Groundwater Explained – World Water Day
March 22, 2022, will be World Water Day and it serves as a key reminder of the importance of freshwater. Around 2.2 billion people in the world live without access to safe water, and the fight is ongoing to ensure that as per the UN’s Sustainable Development Goal 6, water and sanitation will be available to everyone by 2030.
This year, the focus is groundwater, an invisible but vital resource that impacts our lives in a multitude of ways. Here we explain more about groundwater, why it is important and some of the key problems that must be overcome to ensure the world maintains a sustainable level for future generations.
What is Groundwater?
Groundwater is water that exists in saturated zones underground beneath the surface of the land. The top surface of the saturated zones is called the water table.
There is a widely held belief that groundwater forms underground rivers, although this is not true. Instead, in the same way that water fills a sponge, groundwater fills the fractures and pores in underground materials such as gravel, sand and other forms of rock.
Groundwater can also be found in rock materials called aquifers, which can be accessed and removed by pumping it out, or by the water flowing naturally from the source. In an aquifer, groundwater usually moves at a rate of 7-60 cm per day, which means it can remain there for hundreds of years, or sometimes even longer.
Why is Groundwater Important?
On a worldwide scale, groundwater accounts for nearly 30% of freshwater. A small percentage – 0.2% – can be found in streams, lakes and rivers, while 70% is locked into ice and snow on mountains in the polar regions.
As groundwater tends to support rivers and lakes, it is no exaggeration to say that almost all the water used in agriculture and industry is groundwater or was previously groundwater at some point in the water cycle.
Groundwater also plays a huge role in environmental terms, supporting lakes, rivers and wetlands, especially in the hotter, drier months of the year when there is less rainfall. Baseflow, which is the flow of groundwater into rivers as seepage through riverbeds, is vitally important to the health of plants and wildlife that live in water.
In England, groundwater provides around a third of public water supply and is also heavily relied upon in Scotland and Wales. It is a great source for a water supply because the quality is often very good, which means in order to make it safe to drink it requires less treatment. This is because the rocks and soil groundwater pass through helps to remove many pollutants.
For areas of the world such as the Global South, which includes Africa, Asia and Latin America, groundwater is essential, as it is found close to remote villages and can be extracted without incurring the huge costs typically associated with setting up water supplies.
Why is Groundwater Diminishing?
Groundwater resources are being diminished at an alarming and unsustainable rate right across the world. Studies by the likes of NASA found that 21 of largest 37 aquifers in the world are being depleted and have surpassed sustainability tipping points.
For example, individual countries like the United States have a huge reliance on groundwater. Almost 50% of people living there get their drinking water from groundwater, although it is used far more for irrigation (only India and China use it more for this). The Ogallala Aquifer, which covers 8 southern states in the US, provides 30% of groundwater for irrigation in the US, and is steadily being depleted due to overdependence on its resources.
Water tables across large parts of India, China, Iran, Pakistan, Mexico, the Middle East and the western United States are also falling due to over pumping, raising serious cause for concern.
Some of the negative effects of groundwater depletion include:
- Excessive pumping can lead to the lowering of the groundwater table, preventing wells from being able to reach groundwater.
- With the water table falling, pumping must be pushed harder to reach the surface, which requires more energy to be used in the process, increasing costs.
- Lakes, streams and rivers that are connected to groundwater can also be depleted due to over pumping.
- Overuse of groundwater can lead to the collapsing of the soil, compacts and drops and land subsidence continues when there is not enough support below ground.
- When there is excessive pumping along the coast, saltwater can start to move inland and upward, leading to the water supply being contaminated by saltwater.
What Can You Do To Help?
Natural landscapes capture over 50% of rainfall, but in urban and suburbanised cities, towns and villages, this can drop to as low as 15%. So, if we want to continue to rely on groundwater, nature will need a helping hand along the way.
There are several things you can do to reduce groundwater depletion in your immediate area. This includes better management of tap water around the home, using fewer products that contain damaging chemicals and bedding native plants in your garden that won’t need much water or fertiliser.
The biggest contributions you can make is to harvest rainwater. By collecting and reusing rainwater it can be returned to nature at a sustainable rate, helping to replenish the soil and layers beneath. It’s a long-term investment that will transform the way you use water at home and if you have a water meter installed, it gives you a much better chance of lowering your bills.
Rather than turning on the kitchen tap to fill up a bucket to clean the car, or flushing the toilet several times a day, you can use the stored rainwater instead. Harvested rainwater is perfect for watering the garden, and your plants will love because compared to tap water it contains a higher percentage of minerals and nutrients.
At a time when we all have to be more environmentally conscious, rainwater harvesting offers us a chance to tackle an issue that isn’t as visible as melting ice caps and erratic weather conditions. Combined with the financial benefits it will bring to your home, it’s an investment well worth considering.