Changes In Flow Regime Research Articles

Effects of Hydrology on Fish Diversity and Assemblage Structure in a Texan Coastal Plains River

AbstractHigh‐flow pulses affect river ecosystem dynamics in many important ways including by forming connections between the channel and oxbow lakes. This study assessed the influence of discharge on fish assemblage structure and diversity in the channel and oxbows of the Guadalupe River, Texas. Local assemblages of two oxbows and two channel sites were surveyed using standardized methods to test four hypotheses: (1) assemblage structure in oxbow lakes differs from those in the river channel, (2) α diversity decreases during extended periods of low discharge, (3) β diversity decreases during high discharge and increases during extended periods of low discharge, and (4) species turnover and assemblage nestedness decline during periods of high discharge. We found evidence to support the first three hypotheses. Unsurprisingly, lotic‐adapted fishes were observed more frequently in the river channel, whereas lentic‐adapted species generally were more common in the oxbow lakes. Species richness declined during periods of low discharge possibly due to harsher environmental conditions or stronger species interactions (e.g., predation). Discharge was inversely associated with both β diversity and species turnover, suggesting a stronger mass effect during high‐flow pulses, and stronger species sorting during low‐flow conditions. Contrary to our fourth hypothesis, assemblage nestedness increased during periods of high discharge. Finally, we also found evidence to support the hypothesis that species turnover decreased as discharge declined. The results of this study demonstrate the importance of flow pulses for maintaining fish diversity and assemblage structure in floodplain river systems. With additional research involving more sites and longer time series, it should be feasible to define and identify thresholds for flow regime changes that alter assemblage structure and species diversity.

Analyzing Changes in the Flow Regime of the Yangtze River Using the Eco-Flow Metrics and IHA Metrics

Changes in the flow regime of the Yangtze River were investigated using an efficient framework that combined the eco-flow metrics (ecosurplus and ecodeficit) and Indicators of Hydrologic Alteration (IHA) metrics. A distributed hydrological model was used to simulate the natural flow regime and quantitatively separate the impacts of reservoir operation and climate variation on flow regime changes. The results showed that the flow regime changed significantly between the pre-dam and post-dam periods in the main channel and major tributaries. Autumn streamflow significantly decreased in the main channel and in the tributaries of the upper Yangtze River, as a result of a precipitation decrease and reservoir water storage. The release of water from reservoirs to support flood regulation resulted in a significant increase in winter streamflow in the main channel and in the Minjiang, Wujiang, and Hanjiang tributaries. Reservoir operation and climate variation caused a significant reduction in low flow pulse duration in the middle reach of the Yangtze River. Reservoir operation also led to an increase in the frequency of low flow pulses, an increase in the frequency of flow variation and a decrease in the rate of rising flow in most of the tributaries. An earlier annual minimum flow date was detected in the middle and lower reaches of the Yangtze River due to reservoir operation. This study provides a methodology that can be implemented to assess flow regime changes caused by dam construction in other large catchments.

A Multi-GCM Assessment of the Climate Change Impact on the Hydrology and Hydropower Potential of a Semi-Arid Basin (A Case Study of the Dez Dam Basin, Iran)

In this paper, the impact of climate change on the climate and discharge of the Dez Dam Basin and the hydropower potential of two hydropower plants (Bakhtiari and Dez) is investigated based on the downscaled outputs of six GCMs (General Circulation Models) and three SRES (Special Report on Emission Scenarios) scenarios for the early, mid and late 21st century. Projections of all the scenarios and GCMs revealed a significant rise in temperature (up to 4.9 °C) and slight to moderate variation in precipitation (up to 18%). Outputs of the HBV hydrologic model, enforced by projected datasets, show a reduction of the annual flow by 33% under the climate change condition. Further, analyzing the induced changes in the inflow and hydropower generation potential of the Bakhtiari and Dez dams showed that both inflow and hydropower generation is significantly affected by climate change. For the Bakhtiari dam, this indicates a consistent reduction of inflow (up to 27%) and electricity generation (up to 32%). While, in the Dez dam case, the inflow is projected to decrease (up to 22%) and the corresponding hydropower is expected to slightly increase (up to 3%). This contrasting result for the Dez dam is assessed based on its reservoir and hydropower plant capacity, as well as other factors such as the timely releases to meet different demands and flow regime changes under climate change. The results show that the Bakhtiari reservoir and power plant will not meet the design-capacity outputs under the climate change condition as its large capacity cannot be fully utilized; while there is room for the further development of the Dez power plant. Comparing the results of the applied GCMs showed high discrepancies among the outputs of different models.

Affinity Law Modified to Predict the Pump Head Performance for Different Viscosities Using the Morrison Number

The goal of this study is to provide pump users a simple means to predict a pump's performance change due to changing fluid viscosity. During the initial investigation, it has been demonstrated that pump performance can be represented in terms of the head coefficient, flow coefficient, and rotational Reynolds number with the head coefficient data for all viscosities falling on the same curve when presented as a function of ф*Rew−a. Further evaluation of the pump using computational fluid dynamics (CFD) simulations for wider range of viscosities demonstrated that the value of a (Morrison number) changes as the rotational Reynolds number increases. There is a sharp change in Morrison number in the range of 104<Rew<3*104 indicating a possible flow regime change between laminar and turbulent flow. The experimental data from previously published literature were utilized to determine the variation in the Morrison number as the function of rotational Reynolds number and specific speed. The Morrison number obtained from the CFD study was utilized to predict the head performance for the pump with known design parameters and performance from published literature. The results agree well with experimental data. The method presented in this paper can be used to establish a procedure to predict any pump's performance for different viscosities; however, more data are required to completely build the Morrison number plot.

Flow regimes filter species traits of benthic diatom communities and modify the functional features of lowland streams - a nationwide scale study

Changes in land use, climate and flow diversion are key drivers of river flow regime change that may eventually affect freshwater biodiversity and ecosystem functions. However, our knowledge is limited on how the functional features of stream organisms vary along the gradient of hydrological disturbance (i.e. flow regime changes) and how flow regimes mediate the functional features in lowland streams. We analyzed the functional traits of benthic diatoms (unicellular siliceous algae) that are most sensitive and tolerant to flow regime changes along a nationwide scale of 246 sites in Denmark. We combined RLQ and fourth-corner analyses to explore the co-variation between hydrological variables (R table) and species traits (Q table), constrained by the relative abundance of each species (L table) as observed in each of the sampling sites. Further, we examine the relationships between functional features (i.e., functional redundancy and diversity) and hydrological variables by multivariate statistical analyses. Results show that species turnover with displacement of sensitive species by tolerant species was the dominating process in benthic diatom communities during high flow disturbances. Functional features, as indicated by functional diversity and redundancy indices, were mediated mainly by high and low flow magnitude. Median daily flow magnitude shows a consistent positive relationship with functional redundancy and richness indices indicating that larger streams are more resilient to flow perturbations. In addition flow regime changes are less important than median daily flow magnitude and show inconsistent correlation to functional features likely due to the interaction of multiple environmental stressors. Our study highlights the robustness of trait-based approaches for identifying flow regime changes in streams, and strongly suggests that biodiversity conservation and water resource management should focus on protecting natural base flow in headwater streams and generally reduce flow regulation for sustaining stream ecosystems under future global changes.

Development of an eco-geomorphic modeling framework to evaluate riparian ecosystem response to flow-regime changes

Tools that provide decision makers with an understanding of ecosystem response to changes in streamflow attributes are necessary to balance human and ecosystem water needs. Flow response curves provide one such approach for informing management based on modeled relationships between environmental control (e.g., flood magnitude) and response (e.g., plant recruitment) variables, although unidirectional relationships may fail to capture the complex interactions between ecological and physical processes in riparian ecosystems. We take advantage of the linkage between plant functional traits important for (a) determining a plant’s response to environmental conditions and (b) for predicting its impact on the flow of water and transport of sediment, to build a predictive model of riparian ecosystem dynamics. By using plant functional groups (i.e., guilds), our model accounts for process linkages among streamflow properties, physical processes, and plant community response. The model relies on a series of flow response curves built and tested with data collected along semiarid, canyon-bound rivers in Colorado. We built 2D hydrodynamic models and updated them with a flexible vegetation module to represent plant-hydraulic interactions for three study reaches. Plant guild distributions are well described by the model while predictions of the occurrence and direction of topographic change are less deterministic. Our work is among the first to develop response curves for both physical and ecological processes in the same framework. The shape of the resulting curves indicate that the functioning of riparian ecosystems is driven by nonlinear relationships and that clear, identifiable thresholds exist. As such, changes to the flow regime will have a differential impact on physical and ecological processes, depending on the nature of the shift. We discuss the strength and limitations of our model and make suggestions about its applicability to river management.

Cell-resolved blood flow simulations of saccular aneurysms: effects of pulsatility and aspect ratio.

We study the effect of pulsatile flow on the transport of red blood cells (RBCs) and platelets into aneurysm geometries with varying dome-to-neck aspect ratios (AR). We use a validated two-dimensional lattice Boltzmann model for blood plasma with a discrete element method for both RBCs and platelets coupled by the immersed boundary method. Flow velocities and vessel diameters were matched with measurements of cerebral perforating arteries and flow was driven by a synthetic heartbeat curve typical for such vessel sizes. We observe a flow regime change as the aspect ratio increases from a momentum-driven regime in the small aspect ratio to a shear-driven regime in the larger aspect ratios. In the small aspect ratio case, we see the development of a re-circulation zone that exhibits a layering of high (greater than or equal to 7 s) and low (less than 7 s) residence cells. In the shear-driven regime, we see high and low residence cells well mixed, with an increasing population of cells that are trapped inside the aneurysm as the aspect ratio increases. In all cases, we observe aneurysms that are platelet-rich and red blood cell-poor when compared with their respective parental vessel populations. Pulsatility also plays a role in the small aspect ratio as we observe a smaller population of older trapped cells along the aneurysm wall in the pulsatile case when compared with a steady flow case. Pulsatility does not have a significant effect in shear-driven regime aspect ratios.

Predicting the ecological impacts of large-dam removals on a river network based on habitat-network structure and flow regimes.

Large dams provide vital protection and services to humans. However, an increasing number of large dams worldwide are old and not operating properly. The removal of large dams has excellent potential to restore habitat connectivity and flow regimes; therefore, projecting the related ecological consequences is an emerging need for water resource and ecosystem management. However, no modeling methods are currently available for such projections at the basin scale. We devised a scheme that integrates changes in flow regimes and habitat network structure into a basin-scale impact assessment of removal of large dams and applied it to the Nagara-Ibi Basin, Japan. We used a graph-theoretical approach and a hydrological model, to quantify changes in habitat availability for 11 freshwater fishes at the basin scale under multiple removal scenarios. We compared these results with the change predicted using a conventional scheme that considered only changes to the habitat network due to dam removal. Our proposed scheme revealed that an increase in flow variability associated with dam removal projected both positive and negative effects on basin-scale habitat availability, depending on the focal species, endangered species had a negative response to dam removal. In contrast, the conventional approach projected only positive effects for all species. This difference in the outcomes indicates that large-dam removal can have negative and positive effects on watershed restoration due to changes in flow regimes. Our results also suggest the effect of removal of large dams may depend on the dams and their locations. Our study is the first step in projecting ecological trade-offs associated with the removal of large dams on riverscapes at the basin scale and provides a foundation for future process-based watershed restoration.

Feature-based intelligent system for steam simulation using computational fluid dynamics

In the development of products involving fluids, computational fluid dynamics (CFD) has been increasingly applied to investigate the flow associated with various product operating conditions or product designs. The batch simulation is usually conducted when CFD is heavily used, which is not able to respond to the changes in flow regime when the fluid domain changes. In order to overcome this defect, a rule-based intelligent CFD simulation system for steam simulation is proposed to analyze the specific product design and generate the corresponding robust simulation model with accurate results. The rules used in the system are based on physical knowledge and CFD best practices which make this system easy to be applied in other application scenarios by changing the relevant knowledge base. Fluid physics features and dynamic physics features are used to model the intelligent functions of the system. Incorporating CAE boundary features, the CFD analysis view is fulfilled, which maintains the information consistency in a multi-view feature modeling environment. The prototype software tool is developed by Python 3 with separated logics and settings. The effectiveness of the proposed system is proven by the case study of a disk-type gate valve and a pipe reducer in a piping system.

Forecasting effects of angler harvest and climate change on smallmouth bass abundance at the southern edge of their range.

Climate change will affect stream systems in numerous ways over the coming century. Globally, streams are expected to experience changes in temperature and flow regime. Previous work has indicated that these changes will likely affect fish distributions, but little work has been conducted examining population level effects of climate change on warmwater fish at the warmest portion of their range. We model several potential climate change-related stressors and the resulting effects on smallmouth bass Micropterus dolomieu populations in the Buffalo National River, Arkansas, USA, located near the southern extent of smallmouth bass range. Smallmouth bass are a popular recreational fish in the region and angler harvest likely contributes substantially to annual mortality. We created a simulation model parameterized with data collected from the Buffalo National River to evaluate the relative importance of climate stressors and angler harvest on smallmouth bass populations. Our simulations suggest that increases in springtime temperature and reductions in river discharge during the spawning period could increase recruitment, resulting in increases in adult abundance (8% higher). However, when increased flooding and drought probabilities are considered, our model indicates the Buffalo National River could experience large reductions in adult smallmouth bass abundance (≥50% decline) and increased probability of extinction compared to present levels. Simulations showed that harvest reduction could be a viable strategy to reduce the negative effects of climate change, but that even with complete closure of harvest, smallmouth bass population levels would still be well below present abundance (46% lower than present). Efforts to reduce flooding and drought effects related to climate change in the Buffalo National River could help offset the predicted reduction in the smallmouth bass population.

Linking fish-based biological indicators with hydrological dynamics in a Mediterranean river: Relevance for environmental flow regimes

The relationship between flow dynamics and biological communities becomes especially relevant in Mediterranean rivers. Given their natural variability and growing anthropogenic pressures, their low sections are subjected to multiple impacts. The definition of ecohydrological relationships in Mediterranean rivers may constitute a useful management tool. Historically, fishes were the first group used to assess community-level ecological quality, and different indices and metrics have been proposed. However, up to date many of these indicators have showed to be insensitive to flow regime changes or hydrological alteration. There is therefore a need to deepen into the ecohydrological relationships between such indicators and flow regimes in Mediterranean (and other) rivers. This study presents an analysis of the relationship between interannual flow regimes in the lower section of the Ebro River, defined using a set of daily and hourly hydrological indices, and ecological quality based on fish community, assessed through indices designed to fulfill the Water Framework Directive (WFD) in Europe: the Indices of Biotic Integrity in Catalan rivers (IBICAT2010 and IBICAT2b) and the new European Fish Index (EFI+). In order to identify spatiotemporal patterns, hydrological indices were computed using time periods of different amplitude and ecological quality was obtained in different transects along the river section, even within the same water units or ‘water masses’ (subdivisions of surface waters to fulfill the WFD in Spain). Our results showed that IBICAT2010 was the most correlated with hydrological indices, followed by IBICAT2b and EFI+. The latter showed an almost null correlation with hydrological indices, which may be due to issues associated with the sampling technique, the definition of transects and because it does not uses stream typologies. Correlations among some hydrological and biological indices were observed, with temporal and spatial patterns. On one hand, daily hydrological indices showed relationship with ecological quality when they were computed using between 9 and 36 months of flow records (previous to the sampling date) whereas subdaily indices responded better to periods between 3 and 9 months of records. On the other hand, some sampling transects showed clearer relationships than others, even within the same water mass, which suggests an influence of hydromorphological variability on the obtained ecological quality scores.

Changing environmental gradients over forty years alter ecomorphological variation in Guadalupe Bass Micropterus treculii throughout a river basin.

Understanding the degree of intraspecific variation within and among populations is a key aspect of predicting the capacity of a species to respond to anthropogenic disturbances. However, intraspecific variation is usually assessed at either limited temporal, but broad spatial scales or vice versa, which can make assessing changes in response to long‐term disturbances challenging. We evaluated the relationship between the longitudinal gradient of changing flow regimes and land use/land cover patterns since 1980 and morphological variation of Guadalupe Bass Micropterus treculii throughout the Colorado River Basin of central Texas. The Colorado River Basin in Texas has experienced major alterations to the hydrologic regime due to changing land‐ and water‐use patterns. Historical collections of Guadalupe Bass prior to rapid human‐induced change present the unique opportunity to study the response of populations to varying environmental conditions through space and time. Morphological differentiation of Guadalupe Bass associated with temporal changes in flow regimes and land use/land cover patterns suggests that they are exhibiting intraspecific trait variability, with contemporary individuals showing increased body depth, in response to environmental alteration through time (specifically related to an increase in herbaceous land cover, maximum flows, and the number of low pulses and high pulses). Additionally, individuals from tributaries with increased hydrologic alteration associated with urbanization or agricultural withdrawals tended to have a greater distance between the anal and caudal fin. These results reveal trait variation that may help to buffer populations under conditions of increased urbanization and sprawl, human population growth, and climate risk, all of which impose novel selective pressures, especially on endemic species like Guadalupe Bass. Our results contribute an understanding of the adaptability and capacity of an endemic population to respond to expected future changes based on demographic or climatic projection.

Effects of human-driven water stress on river ecosystems: a meta-analysis

Human appropriation of water resources may induce water stress in freshwater ecosystems when ecosystem needs are not met. Intensive abstraction and regulation cause river ecosystems to shift towards non-natural flow regimes, which might have implications for their water quality, biological structure and functioning. We performed a meta-analysis of published studies to assess the potential effects of water stress on nutrients, microcontaminants, biological communities (bacteria, algae, invertebrates and fish), and ecosystem functions (organic matter breakdown, gross primary production and respiration). Despite the different nature of the flow regime changes, our meta-analysis showed significant effects of human-driven water stress, such as significant increases in algal biomass and metabolism and reduced invertebrate richness, abundance and density and organic matter decomposition. Water stress also significantly decreased phosphate concentration and increased the concentration of pharmaceutical compounds. The magnitude of significant effects was dependent on climate, rainfall regime, period of the year, river size and type of water stress. Among the different causes of water stress, flow regulation by dams produced the strongest effects, followed by water abstraction and channelization.

Effects of a rectifier on the hydraulic stability of the draft tube

The effects of a rectifier on the hydraulic stability of the draft tube is explored with research based on a straight cone-shaped draft tube with constant sized diffusion, where the uninstalled rectifier and the installed rectifier in the straight cone section of the draft tube are simulated under different conditions of hydraulic stability. The internal pressure pulsating characteristics of the draft tube, the internal pressure and the output change of the runner, and the internal flow regime change of the draft tube are also analyzed. The results show that the pressure waveform of the draft tube is relatively stable when the rectifier is installed under the typical partial load condition, and the pressure fluctuation amplitude near the tube wall of draft tube is small, the peak value of the mixing peak is large and the frequency component is rich. The installation of a rectifier in the draft tube can guide and rectify the water flow, so that the flow regime of the rectifier inlet tends to be more stable, the differential pressure between the axis and the radial direction decreases, and the recirculation region and secondary flow inside the runner outlet and the straight cone section are reduced. In this way, the production of vortex belt can be inhibited, and the actual water flow and flow uniformity of the inlet cross section of turbine can be improved.

Cooling Water Sufficiency in a Warming World: Projection Using an Integrated Assessment Model and a Global Hydrological Model

Thermoelectric power plants in inland regions use primarily riverine water for cooling. The future availability of riverine water will be affected by climatic change. Power generation is expected to grow throughout the 21st century, accompanied by growth in cooling water demand. We estimated cooling water sufficiency globally under the Shared Socioeconomic Pathway 2 scenario with and without climate mitigation throughout the 21st century (2006–2099) at a spatial resolution of 0.5° × 0.5°. We used the Asia-Pacific Integrated Model Computable General Equilibrium Model (AIM/CGE) to project future thermoelectric cooling-water requirements in 17 global regions with no hydrological constraint on water availability, and the H08 global hydrological model to assess whether consumptive water requirements could be met under particular spatiotemporal and hydrological constraints. The results show that cooling water sufficiency will decrease by 7.9% and 11.4% in 2040–2069 (11.3% and 18.6% in 2070–2099) with and without climate mitigation, respectively. A distinct difference was found between with and without climate mitigation in the Middle East and Africa. The predicted insufficiency was attributable primarily to changes in river flow regimes, particularly a general decrease in low flow levels, and to increased water requirements for thermoelectric power generation and other sectors. The results imply that the growing water demand projected by AIM/CGE will not be fulfilled sustainably in many parts of the world, hence considerable additional efforts of reducing water consumption will be required to secure electric power supply. This confirms the importance of coupling integrated assessment models and global hydrological models for consistent water-energy nexus analyses.

New turbulence modeling for simulation of Direct Contact Condensation in two-phase pressurized thermal shock

Injection of Emergency Core Cooling System (ECCS) water into the primary loops of the Pressurized Water Reactors (PWRs) leads to rapid cooling of Reactor Pressure Vessel (RPV) inside wall after Loss Of Coolant Accident (LOCA). This condition, known as Pressurized Thermal Shock (PTS) intensifies the propagation of the RPV structural defects and would be considered as an ageing mechanism. For structural and fracture analysis of RPV wall, thermal-hydraulic analysis of PTS should be accomplished to obtain the steam/water flow characteristics in the downcomer. For this purpose, simulation of steam/water stratified flow (due to density difference) after the injection point should be done by Computational Fluid Dynamics (CFD) methods. In this region, steam condensation over water layer is considered as the only heat source and controlled by turbulence eddy motion near the steam/water interface. Based on Surface Renewal Theory (SRT), Heat Transfer Coefficient (HTC) would be calculated by evaluation of turbulence length and velocity. Therefore, prediction of turbulence characteristics plays a significant role for estimation of interfacial mass transfer and temperature profile. High gradient of velocity and Turbulence Kinetic Energy (TKE), and interfacial mass and momentum transfer at the steam/water interface needs some modifications for application of traditional turbulence models. Implementation of damping function is one of the common solutions to overcome the overestimation of TKE at the steam/water interface. Although, this function improves flow characteristics of smooth stratified flow, investigation of conservation equations and experimental data implies that the other source function is needed when the flow regime changes to wavy flow. In this paper, a new source function of TKE based on variations of turbulence characteristics is proposed for steam/water interface leading to a special boundary condition of turbulence. To investigate the effects of this modification, simulation of air/water and steam/water stratified flow in three different test facilities is performed. The results show that the implementation of the source function of TKE improves the prediction of turbulence characteristics at the interface of isothermal stratified flow. Also condensation rate and temperature gradient of steam/water stratified flow have a better agreement with experimental data.

Statistical Detection of Flow Regime Changes in Horizontal Hydraulically Fractured Bakken Oil Wells

The application of horizontal and hydraulically fractured wells for producing oil from low permeability formations has changed the face of the North American oil industry. One feature of the production profile of many such wells is a transition from transient linear oil flow to boundary-dominated flow. The identification of the time of this transition is important for the calibration of models that forecast the well’s future production and the expected ultimate recovery. It is preferable that such models generally use data from the boundary-dominated flow regime for parameter calibration. Accurate well production forecasts are needed for operational decisions, long-term planning, commercial transactions, regulatory proceedings, and asset valuation. Petroleum engineers frequently make the call on the transition point based on subjective visual interpretations of log–log plots for individual wells. This is time-consuming and is generally not repeatable by other analysts. This note evaluates statistical approaches that can serve as alternatives to the subjective visual interpretations. Specifically, the predictive performance of production models calibrated with boundary-dominated data based on transition dates calculated with constrained nonlinear least squares and Bayesian regressions was very close to that obtained using the visual method, suggesting that statistical approaches may indeed be constructed to replace less objective visual approaches without loss of accuracy.

Enhanced mass transfer from the installation of a sieve tray subject to the variation of liquid heights and flow regimes in a bubble column

This work addressed the gas–liquid (G/L) mass transfer limitation coming from the increasing liquid height and the circumvention of the limitation by introducing a sieve tray in a bubble column. Either monoethylene glycol (MEG) solution or n-hexane was adopted as a liquid phase and argon was used as a gas phase in the bubble column. The gas holdup and the mass transfer coefficient became lowered by the static liquid height increase due to the increase of bubble size. The loss of mass transfer was overcome by installing a sieve tray inside the column. The two sieve trays with different hole sizes were employed and both bubble diameter and standard deviation of pressure were investigated to understand the effect of the sieve tray on the mass transfer. With a smaller size hole sieve (1mm), the mass transfer deteriorated in both liquid systems (MEG and n-hexane) due to the formation of gas cap below the sieve while with a larger hole sieve (3mm), it was enhanced because of the reduction of bubble diameters without any gas cap formation. However, it was found that the sieve tray effect was weakened when the flow regime changes from homogeneous to heterogeneous.

Impacts of climate change on flow regime and sequential threats to riverine ecosystem in the source region of the Yellow River

Climate change is expected to have substantial impacts on flow regime in the Upper Yellow River (UYR) basin that is one of the most important biodiversity hotspots in the world. These impacts will most possibly exert negative effects on the habitat availability for riverine species. Thus, it is necessary to understand the alteration of river flow regime under climate scenarios. In this paper, we use the modified hydrological model HBV in conjunction with three general circulation models under three representative concentration pathways (RCP 2.6, 4.5, and 8.5) to address changes in flow regime under climate change for the UYR basin in the mid-term (2050s) and end-term (2080s) of the twenty-first century. Flow regime is quantified using the Indicators of hydrological alteration approach. Thereafter, the potential threats to riverine ecosystem in the UYR basin are identified based on the projected alterations of various flow characteristics and their ecological influences. The results showed that the magnitude of monthly flow would increase during the dry period. The date of the annual 1-day minimum streamflow will likely shift toward earlier time under different scenarios, and significant increases in magnitude of annual minimum flow of different durations were detected under both RCP 4.5 and 8.5 scenarios in the 2080s. In addition, assessments of the modification degree of the overall flow regime revealed that climate change would remarkably modify (medium level) the overall flow regime in the UYR basin, particularly by the end of the twenty-first century or under the high emission scenarios. Besides, destruction of habitat and reduced availability of food induced by substantially increased hydrological instability in the 2080s would make two endangered fishes more vulnerable in the UYR basin. These findings provide insights into potential adaptive countermeasures for water resource management and environmental system restoration in the Upper Yellow River.

Link Between the Dynamics of Granular Flows and the Generated Seismic Signal: Insights From Laboratory Experiments

Granular column collapse experiments have been conducted on a flat rough surface tilted at various angles with synchronous measurements of the flow dynamics and the emitted seismic signal. Our results show that the ratio of radiated seismic energy to potential energy lost by the granular flows decreases slightly from 0.033% to 0.017% with increasing slope angle on a poly(methyl methacrylate) (acrylic) plate. This is about 90 times lower than for the impact of a single particle of the same diameter. The experimental granular flows generated signals with frequencies lower than 20 kHz, with a mean value around 5 kHz, which are shown to be similar to the frequencies emitted by a single‐particle impact. The rise phase and maxima of the amplitude and frequencies of the seismic signals generated by our experimental granular flows are mostly controlled by flow motion in the direction normal to the slope, while their decay phase depends on downslope particle speeds. The granular flow regime changes from dense to more agitated flows above a critical slope angle that is about half the friction angle of the granular material. This change is reflected in (1) the shape of the temporal variation of the seismic amplitude and frequencies, with a decay phase lasting much longer and (2) the shape of the cumulative radiated seismic energy, which changes above the same critical slope angle. Implications of these results for the interpretation of seismic emissions from experimental and natural granular flows are discussed.