By Mel Lyons and Catherine Isherwood
Today is World Water Day, and the theme this year is “Groundwater: Making the invisible visible”. But what exactly is groundwater and why is it so critical?
Mel Lyons at RSK Geosciences and Catherine Isherwood at WRc, our hydrogeology experts, talk us through the ‘need to knows’ of working with groundwater, the challenges facing our groundwater resources and what we can do to preserve it.
- What is groundwater?
Catherine: Groundwater is the term used to describe water that is held within the ground. The water can be held in soil, sediment such as sand or gravel deposits, or rock pores. It is critical to life on earth because it can often be accessed in areas where surface water is scarce, absent or seasonal. Groundwater is not susceptible to the same levels of biological contamination as surface water and is less likely to contain significant levels of suspended sediment, although both can occur under some circumstances.
Mel: We use groundwater every day. It gives us life. We abstract it to drink and bathe and wash in, and to use in manufacturing, industry, leisure and agriculture for cooling, washing, swimming, irrigation, etc. We abstract groundwater from aquifers, which are rock formations that can yield useable amounts of water. The volume of groundwater able to be abstracted from a particular aquifer will depend on the nature of the material making up the aquifer, for example, whether it is sand and gravel, chalk or sandstone.
- Why are groundwater resources being depleted?
Catherine: The demands on water supplies from rapidly increasing populations, burgeoning development and the climate crisis mean that, in many areas, more groundwater is being abstracted than is being replaced. This leads to an overall decrease in groundwater levels.
Abstraction is not occurring at the same rate in all areas: some parts of the world have higher demands on groundwater than others, and some areas have larger groundwater resources available. Areas of high demand and low availability experience groundwater scarcity.
Mel: As an example, the construction of basements in cities that requires the removal of aquifer material and, thus, alters groundwater flow, when combined with the construction of large areas of hardstanding, depletes aquifer recharge and discharge. Before appropriate regulation, industry historically significantly depleted the amount of groundwater available in the London basin and other former industrial centres.
- Will groundwater eventually run out? What are the impacts of the climate crisis on our groundwater reserves?
Catherine: Groundwater will not run out, but fresh groundwater may become so scarce in some parts of the world that they no longer have a source of fresh water for drinking, agriculture and industry.
Mel: Sea level rises may increase the incursion of saline waters into fresh groundwater bodies (known as saline intrusion).
Changes in groundwater levels associated with the climate crisis also have the potential to mobilise contamination currently present above the water table, thereby releasing it into groundwater and potentially causing pollution. The effects of climate changes, for example, drier, hotter conditions that may deplete soil moisture in the autumn, on groundwater are likely to vary, depending on the type of aquifer and its location, and they will also vary seasonally.
- What measures can be taken to mitigate this?
Mel: Ways we can mitigate this risk are to increase the use of sustainable drainage systems (SuDS) and to actively manage groundwater recharge schemes, which may help to mitigate the impacts of the climate crisis on aquifer levels.
Catherine: We also need to improve our water efficiency, so that we all use less water for everyday purposes. We also need to think about the produce that we buy that can influence our individual ‘water footprints’.
Additionally, higher intensity storms are more likely to cause flooding, which has an impact on groundwater recharge. For groundwater recharge to take place, rainwater needs to soak into the bedrock. Our habit of creating hard surfaces, such as roofs, tarmac roads and surfaced parking areas, also means that rainfall and surface water cannot get into the ground. If we had more permeable surfaces, such as vegetated areas, green roofs, permeable paving and temporary storage ponds where the water can collect and soak into the ground, this would help to improve groundwater recharge and to mitigate surface water flooding.
We need to improve our water management infrastructure to include measures such as collecting rainwater for use in non-potable situations, including toilet flushing and irrigation. Land use change that helps to slow down runoff water and hold it in temporary storage areas can help to improve the recharge of the groundwater resources.
- How does our work at RSK affect and preserve groundwater?
Catherine: Businesses across RSK provide advice to clients over their water use by offering business-specific water strategies and tools to help reduce water use within their business.
At WRc, we are involved in modelling water use and abstraction to ensure that only the volume of water required is abstracted from surface or groundwater sources. This includes modelling the dewatering associated with excavations or cuttings to permit construction work in a dry environment or to inform long-term drainage design, as well as modelling water abstraction for water usage requirements.
Mel: At RSK Geosciences, we take a risk-based management approach to the assessment and remediation of groundwater contamination from industrial legacies. Our industrial history has led to pollution of groundwater in places that can reduce the quality of water supplies and of surface water, such as in rivers and lakes. Assessing the levels of risk associated with areas of contaminated groundwater and supporting clean-up to an acceptable quality enables groundwater to be returned to beneficial use and improves the wildlife and diversity of our rivers and lakes.
Want to find out more about the work RSK group businesses carry out in the water sector? Teams across our family of more than 130 businesses are specialists in hydrogeology, remediation, risk assessment and pollution response.
Mel Lyons is Associate Technical Director, Hydrogeology at RSK Geosciences, a leading provider of site investigation, contaminated land and geotechnical consultancy services.
Catherine Isherwood is Principal Hydrogeologist at WRc, an independent centre of excellence for innovation and growth delivering technical research and innovation services to the global water sector.