Clean water is without color, odor and taste




Water is a chemical compound that, under standard conditions, is a liquid with a chemical empirical formula H2O. The formula says that one molecule of water is composed of two hydrogen and one oxygen atom. Water molecules attract each other greatly; they create surface tension on the surface, and because of internal tension, water easily penetrates the holes

Water changes aggregate states, therefore it moves constantly and creates planetary circulation. The solid state of water is ice and the gas state is water vapor. Clean water is without color, odor and taste. It is an excellent solvent and it is easy to run.

Water covers about 70% of the Earth’s surface and is found almost everywhere on Earth, it is needed for all known forms of life.

Aggregate water status

Water is the only substance that appears in all three aggregate states at normal temperatures on Earth: hard, liquid and gaseous. The change in the aggregate state is associated with the addition and acceptance of energy. If the ice is heated, it stops. If the water is heated to boiling point, this vapor is then boiled and then boiled, whereby steam is formed. If the steam is again cooled, it condenses and creates liquid water. If the water is cooled under the freezing point, it freezes.

pH value of water

The pH value is a measure of acidity and alkalinity and ranges from 0 to 14. At a water temperature of 25 ° C, its pH is about 7, which means that it is neutral, that is, it is neither acid nor basic. The pH of the water decreases slightly with increasing temperature. If acid is dissolved in water, its pH is reduced, but if the base is dissolved, the pH is increased. The water in contact with the air is slightly acidic, since it dissolves CO2 from the air.

Water density

When cooling water, its volume decreases. Water has a special property, its density is at the maximum at 4.5 ° C, that is, above its freezing point. At 4.5 ° C, the volume of water is the smallest and the density is highest. If the water is cooled below 4.5 ° C, its volume increases unexpectedly and the density decreases, making the water easier. At 0 ° C, ice has a lower density than liquid water and therefore floats on it. Ice density at 0 ° C is 9% less than the water density at the same temperature. The structure of ice is characterized by gaps that are filled during melting, and the density increases with the transition to the liquid phase. The decrease in water density from 4.5 ° C to 0 ° C is associated with an increase in the length of the hydrogen bond.

Specific heat of water

Due to hydrogen bonds, water has a very specific heat. This means that the water must lead to a lot of heat in order to increase its temperature. Water is therefore slowly heated and cooled, allowing living beings to survive in the water. The phenomenon is also useful for industrial water use as a coolant. Due to this characteristic, temperature transitions during the seasons are gradual, especially near the seas and oceans. Because of the high specific heat of the water, the sea maintains large amounts of heat, which affects the climate in seaside resorts.

Water hardness and limescale

The hardness of the water is caused by calcium and magnesium salts in water.

Water-soluble calcium and magnesium are removed from water in the form of limescale. The temperature at which the casting begins is different and depends on the overall chemical composition of the water. With the rise of water temperature, the deposit of limescale increases steeply. Watercooling is accumulated on the walls of water pipes, on heaters, in sanitary fittings, on water supply pipes.

The water hardness is expressed as the sum of the amounts of calcium and magnesium ions and is presented as the content of calcium oxide (CaO) or calcium carbonate (CaCO3). The hardness is most often expressed in German hardness, but also expressed in terms of French hardness degrees and mmol (milie moles per liter).

Water as a solvent

Water is a solvent that dissolves both solid as well as liquid and gaseous substances. We do not know pure water in nature. The solubility of the substance in water depends primarily on the nature of the substance and the temperature. Since the water is a polar solvent, polar and ionic solvents dissolve well in it, for example, a kitchen salt, and poorly soluble non-polar substances, such as fats and oils.

Water acts as a solvent in our body as all biochemical reactions take place in aqueous solutions. Water is at the same time a transport medium for the transfer of nutrients and oxygen to cells and the removal of metabolic waste.


Dissolving kitchen salt in water.

Sweet water temperature

Freeze water at 0 ° C (freezing point) and pass to 100 ° C (boiling point) in water vapor. The freshwater density is at a maximum of 4 ° C. Waters with a temperature at the source of 20 ° C or more are called thermal waters. Depending on the temperature, they are divided into hypothermal (from 20 ° C to 34 ° C, Dobrna Health Resort), homeotermal (from 34 ° C to 38 ° C, Terme Ptuj) and hyperthermal (over 38 ° C, Terme Čatež). Water, at some depths, heats up even above the boiling point and breaks out like a geyser on the surface.

Drinking water

It is water that meets the minimum prescribed requirements that it can be used for drinking, cooking, food preparation and other household purposes, as well as any water used in the production and marketing of foodstuffs.

The requirements for drinking water must be prescribed by the Rules on Drinking Water (Official Gazette of the Republic of Slovenia, Nos. 19/04, 35/04, 26/06, 92/06 and 25/09). It specifies the requirements that drinking water must meet in order to protect human health from adverse effects due to any contamination of drinking water.

Water in nature

All the water on Earth, regardless of the location (under or on the surface) and the physical state (liquid, solid, gas), is called the Earth’s hydrosphere. It consists mainly of oceans, including sea, lake, river and groundwater.

Water is naturally found in all three aggregate flats: hard, liquid and gaseous. The most liquid water is, the less it is in solid form (ice caps around the northern and southern courses, frozen soils, mountain glaciers, highland snežišča and icebergs) and the least in the form of water vapor in the atmosphere (clouds). Although water changes in individual forms vary somewhat, the amount of water on Earth remains the same.

97.5% of water in the hydrosphere is saline. It is located in the oceans, seas and lakes with little or no drain. Only 2.5% of the water in the hydrosphere is sweet.

We often call the Earth “Blue planet” because it has a lot of water in comparison with other planets in our solar system.


Groundwater is also called groundwater because it is located below the surface. About one third of all fresh water is below the surface. It also includes thermal and thermomineral springs. Groundwater is formed by the penetration of precipitation and partly surface water through rocks. When the impermeable layer gets under the surface, it is kept there, from where it is pumped for drinking and other needs. Especially rich in groundwater are sandy and pebbly ground layers. In these layers, there are a number of small spaces between individual floor particles that can be filled by water. In dry periods, groundwater is much deeper than in wetlands.

The Karst world is characterized by rocky or hollow water, which is collected in cracks and caves in a living rock. Due to the CO2 content, the water dissolves limestone and thus creates a system of underground lakes, streams and rivers, which then returns to the surface in the form of springs.

Liquid waters, river basins and water catchment areas

When the geological history of the sea disappeared, a network of running water was formed behind them, including streams and rivers. The water flow is always in the direction of lowering the altitude. The flow rate depends on the drop, the amount of water and the width of the river cross section. However, since all of the source from the spring to the outflow of the river is constantly changing, the characteristics of the river flow are constantly changing.

In the upper stream, rock erosion is constantly underway. In the middle and lower river streams, the materials brought with them sit and slowly fill the riverbed. First, the gravel is pumped, which is pushed and rolled by the river. Fine particles float in the water and therefore they carry the water for longer. Most of them are deposited (sedimentation) only at the ejection and in the sea.

Streams and smaller rivers flow into larger rivers. The river with all the tributaries consists of a river network or a river basin, which we call the main river. A line that delimits two sub-basins is called a distribution line. It runs through the highest parts (ridges) of mountains or hills, but it can also run along valleys. Rivers can be poured into the sea or in the lakes. Part of the Earth’s surface from where water flows into the same river, lake or sea is called a water-catchment area or a water catchment area. We call the water catchment area of ​​the river by the sea or the lake into which it flows.

Rivers running along the western part of Slovenia belong to the Adriatic basin and the rest to the Black Sea catchment area. The largest Slovenian rivers to the Sava, Drava, Soča and Mura rivers.

River flow and river regime

River flow tells us how many m3 of water flows in a riverbed on a certain section in one second. Measure it in m3/s.

River regime is changing the average water flow of the river by months. It depends primarily on climatic conditions in a certain basin. According to the source of water, we classify rivers in different river regimes. A simple river regime has rivers in which flow fluctuations depend only on one climatic factor. These rivers have a yearly increase and lower water. The rain (pluvial) river regime has rivers with the highest flow rate during the rains, the snow (river) regime has the highest flow river at the time of melting snow, and the glacial regime is the river with the highest flow rate during ice melting. Pure simple regimes are very rare.

The more frequent are mixed river regimes, and they have rivers in which two climatic factors are affected by the water level. Therefore, they have two extras and two low water in the river bed over the year. The most common is the snow-raining river regime. In it, the highest water in the river bed is in the spring when melting snow, while the second, and a slightly lower autumn summit occurs due to the increased amount of rainfall. When the autumn surplus is more pronounced than the spring, we are talking about the rain-and-snow river regime.

River regimes are plotted graphically with hydrograms.

Hydrogram of the Mura River.



Flooding is a regular or periodic spillage of water from overflow riverbed, lake or sea. It is a natural phenomenon that is caused by intense or long-term precipitation, rapid snow melting, rising groundwater levels, high tides of the sea or collapse of the dam. The important factors of flooding are the preliminary saturation of the soil with water and the outflow conditions in the precipitation zone (forests in the forests, extensive impermeable surfaces (asphalt, concrete) in urban areas).

Floods are one of the dominant natural geographical transformers of the landscape in the lowland plains and affect the use of space and the dominant use of soil. More frequent and smaller floods can be beneficial in economic terms (for example, greater soil fertility) and play an important role in the preservation of certain ecosystems. In addition, regular floods were once of crucial importance for the development of the first high civilizations, such as the ancient Egyptian. Major floods cause damage to buildings and infrastructure, and may result in fatalities.

Floods at Vič in Ljubljana in 2010.


Lakes are natural terrestrial land, which is constantly or occasionally filled with fresh or salted water.

The lake bunches can be formed by dipping (overburden) the surface or resulting from the drainage of the drain. We distinguish between calcareous (damaging) and damaging (accumulating) lakes. Natural lakes can be tectonic, glacial, volcanic and karst. In addition to natural, we also know artificial lakes.

Lakes can be flowing, which means they have a constant flow and water outflow. For example, there are Lake Bohinj and Bodensee Lake. They can also be unbearable; they only have a constant flow of water, but not a drain. Among such lakes, we include the Caspian Lake, Lake Chad and others.

Bohinj lake from Vogla.

The lakes are constantly changing. Some are produced, while others are reduced and slowly transform into wetlands due to flooding and reduced inflow of rivers.

Most lakes in the world have Finland, where lakes cover almost 10% of the country’s total area.


Wetlands are areas where water is occasionally or permanently stagnant. We distinguish wetlands, marshes, wet meadows, flood plains of rivers, coastal lagoons and coastal parts of the seas.

Ecosystems with typical animal and plant species, adapted to high humidity, acidic soil, and sweet and salt water, are formed in the wetlands area when they are along the coast.

They are characterized by great biotic diversity. Nevertheless, for a long time, he did not know their ecological role, he looked at them as an agricultural unused land and dried them with dykes and dewy ditches.

Sečoveljske soline so mednarodno pomembno mokrišče.


The wetlands are formed due to filling of lakes as a result of melting of the top layer of soil in the permafrost area (permanently frozen soil in the area with cold climate) or as a result of the high level of ground water and its retardation. Many wetlands change over time into the marsh. They often produce peat that was cut by people due to fire, which in many cases led to the destruction of this important ecosystem.

We distinguish high marshes, in which plants do not have contact with groundwater, they are characterized by peat mosses. And the low mud that is formed in the corners, where water is stagnant, is rich in nutrients that plants draw from the groundwater.

Poplavljeno Ljubljansko barje.

Water on the karst

The karst is a rocky area formed by water flowing below the surface. Due to tectonic action, karst karbonate rocks are cracked by cracks, which lead to precipitation of water and accumulate on impermeable lower layers. In precipitation, dissolved CO2 dissolves limestone and forms typical karst phenomena. Karst rivers have a surface flow disrupted due to the overgrowth of rocks, so we talk about downpours. There is a lack of water for the karst area, while in the underground there is an extensive network of rivers and lakes. Karst water is an important source of drinking water. In the karst fields, bays and under steep alpine walls, the karst water comes to the surface. Particularly for karst fields are frequent floods. The systems of sinks and springs of karst water, due to the rise of the water level in the connected karstic caverns, allow the formation of seasonal lakes with increased water supplies. The largest lake in Slovenia is Lake Cerknica.

Voda iz Cerkniškega jezera počasi odteka.

Mineral waters

Various minerals, especially silicon, calcium, potassium, magnesium and iron, are usually present in natural freshwater. Waters that have dissolved more than 1000 mg of mineral matter in a liter of water are mineral waters or spinach (Donat, Radenska). There are 78 springs of mineral and thermal waters in Slovenia, about a quarter of them are natural, the rest are covered with boreholes.

Spring of mineral water called Jezerska slatina.

Circulation of water in nature

Water in nature is constantly circulating. Water circulation is one of the most important natural systems triggered by the Sun’s thermal radiation. A quarter of the solar energy is used to circulate water.

About 85% of the water evaporates from the seas and oceans, the rest from water and living organisms on land. Water passes into the air in the form of water vapor, with evaporation from water surfaces and damp soil, and is also emitted by living beings (plants, animals and humans). Water vapor is lighter than air, so it rises and travels with winds. In higher air layers it cools and combines into the clouds. At a certain temperature, water vapor is converted into droplets or ice crystals (condensation), which, in the form of rain or snow, fall back to Earth. Most precipitation falls back into the sea. Precipitation falling to the land flows overland (streams and rivers) and subterranean towards the sea, and part of this water is again evaporated from the ground and through plants (evapotranspiration) again into the atmosphere.

Due to circulation water is constantly renewed. Water in the atmosphere is rebuilt on average every few days, in rivers in a week, in lakes in a few years, in the underground in centuries and in the oceans in about 3200 years.

Water balance

It is the ratio between the amount of rainfall and the drainage of water on the one hand, and the evaporation of the water on the other side.

Water balance of Slovenia compared to Europe:


Padavine (mm)

Izhlapevanje (mm)

Odtok (mm)

Koeficient odtoka (%)


20.230 km2






10.519.367 km2





Acid Rain

Acid rain is acid rainfall caused by emissions of sulfur dioxide and nitrogen oxides into the air. These gases dissolve in the rainwater and make it sour. Acid rain has a pH lower than 5.6. It has a very great influence on the soil and plants that, due to acid rain, grow more slowly or get sick. Acid rain is also one of the reasons for the rupture of needle forests. It damages the ecological balance in the water, which is felt in the growth and reproduction of plants and animals. Acid rain also ruins monuments from limestone and marble.

Because of sour rain, the forest in Czech is destroyed.

Water in the human body

All living creatures for life need water because water is our basic ingredient. In the human body, it is 57-65% of water, depending on the sex and age of the person. This also applies to most animals. Some aquatic animals, such as jellyfish, contain even more than 98%.

Water is of utmost importance to humans. It is part of cells, intercellular space and blood plasma, and is a transport medium for oxygen, vitamins, minerals and glucose. With its help, toxic toxins are transferred to the kidneys, which are later excreted.

The daily need for a person depends on the individual’s physical activity, health condition and microclimate conditions. The average adult person should drink two and a half liters of water per day, and much more in case of strenuous physical activity. Water strengthens the body, stimulates the spirit, and helps maintain body weight. That’s why it’s still important to plan her drinking, especially during a mature life period, when the ability to retain water in tissues is worse.

The importance of water for man

Water resources are indispensable for the survival of human society. Water supply is possible from rivers and lakes, and from ground water. The settlements were therefore always created near water resources, and their inhabitants were supplied directly from rivers, lakes and wells for a long time. In modern times, water is supplied through public water supply systems, while access to clean drinking water is still a major problem in the poorest regions of the world.

Excessive water consumption is a major problem, especially in large cities where, due to exhaustion and pollution of the nearest water resources, water is supplied from hundreds of kilometers of remote pumping stations, or it is refined for reuse by expensive and energy-consuming processes. Only a handful of countries can afford the production of fresh water by decomposing salty sea or ocean water.

Worldwide, the largest consumer of water is agriculture (60%), followed by industry (28%), households account for only a tenth of the water consumed.

In agriculture, most of the water is used for irrigation of arable land, much less is spent on feeding livestock.

Irrigation of wheat by sprinkling.

In the industry, water is needed for cooling, flushing waste and as a solvent and cleaner. Most of the water is consumed in the paper, metal and chemical industries, somewhat less in the food processing industry.

A human society uses water as an energy source for millennia. Initially, they exploited the mechanical power of water to drive mills, sawmills, blacksmiths and related devices, and with the invention of the turbine, they started to exploit water energy in hydroelectric power plants for electricity generation.


Hydroelectric power station Medvode

In countries with a lot of thermal water, geothermal energy is used to heat buildings and greenhouses and to generate electricity (geothermal power plants).

Water transport continues to play an important role, as it is cheaper compared to road, rail and airline. It is especially important for the transportation of heavy cargo, bulk cargo and oil. Water regulation networks have been established in many countries through the regulation of rivers and the construction of overpasses. The World Sea allows the connection between continents and different countries. Apart from freight, passenger shipping is also developed for tourist purposes.

Suez Canal

From time immemorial, man has exploited the sea as an important source of food. 25% of the animal protein sources are obtained from the sea. Excessive fishing, which does not allow the fishery to restore, is becoming an increasing global problem.

The seafloor of the shallow shallow seas become important pumps of oil and natural gas. The oceans are mined warehouses, of which the longest tradition is the production of salt. In the shallow seas, they also dig coal and iron ore. (King Sera, etc., 2015)


Water contaminants

Intensified water pollution is the result of an industrial revolution that has led to faster urbanization and population growth. The degree of pollution of water resources is an indicator of economic development, industrial composition and technological progress of a certain region. The rule that more developed areas are polluting more. There are three main sources of pollution: industry, agriculture and households. Industry consumes a quarter of pumped water. The manufacturing industry pollutes water with toxic substances and heavy metals, mining and construction with sediments and acids, and food production by organic substances. Since water in the cooling energy of thermal power plants and nuclear power plants uses water that is heated back to the source, the temperature of the water rises. Agriculture is the largest consumer of water, consumes two thirds of all consumed water, and is polluting it with residues of mineral fertilizers, pesticides and natural manure. A higher level of organic and inorganic pollution (phosphorus) is noticeable for household consumption. (Internet 3)

Water protection areas

Drinking water supply is based on the protection of drinking water resources with regulated water protection areas. Any activity or encroachment on the site, which would endanger the quality or quantity of water resources, is prohibited or restricted in these areas. In the immediate vicinity of waterworks and areas, the limits of the activity in the space are very strict, while the protection regime is milder with the distance from the pumping stations. The measures are intended to reduce the risks and risks caused by pre-existing activities or activities that are already being introduced into the space. Water protection areas have a significant impact on the protection of water resources, but at the same time they represent limitations for the development of many activities, which can lead to disagreements among the users of the space. That is why water resources management is an extremely difficult and never completed task.

Code for water protection area.

Water quality

Water has self-purification ability, but it has been polluted by some of its activities even to its extent that it has been greatly reduced. The quality of water is measured by chemical and biological parameters.

The good chemical status of the water is if no average annual concentration of chemicals (mercury, cadmium …) exceeds the environmental quality standard laid down in the European directive. The ecological status of water is a reflection of the quality of the structure and functioning of aquatic ecosystems.

The reasons for poorer chemical and ecological status of water in Slovenia can be found in municipal sewage, agricultural pollution, wild landfills, lack of treatment plants and limited self-cleaning ability, especially karst waters.

In addition to the chemical, the quality of groundwater depends on the quantity of water in the aquifer. During the time of small stocks of water in the aquifer, it is much more sensitive to pollution than in the time of more abundant water supplies. In particular, aquifers that are shallow underground are highly sensitive to local sources of pollution. Smaller stocks of water in aquifers are affected by the absence of precipitation, hot summers, summer storms and others. (King Sera, etc., 2015)

Self-cleaning ability of water

Water is purified in nature. In the waters where waste water is discharged, organisms that use nutrients in it live. The natural self-cleaning decency of the water is therefore the consequence of the action of these organisms, which use organic substances as foods and thus metabolize it. The intensification of water sampling is greater in liquid than in standing water. It is influenced by the velocity of the stream, the shape of the riverbed, the ratio of river and waste water, the temperature and depth of water, the intensity and duration of the solar system, and the size of the suspended particles. Water is purified by physical (dilution, sedimentation, filtration and ventilation) and biochemical processes (chemical reactions between dissolved substances and metabolic processes of aquatic organisms). A stream of particles entering the water through pollution decreases due to the movement of water mass (the greater the water flow, the greater the dilution). The larger particles settle down, the smaller they travel with water. Water flows through sand and other deposits that intercept particles. When contacting water with the atmosphere, ventilation takes place, which is important because the elements react with dissolved gases in water and form insoluble molecules, which then settle on the river bed.

Bacteria, algae and fungi digest in water dissolved organic and inorganic substances or their smallest suspended particles. These substances turn into a new cellular substance or generate energy from them and eliminate water and carbon dioxide. For this process they need oxygen, which they take away from the water. Algae containing chlorophyll can produce a new cellular substance from mineral substances, and during this day, oxygen is secreted. If water is loaded with plant nutrients (eutrophic water) such as nitrogen or phosphorus, excessive reproduction of algae may follow. This can lead to a lack of oxygen, because due to its limited solubility it is only partially dissolved in water, leaving the residue to the atmosphere. In addition, at higher temperatures, less oxygen is dissolved. At night oxygen algae do not produce and may therefore be lacking because other organisms also use it.

Pests, bacteria and algae are kept partly with dissolved organic substances. Crustaceans, worms and worms feed on undissolved, sedimentary or suspended substances, and they also feed on pigs. Artificial pollutants destroy these microorganisms, thereby reducing the self-cleaning ability of water. The strength of self-cleaning is not only affected by the presence of micro-organisms, but also by the formation of a riverbed. In naturally formed riverbeds with a large surface area and strong turbulence (the streams flow with swirling), the living conditions for organisms, in order to better absorb oxygen from the air, are more favorable than in regulated or restricted rivers.

Even minor changes in any of the important biological, chemical or physical factors can significantly affect the self-cleaning ability of water. Excessive pollution of water adversely affects live creatures in the water (dead fish …). (How it works? 1988)


Due to the turbulent flow, the water mixes more, thereby increasing its self-cleaning ability.

Virtual water

Domestic water is not only used for drinking, cooking, washing, washing, cleaning and personal hygiene, but also buying different products. When we buy a product in a store, we do not see the water, we do not take it home. All that invisible water used for the production, processing or manufacture of goods, such as food, clothing, and other products, is called virtual water. The water footprint of an individual is therefore the total amount of indirectly and directly consumed water. In the developed world, we consume 4,000 to 5,000 liters of water a day per capita, huge!

Virtual water consists of three components. The green component represents the amount of precipitation that evaporated during the production process (agriculture). The blue component of the product represents the amount of water consumed during production and does not return to the place from which it was pumped (industry). The brown component represents the amount of water that has been contaminated during production.

Water consumption for production or production:

1 kg wheat

1.500 l virtual water

1 kg of potatoes

800 l virtual water

1 kg of potatoes

180 l virtual water

100 g of chicken meat

433 l virtual water

1 kg of beef

15.500 l virtual water

4 car tires

16.000 l virtual water

cotton short sleeves

2.495 l virtual water

one sheet of paper

10 l virtual water


World Water Day

Every year we celebrate World Water Day on 22 March. Day was proposed at the United Nations Environment Conference in Rio de Janeiro in 1992, as part of Agenda 21, as a day intended to alert the wider world public to the limited and threatened natural water resources. To this end, various United Nations organizations publish a theme every year to summarize the most current issues in relation to water. (Internet 4)

– Year 2010: Water quality
– Year 2011: Water for cities – answer to the challenges of urbanization
– Year 2012: Water and food safety
– Year 2013: Participation in the management of water resources
– Year 2014: Water and Energy
– Year 2015: Water and sustainable development
– Year 2016: Better water, better jobs
– Year 2017: Wastewater
– Year 2018: Nature for water

Sources and literature: