Water scarcity in Scotland

Water scarcity occurs when access to water of sufficient quality to meet human and ecological needs becomes limited.

It occurs due to a long-term imbalance between water supply and demand in a region.

Climate change may create or intensify water scarcity problems in a region, either through a reduction in water supply or through an increase in water demand.

Given Scotland's relatively wet climate you'd think we'd have ample water to support our way of life. However, we also have a climate of extremes.

Scotland has the highest variability of rainfall of any region in the UK. Some areas of western Scotland are wetter than the Amazon rainforest while parts of eastern Scotland are drier than East Anglia.

Rainfall is also highly variable over time, as we've seen from recent flooding. Much of our annual rainfall can fall in a short period of time leaving long periods without any rain.

A drought can be defined as a prolonged dry period in the natural climate cycle, caused by a lack of rainfall and exacerbated by higher temperatures. So is there any evidence that droughts have been getting worse in Scotland?

There is some evidence of a trend in the frequency of low rainfall episodes (meteorological drought).

The image here was produced by the European Environment Agency and indicates that the east of the British Isles (including east Scotland) has seen an increase in the number of meteorological droughts between 1950 and 2015

There's a clearer picture when it comes to rising temperatures.

This is important for water scarcity as higher temperatures lead to more evaporation.

Using rainfall data along with temperature and solar radiation to estimate evaporation, it's possible to estimate the water balance of Scotland. Where evaporation exceeds rainfall, we have a water balance deficit. Over the last 60 years, the east of Scotland in particular has seen a decrease in the water balance in spring and late summer.

As a result of an increased frequency of dry periods and higher temperatures we have seen some decreases in the amount of water moving through our river basins in the driest month in each year between 1951 and 2015

The latest  climate projections  for the UK indicate that Scotland is likely to see hotter, drier summers in the future.

These projections have been used in the  Enhanced Future Flows and Groundwater  project to run models that estimate future water resources.

They indicate median reductions in low flows of anywhere between 10 and 60% by the second half of the century...

...and the amount of water percolating down through soil to top up our groundwater levels is also projected to decrease.

Well through the driest and warmest times of the year we should expect much less water running in our rivers or topping up our lochs, reservoirs and groundwater than we have been used to.

A recent study comissioned by NatureScot shows how these changes could result in droughts becoming more frequent, longer and more severe even over the next 2 decades.

Furthermore, a  report  for the Scottish Government's ‘Climate Change Impacts on Natural Capital’ research project indicates that the region of Scotland in monthly climatic water balance deficit between April and September will expand further west and upland to encompass more of the central highlands.

Between 2003 and 2021, the population supplied by Scottish Water increased by 7% to just under 5.2 million people (WICS 2023).  Over this same period, the amount Scottish Water has taken from our rivers, lochs and groundwater has decreased by 22% (Scottish Government 2023).  Much of this decrease has been due to reduced leakage from the supply network

A key factor to consider for future demand for this water is the projected population of Scotland. The latest population projections indicate that the distribution of population in Scotland is expected to see a broad shift from west to east i.e. wetter to drier water resource zones

The way we use our land in Scotland is changing.

In the last 100 years, forest and woodland cover in Scotland has increased from around 5% to 18.5%.

Over the last 30 years we have also seen over 600,000 hectares of mountain, moorland and heath changing, mostly, to semi-natural grassland, fresh water, wetlands and floodplains, and woodlands.

The nation's climate change plan commits to a further increase in woodland and foresty to reach 21% of land cover by 2032 whilst at the same time restoring 40% (250,000 hectares) of Scotland's peatland.

Each land use type has its own water demand and more knowledge is required to understand how these land use changes in combination with a changing climate will affect the risk of water scarcity.

Assuming the current pattern of land use continues​ and that irrigation is maintained to meet healthy crop water requirements​, then a modelling of crop water requirements for the 2050s indicates some significant increases in irrigation demand.

The largest changes are projected for E Scotland, especially some areas of Fife and Angus

 Aquaculture is a major user of freshwater for fish farms and hatcheries, and this is especially notable where the industry has a significant footprint as in NE Scotland ( Visser-Quinn et al.2021 ). The Scottish Government has identified an objective to double the aquaculture sector by 2030, and with recent trends towards increased infrastructure in freshwater as well as marine zones, this is likely to have important implications for local water demand.

Tourism is a growing industry in Scotland

The number of nights spent in Scotland by international visitors has grown steadily between 2012 and 2022 (with the exception of those years impacted by the pandemic)

We can also see the pattern of seasonality of visits with a peak in the warmest 3 months of July to September.

The additional local demand for water from tourism includes drinking water, sanitiation and laundry from guest accomodation and water used in the food, drink and hospitality industries.

The shift away from fossils fuels and towards renewables for energy production has resulted in reductions in the consumption of cooling water.

Hydropower uses water abstracted from rivers and reservoirs to generate electricity. The use is non-consumptive, in that the water used is returned to the environment, but in some cases this can be many kilometers from the point of abstraction.

Between 2008 and 2018, there has been an increase in the installed capacity of hydropower in Scotland resulting in an increase in the amount of water abstracted.

Since 2018 there has been little growth in hydropower due to the removal of feed in tarrifs.

There are plans in place to develop a number of pumped storage schemes over the next few years to help manage variations in customer demand and fluctuations in renewable energy nature

Scottish Water have modelled the impact of a moderate climate change scenario on the supply demand balance across the water supply network.

It is estimated that the combined deficits of the 189 Scottish water resources zones could amount to 240 Megalitres per day by 2050.

This estimate uses a scenario for a 1 in 150 year return period drought with no additional leakage reduction, no reduction in consumption per person and with a population increase to 5.6 million.

Private water supplies serve around 3% of Scotland's population. The sources of private water supplies are typically eitther springs or shallow borehoes and as such are vulnerable to extended periods of dry weather.

A study looking at the impacts of climate change on the resilience of private water supplies identified the Northeast of Scotland as an area where projected increases in meteorological drought coincided with an area of high number of susceptible private water supplies.

When the water demands of our river and loch plants and animals are not met, several impacts can occur.  Reduced flows and levels lead to contractions of wetted habitat and can potentially strand species that are unable to relocate. Lower flow velocities deposit fine sediment which can clog vital spawning habiatats on river beds. Declining water volumes are also less able to dilute pollutants, and can lead to lower oxygen levels in water that can warm up much quicker.

Because of these impacts, the Scottish Environment Protection Agency authorises water abstraction from our rivers, lochs and groundwater in a way that protects the flows and levels required for a healthy water environment.

In the future, if summer river flows decline , the issue of whether to maintain these environmental flows at the same volume as present, or to reduce the volume as a proportion of the future overall flow, makes a large difference in terms of the water resource available for our use.

Water abstraction in Scotland is largely governed by the Water Environment and Water Services (Scotland) Act 2003 (as amended) and the Water Environment (Controlled Activities) (Scotland) Regulations 2011. These set out the way SEPA will authorise water abstractions to enhance the protection and improvement of the aquatic environment. Water abstraction authorisations are made under the condition that water is used efficiently and that the combination of allowable abstractions within a water body maintain sufficient flows and levels to support at least good ecological status.

The Water Resources (Scotland) Act 2013 has provisions to ensure that public water supplies are maintained during droughts through the making of “water shortage orders” by Scottish Ministers.

To manage Scotland's water resources, a  National Water Scarcity Plan  has been developed to improve communication between SEPA, Scottish Water, the Scottish Government and other water stakeholders. The plan also sets out an indicative hierarchy of action to manage water resources during periods of water scarcity.

In addition to the legislation and plans already mentioned many other policies are relevant to integrated water management.

The aim of this project is to provide a set of recommendations for mitigation and adaptation responses to water scarcity in Scotland. The stakeholder consulation and workshop elements within the project will seek to understand how these responses would interact with the wide range of relevant policies outlined above.