Pollution of water resources
Researcher Emília Novo says that "there has been a degree of control, otherwise things would be much worse"
Researcher Emília Novo says that "there has been a degree of control, otherwise things would be much worse"
The pollution of water resources (seas, rivers, lakes...) is increasingly present in our daily lives and can bring very serious consequences. It was on this subject that we talked to Maria Emília Novo, assistant researcher at the National Civil Engineering Laboratory (Laboratório Nacional de Engenharia Civil - LNEC).
Jornal J3D – What is the relationship between climate change and pollution of water resources?
Emília Novo (EN) – It depends on the area of the globe that we are addressing. If you go to southern Europe, climate change will entail a change in rainfall patterns, that is, according to the predictions of climate models, we will have much stronger rain events. Therefore, it will rain more in a shorter period of time, with are then followed by long periods without rain. Overall, calculations suggest that at the end of the year, we are expected to have less water, in other words, rainwater will go into rivers and the soil. When it penetrates the soil, it enters the underground reservoirs, e aquifers. Hence, if we have less water entering the rivers and less water entering the aquifers, we will have less water for consumption. At the same time, the increase in temperature means that there is an increased evaporation of water, thus more loss. So this creates problems in water management.
J3D – Where does a higher rate of pollution of water resources occur?
EN – That is too broad a question. because things vary greatly: what kind of pollution we are talking about, what is the water resource, whether it is superficial or underground, which is the part of the country ... For example, in coastal areas, a problem that can be placed is pollution from sea water. It is a process in which seawater enters and pollutes the resources with salt. Nowadays, there is a bigger issue that comes from agriculture. In areas of high agricultural activity, very intensive agriculture, where there is much use of pesticides and fertilisers, we have problems. There are at least two, I believe three areas marked in Portugal, as vulnerable to nitrate, that is areas that are already polluted by nitrates. One is the marshland of Tejo. But it is very variable, because it depends. At present, we are beginning to become aware of another type of pollution, which has a much more urban origin: the so-called new pollutants or divergent pollutants, which are hormones, drugs ... and that still have an ill-defined frame of its composition. Probably the rivers, the areas of discharges from sewage treatment plants (ETAR), are in trouble, and we are only speaking of surface water resources.
J3D – Can the pollution of water resources be associated with soil pollution?
EN – It is associated with soil pollution, including pollution from agricultural sources, for example, the issue of nitrate or pesticide pollution. Nowadays, when there is a wide coverage of the health network, pollution of soils comes precisely for agriculture. In the past, there was also the pollution of soil from the pits (septic tanks, tanks that were not septic, etc.). Therefore, soil pollution leads to pollution of water resources, whether they are superficial or underground.
J3D – What will happen if freshwater bodies become totally polluted?
EN – There is a big trouble, first of all. Today, precisely to avoid this problem, the European Community (EC) has a number of rules and regulations which oblige countries to take a series of measures such as the implementation of sewage treatment plants, control of nitrate levels and periodic monitoring, in other words, periodically observe if the waters are polluted or not, precisely to avoid these problems. And things have improved a little, though. If none this existed, things would be much worse than they are, so there has been a degree of control. If the surface water bodies (rivers, lakes, reservoirs, dams) became totally polluted, which means we would have to have a lot of pollution in many places at once, we would have a serious problem of water supply. For instance, in Lisbon, another major source is the Dam of Castelo de Bode (Barragem de Castelo de Bode). If we had especially onerous pollution problems, a substantial portion of the water that is consumed in Lisbon could not be consumed or its consumption would entail risks. There are problems in areas where we have lakes. Sometimes, locally, it happens and it's clear that whoever is supplied by these areas have problems. And we no longer suffer from common Third World diseases that come from water, such as cholera, which results precisely from the water pollution by sewage and human waste.
J3D – Can the rise in the average level of the sea contaminate freshwater aquifers?
EN – In coastal aquifers, there is a link between freshwater and seawater, there is a physical barrier that would prevent one water from mixing with the other. In fact they mix. What happens is that with the rise of sea water, these water depressions pressure freshwater and seawater advances. There is a difference in density, which causes the sea water to fill the interior of the continent and the mixture band to broaden. We also have contamination of wells that are left with brackish water (salt water). In the past the same exact phenomenon took place, not by sea level rising, but by excessively removing freshwater, which physically provides the same result. In the aquifers in the area of Algarve, a few years ago, there was much talk of salinisation. It had to do with precisely that, the sea advances and, if it goes up a certain level, then this problem arises. Then there is another problem associated, that is, if the sea level rises, there are areas that are currently uncovered (mainland) that will be covered. In those covered areas, of course, water infiltration in the soil will also increase. The case of sea water infiltration will also help to contaminate aquifers. Ergo, in coastal areas, this is a potentially serious problem.
Emília Novo (EN) – It depends on the area of the globe that we are addressing. If you go to southern Europe, climate change will entail a change in rainfall patterns, that is, according to the predictions of climate models, we will have much stronger rain events. Therefore, it will rain more in a shorter period of time, with are then followed by long periods without rain. Overall, calculations suggest that at the end of the year, we are expected to have less water, in other words, rainwater will go into rivers and the soil. When it penetrates the soil, it enters the underground reservoirs, e aquifers. Hence, if we have less water entering the rivers and less water entering the aquifers, we will have less water for consumption. At the same time, the increase in temperature means that there is an increased evaporation of water, thus more loss. So this creates problems in water management.
J3D – Where does a higher rate of pollution of water resources occur?
EN – That is too broad a question. because things vary greatly: what kind of pollution we are talking about, what is the water resource, whether it is superficial or underground, which is the part of the country ... For example, in coastal areas, a problem that can be placed is pollution from sea water. It is a process in which seawater enters and pollutes the resources with salt. Nowadays, there is a bigger issue that comes from agriculture. In areas of high agricultural activity, very intensive agriculture, where there is much use of pesticides and fertilisers, we have problems. There are at least two, I believe three areas marked in Portugal, as vulnerable to nitrate, that is areas that are already polluted by nitrates. One is the marshland of Tejo. But it is very variable, because it depends. At present, we are beginning to become aware of another type of pollution, which has a much more urban origin: the so-called new pollutants or divergent pollutants, which are hormones, drugs ... and that still have an ill-defined frame of its composition. Probably the rivers, the areas of discharges from sewage treatment plants (ETAR), are in trouble, and we are only speaking of surface water resources.
J3D – Can the pollution of water resources be associated with soil pollution?
EN – It is associated with soil pollution, including pollution from agricultural sources, for example, the issue of nitrate or pesticide pollution. Nowadays, when there is a wide coverage of the health network, pollution of soils comes precisely for agriculture. In the past, there was also the pollution of soil from the pits (septic tanks, tanks that were not septic, etc.). Therefore, soil pollution leads to pollution of water resources, whether they are superficial or underground.
J3D – What will happen if freshwater bodies become totally polluted?
EN – There is a big trouble, first of all. Today, precisely to avoid this problem, the European Community (EC) has a number of rules and regulations which oblige countries to take a series of measures such as the implementation of sewage treatment plants, control of nitrate levels and periodic monitoring, in other words, periodically observe if the waters are polluted or not, precisely to avoid these problems. And things have improved a little, though. If none this existed, things would be much worse than they are, so there has been a degree of control. If the surface water bodies (rivers, lakes, reservoirs, dams) became totally polluted, which means we would have to have a lot of pollution in many places at once, we would have a serious problem of water supply. For instance, in Lisbon, another major source is the Dam of Castelo de Bode (Barragem de Castelo de Bode). If we had especially onerous pollution problems, a substantial portion of the water that is consumed in Lisbon could not be consumed or its consumption would entail risks. There are problems in areas where we have lakes. Sometimes, locally, it happens and it's clear that whoever is supplied by these areas have problems. And we no longer suffer from common Third World diseases that come from water, such as cholera, which results precisely from the water pollution by sewage and human waste.
J3D – Can the rise in the average level of the sea contaminate freshwater aquifers?
EN – In coastal aquifers, there is a link between freshwater and seawater, there is a physical barrier that would prevent one water from mixing with the other. In fact they mix. What happens is that with the rise of sea water, these water depressions pressure freshwater and seawater advances. There is a difference in density, which causes the sea water to fill the interior of the continent and the mixture band to broaden. We also have contamination of wells that are left with brackish water (salt water). In the past the same exact phenomenon took place, not by sea level rising, but by excessively removing freshwater, which physically provides the same result. In the aquifers in the area of Algarve, a few years ago, there was much talk of salinisation. It had to do with precisely that, the sea advances and, if it goes up a certain level, then this problem arises. Then there is another problem associated, that is, if the sea level rises, there are areas that are currently uncovered (mainland) that will be covered. In those covered areas, of course, water infiltration in the soil will also increase. The case of sea water infiltration will also help to contaminate aquifers. Ergo, in coastal areas, this is a potentially serious problem.
Work by: André Silva, José Bento, Nuno Vaz e Pedro Duarte
8th Grade
Escola Básica e Secundária de Oliveira Júnior (Middle and High School), S.João da Madeira
This work was carried out under the Flash Seminar held on the 23rd of April and the 15th of May 2015 at Escola Básica e Secundária de Oliveira Júnior (Middle and High School), in São João da Madeira. Students developed media content based on interviews with experts in various fields related to climate change and research on the subject.