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Sports journalist and ultra-athlete Vassos Alexander takes the plunge and explores the delights and rewards of wild and open water swimming.

The monitoring of wetland extent is a global imperative, considering loss of ecosystem services and conservation value. To date, the understanding of the variation in the extent of lacustrine (inundated) wetlands has been limited, based on intermittently available, coarse-scale imagery. The aim of this study was to assess the capabilities of the freely available Sentinel-2 sensor in monitoring inundated wetlands. In particular, to demonstrate the ability to determine the maximum extent of inundation for reporting on the Sustainable Development Goal (SDG) 6.6 (Clean Water and Sanitation) and SDG 15.1 (i.e., halting biodiversity loss), the functional diversity and the hydrological regime of depressions were explored in the Mpumalanga Lake District (MLD) of South Africa. Using the monthly inundation data derived from Sentinel-2 images between January 2016 and May 2018, the results showed that the maximum extent of open water can be successfully reported for SDG 6.6. Lacustrine wetlands constituted about 47 of the 416 (but 66% of the total areal extent of) depressions in the MLD, while others were predominantly palustrine (vegetated). The functional diversity varied from predominantly (61% of the extent of) inundated depressions to seasonally (3%) inundated depressions. The Sentinel-2 sensor was able to detect intra- and inter-annual variation of the extent of inundation, making it suitable to monitor these wetlands for global and climate change impacts.

There is growing interest in blue space as a natural environment that may foster well‐being. Blue space encourages mindful, immersive, and connected ways of being in and interacting with place. A popular blue space activity that may promote well‐being is wild swimming (WS). Existing research suggests that swimmers find WS meaningful because it supports well‐being. However, the meanings attributed to WS by wild swimmers likely depend on the characteristics of place, such as water conditions and temperature, which may have a unique influence. The present study aimed to explore the meanings ascribed to WS by a Victorian cohort of wild swimmers. Participants comprised 47 wild swimmers (31 women, 15 men, 1 non‐binary person, mean age = 55.5 (11.7)). Participants answered demographic items and five open‐ended, qualitative questions about WS. Data were analysed using template thematic analysis. Five key themes were identified: ‘Always a swimmer’: Starting wild swimming; ‘You feel euphoric’: Psychological well‐being; ‘Still going strong’: Physical well‐being; ‘Chatting at the buoys’: Social connectedness; and ‘The sea is my home’: Connectedness to nature. Swimmers found WS meaningful because it promoted well‐being by (I) allowing continuity of a ‘swimmer’ identity; (II) promoting positive mood states and possibly facilitating swimmers to feel energised, calm, meditative, focused, authentic and masterful; (III) aiding physical fitness, healthy ageing and physical pleasure; (IV) enhancing social connectedness as swimmers formed friendships and communities; and (V) fostering nature connectedness as swimmers communed with and observed their sea surrounds. The findings indicate that Victorian wild swimmers, like their counterparts elsewhere, value WS because of the enriching ways in which it fosters well‐being. Among the first studies to explore WS in Victoria, Australia, this study contributes to a growing body of research which suggests that engaging in blue space promotes wellbeing. Policy implications. WS may have potential as a strategy for improving well‐being in the wider population. As an activity that cultivates social connectedness, it could form part of a social prescription for those identified as being at risk of loneliness. Additionally, WS may have potential as a complementary, nature‐based therapeutic intervention. Read the free Plain Language Summary for this article on the Journal blog. Read the free Plain Language Summary for this article on the Journal blog.

The sea ice conditions in the Kara Sea have important impacts on Arctic shipping, oil and gas production, and marine environmental changes. In this study, sea ice coverage ( C R ) less than 30% is considered as open water, its onset and end dates are defined as T open and T close , respectively. The sea ice melt onset ( T melt ) is defined as the date when ice-sea freshwater flux initially changes from ice into the ocean. Satellite-based sea ice concentration (SIC) from 1989 to 2019 shows a negative correlation between T open and T close ( r = −0.77, p < 0.01) in the Kara Sea. This phenomenon is also obtained through analyzing the hindcast simulation from 1994 to 2015 by a coupled ocean and sea-ice model (NAPA1/4). The model results reveal that thermodynamics dominate the sea ice variations, and ice basal melt is greater than the ice surface melt. Heat budget estimation suggests that the heat flux is significant correlated with T open ( r = −0.95, p < 0.01) during the melt period (the duration of multi-year averaged T melt to T open ) influenced by the sea ice conditions. Additionally, this heat flux is also suggested to dominate the interannual variation of the heat input during the whole heat absorption process ( r = 0.81, p < 0.01). The more heat input during this process leads to later T close ( r = 0.77, p < 0.01). This is the physical basis of the negative correlation between T open and T close . Therefore, the duration of open water can be predicted by T open and thence support earlier planning of marine activities.

Swimming-induced pulmonary oedema (SIPE) is a potentially fatal condition associated with open-water swims. We sought to quantify the contribution of cardiac dysfunction to SIPE. We aimed to assess the incidence of SIPE during an endurance cold water swim. We determined associations between SIPE and changes in cardiac function through a SIPE questionnaire, lung ultrasound (LUS), cardiac biomarkers (N-Terminal pro-B-type natriuretic peptide (NT proBNP) and cardiac troponin I (cTnI)) and transthoracic echocardiograms (TTE). Twenty open-water swimmers (10 males) underwent a TTE, LUS for pulmonary oedema and cardiac biomarkers before, 2-hours and 24-hours after an 8-hour swim. Swimmers had an additional LUS and rated their breathlessness upon leaving the water. Participants with breathlessness and 3 or more B-lines present in two or more LUS views were considered SIPE positive. Five swimmers (25 % of cohort) presenting with post-event breathlessness and evidence of lung water were considered SIPE positive. SIPE had no demonstrable effect on left systolic function (LV ejection fraction, global longitudinal strain [GLS]), diastolic function (left atrial volume, E/e’) and right ventricular (RV) function (RV fractional area change and RV free wall GLS). SIPE was associated with a small increase in troponin post-swim (at 2 hours SIPE+ 32.1 ng/L, SIPE− 12.6 ng/L, p = 0.004: at 24 hours SIPE+ 12.6 ng/L, SIPE− 4.8 ng/L, p = 0.04) but had no impact on NT proBNP. SIPE is common in open-water swimmers following an endurance swim and is identified using LUS. Whilst SIPE was associated with a small increase in post-swim troponin levels, no further evidence of cardiac dysfunction was identified at two hours after the swim to explain the pulmonary oedema.

【Objective】There has been a growing demand in modern irrigation systems for devices that integrate precise flow measurement with effective water control. Traditional sluice gates lack multifunctionality and adaptability to smart irrigation needs. This paper addresses this by designing a new sluice gate - water separation rotary gate, based on the hydraulic design principle of turbine volute.【Method】A detailed structural design and flow measurement principle of the rotary gate are presented. Numerical simulations were conducted to evaluate the hydraulic performance of the gate under ten rotational speed scenarios, with the flow rate ranging from 3.00 to 10.08 L/s. The accuracy of the model was validated through physical experiments, in which the flow field characteristics, including water depth, velocity distribution and head loss, were analyzed.【Result】The average relative error of the flow measurement formula derived from the physical model was 3.35% and the minimum error was 0.28%. Local head loss accounted for an average of 46.03% of the total upstream stable head, with a minimum value of 16.48%. Rotation of the gate significantly improved water aeration, with the maximum dissolved oxygen increasing by 108.30% and the average increasing by 100.54%. The simulation results agreed well with experimental data. The average error in water depth was 0.77% and the minimum was 0.07%. The average error in simulated flow rate was 4.39% and the minimum error was 0.09%.【Conclusion】The designed water-diverting rotary gate shows accurate flow measurement, effective water control, and enhanced oxygenation capacity. Its simple structure and multifunctionality make it a promising technology for improving irrigation water use efficiency and water quality in irrigation systems.

Marathon open‐water swimming presents extreme thermophysiological challenges, particularly in cold environments. This case report describes continuous core temperature data from a solo crossing of New Zealand's Foveaux Strait, an infamously cold (13°C –14°C), turbulent open‐water swim. A 52‐year‐old male swimmer (body mass index, 27.9 kg m −2 ; body fat, 18%) completed the 37 km swim in 9 h 52 min under standard marathon swimming rules (no wetsuit). Core temperature (measured via an ingestible thermometer pill) decreased rapidly after immersion, falling from 37.9°C to <35.0°C within 50 min. The swimmer reached a nadir of 33.88°C at 2 h 42 min and remained hypothermic for more than half of the swim (total, 369 min). Despite this, he displayed no overt cognitive or motor impairment, completed the swim unaided and did not experience an after‐drop post‐immersion. This case highlights the remarkable thermoregulatory tolerance of a cold‐adapted endurance swimmer. What is the main observation in this case? A cold‐adapted marathon swimmer tolerated prolonged moderate hypothermia (core temperature <35°C for >6 h; nadir 33.88°C) during an open‐water swim in 13–14°C water. What insights does it reveal? This case demonstrates that in a trained and cold‐adapted marathon swimmer, prolonged immersion in cold water can be tolerated at core temperatures traditionally classified as clinically hypothermic, without functional compromise or adverse outcomes.

Frozen rivers serve as important transportation corridors for Alaskans during winter. Open water zones (OWZs, i.e., open leads) in otherwise ice‐covered rivers present a hazard because their location and causes are poorly understood. We studied one persistent OWZ on the Tanana River near Fairbanks using field studies, remote sensing, and hydraulic modeling. Interannual occurrence and duration of the OWZ was identified from 2014 to 2023 using optical satellite images and synthetic aperture radar. In eight out of 10 years, an OWZ occurred when an ice jam occurred at an upstream channel constriction during freeze‐up. In the other 2 years, a partial ice cover developed downstream of the reach and no OWZ occurred. We suspected this initial freeze‐up ice jam where the channel narrowed played an important role in OWZ occurrence. To test this, we performed simulations of various ice covers and discharges in HEC‐RAS to evaluate flow hydraulics restrictive or conducive to ice cover formation. Model results demonstrated that initial ice jam locations influence a range of potential velocities that may prevent ice formation. Long‐term records showing increasing discharge on the Tanana during freeze‐up may impact the occurrence of persistent OWZs and future river ice regimes. Our findings indicate that channel form, discharge, and ice jams may explain the occurrence of many OWZs in otherwise ice‐covered rivers. Thus, considering channel form, hydrology, and ice‐affected flow hydraulics will allow for better prediction of current and future river ice conditions, leading to improved winter travel safety across Alaska.

In 2023, an intense drought impacted the Amazon basin triggered by climate change and a strong El Niño event, with the Negro River reaching its lowest water level in 120 years. However, the spatiotemporal open water extent (OWE) during this drought remains unclear. This study comprehensively evaluates OWE variability in the central Amazon using Sentinel-1 synthetic aperture radar (SAR) data since 2017. Monthly OWE masks were generated through an empirical threshold classification with accuracy >95%. Overall, the central Amazon experienced a reduction of ∼8% in OWE in the 2023 dry season months (November and December) when compared to monthly-average. However, reductions of up to 80% in OWE were observed in several specific lakes. Our analysis underscores the unprecedented severity of the 2023/2024 drought on rivers and floodplains. Utilizing SAR remote sensing technologies, this study emphasizes the urgent need for proactive conservation measures to safeguard the Amazon’s ecological integrity amid escalating environmental challenges. Monthly water masks from January/2017 to September/2024 are available here: https://doi.org/10.5281/zenodo.12751783.