The impacts of climate change on the hydrological cycle display many different patterns. The effects on atmospheric water vapour content or on soil moisture, and changes in precipitation are examples. These effects have been linked to the global warming now observed over several decades. More specifically, higher water temperatures and changes in extremes are projected to affect water quality and exacerbate water pollution. This is likely to lead to negative impacts on ecosystems and human health, as well as on 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 people and ecosystems in coastal areas. Besides this, changes in water quantity and quality due to climate change are expected to affect food security, water access and utilisation, especially in arid and semi-arid areas, as well as the operation of water infrastructure - such as hydropower, flood defences, and irrigation systems.
Policy interventions for climate change mitigation and adaptation must be built on solid science. Yet, our understanding of the complex climate system is still inadequate, and our evaluations of the impacts of climate change are correspondingly uncertain. Creating more dependable impact assessments requires effective partnerships among research organisations and, importantly, partnerships between scientific disciplines. One critical partnership is that between climate scientists and hydrologists. Yet, in the past these groups have not worked effectively together. WATCH has changed that.
As one of the key projects funded by the European Union’s Sixth Framework Programme, WATCH has gathered 25 partners from outstanding European organisations dealing with climate change studies and created an integrated project, which is now delivering new findings about climate change impacts on the global hydrological cycle.
The purpose of projects such as WATCH is to underpin evidence-based policy-making. This requires that the scientific results are presented in a straightforward, jargon-free way that can be readily understood by the non-specialist. This "Outreach Report" meets that requirement. The report describes how the project has brought together the hydrological and climate communities to analyse, quantify and predict the components of the current and future global water cycle. It shows how WATCH evaluated the attached uncertainties and clarified the overall vulnerability of global water resources related to the main societal and economic sectors.
Policy-makers and stakeholders will benefit from reading this Outreach Report. I am certain the results from WATCH will be a cornerstone of future action in this field.