| 1. |
- Tabiri, S, et al.
(author)
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- 2021
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swepub:Mat__t
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| 2. |
- Bravo, L, et al.
(author)
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- 2021
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swepub:Mat__t
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| 3. |
- Khatri, C, et al.
(author)
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Outcomes after perioperative SARS-CoV-2 infection in patients with proximal femoral fractures: an international cohort study
- 2021
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In: BMJ open. - : BMJ. - 2044-6055. ; 11:11, s. e050830-
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Journal article (peer-reviewed)abstract
- Studies have demonstrated high rates of mortality in people with proximal femoral fracture and SARS-CoV-2, but there is limited published data on the factors that influence mortality for clinicians to make informed treatment decisions. This study aims to report the 30-day mortality associated with perioperative infection of patients undergoing surgery for proximal femoral fractures and to examine the factors that influence mortality in a multivariate analysis.SettingProspective, international, multicentre, observational cohort study.ParticipantsPatients undergoing any operation for a proximal femoral fracture from 1 February to 30 April 2020 and with perioperative SARS-CoV-2 infection (either 7 days prior or 30-day postoperative).Primary outcome30-day mortality. Multivariate modelling was performed to identify factors associated with 30-day mortality.ResultsThis study reports included 1063 patients from 174 hospitals in 19 countries. Overall 30-day mortality was 29.4% (313/1063). In an adjusted model, 30-day mortality was associated with male gender (OR 2.29, 95% CI 1.68 to 3.13, p<0.001), age >80 years (OR 1.60, 95% CI 1.1 to 2.31, p=0.013), preoperative diagnosis of dementia (OR 1.57, 95% CI 1.15 to 2.16, p=0.005), kidney disease (OR 1.73, 95% CI 1.18 to 2.55, p=0.005) and congestive heart failure (OR 1.62, 95% CI 1.06 to 2.48, p=0.025). Mortality at 30 days was lower in patients with a preoperative diagnosis of SARS-CoV-2 (OR 0.6, 95% CI 0.6 (0.42 to 0.85), p=0.004). There was no difference in mortality in patients with an increase to delay in surgery (p=0.220) or type of anaesthetic given (p=0.787).ConclusionsPatients undergoing surgery for a proximal femoral fracture with a perioperative infection of SARS-CoV-2 have a high rate of mortality. This study would support the need for providing these patients with individualised medical and anaesthetic care, including medical optimisation before theatre. Careful preoperative counselling is needed for those with a proximal femoral fracture and SARS-CoV-2, especially those in the highest risk groups.Trial registration numberNCT04323644
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| 4. |
- McDonnell, J.J., et al.
(author)
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How old is streamwater? : Open questions in catchment transit time conceptualization, modelling and analysis
- 2010
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In: Hydrological Processes. - : John Wiley & Sons. - 0885-6087 .- 1099-1085. ; 24:12, s. 1745-1754
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Journal article (peer-reviewed)abstract
- The time water spends travelling subsurface through a catchment to the stream network (i.e. the catchment water transit time) fundamentally describes the storage, flow pathway heterogeneity and sources of water in a catchment. The distribution of transit times reflects how catchments retain and release water and solutes that in turn set biogeochemical conditions and affect contamination release or persistence. Thus, quan- tifying the transit time distribution provides an important constraint on biogeochemical processes and catchment sensitivity to anthropogenic inputs, contamination and land-use change. Although the assumptions and limitations of past and present transit time modelling approaches have been recently reviewed (McGuire and McDonnell, 2006), there remain many fundamental research challenges for understanding how transit time can be used to quantify catchment flow processes and aid in the development and testing of rainfall–runoff models. In this Commen- tary study, we summarize what we think are the open research questions in transit time research. These thoughts come from a 3-day workshop in January 2009 at the International Atomic Energy Agency in Vienna. We attempt to lay out a roadmap for this work for the hydrological commu- nity over the next 10 years. We do this by first defining what we mean (qualitatively and quantitatively) by transit time and then organize our vision around needs in transit time theory, needs in field studies of tran- sit time and needs in rainfall – runoff modelling. Our goal in presenting this material is to encourage widespread use of transit time information in process studies to provide new insights to catchment function and to inform the structural development and testing of hydrologic models.
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| 5. |
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| 6. |
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| 7. |
- Ala-aho, P., et al.
(author)
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Permafrost and lakes control river isotope composition across a boreal Arctic transect in the Western Siberian lowlands
- 2018
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In: Environmental Research Letters. - : IOP Publishing. - 1748-9326. ; 13:3, s. =20-=20
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Journal article (peer-reviewed)abstract
- The Western Siberian Lowlands (WSL) store large quantities of organic carbon that will be exposed and mobilized by the thawing of permafrost. The fate of mobilized carbon, however, is not well understood, partly because of inadequate knowledge of hydrological controls in the region which has a vast low-relief surface area, extensive lake and wetland coverage and gradually increasing permafrost influence. We used stable water isotopes to improve our understanding of dominant landscape controls on the hydrology of the WSL. We sampled rivers along a 1700 km South-North transect from permafrost-free to continuous permafrost repeatedly over three years, and derived isotope proxies for catchment hydrological responsiveness and connectivity. We found correlations between the isotope proxies and catchment characteristics, suggesting that lakes and wetlands are intimately connected to rivers, and that permafrost increases the responsiveness of the catchment to rainfall and snowmelt events, reducing catchment mean transit times. Our work provides rare isotope-based field evidence that permafrost and lakes/wetlands influence hydrological pathways across a wide range of spatial scales (10-105 km2) and permafrost coverage (0%-70%). This has important implications, because both permafrost extent and lake/wetland coverage are affected by permafrost thaw in the changing climate. Changes in these hydrological landscape controls are likely to alter carbon export and emission via inland waters, which may be of global significance.
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| 8. |
- Ala-aho, P., et al.
(author)
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Using stable isotopes to assess surface water source dynamics and hydrological connectivity in a high-latitude wetland and permafrost influenced landscape
- 2018
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In: Journal of Hydrology. - : Elsevier. - 0022-1694 .- 1879-2707. ; 556, s. 279-293
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Journal article (peer-reviewed)abstract
- Climate change is expected to alter hydrological and biogeochemical processes in high-latitude inland waters. A critical question for understanding contemporary and future responses to environmental change is how the spatio-temporal dynamics of runoff generation processes will be affected. We sampled stable water isotopes in soils, lakes and rivers on an unprecedented spatio-temporal scale along a 1700 km transect over three years in the Western Siberia Lowlands. Our findings suggest that snowmelt mixes with, and displaces, large volumes of water stored in the organic soils and lakes to generate runoff during the thaw season. Furthermore, we saw a persistent hydrological connection between water bodies and the landscape across permafrost regions. Our findings help to bridge the understanding between small and large scale hydrological studies in high-latitude systems. These isotope data provide a means to conceptualise hydrological connectivity in permafrost and wetland influenced regions, which is needed for an improved understanding of future biogeochemical changes.
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| 9. |
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| 10. |
- Geris, J., et al.
(author)
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Conceptual modelling to assess hydrological impacts and evaluate environmental flow scenarios in montane river systems regulated for hydropower
- 2014
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In: Rivers Research and Applications. - : Wiley. - 1535-1459 .- 1535-1467.
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Journal article (peer-reviewed)abstract
- To improve understanding of natural and managed flow regimes in data-sparse regulated river systems in montane areas, the commonly used Hydrologiska Byråns Vattenbalansavdelning (HBV) conceptual run-off model was adapted to incorporate water regulation components. The extended model was then applied to the heavily regulated river Lyon (391 km2) in Scotland to reconstruct the natural flow regime and to assess the impacts of regulation at increasing spatial scales. Multi-criteria model evaluation demonstrated that the model performed well in capturing the dominant catchment processes and regulation effects, especially at the timescales at which operation rules apply. The main change as a result of regulation in the river Lyon is a decrease in inter-annual and intra-annual variability of all elements of the flow regime, in terms of magnitude, frequency, and duration. Although these impacts are most pronounced directly downstream of the impoundments, the regulation effects propagate throughout the river system. The modelling approach is flexible and widely applicable and only limited amounts of data are required. Moreover, results are easily communicated to stakeholders. It has the potential to contribute to the development of flow regimes that may be more beneficial to the ecological status of rivers. In the case of the river Lyon, it is likely that this involves a more variable release regime. The approach developed here provides a tool for assessing impacts on flow regimes and informing environmental flows in other data-sparse regions with heavily regulated montane river systems. Copyright © 2014 John Wiley & Sons, Ltd.
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| 11. |
- Kruitbos, L. M., et al.
(author)
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Hydroclimatic and hydrochemical controls on Plecoptera diversity and distribution in northern freshwater ecosystems
- 2012
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In: Hydrobiologia. - : Springer Science and Business Media LLC. - 0018-8158 .- 1573-5117. ; 693:1, s. 39-53
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Journal article (peer-reviewed)abstract
- Freshwater ecosystems in the mid- to upper-latitudes of the northern hemisphere are particularly vulnerable to the impact of climate change as slight changes in air temperature can alter the form, timing, and magnitude of precipitation and consequent influence of snowmelt on streamflow dynamics. Here, we examine the effects of hydro-climate, flow regime, and hydrochemistry on Plecoptera (stonefly) alpha (alpha) diversity and distribution in northern freshwater ecosystems. We characterized the hydroclimatic regime of seven catchments spanning a climatic gradient across the northern temperate region and compared them with estimates of Plecoptera genera richness. By a space-for-time substitution, we assessed how warmer temperatures and altered flow regimes may influence Plecoptera alpha diversity and composition at the genus level. Our results show wide hydroclimatic variability among sites, including differences in temporal streamflow dynamics and temperature response. Principal component analysis showed that Plecoptera genera richness was positively correlated with catchment relief (m), mean and median annual air temperature (A degrees C), and streamflow. These results provide a preliminary insight into how hydroclimatic change, particularly in terms of increased air temperature and altered streamflow regimes, may create future conditions more favorable to some Plecopteras in northern catchments.
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| 12. |
- Laudon, Hjalmar, et al.
(author)
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Cross-regional prediction of long-term trajectory of stream water DOC response to climate change
- 2012
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In: Geophysical Research Letters. - : John Wiley & Sons. - 0094-8276 .- 1944-8007. ; 39
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Journal article (peer-reviewed)abstract
- There is no scientific consensus about how dissolved organic carbon (DOC) in surface waters is regulated. Here we combine recent literature data from 49 catchments with detailed stream and catchment process information from nine well established research catchments at mid- to high latitudes to examine the question of how climate controls stream water DOC. We show for the first time that mean annual temperature (MAT) in the range from -3 degrees to +10 degrees C has a strong control over the regional stream water DOC concentration in catchments, with highest concentrations in areas ranging between 0 degrees and +3 degrees C MAT. Although relatively large deviations from this model occur for individual streams, catchment topography appears to explain much of this divergence. These findings suggest that the long-term trajectory of stream water DOC response to climate change may be more predictable than previously thought. Citation: Laudon, H., J. Buttle, S. K. Carey, J. McDonnell, K. McGuire, J. Seibert, J. Shanley, C. Soulsby, and D. Tetzlaff (2012), Cross-regional prediction of long-term trajectory of stream water DOC response to climate change, Geophys. Res. Lett., 39, L18404, doi: 10.1029/2012GL053033.
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| 13. |
- Peralta Tapia, Andres, et al.
(author)
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Connecting precipitation inputs and soil flow pathways to stream water in contrasting boreal catchments
- 2015
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In: Hydrological Processes. - : Wiley-Blackwell. - 0885-6087 .- 1099-1085. ; 29:16, s. 3546-3555
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Journal article (peer-reviewed)abstract
- Stable isotopes of water are one of the most widely used tools to track the pathways of precipitation inputs to streams. In the past, soils have often been treated as black-boxes through which precipitation is routed to streams without much consideration of how, when, and where water is transported along soil and groundwater flow paths. Here, we use time series of stable isotopes (O-18) in precipitation, soil/groundwater, and stream water to evaluate how landscape structure and heterogeneity influence seasonal hydrological patterns characteristic of boreal headwater catchments. To do this, we collected water throughout a full year at three adjacent catchments draining forest, mire, and mire/lake ecosystems within the Krycklan Experimental Catchment of northern Sweden. Isotope time series from forest and mire groundwater piezometers showed spatial and temporal heterogeneity in the dominant hydrologic flow pathways connecting precipitation to stream flow at different sites. The isotopic signature of stream water suggested strong connections to the dominant landscape elements within each catchment. These connections translated into greater temporal variability in the isotopic response of streams draining lake and wetland patches, and a much more attenuated pattern in the forest-dominated catchment. Overall, seasonal changes in the isotopic composition of streams and groundwater illustrate how differences in landscape structure result in variable hydrological patterns in the boreal landscape.
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| 14. |
- Peralta Tapia, Andres, et al.
(author)
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Hydroclimatic influences on non-stationary transit time distributions in a boreal headwater catchment
- 2016
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In: Journal of Hydrology. - : Elsevier BV. - 0022-1694 .- 1879-2707. ; 543:A, s. 7-16
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Journal article (peer-reviewed)abstract
- Understanding how water moves through catchments - from the time it enters as precipitation to when it exits via streamflow - is of fundamental importance to understanding hydrological and biogeochemical processes. A basic descriptor of this routing is the Transit Time Distribution (TTD) which is derived from the input-output behavior of conservative tracers, the mean of which represents the average time elapsed between water molecules entering and exiting a flow system. In recent decades, many transit time studies have been conducted, but few of these have focused on snow-dominated catchments. We assembled a 10-year time series of isotopic data (delta O-18 and delta H-2) for precipitation and stream water to estimate the characteristics of the transit time distribution in a boreal catchment in northern Sweden. We applied lumped parameter models using a gamma distribution to calculate the Mean Transit Time (MTT) of water over the entire period of record and to evaluate how inter-annual differences in transit times relate to hydroclimatic variability. The best fit MTT for the complete 10-year period was 650 days (Nash-Sutcliff Efficiency = 0.65), while the best fit inter-annual MTT ranged from 300 days up to 1200 days. Whilst there was a weak negative correlation between mean annual total precipitation and the annual MTT, this relationship was stronger (r(2) = 0.53, p = 0.02) for the annual rain water input. This strong connection between the MTT and annual rainfall, rather than snowmelt, has strong implications for understanding future hydrological and biogeochemical processes in boreal regions, given that predicted warmer winters would translate into a greater proportion of precipitation falling as rain and thus shorter MTT in catchments. Such a change could have direct implications for the export of solutes and pollutants.
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| 15. |
- Serikova, Svetlana, et al.
(author)
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High riverine CO2 emissions at the permafrost boundary of Western Siberia
- 2018
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In: Nature Geoscience. - : Nature Publishing Group. - 1752-0894 .- 1752-0908. ; 11:11, s. 825-
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Journal article (peer-reviewed)abstract
- The fate of the vast stocks of organic carbon stored in permafrost of the Western Siberian Lowland, the world's largest peat-land, is uncertain. Specifically, the amount of greenhouse gas emissions from rivers in the region is unknown. Here we present estimates of annual CO2 emissions from 58 rivers across all permafrost zones of the Western Siberian Lowland, between 56 and 67 degrees N. We find that emissions peak at the permafrost boundary, and decrease where permafrost is more prevalent and in colder climatic conditions. River CO2 emissions were high, and on average two times greater than downstream carbon export. We suggest that high emissions and emission/export ratios are a result of warm temperatures and the long transit times of river water. We show that rivers in the Western Siberian Lowland play an important role in the carbon cycle by degassing terrestrial carbon before its transport to the Arctic Ocean, and suggest that changes in both temperature and precipitation are important for understanding and predicting high-latitude river CO2 emissions in a changing climate.
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| 16. |
- Soulsby, C., et al.
(author)
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Catchment-scale estimates of flow path partitioning and water storage based on transit time and runoff modelling
- 2011
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In: Hydrological Processes. - : Wiley. - 0885-6087 .- 1099-1085. ; 25:25, s. 3960-3976
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Journal article (peer-reviewed)abstract
- Tracer-derived mean transit times (MTT) and rainfallrunoff modelling were used to explore stream flow generation in 14 Scottish catchments. Both approaches conceptualise the partitioning, storage, and release of water at the catchment scale. The study catchments were predominantly upland and ranged from 0.5 to 1800?km2. Lumped convolution integral models using tracer inputoutput relationships generally provided well-constrained MTT estimates using a gamma function as the transit time distribution. These ranged from 60?days to >10?years and are mainly controlled by catchment soil cover and drainage density. The HBV model was calibrated using upper and lower storage layers to conceptualise rapidly responding near-surface flow paths and slower groundwater contributions to runoff. Calibrated parameters that regulate groundwater recharge and partitioning between the two storages were reasonably well-identified and correlations with MTTs. The most clearly identified parameters and those with the strongest correlations with MTT and landscape controls (particularly soil cover) were the recession coefficients which control the release of water from the upper and lower storage layers. There was also strong correlation between the dynamic storage estimated by HBV and the total catchment storage inferred by tracer damping, although the latter was usually two orders of magnitude greater. This is explained by the different storages estimated: while the total storage inferred by tracers also includes the passive storage involved in mixing, the model estimates dynamic storage from water balance considerations. The former can be interpreted as relating to total porosity, whereas the latter rather corresponds to the drainable porosity. As MTTs for Scottish the uplands can be estimated from catchment characteristics, landscape analysis can be used to constrain sensitive model parameters when modelling in ungauged basins. Furthermore, the dynamic storage inferred by HBV may also be used to provide a first approximation of minimum total catchment storage. Copyright (c) 2011 John Wiley & Sons, Ltd.
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| 17. |
- Tetzlaff, D., et al.
(author)
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How does landscape structure influence catchment transit time across different geomorphic provinces?
- 2009
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In: Hydrological Processes. - : Wiley. - 0885-6087 .- 1099-1085. ; 23:6, s. 945-953
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Journal article (peer-reviewed)abstract
- Despite an increasing number of empirical investigations of catchment transit times (TTs), virtually all are based on individual catchments and there are few attempts to synthesize understanding across different geographical regions. Uniquely, this paper examines data from 55 catchments in five geomorphic provinces in northern temperate regions (Scotland, United States of America and Sweden). The objective is to understand how the role of catchment topography as a control on the TTs differs in contrasting geographical settings. Catchment inverse transit time proxies (ITTPs) were inferred by a simple metric of isotopic tracer damping, using the ratio of standard deviation of delta O-18 in streamwater to the standard deviation of delta O-18 in precipitation. Quantitative landscape analysis was undertaken to characterize the catchments according to hydrologically relevant topographic indices: that could be readily determined from a digital terrain model (DTM). The nature of topographic controls on transit times varied markedly in different geomorphic regions. In steeper montane regions. there are stronger gravitational influences on hydraulic gradients and TTs tend to he lower in the steepest catchments. In provinces where terrain is more subdued, direct topographic control weakened; in particular, where flatter areas with less permeable soils give rise to overland How and lower The steeper slopes within this flatter terrain appear to have a greater coverage of freely draining soils, which increase sub-surface flow, therefore increasing TTs. Quantitative landscape analysis proved a useful tool for intercatchment comparison. However, the critical influence of sub-surface permeability and connectivity may limit the transferability of predictive tools of hydrological function based on topographic parameters alone. Copyright (C) 2009 John Wiley & Sons, Ltd.
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| 18. |
- Tetzlaff, D., et al.
(author)
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Inter-catchment comparison to assess the influence of topography and soils on catchment transit times in a geomorphic province; the Cairngorm mountains, Scotland
- 2009
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In: Hydrological Processes. ; 23:13, s. 1874-1886
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Journal article (peer-reviewed)abstract
- A quantitative, process relevant analysis of ten mesoscale (ca 10-90 km(2)) catchments in the Cairngorm mountains, Scotland was carried out using 10-m digital terrain models (DTMs). This analysis produced a range of topographic indices that described differences in the landscape organisation of the catchments in a way that helped explain contrasts in their hydrology. Mean transit time (MTT)-derived from isotopic tracer data-was used as a metric that characterised differences in the hydrological function of the ten catchments. Some topographic indices exhibited significant correlations with MTT. Most notably, the ratio of the median flow path length to the median flow path gradient was negatively correlated with MTT, whilst the median upslope area was positively correlated. However, the relationships exhibited significant scatter which precluded their use as a predictive tool that could be applied to ungauged basins in this region. In contrast, maps of soil hydrological properties could be used to differentiate hydrologically responsive soils (which are dominated by overland flow and shallow sub-surface storm flow) from free draining soils (that facilitate deeper sub-surface flows). MTT was negatively correlated with the coverage of responsive soils in catchments. This relationship provided a much better basis for predicting MTT in ungauged catchments in this geomorphic province. In the Cairngorms, the extensive cover of various glacial drift deposits appears to be a first order control on soil distributions and strongly influences the porosity and permeability of the sub-surface. These catchment characteristics result in soil cover being a much more discerning indicator of hydrological function than topography alone. The study highlights the potential of quantitative landscape analysis in catchment comparison and the need for caution in extrapolating relationships between landscape controls and metrics of hydrological function beyond specific geomorphic provinces. Copyright (C) 2009 John Wiley & Sons, Ltd.
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