Water Sustainability and Climate Change in the EU and Global Context – Policy and Research Responses

ABSTRACT

Climate change impacts on the hydrological cycle (e.g. effects on atmospheric water vapour content, changes of precipitation patterns) have been linked to observed warming over several decades. Higher water temperatures and changes in extremes, including floods and droughts, are projected to affect water quality and exacerbate many forms of water pollution with possible negative impacts on ecosystems and human health, as well as water system reliability and operating costs. In addition, sea-level rise is projected to extend areas of salinisation of groundwater and estuaries, resulting in a decrease of freshwater availability for humans and ecosystems in coastal areas. Besides this, changes in water quantity and quality due to climate change are expected to affect food availability, water access and utilisation, especially in arid and semi-arid areas, as well as the operation of water infrastructure (e.g. hydropower, flood defences, irrigation systems). This chapter discusses how climate change might impact the reliability of current water management systems on the basis of expert reports prepared at global or EU level, namely reports of the Intergovernmental Panel on Climate Change (IPCC) and guidance documents of the Water Framework Directive Common Implementation Strategy. Examples of international research trends are described to illustrate on-going efforts to improve understanding and modelling of climate changes related to the hydrological cycles at scales that are relevant to decision making (possibly linked to policy).

1 Introduction

According to the Technical Paper VI of the Intergovernmental Panel on Climate Change (IPCC), observational records and climate projections provide abundant evidence that freshwater resources are vulnerable toward climate change, with wide-ranging consequences for human societies and ecosystems in Europe and worldwide. In particular, observed warming over several decades has been linked to changes in the large-scale hydrological cycle (e.g. effects on atmospheric water vapour content, changes of precipitation patterns with consequences on extreme floods and droughts). Higher water temperatures and changes in extremes, including floods and droughts, are projected to affect water quality and exacerbate many forms of water pollution from sediments, nutrients, dissolved organic carbon, pathogens, pesticides and salt, with possible negative impacts on ecosystems, human health, and water system reliability and operating costs. In addition, sea-level rise is projected to extend areas of salinisation of groundwater and estuaries, resulting in a decrease of freshwater availability for humans and ecosystems in coastal areas. Besides this, changes in water quantity and quality due to climate change are expected to affect food availability, stability, access and utilisation, especially in arid and semi-arid areas, as well as the function and operation of water infrastructure (e.g. hydropower, flood defences and irrigation systems).

The consequences of climate change may alter the reliability of current water management systems. While quantitative projections of changes in precipitation, river flows and water levels at the river-basin scale remain uncertain, it is very likely that hydrological characteristics will change in the future. Adaptation options are currently designed to ensure water supply during average and drought conditions, while mitigation measures are also developed to reduce the magnitude of impacts of global warming on water resources, in turn reducing adaptation needs (with, however, possible negative side effects such as, for example, increased water requirements for bio-energy crops, reforestation, etc.). The options to respond to climate change are closely linked to a range of policies covering different sectors, e.g. energy, health, food security, water and nature conservation. This requires that adaptation and mitigation measures are evaluated across multiple water-dependent sectors.

2 Climate Change Impacts on Water

There is far-reaching consensus among scientists that climate change is, at least to a certain extent, caused by human activities. According to the terminology of the EU Water Framework Directive (2000/60/EC) or WFD discussed in section 3, direct climate change impacts on water resources should not be classified as an "anthropogenic pressure" in the narrow sense, since they cannot be mitigated by water managers' action. However, climate change impacts interact with and potentially aggravate other anthropogenic pressures and could therefore be considered as an anthropogenic pressure. For example, changes in precipitation and hotter/drier summer periods alter both the availability of water and the demand for water for uses such as agriculture. Lower water levels as a result of climate change may lead to an increase in the concentration of pollutants (less dilution). In addition, pressures on water from human activities may change as a result of climate change mitigation efforts, e.g. targets for bioenergy production to reduce CO2 emission from burning oil tend to increase pressures on water in several places while, on the other hand, the requirement of cleaner production techniques to reduce CO2 emission might also support the development of more water-protective technologies.

With the change of rainfall patterns, seasonality and spatial distribution, impacts of climate change are reflected in influences on the quantity and quality of water resources and impacts on their uses, e.g. abstraction of both surface and ground waters. Sustainable water resource management is hence closely connected to various drivers, including climate change, land cover and increasing water consumption (see Figure 1).

Long-term threats to groundwater resources could be linked to intense rainfalls, resulting in surface flooding rather than infiltration to groundwater. Water quality will also be affected in that run-off takes nutrients and pesticides from agricultural land and transfer them into rivers and lakes, for instance. Less availability of water resources will mean lower quality in some cases, e.g. droughts can have an impact on the ecology of rivers. Extremes may also have adverse effects on aquatic ecosystems, turning into not only a water shortage...