|Ó Dochartaigh, B É, MacDonald, A M, Fitzsimons, V, and Ward, R. 2015. Scotland’s aquifers and groundwater bodies . British Geological Survey Internal Report, OR/15/028.|
Overview—using these articles
These articles describe the results of a collaborative project between BGS and SEPA to delineate the groundwater bodies within Scotland and describe the different aquifers in the country. There were three main aims:
- To explain how Scotland’s groundwater bodies were delineated. These bodies are a vital component of Scotland’s River Basin Management planning which is the means by which the water environment is managed in Scotland.
- To provide a summary of the current understanding of Scotland’s aquifers at a regional scale, with references to more detailed information where available.
- To provide information to underpin Scotland’s submissions to the European Union to demonstrate compliance with the Water Framework Directive.
This Introduction article provides context and a brief introduction to groundwater and groundwater management in Scotland. It is written for policy makers and those with a role in delivering sustainable development. Data sources and Groundwater bodies in Scotland articles provide technical details of the development of aquifer groups and groundwater bodies. Aquifer characteristics presents an overview of the hydrogeology of each of the aquifer groups in Scotland. It is written in the form of a manual for those with some technical groundwater (hydrogeological) knowledge, but includes summaries which may be useful for non hydrogeologists.
Groundwater in Scotland
Scotland’s groundwater is described in some detail on Scotland’s Environment website (Scottish Government 2014a), with contributions from the British Geological Survey (BGS), the Scottish Environment Protection Agency (SEPA) and the Drinking Water Quality Regulator (DWQR). Here we provide a summary.
Almost all groundwater starts life as rainfall. Some rain is taken up by plants, some runs over the land surface or through soils to rivers, and some soaks down through the soil into aquifers. Below the water table, all the spaces in the soil or rock are completely filled with water — groundwater (Figure 1). In Scotland, groundwater occurs almost everywhere beneath our feet, and the water table is usually within 10 m of the ground surface. As a store of water that can provide a reliable source of water for drinking and other purposes, groundwater is often accessible close to where it is required, and is cheaper to treat than surface water in lochs and/or reservoirs. In rural areas in particular, groundwater is a vital water source, and it plays an important role in Scotland’s economy.
Groundwater’s value to society is partly in its provision of drinking water, providing 73 per cent of Scotland’s private water and 5 per cent of public water supplies, for at least 330 000 people in total (DWQR, 2013). Groundwater for public water supply is abstracted from approximately 100 boreholes and springs across Scotland, and supplies some of our major rural towns. More than 4000 boreholes, and some large springs, are used for large private, industrial or agricultural supplies; and many more — approximately 20 000 — boreholes, small springs and wells provide private water supplies for at least 80 000 people (MacDonald et al., 2005, DWQR, 2013).
Groundwater is also very important for Scotland’s economy. Groundwater provides almost all of the water sold by the bottled water industry (DWQR, 2013); and underpins Scotland’s whisky exports, providing 70 per cent of the water bottled by the whisky distilling industry. It is widely used in other industries, such as brewing and fish farming, and for agricultural and recreational (including golf course) irrigation. The approximate volumes of groundwater abstracted for different uses are shown in Figure 2.
Groundwater plays an important environmental role, supporting surface water ecosystems through baseflow to rivers and lochs throughout the year. This is particularly critical in dry summers, and in the east of Scotland where lochs do not provide significant alternative sources of water storage. On average, it is estimated that groundwater sustains more than a third of the annual flow in all river bodies, even in small upland streams, rising to over 60 per cent in some rivers in drier eastern Scotland (Gustard et al., 1987). Groundwater baseflow to rivers is invaluable in maintaining healthy river ecosystems, including for salmon populations (Soulsby et al., 2000) — hence indirectly supporting another part of the Scottish economy — and in sustaining wetlands and fragile ecosystems, such as our coastal machairs.
Another role of groundwater is its ability to assimilate, dilute and break down contaminants and waste. One example is domestic septic tank discharges, which are specifically designed to make use of the ability of soil and groundwater to break down microbes and nutrients. By accepting excess surface water flows, groundwater also helps to mitigate flooding, for example through the increased use of infiltration-based sustainable drainage schemes (SuDS).
Groundwater management and groundwater bodies in Scotland
Groundwater occurs across the whole of Scotland. In some areas, groundwater is more at risk of contamination or overabstraction than in others, due both to the pressures put on groundwater and also the inherent nature of the soil and geology. More than 80 per cent of Scotland’s groundwater resources are considered to be in good condition (Scottish Government, 2014a); of the remainder, three main areas of impact are observed:
- larger-scale pollution impacts in eastern and southern Scotland and the Central Belt, from legacy industrial activity and agricultural nutrients;
- more localised and dispersed impacts from isolated instances of poor practice in waste management; and
- localised instances of overabstraction
To help manage groundwater it is important to define the areas most vulnerable to contamination or overexploitation, and areas that are already showing degradation. The process of definition is based on two concepts: aquifers and groundwater bodies. An aquifer is a subsurface geological layer which is sufficiently permeable to allow a significant flow or abstraction of groundwater. In Scotland, due to its particular geological history and to its rainfall, all rock types and most unconsolidated superficial deposits can be aquifers. Groundwater that can be abstracted for human use therefore occurs underneath most of Scotland.
However, Scotland’s aquifers vary markedly depending on their hydraulic characteristics, natural geochemistry, thickness, and extent (MacDonald et al., 2005). Some aquifers are capable only of supplying small amounts of groundwater, enough to support dispersed small domestic demand, whilst others can provide yields sufficient to supply towns such as Dumfries and Aviemore. Many aquifers act as natural filters and are able to provide natural protection from pollutants, whilst others are much more vulnerable. Some aquifers have large natural storage which can buffer low rainfall over periods of several months or years, whilst others cannot. Particular aquifers are under much more pressure from industrial pressures than others. These differences all mean they require different management strategies.
To address this, Scotland’s aquifers have been first differentiated and characterised on the basis of relevant criteria, and then subdivided into management units, called groundwater bodies. These delineations are a helpful tool for managing groundwater, and the identification of groundwater bodies is a requirement of the EU Water Framework Directive (2000/60/EC). The remainder of this report is focussed on explaining the key differences between Scotland’s aquifers.
Groundwater protection in Scotland
Scotland’s groundwater, rivers, lochs, and coastal waters have all been subdivided into water bodies. These bodies form the basis of River Basin Management Planning in Scotland. Groundwater is different from surface and coastal waters in a number of ways:
- Groundwater is a hidden resource, and poorly understood by the public.
- Groundwater is the key resource for small, widely distributed private drinking water supplies, for which expensive forms of treatment are not practical.
- Groundwater occurs almost everywhere below the land surface of Scotland, at various depths.
- Groundwater is more resilient to degradation than surface water, but, if degraded, the effects can last for decades or centuries.
- Groundwater is difficult and expensive to monitor.
For these reasons, in groundwater management there is a significant emphasis on preventing problems arising, rather than treating the impacts. However, because groundwater occurs almost everywhere and is widely relied on, it is not practical to attempt to eliminate all pressures on and risks to groundwater. The greatest risk is posed by hazardous chemical pollutants, and so a key aim is to prevent these from entering groundwater in the first place. For lower risk pollutants, and for abstraction pressures, a risk based approach to regulation means assessing each new pressure against the capacity of the groundwater body to assimilate the pressure. To address historic problems, the status of Scotland’s groundwater bodies are classified (and reclassified) on a regular basis, into one of five categories: high, good, moderate, poor or bad; those bodies at risk of deteriorating status are also identified. Where the status of a groundwater body is identified as poor or at risk of deterioration, these bodies are prioritised for action to improve the situation. More details can be found in the River Basin Management Plans for Scotland (SEPA, 2009a).
Groundwater bodies are therefore the fundamental basis for both identifying existing problems of groundwater management in Scotland, and for preventing new risks to groundwater arising. They help to inform decisions on where groundwater monitoring is required in order to help clarify risks and demonstrate that any actions taken are effective.
The Scottish Environment Protection Agency (SEPA) is responsible for the regulation of most issues related to groundwater in Scotland. The key pieces of primary legislation in this regard are the European Water Framework Directive (WFD) (2000/60/EC) and the Groundwater Directive (2006/118/EC). These establish a series of environmental objectives for groundwater that must be achieved within a framework protecting the wider water environment and ecosystem health. More information on the legislation that SEPA implements, and on other authorities involved in regulation, can be found in the River Basin Management Plans for Scotland and on Scotland’s Environment Website (Scottish Government, 2014b).
- Scottish Government. 2014a. Scotland’s environment: Groundwater. http://www.environment.scotland.gov.uk/our_environment/water/groundwater.aspx Accessed 18 March 2014.
- DWQR. 2013. Drinking water quality in Scotland 2012. (Edinburgh: Drinking Water Quality Regulator.)
- MacDonald, A M, Robins, N S, Ball, D F, and Ó Dochartaigh, B É. 2005. An overview of groundwater in Scotland. Scottish Journal of Geology, Vol. 41, 3–11. Available at http://nora.nerc.ac.uk/12230/
- Gustard, A, Marshall, D C W, and Sutcliff, M F. 1987. Low flow estimation in Scotland. (Wallingford: Institute of Hydrology.)
- Soulsby, C, Malcolm, R and Malcolm, I. 2000. Groundwater in headwaters: hydrological and ecological significance. Geological Society of London Special Publications, No. 182 (1), 19–34.
- SEPA. 2009a. The river basin management plan for the Scotland river basin district 2009–2015. http://www.sepa.org.uk/water/river_basin_planning/scotland.aspx Accessed 13 August 2014.
- Scottish Government. 2014b. Scotland’s environment: Groundwater: Response by Society. http://www.environment.scotland.gov.uk/our_environment/water/groundwater/response.aspx Accessed 18 March 2014.