• Energy Research

Assessments of climate change impacts on freshwater ecosystems are generally based on global climate models (GCMs) and ecologically relevant “time-averaged” hydrological indicators derived from long-term records. Although uncertainties from GCMs have been recognized, the influence of downscaling methods remains unclear. This paper evaluates the influence of applying different downscaling methods of increasing complexity (annual scaling, monthly scaling, quantile scaling, and weather generator method) on the assessment of ecological outcomes. In addition to time-averaged indicators, “sequence-dependent” metrics which involve ecological dynamics by considering the impacts of flow sequencing are also adopted. In a case study in Australia, the condition of river red gum forest was assessed. Results show that the choice of downscaling methods can be of similar importance as that of GCMs in ecological impact studies. Where sequence-dependent metrics are adopted, more sophisticated downscaling techniques should be used to better represent changes in the frequency and sequence of flow events.

A decade ago, scientists and practitioners working in environmental water management crystallized the progress and direction of environmental flows science, practice, and policy in The Brisbane Declaration and Global Action Agenda (2007), during the 10th International Riversymposium and International Environmental Flows Conference held in Brisbane, Australia. The 2007 Declaration highlights the significance of environmental water allocations for humans and freshwater-dependent ecosystems, and sets out a nine-point global action agenda. This was the first consensus document that bought together the diverse experiences across regions and disciplines, and was significant in setting a common vision and direction for environmental flows internationally. After a decade of uptake and innovation in environmental flows, the 2007 declaration and action agenda was revisited at the 20th International Riversymposium and Environmental Flows Conference, held in Brisbane, Australia, in 2017. The objective was to publicize achievements since 2007 and update the declaration and action agenda to reflect collective progress, innovation, and emerging challenges for environmental flows policy, practice and science worldwide. This paper on The Brisbane Declaration and Global Action Agenda on Environmental Flows (2018) describes the inclusive consultation processes that guided the review of the 2007 document. The 2018 Declaration presents an urgent call for action to protect and restore environmental flows and aquatic ecosystems for their biodiversity, intrinsic values, and ecosystem services, as a central element of integrated water resources management, and as a foundation for achievement of water-related Sustainable Development Goals (SDGs). The Global Action Agenda (2018) makes 35 actionable recommendations to guide and support implementation of environmental flows through legislation and regulation, water management programs, and research, linked by partnership arrangements involving diverse stakeholders. An important new element of the Declaration and Action Agenda is the emphasis given to full and equal participation for people of all cultures, and respect for their rights, responsibilities and systems of governance in environmental water decisions. These social and cultural dimensions of e-flow management warrant far more attention. Actionable recommendations present a pathway forward for a new era of scientific research and innovation, shared visions, collaborative implementation programs, and adaptive governance of environmental flows, suited to new social, and environmental contexts driven by planetary pressures, such as human population growth and climate change.

Wetlands are biodiversity hotspots, providing refuge to threatened species globally, and diverse ecosystem services for humans. Wetland values are threatened by changes to hydrological regimes caused by anthropogenic degradation and climate change. Utilizing improved, large-scale datasets to characterize regional trends in wetland stress allows us to identify regions of concern and prioritise conservation and adaptation responses. We developed a novel approach to characterizing wetland hydrologic stress that accounts for natural variability in wetland water regimes. Our approach integrated remotely sensed inundation observations over the period 1988 to 2018 to enable a large-scale assessment of ∼ 37,000 wetlands in south-east Australia. We assessed stress in six hydrologic inundation regime metrics: mean magnitude, maximum magnitude, duration, timing, frequency, and rate of change. In wetlands across the region, we observed a general decreasing trend over the historical period 1988 to 2018 in four of six stress indices: magnitude (mean), magnitude (max), duration, and frequency. More than 20 % of wetlands had a stress index of ± 1 for magnitude (mean) and duration, indicating significant departure from the existing hydrologic regime. These results are consistent with the impacts of observed reductions in cool season rainfall, which supports evidence that climate change has already impacted this region. The findings reinforce the importance of wetland management under a future changing climate. Our approach can be used to characterize trends in wetland hydrologic stress globally, given the compatibility with remotely sensed data. Management agencies will benefit from using these approaches to better understand how wetland hydrology is shifting across regional scales, and where to prioritise their resources to persist, adapt or transform wetlands under continued future change.

Environmental flows (e-flows) aim to mitigate the threat of altered hydrological regimes in river systems and connected waterbodies and are an important component of integrated strategies to address multiple threats to freshwater biodiversity. Expanding and accelerating implementation of e-flows can support river conservation and help to restore the biodiversity and resilience of hydrologically altered and water-stressed rivers and connected freshwater ecosystems. While there have been significant developments in e-flow science, assessment, and societal acceptance, implementation of e-flows within water resource management has been slower than required and geographically uneven. This review explores critical factors that enable successful e-flow implementation and biodiversity outcomes in particular, drawing on 13 case studies and the literature. It presents e-flow implementation as an adaptive management cycle enabled by 10 factors: legislation and governance, financial and human resourcing, stakeholder engagement and co-production of knowledge, collaborative monitoring of ecological and social-economic outcomes, capacity training and research, exploration of trade-offs among water users, removing or retrofitting water infrastructure to facilitate e-flows and connectivity, and adaptation to climate change. Recognising that there may be barriers and limitations to the full and effective enablement of each factor, the authors have identified corresponding options and generalizable recommendations for actions to overcome prominent constraints, drawing on the case studies and wider literature. The urgency of addressing flow-related freshwater biodiversity loss demands collaborative networks to train and empower a new generation of e-flow practitioners equipped with the latest tools and insights to lead adaptive environmental water management globally. Mainstreaming e-flows within conservation planning, integrated water resource management, river restoration strategies, and adaptations to climate change is imperative. The policy drivers and associated funding commitments of the Kunming–Montreal Global Biodiversity Framework offer crucial opportunities to achieve the human benefits contributed by e-flows as nature-based solutions, such as flood risk management, floodplain fisheries restoration, and increased river resilience to climate change.