- Currently, Ireland has one of the highest rates of water availability in Europe. However, there is pressure to meet increasing demand due to a number of factors;
- There is an imbalance between the places where water availability is greatest (the west of Ireland) and where water is most needed (the east of Ireland);
- The antiquity of Ireland's water supply system means that a relatively large amount of water is lost through leakages;
- Regardless of climate change, there is now a pressing need to identify new sources of water for the east of Ireland;
- Projections indicate an overall decrease in levels of precipitation during the summer months and this will lead to significant decreases in annual effective runoff and the availability of water supply for all sectors;
- Critically, for the areas where demand is currently greatest, e.g. the Dublin region, the greatest decreases are expected and this may make the provision of potable water problematic, during the summer months in particular.
In Ireland, water resources are dominated by surface waters (81.5%), while the remainder originates from groundwaters (11.5%), located primarily in the east and southeast of the country, and springs (7%). Demand for water comes primarily from the east of the country, the industrial and domestic sectors in particular. Increases in domestic demand are due primarily to population growth and increasing water consumption per capita.
Supply and demand
For Ireland, the spatial distribution of rainfall (highest in the west) is in contrast to population density which shows the highest levels of population in the east of Ireland. Currently, the water required to meet this demand is largely sourced from freshwater resources situated in the Wicklow mountains and there is little excess capacity/headroom in meeting water demand. This is important because:
- For a water supply system with large excess capacity (a resilient water supply system), a large change in climate may have little effect.
- For a water supply system with little excess capacity and that is operating at, or close to capacity, even a small change in climate can have a large effect and may tip the system past a critical threshold where demand for water exceeds supply.
In addition, the antiquity of the water supply system adds additional pressure on the capacity of the system to meet demand. For example, in 2008, the national average level of unaccounted water was 43%. This high level of water loss is thought to be due to, amongst others, the antiquity of the system, with some parts of the water supply system dating to the Victorian era, breakages, and the failure of building inspection regimes.
As a result, currently, the resilience of the Ireland’s water supply system is already under threat with little excess capacity. This is reflected in the fact that due to projected increases in demand as a result of population growth, the identification and development of new supplies is now a necessity, regardless of any effects that climate change might have.
In projecting changes for Ireland's water supply, hydrological models have been developed for specific catchments. These models are used to project changes in hydrological regimes and are driven by projected changes in climate variables such as temperature and precipitation.
We can have a relatively high degree of confidence in the temporal variations of projected changes for hydrological regimes with drier summers resulting in reduced water flows. In contrast, projected changes in the spatial distribution of precipitation is less certain, and the actual location of future water resources remains unclear. Nonetheless, current projections indicate that the west of Ireland will become wetter and this would suggest that future significant water resources will likely be located in the west.
Surface water catchments
For surface water dominated catchments in Ireland, projections consistently indicate substantial decreases in streamflow during the summer months, which is particularly the case for those catchments located in the east of the country.
For example, significant reductions have been projected for the Boyne catchment by the 2020s in early summer and autumn with reductions becoming more pronounced as the century progresses.
For groundwater dominated catchments, it is thought that reductions during summer will not be as substantial as for those dominated by surface-waters. Nonetheless, climate change does have significant implications for aquifer levels as decreases in precipitation during the summer and autumn months will result in a delay to the seasonal recharge of aquifers.
For example, given that the variability of precipitation may increase, a year with below average winter and spring precipitation could result in a severe groundwater deficit.
Available water supply
Projected decreases in supply are expected to coincide with periods of increasing demand due to non-climatic drivers such as population growth.
For example, when compared the levels of population in 2010, Ireland's population is projected to increase by 46.5% by 2060, the strongest population growth rate of any European country. In addition, projected increases in temperature are expected to result in increased levels of water demand during the summer months.
A widespread reduction in runoff resulting in the increased frequency and duration of flows will also lead to water quality problems, as many rivers would not have sufficient capacity to dilute effluent discharged into them. Moreover, under projected increases in population, the quantity of discharge will likely increase. Projected increases in the occurrence of extreme events will also have a detrimental impact on water quality and will affect the availability of potable water. This is due to increased levels of runoff and associated contaminants to watercourses.
Implication for management
To date the water supply system has remained resilient to current climate variability but this cannot be taken for granted as exemplified by water shortages due to floods and cold weather during recent years. Future changes in climate will have substantial implications for the availability of surface waters as well as for both water supply and quality.
Although the exact nature of these changes remain uncertain, evidence indicates that substantial decreases in levels of surface water during the summer months can be expected. It must also be recognised that climate change is not the only pressure on water resources and levels of demand due to population growth and development may also be problematic. This is particularly the case large parts of Ireland, as the water supply system is currently operating at or close to capacity.
In the near term, many elements of adaptation planning can be identified that are robust to uncertainty and flexible. These strategies should form an important aspect of adaptation planning.
- Detection of water loses and leakage control should be a priority in order to reduce leakage to acceptable levels. All water authorities should set targets to be achieved in specified time periods.
- Currently, levels of water usage in Ireland are significantly higher than elsewhere in Europe. Climate change and a growing population could lead to significant water shortages in the medium to long term. As a result, measures to reduce demand should be implemented.
In the medium to long term, a range of measures can be identified that are also robust to climate change.
- Climate, demographic and economic change will alter the needs and demands of water users in Ireland and, as a result, the abstraction of water represents a threat to water availability. In order to effectively manage competing needs, the volume, location, user and purpose for which water is being abstracted needs to be examined.
- Water infrastructure represents long-term assets. Where investment in new infrastructure is required, these infrastructure should be subjected to a full sensitivity analysis of performance under a full range of uncertainty associated with climate change.