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Abstract: While the number of environmental flows and water science programmes continues to grow across the globe, there remains a critical need to better balance water availability in support of human and ecological needs and to recognise the environment as a legitimate user of water. In water‐stressed areas, this recognition has resulted in friction between water users in the public and private sectors. An opportunity exists for practitioners to be on the forefront of the science determining best practices for supporting environmental water regimes. This Special Issue brings together a collection of environmental flows science and water management papers organised around three major themes: (1) method development and testing; (2) application case studies; and (3) efficacy evaluation. Contents of this Special Issue are intended to foster collaboration and broaden transferability of the information, technical tools, models and methods needed to support environmental water management programmes. The technical sophistication of methods and modelling tools, while important to the advancement of environmental water science, may come at the expense of easily interpretable outcomes that positively influence management decisions. Researchers need to be more proactive in translating the results of advanced modelling methodologies into user‐friendly tools and methods. This will allow stakeholders and water managers to proactively test alternative water allocation scenarios to help address growing human water demands in the face of droughts and changes in climatic patterns. The application of environmental flows science and water management strategies cannot be done in isolation. Implementation involves a complex decision‐making process that integrates ecological, hydrologic and social science across diverse multifaceted governance systems and requires active stakeholder involvement. Scientists and managers must strengthen partnerships at multiple scales to develop sensible science investment strategies so that collective knowledge can be translated into wise environmental water management decisions. [ABSTRACT FROM AUTHOR]

Abstract: Streamflow is essential for maintaining healthy aquatic ecosystems and for supporting human water supply needs. Changes in climate, land use and water use practices may alter water availability. Understanding the potential effect of these changes on aquatic ecosystems is critical for long‐term water management to maintain a balance between water for human consumption and ecosystem needs. Fish species data and streamflow estimates from a rainfall‐runoff and flow routing model were used to develop boosted regression tree models to predict the relationship between streamflow and fish species richness (FSR) under plausible scenarios of (1) water withdrawal, (2) climate change and (3) increases in impervious surfaces in the Piedmont ecoregion of North Carolina, U.S.A. Maximum monthly flow, the fraction of total flow originating from impervious surface runoff, coefficient of monthly streamflow variability, and the specific river basin accounted for 50% of the variability in FSR. This model was used to predict FSR values for all twelve‐digit Hydrological Unit Code catchments (HUC‐12s) in the North Carolina Piedmont under current flow conditions and under water withdrawal, climate change and impervious surface scenarios. Flow–ecology modeling results indicate that predicted FSR declined significantly with increased water withdrawals. However, the magnitude of decline varied geographically. A “hot‐spot” analysis was conducted based on predicted changes in FSR under each scenario to understand which HUC‐12s were most likely to be affected by changes in water withdrawals, climate and impervious surfaces. Under the 20% withdrawal increase scenario, 413 of 886 (47%) HUC‐12s in the study area were predicted to lose one or more species. HUC‐12s in the Broad, Catawba, Yadkin and Cape Fear river basins were most susceptible to species loss. These findings may help decision making efforts by identifying catchments most vulnerable to changing water availability. Additionally, FSR‐discharge modeling results can assist resource agencies, water managers and stakeholders in assessing the effect of water withdrawals in catchments to better support the protection and long‐term conservation of species. [ABSTRACT FROM AUTHOR]

Abstract: Environmental flow assessments are becoming increasingly central to ecologically‐sustainable river management. Rigorous evaluations of flow–ecology relationships serve a vital role in guiding these assessments to meet targeted ecosystem objectives. However, limited resources and widespread environmental change are outpacing the ability to gain knowledge of species’ flow responses and assess environmental needs for rivers individually. Successfully transferring flow–ecology relationships across space and time would facilitate regional‐scale environmental flow assessments, yet the necessary contexts for such success remains a knowledge gap. Here, we leverage long‐term, multi‐species datasets across multiple river basins in southwestern United States as a case study to explore whether relationships between species abundances and hydrological conditions are transferable across space and time. Additionally, we evaluate the potential for ecological guilds based on fluvial dependence and life‐history strategies to facilitate the transfer of flow–ecology knowledge across taxonomic boundaries. Species varied in the spatial transferability of their flow–ecology relationships. Spatial transferability was similar when comparing a species’ flow–ecology relationships within a river basin versus across different river basins, although transferability was considerably greater across free‐flowing rivers compared to regulated rivers. Species’ flow–ecology relationships transferred through time just as well as across space. Ecological guilds defined according to fluvial dependence and life‐history strategies offered just as much potential for transferring flow–ecology knowledge among species as transferring within species across space or time. Our study provides insights into transferring flow–ecology knowledge to support effective, regional‐scale environmental flows. Further research into developing transferable flow–ecology relationships for a wide range of environmental predictors and biological responses across different spatial scales and flow regimes will enable us to keep pace with the increasing demand for science to inform sustainable river management. [ABSTRACT FROM AUTHOR]