Why Does Groundwater Fluctuate Seasonally?

Why Does Groundwater Fluctuate Seasonally?

November 25, 2022

Most people are not aware that groundwater quality goes through seasonal fluctuations. This can be important information for homeowners who use a well for their home’s water supply. This quick guide will provide you with information on why this happens and why it is important to you.

What Causes Groundwater Fluctuations

There can be many reasons that affect groundwater levels and quality. Some of the changes are caused by natural occurrences, and others are caused by man’s activities above ground. Below ground, there are many aquifers located throughout a state. Some of the more shallow aquifers will be dramatically affected by fluctuations and actions above ground. This can include building, pollution, and digging.

The deeper aquifers are made up of bedrock units. Some aquifers are more heavily used than others, so levels can change dramatically depending on how much water is being drawn upon.

How Are Seasonal Groundwater Fluctuations Measured?

Observation wells are used to record water levels every 30 minutes or so. This data is then graphed to show the depth of the water below the surface. This information is then sent to the USGS to be used by the National Water Information System.

Types of Water Level Changes

There are different types of water level changes.

Short-term changes – This type of change is only seen when water level measurements are made several times a day.

Long-term changes – These types of changes are seen when water levels have been observed and collected over several years.

The different types of data are used for different purposes.

Aquifer Storage Changes

One of the most significant contributors to water level fluctuations is aquifer storage. Groundwater is part of a flowing system. The water does not simply stay in one place. The water moves in and through the aquifers. The water flows from high levels to lower levels. The aquifer storage changes will be based on how much water is moving and how much water is moving out during a certain period of time.

Water charging happens when more water is flowing into the aquifers. This is affected greatly by the state of the earth above the aquifer. During certain times of the year, the earth more readily releases water down into lower elevations. This is called the porosity of the earth. When the porosity of the aquifer is high water can more easily move in.

High Charge Seasons

Springtime is considered a high charge season for aquifer levels. This is mostly due to melting ice and snow in parts of the world. This new introduction of water will make its way down into the aquifers, raising the water levels significantly.

In like manner, summer and fall are often considered to be low-charge seasons. When there is less water available above ground, there will be less water available in the aquifers.

This information can be important for those who are attempting to drill for wells or for building projects in a certain area.

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