least in relation to Central Europe - although it lacks a metro, but that’s a different story. Developers like to offer model constructions with views of the city or its surroundings. And where is the best place to build such structures if not with a view of the Castle, the Danube... The construction of the Sky Park buildings near Mlynské Nivy and other high-rise buildings near the river - past Euroveoa towards Apollo bridge, where the tallest building in Bratislava is in the process of construction, is accomplished by digging deep foundations, mostly all the way to impermeable subsoils. Let’s imagine it as an impermeable encapsulation of the toxic waste dump in Vrakuňa. We do not create pollution, but we build a barrier for penetrating groundwater from the Danube in the huge reservoir of drinking water under Žitný ostrov. This again diminishes the capacity of percolation of water on the left bank of the Danube.
Only a small section on the right Petržalka side has remained... If the construction of high rise structures would be permitted there, deep foundations which would obstruct the percolation of water, would be really bad. Plans for the construction of Nove Lido are underway on the location of one of the last remnants of the original alluvial forest by the Danube. From a geological and hydrological perspective, it is one of the few original natural percolation sites of Danube water into the Žitný ostrov reservoir. It is also a unique location for developers, offering a beautiful view of the high-rise section around Eurovea with the Castle and the Little Carpathians on the horizon. Well, don’t go for it. The view alone will cost hundreds of thousands. But, the underground Danube once flowed in the area below the third underground floor of the projected location of the parking garage for ecological electric cars.
Even though we will clean the groundwater under Istrochem and Slovnaft, the supply of the Danube water into Žitný ostrov is necessary. Žitný ostrov is an agricultural region and its groundwater is constantly polluted by nitrogen and phosphate fertilizers. Today the fertilizer contamination of shallow groundwater (20 to 40 m) is so bad that it may only be used for irrigation and not for drinking. That is why the wells must be much deeper in order to eliminate contamination. New groundwater from the Danube (an amount that is decreasing by the day) can at least dilute the shallow pollution. If this is not impossible, the entire Žitný ostrov will become contaminated land.
Drinking water, either without treatment or after hygienic treatment, designated for the network of public water pipes in Slovakia, comes from multiple sources. The best quality water is drawn from wells with a maximum depth of several dozen meters down to the gravel and sand layers, where filtered river water is cumulated. We emphasize again that we have the best quality sources and the largest drinking water supplies at the gravel sand locations of the Danube alluvial deposits at Žitný ostrov. After the construction of the infrastructure, the Šamorín water source alone will be capable of supplying more than 2 million people in Slovakia with drinking water. Thus, the entire Žitný ostrov could do the same for all of Slovakia and even parts of surrounding countries. Since the circulation of river water within its percolation into the gravel and sand subsoil lasts for no more than several years, the drinking water does not have enough time to mineralize, i.e. become enriched by soluble and insoluble mineral components and elements, to an increased extent in comparison with surface river water. River water or rainwater quite easily soaks into porous layers of sedimentary rock, where it is properly filtered mechanically and biologically, and cleansed of slight natural inorganic and organic contamination; however, this water is vulnerable to artificial pollution from agricultural activities (inorganic and organic fertilizers), industrial activities and road traffic (chemical compounds and petroleum products). Therefore, protective hygienic zones of the third degree should be built around water sources in order to partially or completely eliminate the risk of the pollution of the groundwater. This also applies to all drinking water sources, sources of mineral and thermal water for drinking, and therapeutic and spa purposes.
Instant Profit vs Strategic Protection of Natural Resources
If you’ve made it all the way to this point, you understand that this is a recipe for big problems, a bleak inheritance, joyless reality and the same future if something is not radically changed. The fact is that the amount and acceleration of the natural flow of surface Danube water into the groundwater still supplying our largest drinking water reservoir is growing smaller. Most probably, the speed of groundwater movement will not grow due to additional restrictions, in fact the opposite is more likely. Further, the change in the direction of the flow of underground water is also questionable. In certain places the speed will drop, in other places the underground flows will create new “channels” (please, take this image with a grain of salt; it is not a free space, rather it is filled with gravel and sand), through which groundwater will reach those sections of waste dump pollution, which up to now were relatively dry (safe). Gravel and sand subsoil is not homogenous. In certain places it is more permeable, and less so in other places. In some places only gravel is found, in others there is just sand, clayey sand or loam in the former river branches. It is a complicated system and so is the modeling, but changing conditions can be approximately presented. Modeling is based on available data from construction pits, profiles of exhausted gravel pits, and hydrogeological and civil engineering geological drills.
In any case, further construction activities in the form of high-rise buildings near the Danube will not contribute to the quality of groundwater under Bratislava. The impact of any extensive construction activity near the Danube will affect the groundwater and its dynamics. The river and gravel and sand sediments of the Danube are interconnected vessels and although changes happen with a certain delay, they will happen eventually.
It is up to us to take facts from experts seriously. There are no doubts about the fact that the city needs to be further developed, but it must be sensible. If we don’t protect drinking water sources and non-contaminated agricultural soil for future generations, we will face disaster. Modern development in the Mlynské Nivy area where the Apollo refinery once stood is proof that smart solutions can be found even for large construction activities. Although its construction partially cemented the directions of groundwater flows, the removal of petroleum pollution under the old refinery was good news. Such development would also be possible on the Istrochem grounds. The costs connected with the cleaning of contaminated subsoil would be high, but very beneficial from the perspective of the environment. If we don’t want future generations to look at our present-day activities with disdain, this is our chance to show them a change.
So, what to do with future Lido? Naturally, leaving this territory as it would be the best solution. Perhaps it is a deeply naïve idea, but even here there is a compromise solution: the sensitive harmonization of new development and natural heritage. It failed in the case of Petržalka. The original plans to create a modern city borough, a kind of Bratislavian Venice or Amsterdam with sensitively placed architecture in contact with flowing branches of the Danube, water channels and alluvial forests preserved to a great extent. We already know, how this ended up. There is still a chance for Nove Lido.
RNDr. Ján Madarás, PhD.
Scientist, geologist, general director of the Earth Science Institute of the Slovak Academy of Sciences