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An integrated modeling approach was used to connect socioeconomic factors and nutrient management to river export of nitrogen, phosphorus, silica and carbon based on an updated Global NEWS model. Past trends (1970–2000) and four future scenarios were analyzed. Differences among the scenarios for nutrient management in agriculture were a key factor affecting the magnitude and direction of change of future DIN river export. In contrast, connectivity and level of sewage treatment and P detergent use were more important for differences in DIP river export. Global particulate nutrient export was calculated to decrease for all scenarios, in part due to increases in dams for hydropower. Small changes in dissolved silica and dissolved organics were calculated for all scenarios at the global scale. Population changes were an important underlying factor for river export of all nutrients in all scenarios. Substantial regional differences were calculated for all nutrient elements and forms. South Asia alone accounted for over half of the global increase in DIN and DIP river export between 1970 and 2000 and in the subsequent 30 years under the Global Orchestration scenario (globally connected with reactive approach to environmental problems); DIN river export decreased in the Adapting Mosaic (globally connected with proactive approach) scenario by 2030, although DIP continued to increase. Risks for coastal eutrophication will likely continue to increase in many world regions for the foreseeable future due to both increases in magnitude and changes in nutrient ratios in river export.

Climate change impacts on water availability and hydrological extremes are major concerns as regards the Sustainable Development Goals. Impacts on hydrology are normally investigated as part of a modelling chain, in which climate projections from multiple climate models are used as inputs to multiple impact models, under different greenhouse gas emissions scenarios, which result in different amounts of global temperature rise. While the goal is generally to investigate the relevance of changes in climate for the water cycle, water resources or hydrological extremes, it is often the case that variations in other components of the model chain obscure the effect of climate scenario variation. This is particularly important when assessing the impacts of relatively lower magnitudes of global warming, such as those associated with the aspirational goals of the Paris Agreement. In our study, we use ANOVA (analyses of variance) to allocate and quantify the main sources of uncertainty in the hydrological impact modelling chain. In turn we determine the statistical significance of different sources of uncertainty. We achieve this by using a set of five climate models and up to 13 hydrological models, for nine large scale river basins across the globe, under four emissions scenarios. The impact variable we consider in our analysis is daily river discharge. We analyze overall water availability and flow regime, including seasonality, high flows and low flows. Scaling effects are investigated by separately looking at discharge generated by global and regional hydrological models respectively. Finally, we compare our results with other recently published studies. We find that small differences in global temperature rise associated with some emissions scenarios have mostly significant impacts on river discharge-however, climate model related uncertainty is so large that it obscures the sensitivity of the hydrological system.

This paper presents a new reconstruction of the 20th century global hydrography using fully coupled water balance and transport model in a flexible modeling framework. The modeling framework allows a high level of configurability both in terms of input forcings and model structure. Spatial and temporal trends in hydrological cycle components are assessed under \"pre-industrial\" conditions (without modern-day human activities) and contemporary conditions (incorporating the effects of irrigation and reservoir operations). The two sets of simulations allow the isolation of the trends arising from variations in the climate input driver alone and from human interventions. The sensitivity of the results to variations in input data was tested by using three global gridded datasets of precipitation. Our findings confirm that the expansion of irrigation and the construction of reservoirs has significantly and gradually impacted hydrological components in individual river basins. Variations in the volume of water entering the oceans annually, however, are governed primarily by variations in the climate signal alone with human activities playing a minor role. Globally, we do not find a significant trend in the terrestrial discharge over the last century. The largest impact of human intervention on the hydrological cycle arises from the operation of reservoirs that drastically changes the seasonal pattern of horizontal water transport in the river system and thereby directly and indirectly affects a number of processes such as ability to decompose organic matter or the cycling of nutrients in the river system.

The engineering of rivers by dams is a formative feature of human‐nature systems and the interconnectivity of water, energy, and the climate. Sufficient and broad‐based representations of dams in large‐scale hydrological models prove essential to mapping their extensive regulation of river flow and biogeochemistry and gauging climate‐linked provisions, including freshwater supply and hydropower. We present an integrated modeling framework to investigate future streamflow and hydropower generation in the Contiguous U.S. (1990–2075), leveraging an ensemble of six downscaled and bias‐corrected General Circulation Models (GCMs) from the high‐end SSP585 scenario of the CMIP6. To achieve this, we develop a reservoir operations and parameterization scheme for 1,384 dams in a high‐resolution river network, including simulated hydropower generation for 326 dams. For the GCM ensemble mean, we simulate a widespread increase in regulated streamflow into the late‐century (11% annual and 17% in winter for the dam median) with region‐specific changes in summer streamflow that feature prominent declines in the Northwest (−7%). Mediation by reservoirs is shown to dampen intra‐annual streamflow changes, delivering additional summer releases that partially mitigate declining flows. Total hydropower generation is projected to increase modestly (+3%), with boosted generation in the winter (+9%) and spring (+5%) offsetting declined summer generation (−3.4%), suggesting strong adaptation potential for hydropower in the future energy portfolio. Further analysis reveals that the choice of GCM, particularly in western regions, has significant bearing on projected streamflow and hydropower changes. Plain Language Summary Dams are a central feature of society's dependence and influence on the natural environment. Simulating the operations of reservoirs is an essential way to understand their impacts on rivers and to assess climate risks to important services like water supply and hydroelectricity. Our study develops a framework composed of multiple climate and hydrological simulation models to examine the impacts of climate change on future streamflow and hydropower in the U.S. We find that streamflow will largely increase in the future across most of the U.S., with dams helping to stabilize the intensity of winter increases and summer declines in streamflow. The nation's hydropower fleet benefits from runoff and streamflow increases in the winter and spring, which more than make up for falling summer generation, suggesting that hydropower can continue to be a reliable renewable energy source by adapting to future climate conditions. Conclusions regarding future streamflow and hydropower generation depend strongly on the climate model driving the future simulations, especially in western regions. Key Points The majority of U.S. dams project increased streamflow into the late century, leading to a moderate rise in total hydropower generation Climate‐driven shifts in seasonal hydrology yield gains in winter and spring hydropower, losses in summer, signaling adaptation potential General Circulation Model uncertainty is inherent in projections, notably for Western U.S., creating diverse regional outcomes for water and hydropower planning

Simulations of soil water and evapotranspiration with physically based models at broad scales vary in both complexity of processes modeled and in parameterization of soil and root properties. Sensitivity of annual evaporationE annto some of these processes and parameters was tested with both a model allowing multiple soil layers (BROOK90) and a single-layered water balance model (WBM). For nine widely scattered locations in North AmericaE annwas controlled primarily by climate and cover type, but within a location–type combination,E annwas controlled primarily by the available water capacityW ac, which is the product of available water fraction and effective root depth. The definition of the upper limit of available water is important; it is precisely defined here as the water volume fraction at 30-cm depth after 48 h of drainage from an initially saturated, homogeneous profile with a fixed gravity potential gradient at 2-m depth. Specification of root depth was as important as specification of available water fraction in determiningW ac. In climates of intermediate wetness a 100-mm change inW accaused a similar change inE annat lowW ac, but little change inE annat highW ac. WBM responded similarly to BROOK90. In BROOK90, texture-dependent hydraulic properties caused additional effects of less than ±50 mm inE annfor short covers and even less for tall covers. Effective root depth interacted with both distribution of infiltration and upward movement of water in the soil profile, but the effects were also on the order of only 50 mm. A multilayered model does not seem necessary for simulatingE annat the global scale if the primary objective is budget closure. Improvement in estimatingE annwith WBM or similar global water budget models is not likely to result from making the model more complicated with respect to soil and root properties in the context of much larger uncertainties in atmospheric forcings.

The theoretical investigation of wakefield acceleration of electrons by CO2-laser pulse with central wavelength of 10.6 μm and input peak intensity of ∼1017 W/cm2 in transient hydrogen-plasma waveguide has been conducted. The plasma waveguide is produced by the fast Z-pinch discharge inside a 3 mm inner diameter and 50 mm long capillary. The waveguide properties of the capillary Z-pinch plasma were obtained from the space and frequency dependent wave equation that combines the attenuated charged particle inertia and the light wave effects in the plasma for the ideal Gaussian laser beam. For simulation of temporal and spatial evolution of electron density and other plasma variables during the capillary discharge, we used a standard one-fluid, two-temperature one-dimensional magnetohydrodynamic (MHD) model complemented with atomic data of hydrogen. Simulations showed that the guiding channel occurs far from capillary wall and exists for a few nanoseconds. In terms of laser driven plasma wakefield accelerators (LWFA), the Z-pinch waveguide is able to extend the acceleration length over the whole capillary, assuming that a single-mode transmission takes place. To quantify such ability of the channel, a correlation coefficient was introduced and computed at different input beam spot sizes. An optimal beam spot size was determined by taking maximum of time average of the coefficient over the channel lifetime. At the end of the guiding channel existence, the repetitive focusing and defocusing patterns were observed with intensity increase at the focal points. For simulation of the wakefield acceleration of electrons in the different waveguiding regimes we used the particle-in-cell (PIC) combined with the aforementioned MHD model. Influence of the waveguiding regimes on the electron acceleration was demonstrated.

Despite the recognized importance of reservoirs and dams, global datasets describing their characteristics and geographical distribution are largely incomplete. To enable advanced assessments of the role and effects of dams within the global river network and to support strategies for mitigating ecohydrological and socioeconomic costs, we introduce here the spatially explicit and hydrologically linked Global Reservoir and Dam database (GRanD). As of early 2011, GRanD contains information regarding 6862 dams and their associated reservoirs, with a total storage capacity of 6197 km 3 . On the basis of these records, we estimate that about 16.7 million reservoirs larger than 0.01 ha - with a combined storage capacity of approximately 8070 km 3 - may exist worldwide, increasing Earth's terrestrial surface water area by more than 305 000 km 2 . We find that 575 900 river kilometers, or 7.6%% of the world's rivers with average flows above 1 cubic meter per second (m 3 s −1 ), are affected by a cumulative upstream reservoir capacity that exceeds 2%% of their annual flow; the impact is highest for large rivers with average flows above 1000 m 3 s −1 , of which 46.7%% are affected. Finally, a sensitivity analysis suggests that smaller reservoirs have substantial impacts on the spatial extent of flow alterations despite their minor role in total reservoir capacity.

Background The method of estimating distance traveled by the pulse wave, used in the calculation of pulse wave velocity (PWV), is not standardized. Our objective was to assess whether different methods of distance measurement influenced the association of PWV to cardiovascular mortality in hemodialysis (HD) patients. Methods Ninety-eight chronic HD patients had their PWV measured usingthree methods for distance estimation; PWV1: suprasternal notch-tofemoral site minus suprasternal notch-to-carotid site, PWV2: carotidto- femoral site, PWV3: carotid-to-femoral site minus suprasternal notch-to-carotid site. Carotid-to-femoral distance was used to approximate torso length. Patients were followed for a median of 30 months and the association of PWV and cardiovascular mortality was assessed using survival analysis before and after stratification for torso length. Results The three methods resulted in significantly different PWV values. During follow-up 50 patients died, 32 of cardiovascular causes. In log-rank tests, only tertiles of PWV1 was significantly related to outcome (P values 0.017, 0.257, 0.137, for PWV1, PWV2, and PWV3, respectively). In adjusted Cox, proportional hazards regression only PWV1 was related to cardiovascular mortality. In stratified analysis, however, among patients with below median torso length all PWV values were related to outcome, whereas in patients with above median torso length none of the PWV methods resulted in significant relationship to outcome. Conclusions PWV calculated using suprasternal notch-to-femoral distance minus suprasternal notch-to-carotid distance provides the strongest relationship to cardiovascular mortality. Longer torso weakens the predictive value of PWV, possibly due to more tortuosity of the aorta hence, more error introduced when using surface tape measurements. American Journal of Hypertension, advance online publication 4 November 2010 doi:10.1038/ajh.2010.220

In this study we analyze the scope and potential impact of reservoir construction on the world's river systems. Water storage behind the global population of large dams represents a 700% increase in the standing stock of natural river water, with residence times for individual impoundments spanning less than one day to several years. The imprint of such storage persists downstream. The mouths of several large rivers show a reservoir-induced aging of continental runoff that exceeds three months. Globally, the mean age of river water has likely tripled to well over one month. From both case studies and global synthesis, we find that this aging can lead to significant changes in net water balance, flow regime, reoxygenation of surface waters, and sediment transport. The pandemic construction of large reservoirs represents an important component of the terrestrial water cycle and one that merits due consideration in future global change studies.

Vascular calcification and hemodynamical abnormalities lead to reduced arterial elasticity in end stage renal disease. Fibroblast growth factor-23 (FGF23) predicts cardiovascular mortality in advance stages of renal failure possibly indicating more advanced vascular calcification. The relation of FGF23 to arterial stiffness in chronic kidney disease is currently under investigations. The aim of our cross sectional study was to assess the potential associations between FGF23 and arterial distensibility. FGF23 (ELISA), pulse wave velocity (PWV), augmentation index (AI) and central pulse pressure (CPP) (PulsePen), were measured in patients with different stages of renal insufficiency (n = 103, 64.8±13.3 years, 50 males, eGFR 40±21 mL/min/1.73m 2 ). Univariate and multiple linear regression models were used for the statistical analysis. According to our results, logFGF23 showed significant relation with serum phosphate, PTH levels and renal function. There were no significant correlations between FGF23 and PWV or CPP. AI, however, correlated negatively with logFGF23 (r = -0.24, p<0.05). By multiple regressions, serum phosphate, logFGF23, systolic blood pressure and heart rate proved to be the individual predictors of AI. (R 2 = 0.31, ß = 0.31, -0.33, 0.21, -0.27, p<0.05). In the subgroup of patients with <45 mL/min/1.73m 2 eGFR, serum phosphate and logFGF23 remained the significant predictors (R 2 0.21, ß = 0.31, -0.39, p<0.05) FGF23 may be a determinant of peripheral arterial elasticity independently of serum phosphate level especially in advanced stages of chronic kidney disease. (Supported by the Hungarian Kidney Foundation and the Hungarian Society of Hypertension)