This paper presents an analysis of future research and development needs to assess the effectiveness of nature-based solutions for climate adaptation in watersheds at scale using hydrological models. Two main questions are addressed: to what extent are hydrological model approaches able to support decision making on nature-based solutions and adaptation, and how well is this hydrological analysis embedded in the broader planning process? To support the research, case studies in Bhutan, Zimbabwe and the Netherlands are presented. The Climate Risk Informed Decision Analysis approach is used to structure the planning process. All three case studies demonstrate how the hydrological system and full landscape of land and water use in watersheds can be simulated to better understand hydrometeorological hazards under current and future climate. Also, simulations of nature-based solutions are demonstrated, which need creativity and profound expert knowledge. In contrast to the assessment of grey infrastructure, no rules or guidance exists for the hydrological assessment of nature-based solutions. Physically-based models are better able to support the understanding of the functioning of the ecohydrological system and, therefore, the effectiveness of adaptation using nature-based solutions. There are however trade-offs between the computational complexity, the computation time and the multiple scenarios and sensitivity analyses of adaptation options needed for climate stress testing. Often there is a lack of monitoring data for verification of model outcomes. Several recommendations on how to improve modelling in an adaptation process are given. In addition, it is recommended to develop and rectify a set of nature-based solutions performance indicators, rules and algorithms to be adopted in models in order to quantify the effectiveness of these solutions.

The Intergovernmental Panel on Climate Change projects climate change effects based on several scenarios and highlights the potential regional changes of bioclimatic pressures up until 2100. Understanding the effects of climate change on the ecosystems is of utmost importance for nature conservation; biodiversity in riverine and coastal areas is threatened by temperature increase by weather-related events like floods and droughts. This study evaluates the impact of climate change on the performance of a given nature-based solution and nature conservation management plan's success (or failure) to account for climate change. For the purpose of the evaluation, management plans are analysed against the UN Sustainable Development Goals targets.

The case studies analysed include twelve nature-based solution sites in riverine and coastal areas, distributed across Europe, Oceania and North America. Their sustainable development goals performance is analysed quantitatively for the Sustainable Development Goals-Sustainable Index Score, open-source indicator data and qualitatively for the nature conservation management plans. Sustainable development goals consideredinclude the following: clean water andsanitation (6); industry, innovation &infrastructure (9); sustainable cities and communities (11); responsible consumption and production (12); climate action (13); life below water (14); life on land (15). The International Panel on Climate Change projections under the Shared Socio-economic Pathways1-2.6 and Shared Socio-economic Pathways5-8.5 scenarios are used to gain evidence of the role nature-based solutions and nature conservation management plans can play in adaptation trajectories for climate change and biodiversity conservation.

The results highlight that most nature conservation management plans and the nature-based solution they typically rely upon, do not pay sufficient attention to climate change. The evidence suggests that the studied nature-based solution sites are not on track to achieve selected sustainable development goals when climate change impacts under the Shared Socio-economic Pathways1-2.6 and Shared Socioeconomic Pathways5-8.5 scenarios are factored in. Through this evaluation, riverine conservation areas are identified as requiring more rigorous climate adaptation strategies and nature conservation planning to enhance resilience and to have the potential of fulfilling the addressed SDGs.

Since the soil quality Tool for Risk Identification, Assessment and Display (TRIAD) approach introduced the “three lines of evidence” accounting for chemical, toxicological and ecological stressors to explain adverse effects in biota, the assessment of contaminant risks in the environment has significantly evolved. The concept of chemical speciation, related to water characteristics, boosted the understanding of the role of free-ion activities in the overall accumulation of pollutants in biota. New modeling concepts (e.g. biotic ligand models) and measuring techniques were developed. This in turn triggered widespread research addressing the quantitative role of sediment in the overall water quality, focusing on redox interfaces. For contaminant mixtures in river catchments, complex relations between (bio)availability of compounds, including nutrients, help to explain aquatic toxicity. Variation in ecological patterns and processes across environmental or spatiotemporal gradients occur, which may identify ecological factors that influence contaminant fate and effects. Empirical evidence by meta-analysis and theoretical underpinning by modelling showed relationships between population growth rates and carrying capacities, across chemicals and across species. The potentially affected fraction of species may be related to the mean species abundance, an often-used indicator in global change studies. Knowledge gaps remain on how pollutants travel through ecological communities and which species and species-relationships are affected. Outdoor experimental systems that examine the natural environment under controlled conditions may be useful at the higher biological level to investigate the impact of stressors on a variety of species, including mutual interactions.

The health of soil-sediment-water ecosystems is under pressure from economic activities and a changing climate. This decreases health and hampers the service provision capacity of these ecosystems and thus impacts human well-being. Protecting and where feasible restoring of ecosystem health has currently become the key European environmental policy objective and for this it is needed to take an entire system approach and engage stakeholders. ‘Entire’ means that soil, sediment and water are regarded as closely interlinked environmental matrices that need to be managed by taking a ‘river (or mountain) to sea’ perspective, crossing spatial, discipline, political and cultural boundaries. This paper presents a conceptual model to support that purpose. Essentially, the conceptual model presents an approach for ecosystem-based management aimed to achieve healthy ecosystems, i.e. soil-sediment-water ecosystems that have the continued capacity to support ecosystem services to the benefit of their users. The model proposes a cyclic (iterative, learning-by-doing) approach and integrates soil-sediment-water, ecosystems, ecosystem services, users (stakeholders), pressures, information, management strategy and program of measures as building blocks. To successfully apply the model, it is above all needed to take an entrepreneurial approach, i.e. leave comfort zones, take an adventurous road, learn together to manage together, be adaptive and consider other than only command-and-control solutions. Furthermore, authorities should become facilitative leaders to engage users in co-creation of an ecosystem-based management strategy. Real live and place-based experimenting with multiple stakeholders, such as in the Living Labs and Lighthouses that are proposed in the EU soil mission, may provide an ideal instrument for such application, i.e. where the conceptual model can be used and support the achievement of European environmental policy objectives.

Deltas are areas where pressures (e.g. climate change, rapid urbanization, water related shocks and stressors) as well as opportunities (e.g. economic growth, delta-city metabolism, sustainable development) collide to an unprecedented extent. The deltas are considered to become the most vital and critical hotspots in the world for sustainable development. Consequently, immediate acceleration in hands-on knowledge partnerships is required for sustainable low-carbon emission and resilient investments in delta areas. The mission of the Delta Alliance is to improve the resilience of the deltas in the world through knowledge sharing and capacity building. In this paper we elaborate on the various roles that the Delta Alliance has played and how this has been of significance for other developing delta regions in the world. Some of the successes and lessons learned are highlighted, with a particular focus on the African deltas. We argue that increasing investments in knowledge sharing and capacity building among - and with - those working in the deltas for creating equitable and trusted partnerships are a necessary condition for an integrated approach to the challenges in the deltas.

Multilateral Environmental Agreements are important international instruments for achieving sustainable development. Nevertheless, their implementation is often not easy and integration with scientific knowledge during implementation can be troublesome. The 1992 Convention on the Protection and Use of Transboundary Watercourses and International Lakes (Water Convention) has developed a way of implementing its' program of work that can best be described as a Community of Practice that combines scientific developments with practical implications. This approach has attracted much attention from practitioners in the field of water management and has been highly successful in many practical applications of its principles. This paper will describe how the Water Convention operates and will argue why this can be termed a Community of Practice. Different examples will be presented to underscore how the Water Convention through this approach has been able to attain progress towards its goals.

Dams have often been constructed for hydropower, water storage and to support socio-economic development, particularly in areas of water stress. In many places, the water stored in human-made reservoirs is essential to meet the development objectives of water supply, agriculture, industry, energy generation and other sectors. However, in the absence of adequate foresight and planning, many past dams have had considerable negative impacts on ecosystems and the livelihoods of affected communities, resulting in conflicts and health hazards. While enhanced human health and well-being could be considered as the ultimate outcome of development programs, the public health impact of dams remains an issue that is often neglected by policy makers and investors. National policies and international guidelines, such as those of the World Commission on Dams (WCD), have been used to improve planning and impact assessment of dams. Here, we provide an analysis of four large dams, across three continents, and show that they had limited consistency with WCD principles and guidelines. Moreover, health aspects were largely neglected during planning, construction and operation of these dams, but seriously undermine their intended benefits. This perspective paper discusses impacts of dams on energy and food, ecosystem health, inclusion, and ultimately human health and wellbeing. We argue that a One Health perspective, based on these four categories, can support the systematic consideration of environmental, animal, and human health determinants. A dedicated One Health approach to dams and reservoirs remains to be developed but could potentially improve how dams, both existing and future, support more inclusive development.