This state-of-the-art report encapsulates the main impacts of climate change on the water cycle and highly water-dependent sectors. Its authors explore relevant models, projections and uncertainties and discuss global trends while evaluating several regional case studies. On this basis, the study develops recommendations for future action and enables a better understanding of how the water sector and water-related activities can contribute towards the policy goals of climate mitigation and adaptation.
Water and climate change are inextricably linked. As rising temperatures modify the hydrological cycle, climate change will affect water availability and quality, as well as hydrological variability and extremes, such as floods and droughts. Actions in the water sector, such as how sustainably water resources are managed, as well as the quality of water supply and sanitation services, will substantially shape the resilience of humans and ecosystems. At the same time, sustainable water management and energy-efficient wastewater treatment play an important role in lowering greenhouse gas emissions.
Even small changes in climate can have significant impacts on water availability and extreme events, such as droughts and floods.
What are the key messages springing from the study?
The report primarily targets water practitioners, and decision-makers in the water sector, and the water expert community, aiming to help them better understand how the water sector and water-related activities can contribute to climate mitigation and adaptation goals, with the following messages being central outcomes of its analysis:
Climate change mainly manifests in the water cycle. Its impacts, that will gradually intensify over time, vary from one region to another, but we often do not know exactly how.
The water sector and other water-intensive industries have long-standing experience with and can provide solutions for dealing with climate uncertainties, e.g. through resilient water infrastructure and robust and flexible storage solutions.
Sustainable water management holds a tremendous potential for mitigating global warming, which however remains undervalued and largely untapped
Water management in different sectors is well-positioned to bridge development and climate agendas by harnessing mutual benefits.
Regional impacts of climate change on water resources in six river basins
Representing different continents and climate zones, most of them located in the Global South, with a specific focus on Africa, the study analysed six river basins (see below), showing that climate changes impacts vary in type and magnitude while interacting with human interventions.
The Gesellschaft für Internationale Zusammenarbeit (GIZ), adelphi and Potsdam Institute for Climate Impact Research (PIK) jointly carried out the research to develop the study, drawing on a literature review as well as on a workshop and interviews with selected experts.
The degradation and destruction of peatlands alone might be responsible for 5 percent of global anthropogenic CO2 emissions. Nature-based solutions, such as ecosystem-based mitigation approaches, can significantly contribute to global GHG mitigation efforts through water.
Water management – the potential for climate change mitigation
The water sector, as well as water-related activities in other sectors, contribute to climate change by emitting different GHG – in parts highly potential ones. Collectively, GHG emissions from the six categories shown in the figure below might cause more than 10% of global anthropogenic GHG emissions. It renders water a vital element of global climate mitigation activities and strategies, however, one that is yet widely overlooked.
Structure and approach of the study
The structure of the study is as follows:
Climate change impacts throughout the water cycle
Critical review of climate impact modelling on water resources
Climate change impacts on hydrology and water resources: global trends
Climate change impacts on hydrology and water resources: regional case studies
Climate resilience through water – coping with uncertainties
Mitigation of greenhouse gases through water
Achieving international climate and development goals through water