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Disruption of blood flow promotes endothelial dysfunction and predisposes vessels to remodeling and atherosclerosis. Recent findings suggest that spatial and temporal tuning of local Ca2+ signals along the endothelium is vital to vascular function. In this study, we examined whether chronic flow disruption causes alteration of dynamic endothelial Ca2+ signal patterning associated with changes in vascular structure and function. For these studies, we performed surgical PL of the left carotid arteries of mice to establish chronic low flow for 2 weeks; right carotid arteries remained open and served as controls (C). Histological sections showed substantial remodeling of PL compared to C arteries, including formation of neointima. Isometric force measurements revealed increased PE-induced contractions and decreased KCl-induced contractions in PL vs C arteries. Endothelium-dependent vasorelaxation in response to ACh; 10−8 to 10−5 mol/L) was significantly impaired in PL vs C vessels. Evaluation of endothelial Ca2+ using confocal imaging and custom analysis exposed distinct impairment of Ca2+ dynamics in PL arteries, characterized by reduction in active sites and truncation of events, corresponding to attenuated vasorelaxation. Our findings suggest that endothelial dysfunction in developing vascular disease may be characterized by distinct shifts in the spatial and temporal patterns of localized Ca2+ signals. [ABSTRACT FROM AUTHOR]

In the paper the possibility of using statistical method for data agglomeration, i.e. nonhierarchical cluster analysis for low flow grouping was made. The study material included daily flows from the multi-year period of 1963-983 collected for 19 catchments, located in the upper Vistula basin. Regions with the same flow were determined with the use of nonhierarchical cluster analysis (K-means). Groups were characterized by low flow and selected physiographic and meteorological features of the catchments. The procedure of catchments assigning to the clusters was started from two clusters and finished at five. The next moving and assigning of catchments into clusters resulted in a cluster in which there was only one catchment (for five clusters). Another objects' delineation did not give an objective effects, based on which it was difficult to determine a clear criterion of assigning each catchments into the clusters. The last step involved development of the models reflecting correlation and regression relationships. The identified clusters comprised catchments similar in terms of unit runoff, watercourse length, mean precipitation, median altitude, mean catchment slope, watercourse staff gauge zero, area covered by coniferous forests, arable lands, and soils. [ABSTRACT FROM AUTHOR]

Hydrological impact studies of climate change increasingly take land use changes into account. However, the Midwestern USA is still understudied in this context. This study investigated the impacts of potential climate change and urban growth on the streamflow characteristics of the Milwaukee River located in southeastern Wisconsin. The Hydrological Simulation Program-Fortran (HSPF) was set up for the catchment and calibrated against observed streamflow data. The calibrated HSPF model was run with a series of climate and urban growth scenarios generated from nine global climate models (GCMs) and a land use simulation model, respectively. The outcomes from the GCMs, statistically downscaled at 10-km grid spacing, generally indicated a warmer and wetter climate by the mid-twenty-first century, and the land use simulation model projected moderate urban growth by the time. Major findings from the study include: (1) land use changes alone resulted in negligible streamflow changes; (2) low flows showed more sensitivity than mean streamflow to climate change; (3) streamflow variability increased with both land use and climate changes, and (4) uncertainty in simulated streamflow among GCMs was larger than uncertainty among the GCM output themselves. The findings suggest that the current pace of urban growth would not pose much threat to the water resources in the area. Considering that low flow indices responded more sensitively than mean streamflow to climate change, measures to improve resilience to drought conditions are recommended. Because land use change impacts were quite small, considering the impact of both climate and land use scenarios did not produce a significantly different result. [ABSTRACT FROM AUTHOR]

Up to 40% of patients with aortic stenosis (AS) harbor discordant Doppler-echocardiographic findings, the most common of which is the presence of a small aortic valve area (≤1.0 cm 2 ) suggesting severe AS, but a low gradient (<40 mm Hg) suggesting nonsevere AS. The purpose of this paper is to present the role of multimodality imaging in the diagnostic and therapeutic management of this challenging entity referred to as low-gradient AS . Doppler-echocardiography is critical to determine the subtype of low-gradient AS: that is, classical low-flow, paradoxical low-flow, or normal-flow. Patients with low-flow, low-gradient AS generally have a worse prognosis compared with patients with high-gradient or with normal-flow, low-gradient AS. Patients with low-gradient AS and evidence of severe AS benefit from aortic valve replacement (AVR). However, confirmation of the presence of severe AS is particularly challenging in these patients and requires a multimodality imaging approach including low-dose dobutamine stress echocardiography and aortic valve calcium scoring by multidetector computed tomography. Transcatheter AVR using a transfemoral approach may be superior to surgical AVR in patients with low-flow, low-gradient AS. Further studies are needed to confirm the best valve replacement procedure and prosthetic valve for each category of low-gradient AS and to identify patients with low-gradient AS in whom AVR is likely to be futile. [ABSTRACT FROM AUTHOR]

This study presents a regional, probabilistic framework for seasonal forecasts of extreme low summer flows in the northeastern United States conditioned on antecedent climate and hydrologic conditions. The model is developed to explore three innovations in hierarchical modeling for seasonal forecasting at ungaged sites: (1) predictive climate teleconnections are inferred directly from ocean fields instead of predefined climate indices, (2) a parsimonious modeling structure is introduced to allow climate teleconnections to vary spatially across streamflow gages, and (3) climate teleconnections and antecedent hydrologic conditions are considered jointly for regional forecast development. The proposed model is developed and calibrated in a hierarchical Bayesian framework to pool regional information across sites and enhance regionalization skill. The model is validated in a cross-validation framework along with five simpler nested formulations to test specific hypotheses embedded in the full model structure. Results indicate that each of the three innovations improve out-of-sample summer low-flow forecasts, with the greatest benefits derived from the spatially heterogeneous effect of climate teleconnections. We conclude with a discussion of possible model improvements from a better representation of antecedent hydrologic conditions at ungaged sites. [ABSTRACT FROM AUTHOR]

Land cover has been increasingly recognized as an important factor affecting hydrologic processes at the basin and regional level. Therefore, improved understanding of how land cover change affects hydrologic systems is needed for better management of water resources. The objective of this study is to investigate the effects of land cover change on the duration and severity of high and low flows by using the Soil Water Assessment Tool model, Bayesian model averaging and copulas. Two basins dominated by different land cover in the Ohio River basin are used as study area in this study. Two historic land covers from the 1950s and 1990s are considered as input to the Soil Water Assessment Tool model, thereby investigating the hydrologic high and low flow response of different land cover conditions of these two basins. The relationships between the duration and severity of both low and high flow are defined by applying the copula method; changes in the frequency of the duration and severity are investigated. The results show that land cover changes affect both the duration and severity of both high and low flows. An increase in forest area leads to a decrease in the duration and severity during both high and low flows, but its impact is highest during extreme flows. The results also show that the land cover changes have had significant influences on changes in the joint return periods of duration and severity of low and high flows. While this study sheds light on the role of land cover change on severity and duration of high and low flow conditions, more studies using various land cover conditions and climate types are required in order to draw more reliable conclusions in the future. Copyright © 2016 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

• The models were more skilled in simulating high flow than low flow. • The model ensemble mean has the best performance than individual models. • The mean annual runoff shows a positive trend (8.03%) in the study area for 1971–2010. • About 32% (70%) of the basin became drier (wetter) in the dry (wet) season. Runoff changes are critical to the sustainable water resource in the Lancang-Mekong River Basin (LMRB). Changes in the LMRB's runoff over the past decades are unclear because of inadequate streamflow observations. The advancement of global hydrological models (GHMs) has facilitated the understanding of runoff change worldwide. However, it is required to evaluate the performance of GHMs in simulating historical runoff change in the LMRB before assessing the runoff changes. This study aims to conduct a multi-model analysis of temporal-spatial changes in runoff in the LMRB for 1971–2010 using ten GHMs from the Inter-Sectoral Impact Model Intercomparison Project (ISIMIP) and evaluate the corresponding uncertainties among models. Results show that the model ensemble mean has the best performance than the individuals when compared with the reference data. Based on the model ensemble mean, large spatial heterogeneity of runoff is found in the LMRB, with an overall slightly positive trend (8.03%). Besides, the models perform better in estimating the trends of high flow than low flow. As to the trend of runoff in the wet and dry seasons, about 32% (70%) of the basin became drier (wetter) in the dry (wet) season. Meanwhile, 17% of the basin has experienced a trend of drier dry seasons and wetter wet seasons. Overall, our results highlight the uncertainty of the runoff changes in the LMRB in the low flow simulation, particularly requiring more attention in future model improvement. The complex change patterns of the runoff suggest the importance of accurate runoff observations and projections for better water management. [ABSTRACT FROM AUTHOR]

Aims: The prognostic impact of flow trajectories according to stroke volume index (SVi) and transvalvular flow rate (FR) in patients with severe aortic stenosis (AS) undergoing transcatheter aortic valve replacement (TAVR) remains poorly assessed. We evaluated and compared SVi and FR prior and after TAVR for severe AS., Methods and Results: Patients were categorized according to SVi (<35 mL/m2) and FR (<200 mL/s). The association of pre- and post-TAVR SVi and FR with all-cause mortality up to 3 years was assessed with multivariable Cox regression models. Among 980 patients with pre-TAVR flow assessment, SVi was reduced in 41.3% and FR in 48.1%. Baseline flow status was not an independent mortality predictor [SVi: hazard ratio (HR) 1.22, 95% confidence interval (CI) 0.85-1.82, FR: HR 0.78, 95% CI 0.48-1.27]. Among 731 patients undergoing early (5 days, interquartile range 2-29) post-TAVR flow assessment, SVi recovered in 40.1% and FR in 49.0% patients with baseline low flow. Reduced FR following TAVR was an independent predictor of mortality (HR 1.67, 95% CI 1.02-2.74), whereas SVi was not (HR 0.97, 95% CI 0.53-1.78). Three-year estimated mortality in patients with recovered FR was lower than that in patients with reduced FR (13.3 vs. 37.7% vs, P = 0.003) and similar to that in patients with normal baseline FR (P = 0.317)., Conclusion: Baseline flow status was not an independent predictor of mid-term mortality among all-comers with severe AS undergoing TAVR. Flow recovery early after TAVR was frequent. Post-TAVR FR, but not SVi, was independently associated with mid-term all-cause mortality. By impacting flow status, AV replacement modifies the association of flow status with outcomes., Competing Interests: Conflict of interest: M.M. received consultant fees from Abbott, Boston Scientific, Kardia, and Medtronic. The other authors have no conflicts of interest to declare., (© The Author(s) 2023. Published by Oxford University Press on behalf of the European Society of Cardiology. All rights reserved. For permissions, please e-mail: journals.permissions@oup.com.)

Extreme hydrological events are significant for river basin management and very important input for future development. However, comparison between pre and post development conditions is often neglected in extreme events assessment. Analyses of low flow conditions as a significant hydrological parameter are of the great importance for transboundary Drina River Basin, since it is a source of clean fresh water with significant potential for hydropower development. Hydrological analyses presented here reflect low flow statistics comparison for pre and post development conditions. Evaluated time series correspond to periods prior and after development of existing dams, reservoirs and hydropower plants. Confidence intervals estimation for different scenarios underline uncertainty associated with low flow assessment. The results indicate importance of comparison for pre and post development conditions with respect to extreme events and generate recommendations for future hydrological analyses in Drina River Basin and other river basins. [ABSTRACT FROM AUTHOR]

There are numerous anecdotal examples of drought terminations documented throughout the historical record on most continents. The end of a drought is the critical time during which water resource managers urgently require information on the replenishment of supplies. Yet this phase has been relatively neglected by the academic community, with much of the existing body of research on drought termination assessing the likelihood of droughts ending rather than its temporal profile. In particular, there has been little effort to characterise drought termination events themselves. This is partly explained by existing definitions of drought termination as a specific point in time when drought is considered to have finished, rather than a more holistic consideration based on approaches developed within biological sciences. There is also a lack of understanding about how drought termination propagates through the hydrological cycle. This paper specifically examines and reviews available research on drought termination, highlighting limitations associated with current definitions and offering suggestions for characterising the temporal stages of drought. An alternative definition of drought termination is proposed: a period between the maximum negative anomaly and a return to above-average conditions. Once this phase has been delineated, the duration, rate and seasonality of drought termination can be derived. The utility of these metrics is illustrated through a case study of the 2010-2012 drought in the UK, and the propagation of drought termination between river flows and groundwater levels. [ABSTRACT FROM AUTHOR]

Oxygen, an essential molecule for life, is a colorless, tasteless, and odorless gas. It is important to put the right indication for oxygen therapy in the appropriate patient. Indications for oxygen therapy can be reviewed in two subsections: acute and long-term oxygen therapy. Oxygen can be administered via different systems after the need for oxygen support is determined in the acute or chronic settings. Degree of hypoxemia, patient's tolerance, and the underlying disease are the main criteria to be considered for the choice of delivery system. Oxygen can be delivered through low-flow systems (<15 L/min), such as nasal cannula, simple face mask, mask with a reservoir, and diffuser mask, or high-flow systems, such as venturi mask and high-flow nasal cannula. The aim of this review is to describe oxygen delivery systems in patients with respiratory insufficiency. [ABSTRACT FROM AUTHOR]

Flow variability drives important instream ecohydrological processes. Nonetheless, generalizations about ecological responses to flow variability are elusive and complicated by interacting factors. Hydrogeological controls on groundwater inputs into streams are often an overlooked factor that may interact with flow variability and influence instream ecology. Flow effects on ecology are also complicated by flora and fauna trait diversity, which makes some organisms more sensitive to flow variability than others. To improve understanding regarding the effects of flow variability on instream communities, we utilized a long-term 17-year data set of macroinvertebrate communities from eight sites on the Upper Murrumbidgee River catchment, south eastern Australia. Hydrogeological mapping provided a proxy of groundwater influence on instream ecology. Generalized linear mixed models were used to test hydrogeology (i.e. groundwater influence) and flow variability effects on selected taxa and trait groups. Trait groups tested were those with drought-resistant life stages, no drought-resistant life stages and those with poor dispersal traits. Non-drought resistant and poor dispersing taxa responded to hydrogeology and stream flow variables, while taxa with drought-resistant traits did not. Poor dispersing taxa displayed the strongest positive response to interactions between high mean flow and hydrogeological conditions that facilitate groundwater inputs. While the importance of flow variability is widely recognized, the combined role of hydrogeology and trait groups on macroinvertebrate responses has not been widely considered thus far. This study demonstrates that the consideration of hydrogeology and faunal traits can help improve the understanding of macroinvertebrate population and community responses to flow regime variability. Copyright © 2016 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

A breathing system is defined as an assembly of components, which delivers gases from the anesthesia machine to the patients′ airways. When the components are arranged as a circle, it is termed a circle system. The flow of exhaled gases is unidirectional in the system. The system contains a component (absorber), which absorbs exhaled carbon dioxide and it is not necessary to give high fresh gas flows as in Mapleson systems. When the adjustable pressure limiting (APL) valve is closed and all the exhaled gases without carbon dioxide are returned to the patient, the system becomes a totally closed one. Such a circle system can be used with flows as low as 250 to 500 mL and clinically can be termed as low-flow systems. The components of the circle system can be arranged in different ways with adherence to basic rules: (1) Unidirectional valve must be present between the reservoir bag and the patient on both inspiratory and expiratory sides; (2) fresh gas must not enter the system between the expiratory unidirectional valve and the patient; and (3) the APL valve must not be placed between the patient and the inspiratory unidirectional valve. The functional analysis is explained in detail. During the function, the arrangement of components is significant only at higher fresh gas flows. With the introduction of low resistance valves, improved soda lime canisters and low dead space connectors, the use of less complicated pediatric circle systems is gaining popularity to anesthetize children. There are bidirectional flow systems with carbon dioxide absorption. The Waters to and fro system, a classic example of bidirectional flow systems with a canister to absorb carbon dioxide, is valveless and portable. It was widely used in the past and now is only of historical importance.

The availability of using hypothesis test techniques to identify the long-term trends of hydrological time series is investigated in this study. The aim is to analyse trends of low flows at streams in eastern Slovakia, namely Poprad, Hornád, Bodva, Bodrog river basins. The article presents a methodology for prediction of hydrological drought based on statistical testing of low stream flows by non-parametric statistical test. The main objective is to identify low flow trends in the selected 63 river stations in eastern Slovakia. The stations with human impacts are also evaluated. The Mann-Kendall non-parametric test has been used to detect trends in hydrological time series. Statistically significant trends have been determined from the trend lines for the whole territory of eastern Slovakia. The results indicate that the observed changes in Slovakian river basins do not have a clearly defined trend.

The identification of base flow from an available record of streamflow measurements for recession rate analysis is often a difficult and time-consuming process affected by unavoidable errors and subjective aspects. Here, several stringent criteria are proposed for automated selection of base flows for this method and are applied to select pure base flows in 26 catchments from the United States, Australia, and China. The characteristic drainage timescale parameter (K) of the linear response function was chosen as the effectiveness measure of the automated method; the K values estimated using this method are 44.5 ± 13.2 days compared with 45.7 ± 10.5 days estimated manually for the catchments with long records. The effects of different imposed criteria on the base flow selection are also quantified using this parameter. The proposed algorithm provides a faster and more objective methodology for automated selection of base flows for recession rate analysis and will thus greatly facilitate its application. [ABSTRACT FROM AUTHOR]

The study involves evaluation of basin area, slopes, shape of the basin as morphological parameters and analysis of flow frequencies for flood and low flows, developing unit hydrograph and analysis of rainfall intensity distribution in the study area as hydrological parameters. The morphological analysis of the basin yielded basin area, slope, elongation and circulatory ratio of 830km², 0.57%, 0.46 and 0.35 respectively. For hydrological analysis, flow frequency, unit hydrograph and rainfall analysis were evaluated. The flood (peak) and low flows were fitted with Gumbel Extreme Value Type I & III model, and the recurrence intervals for low and peak flows of 0.0004m³/s and 3.5772m³/s were obtained as 4 and 44 years respectively. The mean annual maximum flow and mean annual runoff depth were estimated to be 7.97m³/s and 6.5mm respectively. This showed that the intensity of rainfall contributing to the volume of river discharge was 6.5mm/day. Unit hydrograph was developed for the river basin using SCS approach. More so, rainfall analysis was carried out to determine the flood and drought periods. The results indicated that Oyun river basin is relatively small watershed with elongated narrow shape and non-steep slope which contributed to relatively slower draining of water into the river. From the analysis, flooding is expected in the month of September while drought may be expected in the months of December to February. The results of this study will be useful to river basin managers in managing and planning of water resources and facilities development. [ABSTRACT FROM AUTHOR]

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Frequency analysis of streamflow provides an essential ingredient in our understanding of hydrologic events and provides needed guidance in the design and management of water resources infrastructure. However, traditional hydrologic approaches often fail to include important external effects that can result in unpredictable or unforeseen changes in streamflow. Moreover, previous studies investigating multiple characteristics of streamflow do not address a nonstationary approach. This study explores nonstationary frequency analysis of bivariate characteristics, including occurrence and severity, of annual low flow in the Connecticut River Basin, United States. To investigate bivariate low flow frequency, copulas and their marginal distributions are constructed by using stationary and nonstationary approaches. Our study results indicate that streamflow used in this study demonstrate significant nonstationarity. Over time, the occurrence and severity of low flows are shown to be lower with the same probability based on the results of nonstationary copulas. Bivariate low flow frequencies in the years 1970, 2000, and 2030, and their joint return periods are estimated under the nonstationary copulas. Copyright © 2016 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

An important proportion of patients with aortic stenosis (AS) have a 'low-gradient' AS, i.e. a small aortic valve area (AVA, 1.0 cm²) consistent with severe AS but a low mean transvalvular gradient (,40 mmHg) consistent with non-severe AS. The management of this subset of patients is particularly challenging because the AVA-gradient discrepancy raises uncertainty about the actual stenosis severity and thus about the indication for aortic valve replacement (AVR) if the patient has symptoms and/or left ventricular (LV) systolic dysfunction. The most frequent cause of low-gradient (LG) AS is the presence of a low LV outflow state, which may occur with reduced left ventricular ejection fraction (LVEF), i.e. classical low-flow, low-gradient (LF-LG), or preserved LVEF, i.e. paradoxical LF-LG. Furthermore, a substantial proportion of patients with AS may have a normal-flow, low-gradient (NF-LG) AS: i.e. a small AVA--low-gradient combination but with a normal flow. One of the most important clinical challenges in these three categories of patients with LG AS (classical LF-LG, paradoxical LF-LG, and NF-LG) is to differentiate a true-severe AS that generally benefits from AVR vs. a pseudo-severe AS that should be managed conservatively. A low-dose dobutamine stress echocardiography may be used for this purpose in patients with classical LF-LG AS, whereas aortic valve calcium scoring by multi-detector computed tomography is the preferred modality in those with paradoxical LF-LG or NF-LG AS. Although patients with LF-LG severe AS have worse outcomes than those with high-gradient AS following AVR, they nonetheless display an important survival benefit with this intervention. Some studies suggest that transcatheter AVR may be superior to surgical AVR in patients with LF-LG AS. [ABSTRACT FROM AUTHOR]

The Danube floodplain is disconnected from its river, and natural water dynamic is inhibited by regulation and hydropower generation. Notwithstanding the hydropower dams, this restoration project aims to bring back natural water dynamics to the floodplain by a new floodplain stream, by ecological flooding and by temporary groundwater drawdown during summer months. Due to the new floodplain stream, former fluctuating water zones which are habitat for the target species Oenanthe aquatica changed to aquatic habitats which are also required. The measure groundwater drawdown aims to enhance the abiotic conditions for this pioneer species of muddy streambanks. The scientific efficiency control compares the situation before restoration implementation with the effects of three different types of groundwater drawdown. For these three types, the hydrological situation was investigated, and the effects on the potential area and on the occurrence of O. aquatica were mapped. The outcome is that one type can enhance germination of O. aquatica, but is detrimental for aquatic organisms. The other type is able to provide the same suitable conditions for O. aquatica, without severely harming the aquatic habitats. The third type cannot reach the needed low water levels and is therefore not a comparable option. The results show that an interdisciplinary monitoring is able to develop a measure suitable for both competing habitat types. [ABSTRACT FROM AUTHOR]

Piscivory by birds can be significant, particularly on fish in small streams and during seasonal low flow when available cover from predators can be limited. Yet, how varying amounts of cover may change the extent of predation mortality from avian predators on fish is not clear. We evaluated size-selective survival of coastal cutthroat trout ( Oncorhynchus clarkii clarkii) in replicated semi-natural stream sections. These sections provided high (0.01 m2 of cover per m2 of stream) or low (0.002 m2 of cover per m2 of stream) levels of instream cover available to trout and were closed to emigration. Each fish was individually tagged, allowing us to track retention of individuals during the course of the 36-day experiment, which we attributed to survival from predators, because fish had no other way to leave the streams. Although other avian predators may have been active in our system and not detected, the only predator observed was the belted kingfisher Megaceryle alcyon, which is known to prey heavily on fish. In both treatments, trout >20.4 cm were not preyed upon indicating an increased ability to prey upon on smaller individuals. Increased availability of cover improved survival of trout by 12% in high relative to low cover stream sections. Trout also survived better in stream sections with greater shade, a factor we could not control in our system. Collectively, these findings indicate that instream cover and shade from avian predators can play an important role in driving survival of fish in small streams or during periods of low flow. [ABSTRACT FROM AUTHOR]

One of the most severe anthropogenic impacts on river systems worldwide has been alterations to the natural flow regime. Understanding biological responses to altered flow regimes is critical to effectively rehabilitate aquatic ecosystems. This study investigated changes in the larval fish assemblages during varying hydrological conditions over 5 years in the lower River Murray, in south-eastern Australia. Larval fish were sampled during spring/summer during three distinct hydrological periods: under a within-channel flow pulse and a water level raising (2005); during a drought with very low flows and stable water levels (2006, 2007 and 2008); and during an overbank flow (2010). Data were analysed for annual, spatial and seasonal variations, and correlations were examined between changes in larval assemblages and environmental variables. Hydrology was a key driver in inter-annual variation in larval fish assemblages. High abundances of small-bodied to medium-bodied native species were recorded under low flows, while for other species, abundance was more strongly correlated to temperature, representing seasonal variation. Two large-bodied species were only recorded during the within-channel flow pulse and overbank flow conditions, and significant increases in larval abundances were recorded during overbank flow conditions. We suggest groupings based on species response to hydrology (low-flow to medium-flow spawners, high-flow spawners or seasonal spawners). This study suggests that a range of conditions (low flows and overbank flows) are required to maintain a diverse and abundant native fish fauna in the lower River Murray. Copyright © 2015 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

Frequent forest disturbances can significantly affect flow regimes (magnitude, timing, frequency, duration, and variability) and associated aquatic ecological functions. However, the lack of a comprehensive understanding of the impacts of forest disturbances on flow regimes impedes the development of adaptive strategies for sustainable water resource management and ecosystem protection. In this study, an innovative methodology that combines the time series cross-correlation analysis and paired-year approach was developed and applied in two snow-dominated large watersheds (the Baker Creek and Willow River watersheds in the central interior of British Columbia (BC)) to provide a quantitative assessment on how forest disturbances affect the components of flow regimes at a large watershed scale. The results showed that the magnitude, variability, and return period of high flows in the Baker Creek watershed were increased on average by 154.3%, 324.2%, and 11 years, respectively, and the timing of high flows was advanced by about 9 days during the disturbed periods. In contrast, forest disturbances caused only a 36.2% increment in the magnitude and a 4-day increase in the duration of high flows in the Willow River watershed. The responses of low flow regimes were less sensitive than those of high flow regimes. Only the magnitude and variability of low flows in the Baker Creek watershed and the duration of low flows in the Willow River watershed were significantly altered by forest disturbances. These findings can have implications for water management and ecosystem protection in the context of growing anthropogenic disturbances. Copyright © 2015 John Wiley & Sons, Ltd. Copyright © 2015 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

This study analyses trends in low flows in Spain in the period 1949–2009, based on daily flow data collected at 60 gauging stations located in near-natural catchments. Two low-flow indicators were considered: (i) the seven-day annual minimum streamflow and (ii) the 10th percentile of the yearly flow duration curve. Catchments were clustered into three regions in terms of monthly mean flows. The Mann-Kendall test was used considering four periods between 1949 and 2009. A multi-temporal trend analysis was also applied to the longest series to identify wet and dry periods that could influence the results. Lastly, a field significance test provided a regional assessment of the at-site detected trends at each region. The results for each indicator reveal a clearly decreasing trend in low flows throughout the northern half of Spain that was found to be field-significant over the (Atlantic and Mediterranean) regions.Editor Z.W. Kundzewicz; Associate editor not assigned [ABSTRACT FROM PUBLISHER]

Climate change will have a significant impact on the hydrological cycle. This paper presents the results of a pilot project for the Yamaska River in Québec. The objective of this project is to evaluate the river's vulnerability to low flows attributable to climate change and to analyze a no-regrets adaptation strategy at locations identified as vulnerable. The vulnerability was evaluated using statistical indicators (low flow indices) based on long-term observations at four locations in the basin. A distributed physically-based hydrological model in use in Québec was calibrated and validated against observed streamflow data to properly represent low flows. Hydrological simulations used seven climate projections provided by the north american regional climate change assessment program (NARCCAP) s project. Also, five members of the canadian regional climate model (CRCM), nested with the coupled global climate model (CGCM) under the special report on emission scenarios (SRES) A2 emission scenario, were run for a reference (1971-2000) period and a future (2041-2070) period. Streamflow simulations indicate a degradation of future low flow conditions, particularly in June and August, when compared to the reference period. In addition, the 7-day low flow value with a 2-year return period (7Q2) and the 7-day low flow value with a 10-year return period (7Q10) decrease by 16-64% and 18-45% respectively. A no-regrets adaptation strategy allowing stakeholders to reduce withdrawal according to alert levels was implemented. Simulations of the application of the no-regrets adaptation strategy reduced the number of days where streamflows are below the Crisis level in the future period by at least 20%. [ABSTRACT FROM AUTHOR]

Human water use can place considerable stress on hydrologic systems. Humans directly affect the water cycle through water withdrawals and return flows. Aside from climate change, humans indirectly impact hydrologic systems through dam building, land use change, and urbanization. Given the increasing incidence of water overdraft and water scarcity globally, there is a growing need to understand and quantify these effects so that appropriate water management and policy decisions can be made both in the United States and abroad. Massachusetts, in the northeastern United States, is located in a "water-rich" region, and yet issues of water overdraft and exceptional low flows have been documented throughout the state. This study demonstrates the application of water use regimes for characterizing the water balance in two suburbanized basins in easternMassachusetts: The Charles River watershed (CRW) and the Ipswich River watershed (IRW).Water use regimes categorize river basins based on the magnitude of human water withdrawals and return flows relative to streamflow. Water use regimes for the upper/middle portions of the CRWand the IRW were examined at annual and subannual timescales for the period 2000-2004, which was the only time during which detailed water use data were available. Although the water use regimes of these watersheds displayed only minor alterations on an average annual scale, increased regime indicator values were noticeable at the annual scale of a low-flow (drought) year. At the subannual scale, water use intensity was low in high-flow months (e.g., April), but increased by more than an order of magnitude during low-flow months (e.g., August). A shift in water regime, from natural flow-dominated toward withdrawal-dominated, was observed at the average monthly timescale and during the low-flow months of a single low-flow year. Despite the fact that the CRW and IRW are similar in their suburban characteristics and experience a similar climate, the two displayed different water use characteristics and variability in regime change. Therefore, water use characteristics and subannual variability in water regime shifts should be emphasized when examining the relationship between water use and water resource availability. [ABSTRACT FROM AUTHOR]

This paper examines model uncertainties associated with streamflow by characterizing it into extreme high (peak) flows and low flows in two different catchments, viz. a snowmelt-induced hilly catchment (Satluj) and an inland catchment (Tungabhadra). The stream-flow was initially simulated and calibrated using the soil and water assessment tool (SWAT) model and SWAT CUP (calibration and uncertainty program) based sequential uncertainty fitting approach (SUFI2) by analyzing 14 different hydrological parameters. The multiple criteria evaluation was based on the multiple linear regression equations and noncommensurable measures of information derived from river flow series by means of a number of sequential time-series processing tasks, including separation of the river flow series into extreme peak flows and low-flow hydrograph periods. A reliable set of rules for model calibration was applied to all linear-regression-based objective functions. The authors found that extreme peak flow conditions were more critical than low-flow conditions and that the streamflow corresponding to the snowmelt process was more uncertain. Factors such as temperature (p-value-0.027) and snowmelt (p-value-0.000) were identified as sensitive parameters which showed large influence on the calibration parameters for mountainous hilly terrain conditions. Overall, calibration of the SWAT modeling was found more reliable for the Tungabhadra catchment in both extreme peak flow and low flow simulations whereas the model performance was slightly complex for the snowmelt-induced Satluj catchment, especially during extreme peak flow events. [ABSTRACT FROM AUTHOR]

During the long rainless spells of the dry season, flows in medium and small streams get reduced to what is generally known as "low flow". For ungauged streams, the controlling "low flows" are determined using the regional analysis method. In the presently described exploration, the method applied was based on the assumption that dry weather discharges in medium and small rivers depended on the hydrogeological conditions. The controlling effect of hydrogeology on the natural low flow in medium and small streams of the hilly and mountainous part of Serbia was analyzed applying the theory of multiple linear regression. The thirty-day minimum mean 80 and 95 per cent exceedance flows were taken for dependent variables, and quantified hydrogeological elements as independent variables. The analysis covered streams that had small or medium size catchment areas. The treated example encompassed sixty-one gauged catchments. The resulting regional relations for the thirty day minimum mean 80 and 95 per cent exceedance flows are presented in this paper. The quality of the established relation was controlled by relevant statistic tests.

The most true selection probability distribution is important to describe the low flow statistics for the studies related to drought analysis. The aim of this study is to derive appropriate probability distributions for frequency analysis of 7-day annual low flows at three gauging stations of the Çekerek Stream. The lowest 7-day flow series were constituted from daily flow data for 7-day periods of each year. A minimum 7-day flow is the lowest flow that occurred within a 7-consecutive day period. L-moment technique was used to predict the parameters of the selected distributions. Two goodness of fit indices, including MADI and MSDI, were used to compare the performances of the probability distributions for fitting. According to results, the best performance was obtained for generalized pareto GPA distribution. The distributions produced negative values were discarded. The predicted low flows obtained from the distributions that produced positive values except Log Pearson type three for empirical probability levels Gringorten formula sufficiently represent the actual low flows for probability levels higher than 75%. The statistics having reoccurrence interval of ten years Q7,10 based on GPA distribution were predicted as 0.29, 1.27 and 2.11 m3/s for gauging stations 1424, 1409 and 1404, respectively

An approach for regional low flow frequency analysis is to use multiple regression techniques for obtaining relationships between low flows with specific return periods and catchments characteristics. In this paper, this method has been used. After single-site frequency analysis for 20 stream gauging stations, homogeneity test was performed. Regional relationships between low flows with return periods 2 , 5 , 10, and 20 years and catchments characteristics were derived. For this purpose, catchment area, mean elevation, minimum elevation, shape factor, main channel length, length of main chanel from catchment centroid to outlet, forest area, mean annual rainfall, and mean catchment slope as model inputs were examined and cachment area, mean elevation, and mean catchment slope entered to the models. Finally, the mean relative error of models for different return period, 2, 5, 10, and 20 years, was computed 41.1, 41.3, 45.0, 47.2 percent, respectively that in comparison with other studies, it displays smaller errors.

Aim: To explore the aetiological factors, pathogenesis and management of priapism and highlight its peculiar features in Nigerians. Materials & Methods: A literature search was carried out using MEDLINE, these were reviewed in line with the aims for meaningful findings and case reports. Results: Priapism is currently classified into low flow (Ischaemic) and high flow (nonischaemic) priapism, with low flow being commoner, in all communities and in association with sickle cell disease. Hypoxia associated with low flow priapism is usually associated with varying degress of erectile dysfunction [ED]. High flow priapism is usually associated with trauma and is a non-ischaemic painless event. Low flow priapism also associated with drug treatment of erectile dysfunction, psychiatric disorders and malignant infiltration of the penis. Management ranges from conservative to a spectrum of surgical interventions. In Nigeria some patients, are noted to have developed priapism following ingestion of oral herbal aphrodisiacs. Conclusion: Priapism is an emergency with dire effects on erectile function when treatment is delayed. A clear understanding of the aetiological factors and pathogenesis is useful in aiding rapid diagnosis and treatment. Preventive strategies need to be established where possible.