Women advancing research on hydrological processes: Preface

This Special Issue (SI) of Hydrological Processes features invited contributions led by women scientists at an advanced career stage who have made sustained contributions to the study of hydrological processes, advancing the field. The papers, with contributions from 16 women from 8 countries, reflect a wide diversity of research topics and methods. The contributions were by invitation. Work by these featured colleagues have become benchmarks through which other studies have been measured and implemented, because of their original ideas, concepts and theories from thorough field-based observations and modelling experiments. While this SI can only feature a few contributions, we recognize and want to emphasize that other women have and continue to pro-duce outstanding scientific contributions to the field. We aimed to highlight female role models as lead authors and representing the breadth of the hydrologic sciences research they lead. This SI cele-brates the whole community of women in STEM (science, technology, engineering, mathematics), not just the women scientists presented

While this SI can only feature a few contributions, we recognize and want to emphasize that other women have and continue to produce outstanding scientific contributions to the field. We aimed to highlight female role models as lead authors and representing the breadth of the hydrologic sciences research they lead. This SI celebrates the whole community of women in STEM (science, technology, engineering, mathematics), not just the women scientists presented within this SI. Further working toward that goal, leadership from the journals Hydrological Processes, Water Resources Research, and Earth Surface Processes and Landforms have co-organized an online seminar series on 'Women Advancing River Research', (https://www.cee.psu. edu/events/women-advancing-river-research.aspx). We are convinced that the celebration of women role models and recognizing their contributions will help to reduce barriers and professional challenges, and perhaps inspire others to pursue careers in the hydrologic sciences.
We had initially planned to publish this SI much earlier, but the onset of the global COVID19 pandemic in 2020, which continues to date, caused delays. Several recent publications discuss issues researchers face due to COVID-19 and how the resulting changed circumstances differentially affect individuals based on gender. Early studies of impacts suggest that women's publishing rate has fallen relative to men's amid the pandemic (Frederickson, 2020;Viglione, 2020;Vincent-Lamarre et al., 2020). Several contributors to this SI certainly experienced just that-and had to work even harder to get their papers submitted amidst additional challenges related to family, caregiving, online teaching, and homeschooling, to name a few. Some planned contributions were disrupted entirely. The U.S. National Academies documented how the COVID-19 pandemic disrupted individual schedules and work environments, blurring the lines between personal and professional life; and how it disrupted work in institutional laboratories and facilities, as well as global scientific conferences, in their study of 'Impact of COVID-19 on the Careers of Women in Academic Sciences, Engineering, and Medicine' (NASEM, 2021). In the coming months and years, it will be critical that universities and research institutes account for the gender dynamics of pandemic impacts when considering recruitment, retention, and promotion of hydrologic scientists (Malisch et al., 2020, NASEM, 2021. The obstacles imposed by COVID19 are just the latest example of professional challenges that disproportionately affect women's careers in hydrological science and beyond. The fact that women are underrepresented in STEM is well-documented in many countries. This is exemplified in reports about representation, diversity, and inclusion such as Hill et al., 2010 (Mason et al., 2013); 'Faculty service loads and gender: are women taking care of the academic family?' (Guarino & Borden, 2017); 'Gender differences in recommendation letters for postdoctoral fellowships in geoscience' (Dutt et al., 2016); and 'Journals invite too few women to referee' (Lerback & Hanson, 2017).
While we celebrate the accomplishments of the women included in this SI, we recognize that many voices are missing, and insights undiscovered, from our research community.
The hydrologic processes community is strongest and the science is advanced most quickly when colleagues of all genders work together collectively and collaboratively. We briefly introduce the contributors and their papers below.
The subject matters of the papers address how we can enhance our understanding of hydrological processes, but they are also interdisciplinary and extremely timely with focuses on the dynamics of ecohydrological processes, climate change, and human behaviour:  Her research aims at understanding the spatial and temporal variability of how catchments function hydrologically at different scales; understanding the physical processes that generate stream flow, and the way these processes influence the hydrochemistry and hydroecology of streams. Tetzlaff et al. (2021) present results from an international inter-comparison study using stable isotopes of water in plant stem (xylem) and soils. Their findings suggest that the xylem water of angiosperms was influenced by the isotopic composition of water retained in the soil weeks or months prior to plant sampling, whereas gymnosperms generally did not exhibit such a memory effect. They also discuss several future research challenges which need to be addressed to improve understanding of soil-plantatmosphere interactions.
Dr. Cherie Westbrook is a Professor in the Department of Geography & Planning, and Global Institute for Water Security at the University of Saskatchewan, Canada. She is an expert on the co-evolution of ecological and hydrological processes that explain wetland structure, function and resilience (and especially beaver impacts to wetlands) informing policy and regulatory discussions about their conservation, management and restoration. Westbrook et al. (2020) provide new insights about the opportunities and risks of relying on beaver as a nature-based flood solution. Obviously, beaver dams are unlikely to provide 100% flood protection. However, they can transiently store water even in large rainfall events, and so this naturebased solution should be included in regional water management strategies. Further understanding is needed on how water is stored and transmitted through beaver ponds with variable dam structural integrity.
Dr. Ellen Wohl is a Professor of Geology and University Distinguished Professor Department of Geosciences, Colorado State University, USA. She is an expert in physical-ecological interactions in river ecosystems, implications of physical riverine complexity for organic carbon storage, large wood in river floodplains and the effects of beaver activities on downstream fluxes of material in river corridors. Wohl and Scamardo (2021) showed that the longitudinal distribution of channel-spanning logjam populations is resilient to disturbance, based on investigating the temporal patterns of intrareach and inter-reach logjam distribution densities over a decade that included substantial variations in snowmelt peak flow and a large rainfall flood. Such resilience of the longitudinal distribution of log-jams and associated changes in river corridor form and function suggest that introducing wood or engineered logjams to beads in small to moderate rivers can create persistent benefits in river corridors.

DATA AVAILABILITY STATEMENT
Data sharing is not applicable to this article as no new data were created or analyzed in this study.