Water is one of Earth's most fundamental and vital resources. The water we use every day – for drinking, cooking, washing, and irrigation – is part of an eternal cycle that has been going on for millions of years. Understanding the water cycle and how groundwater is formed gives us a deeper appreciation for why it is so important to protect and manage our water resources sustainably.
The Water Cycle – An Eternal Circle
The water cycle, also known as the hydrological cycle, describes how water constantly moves between the oceans, atmosphere, land, and back again. It is a process driven by the sun's energy and Earth's gravity, creating the conditions for all life on our planet.
The cycle consists of several important steps:
Evaporation: When the sun heats water in oceans, lakes, and watercourses, it evaporates and rises as water vapor into the atmosphere. Plants also contribute by releasing water through their leaves in a process called transpiration.
Condensation: As water vapor rises high into the atmosphere, it encounters colder air and condenses into tiny water droplets, forming clouds.
Precipitation: When the droplets in the clouds become large and heavy enough, they fall back to Earth as rain, snow, hail, or drizzle.
Infiltration and Runoff: Some of the precipitation runs off the land surface and reaches lakes, watercourses, and oceans. Another part infiltrates the ground, helping to replenish groundwater reservoirs.
Groundwater – A Hidden Resource
Groundwater is the water found beneath the Earth's surface in rock fractures and in the pores between sand, gravel, and soil particles. It forms when precipitation and meltwater seep through the ground and collect in what are called aquifers – geological formations that can store and transport water.
Sweden's groundwater is one of our most important water resources. Approximately 1.5 million Swedes rely on private wells for their drinking water, and groundwater also constitutes an important source for many municipal waterworks.
Why is groundwater so valuable?
Natural filtration: As water passes through soil layers, it is filtered from many pollutants and achieves high quality.
Long-term storage: Groundwater acts as an enormous natural water reservoir, providing a stable supply year-round.
Drought protection: Unlike surface water, groundwater is not as quickly affected by periods of low rainfall.
Stable temperature: Groundwater maintains a relatively constant temperature throughout the year, ensuring good water quality.
Groundwater quality is affected by the bedrock, the soil layers it passes through, how long it has been in the ground, and any human activities on the surface. It is therefore crucial that we protect our groundwater resources from contamination. Learn more about common problems in our blog about well water and water quality.
Different Types of Wells
To access groundwater, we use wells. There are several different types of wells, and the choice depends on local geological conditions, water needs, and economic factors.
Drilled Wells (Rock-drilled Wells)
A drilled well is the most common type of well in Sweden today. It is drilled into solid rock, often to a depth of 50–150 meters, but can sometimes go even deeper.
Advantages:
- Often provides a stable and good water supply year-round
- Less susceptible to surface contamination compared to dug wells
- Long lifespan – can function for 50–100 years with proper maintenance
- Less affected by drought and seasonal variations
Disadvantages:
- Higher initial drilling cost
- Requires specialized equipment and a professional driller
- Water quality depends on the bedrock and may contain high levels of iron, manganese, or radon
Drilled wells draw their water from fissures and cavities in the bedrock, and a water analysis for drilled well shows exactly what substances your water contains. Since the water has often been in the ground for a long time and passed through several rock layers, it may have dissolved minerals from the rock, affecting water quality.
Dug Wells
A dug well is an older type of well dug into soil and gravel layers, typically to a depth of 3–10 meters. Historically, this was the most common type of well, but today they are less common for new installations.
Advantages:
- Lower installation cost compared to drilled wells
- Easier to maintain and repair
- Can provide plenty of water in areas with shallow groundwater levels
Disadvantages:
- More susceptible to surface contamination from the ground surface
- Greater risk of seasonal variation in water supply
- Can dry up during drought as the groundwater level drops
- Requires more careful protection against pollutant intrusion
Since dug wells draw their water from shallow soil layers, they are more exposed to the effects of human activities on the surface, such as runoff from sewage, agriculture, or industry. It is therefore especially important to regularly analyze the water from a dug well.
Lake Water as a Water Source
In some cases, especially on islands and in coastal areas, lake water is used as a source for drinking water. This means that water is drawn directly from a lake through an infiltration line or connected to a pump.
Advantages:
- Unlimited water supply
- Less investment than drilling deep wells
- Works well where groundwater is absent or difficult to access
Disadvantages:
- Often requires more extensive purification before the water is potable
- Sensitive to pollution and algal blooms
- Can be affected by seasonal variations in water quality
- Risk of filter clogging with high organic matter
Lake water as a drinking water source requires special care and regular monitoring. The water often needs to be treated with UV light, filtration, and possibly chemical purification to ensure it meets drinking water requirements.
Regardless of well type – regular analysis is crucial
Anyone using a private well or lake water as a drinking water source should regularly analyze their water. The Swedish Food Agency recommends analysis at least every three years, or more frequently if there are small children in the household or if the water quality changes.
A water analysis provides you with knowledge of any problems and the opportunity to take timely action. It is your assurance that the water you drink is safe and healthy.
Protecting Our Most Important Resource
By understanding the water cycle, how groundwater is formed, and the different types of wells available, we gain a deeper respect for this unique and vital resource. Every well, regardless of type, is a link to the vast and sensitive groundwater system that supplies us with clean water.
By taking care of our wells, monitoring water quality, and acting responsibly regarding groundwater protection, we all contribute to securing the availability of clean and safe drinking water – both for ourselves and for future generations.