Groundwater – what is it and why do levels change? Do I need to know?
Aqvify asked Anders Nordström, senior lecturer at Stockholm University, to explain a few things about groundwater…and why it is so important to keep track of.
Anders is the author of the book “Drinking water – Our most important grocery” and is a nestor in the field.
He is also one of the longest users of Aqvify, something we are very happy and proud of!
“The United Nations has declared 2022 as the Year of Groundwater and on 22 March, World Water Day, authorities and organizations will seek to raise awareness of what groundwater is and how important it is for all water users (especially drinking water) to understand the importance of managing groundwater and protecting groundwater recharge areas from pollution that can affect groundwater quality.
What is groundwater?
Groundwater is the water in rock and soil where all the pores (cavities) are filled with water. The upper limit where the pores are filled is called the water table. Below the water table, all pores and cracks are completely filled with water.
Above the water table, the pores are partially filled with water or dry. The water here is called soil water or green water (plant water). This water is used by the roots of plants and is mostly below the soil surface but above the water table.
Rainwater and meltwater that penetrates the ground (infiltration) sinks by gravity into the ground (soil and rock). Below the water table, groundwater continues to move by gravity and can emerge on slopes to form a spring that creates a stream. Several streams join together to form a river that flows into a lake. Groundwater seeks out low points in nature and in many cases the water flows into the sea invisible to us.
How does ground water level change?
Groundwater is normally formed only during the period from October to April by rain and snowmelt. Rain during May-September is used by the roots of plants and evaporates into the atmosphere. Thus, the rainiest months of July and August do not create new groundwater. The use of groundwater is highest in the summer. Wells for summer houses are usually drilled in rocks with small, thin cracks (no pores) and therefore cannot store large volumes of water. It also takes some time to replenish the water after a certain withdrawal.
Most of us have understood that we have climate change. The changes have already started but will continue and at an increasing rate. The amount of precipitation is increasing or decreasing and its distribution throughout the year may change. Heavier rainfall in a short time will alternate with longer dry periods. Higher temperatures will increase evaporation. All this affects the formation of groundwater. Our lakes and rivers are fed by flowing groundwater, so these aquatic environments will also be affected.
Do you need to check your well’s groundwater level?
During the fall-winter 2021/22, the replenishment of new groundwater has been much less than in normal years. This applies to large parts of southern and central Sweden. Many people probably remember the summer of 2018. This wonderfully warm summer, many private wells and even municipal wells were affected by the groundwater surface dropping below the level where the pump pipe ended. In other words, the well became “dry”. Some wells experienced saltwater intrusion. The main reason why the wells became dry was that the groundwater reservoir was poorly replenished after the previous year’s summer withdrawals. The heat during summer 2018 also created a greater need to use more water than usual (showers, irrigation and more guests, etc.).
A warning could have been given before it went dry or salt water entered the well. By installing a level meter in the borehole, level changes can be recorded and possible savings made. This can be effectively created by using Aqvify’s product.”
If you want to know more about groundwater – formation and extraction possibilities, groundwater quality and the material (soil and rock) in which groundwater is stored, read:
Drinking water – our most important food. Author Anders Nordström, senior lecturer, Stockholm University. Publisher Studentlitteratur, published 2019, 258s.
The book’s text is adapted to well owners and other people interested in drinking water without special prior knowledge.
With Aqvify, you can continuously monitor your well’s available water quantity, level, inflow and groundwater level – and receive alarms at selected levels. All easily accessible in the Aqvify app.
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