Climate change is one of the significant threats for the society. Water is the primary medium through which climate change influences the Earth’s ecosystems and therefore people’s livelihoods and well-being. Changes in hydrological cycle due to climate change can lead to diverse impacts and risks (Bates et al. 2008; Jiménez Cisneros et al. 2014). Jiménez Cisneros et al. (2014) synthesized water-related impacts on humans and Earth biomes. Renewable surface water and groundwater resources in most dry subtropical regions are projected to reduce due to climate change. The fraction of global population that will be affected by water scarcity and riverine floods is projected to increase with the level of warming in current century. Agriculture is directly related to water and therefore, food security will be potentially affected by climate change, including food production, transportation, process, access, use and price stability. Climate change and the associated impacts on water are expected to lead to increases in water-related diseases in many regions and especially in the low-income developing countries. In urban areas, climate change is projected to increase risks for people, assets, economies and ecosystems, including risks from heat stress, storms and extreme precipitation, inland and coastal flooding, landslides, air pollution, drought, water scarcity, sea level rise and storm surges. Rural areas are expected to experience major impacts on water availability and supply, food security, infrastructure and agricultural incomes, including shifts in the production areas of food and non-food crops around the world. Beside climatic drivers, other non-climatic drivers such as current demographic trends, economic development and related land-use changes have direct impact on social and ecological systems and their processes. These drivers of change are closely linked to each other and pose complex management problems for land and water resources.

In order to deal with these complex problems, water management issues should generally consider multiple decisional criteria and large numbers of possible alternatives, usually characterized by high uncertainty, complex interactions and conflicting interests of multiple stakeholders, but also of a multiplicity of compartments, such as river, land or coastal ecosystems or different economic sectors. Therefore, the traditional fragmented approach of management has to be replaced by more holistic system view approaches. Integrated water resources management (IWRM) is such an approach that has been widely accepted internationally as the way forward for efficient and equitable management of water and related resources.

Climate change adaptation (CCA) is emerging in the policy agenda of policy-makers worldwide. In the field of water resources, one of the challenges for adaptation is to integrate and mainstream it into the paradigmatic IWRM concept. Integrating and mainstreaming adaptation with IWRM increases additional implementation burden on IWRM. However, this also fosters innovative governance arrangements and practices to build adaptive capacity to climate change impacts. Despite the main focus of IWRM is on current and historic issues compared to the long-term focus of adaptation (Ludwig et al. 2014), they both (IWRM and adaptation) share the same goal of promoting sustainable development and both of them require some identical key elements (e.g. public participation, information sharing and disclosure, and concern for social justice) for their successful implementation (He 2013). According to Jiménez Cisneros et al. (2014), IWRM continues to be a promising instrument for exploring adaptation to climate change. Ongoing attempts at mainstreaming climate change in water management provide a unique opportunity for lessons drawing and knowledge exchange on IWRM and CCA, in particular how they may contribute to, or undermine, each other. Moreover, the recent approval of Agenda 2030 by the United Nations (UN 2015) has provided a new framework in which IWRM and CCA are considered as components of the planetary efforts towards sustainable development and, in particular as elements contributing respectively to sustainable development goal (SDG) 6 (ensure availability and sustainable management of water and sanitation for all) and 13 (take urgent action to combat climate change and its impacts). Within goal 6 of SDGs (Gain et al. 2016), the target (6.5) is focused on the implementation of ‘integrated water resources management [IWRM] at all levels, including through transboundary cooperation as appropriate’, to be achieved by 2030.

The goal of this special issue is to analyse IWRM as a governance approach at regional level in the context of adaptation for social ecological systems to environmental changes. This special issue comprises papers that contribute, through review, theory and practical applications, to analyse IWRM and related integrated management as governance approach for mainstreaming climate change adaptation at different regional contexts.

Rouillard and Spray (2017) examine the links between top-down and bottom-up processes, where governments and communities play crucial roles for water management. They explore how those processes may contribute to working across scales, aligning planning processes, and engaging with stakeholders. Results of a survey of 14 regional experiences with catchment management are presented, reflecting a diversity of scales, histories and governance arrangements, with a focus on the institutional dimension at national and local scale and on the role of intermediaries and engagement processes. The paper presents also in grated details an illustrative example in Scotland, where top-down and bottom-up processes were linked, thanks to successful trusted intermediaries promoting water and land management in the Tweed river basin for over 25 years. The paper concludes by presenting the lessons learned for increasing adaptive capacity to climate change.

Giupponi and Gain (2017) examine several paradigms for sustainable water management—integrated water resources management (IWRM), adaptive management (AM) and water-energy-food (WEF) nexus—and focus on the last, which narrows down the consideration of intersectoral linkages to three dimensions that are of prominent interest, in particular in developing countries. They propose a comprehensive indicator-based approach for the assessment of water, energy and food securities, with reference to the sustainable development goals of the United Nations, and they demonstrate its implementation in the Ganges-Brahmaputra-Meghna (GBM) River Basin in Asia and to the Po River Basin in Europe. The indicator-based approach provide a tool to monitor progresses, compare different geographical areas, highlight synergies and conflicts amongst and within the three dimensions of the WEF Nexus, thus supporting improved management strategies to meet the SDGs.

Roy et al. (2017) investigate the south-west coastal region of Bangladesh through the lens of human-delta co-evolutionary system. Historical time series and the literature are reviewed explore the interconnectivity of social and ecological systems, and identifying the most relevant territorial trends, deriving from the combination of the physical characteristic and the human activities of the delta, for example increased water and soil salinity. A common feature of the observed trends is their accelerated in recent times, which may induce dramatic environmental and social crises in the future. Results point out the need for implementing a combination of IWRM and ICZM (integrated coastal zone management (ICZM) approaches, to preserve the integrity of the coastal ecosystem and guarantee multiple used of resources of adequate quality and quantity.

Sebesvari et al. (2017) present the case of the Mekong River Basin (MRB), where ongoing increasing alteration of the river hydrology, land use and water quality challenge efficient, equitable and transboundary management of the water resources, also in consideration of the uncertainties associated with climate change and its future impacts. IWRM institutions and mechanisms offer a good entry point for the uptake and implementation of climate change adaptation measures. The authors provide an historical review of IWRM approaches in the MRB and ongoing processes as well as of opportunities to mainstream climate change adaptation into existing basin strategies and water management instruments. Results show that the approaches adopted by regional institutions for transboundary water resources management are largely complementary and synergies could be increased to incorporate climate change adaptation into existing schemes. The potential of ecosystem-based adaptation (EbA) is pointed out for a region where the economy is still largely based on the use of natural resources, even if mainstreaming EbA measures in climate change adaptation strategies is still relatively new in the MRB context. EbA measures offers no-regret and flexible solutions for IWRM planning, despite considerable uncertainties associated to CCA decision making.

Benson and Lorenzoni (2017) explore the policy coherence of climate change adaptation and flood risks management in IWRM in the UK, focusing in particular on concerns over intersectoral policy coherence between implementing institutions in the context of CCA and threats from coastal inundation and surface water flooding. The authors investigate the multilevel institutional frameworks, examine their interactions and coordination and assess the degree of coherence. Overall, the analysis of complex governance arrangements show good coherence between some of the cognate policies examined, but also increasing decoherence over time due to ongoing institutional fragmentation, thus requiring a shift towards greater spatial planning and greater coordination of water and land use objectives.

Also the paper by Fritsch (2017) deals with the UK, where water resources management is analysed with focus on public participation, in an attempt to explore empirically the parallel implementation and co-existence of integrated and adaptive approaches, with the ambition to review and complement current frameworks conceptualising the impact of integrated water resources management on adaptive capacity. In particular, the article analyses, the involvement of non-state actors in water and flood risk management, after 15 years of major efforts to enhance collaboration and stakeholder participation, under the effects of two European Union directives: the water framework directive and the floods directive. Given the empirical evidence of spurious links between the two, the author proposes three theory-informed arguments—relating to conceptual diversity, path dependency, and the nature of the dependent variable—to contribute to theory building and overcome current limitations.