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Plastic pollution in aquatic environments is a growing concern, with rivers recognized as major pathways. However, rivers themselves are also subject to pollution. Hence, understanding riverine plastic transport dynamics is essential for mitigating environmental impacts. Although plastic-related research focus has shifted from marine environments towards rivers, challenges remain in standardizing methods for monitoring and integrating spatiotemporal variabilities of riverine plastic occurrence into flux determination. This study addresses these challenges by adopting established methods from sediment research. Utilizing data from a net-based cross-sectional multi-point approach, it examines spatio-temporal and discharge-dependent variations. It comprehensively analyzes the complex dynamics of plastic transport in the Danube River, contrasting an impounded section near Aschach, Austria, with a free-flowing reach near Hainburg, Austria. The paper emphasizes the significance of applying these methodologies for accurate flux determination and underscores the risks of neglecting them. By incorporating average microplastic particle weights, we aim to overcome limitations in prior methodologies that solely emphasize qualitative aspects or rely on item numbers. Spatial distribution analysis revealed a pronounced stratification at low flow and a more variable distribution in the free-flowing section, attributed to higher turbulence. As discharge increased, vertical mixing occurred, along with distinct lateral patterns displaying increased concentrations toward the riverbanks. Encountering plastic particles throughout the river profile underscores their properties of both suspended and floating matter, emphasizing the importance of hydro-morphology and multi-point cross-sectional measurement approaches. Microplastic loads were calculated to be <6.9 t a-1 in Aschach and <17.1 t a-1 in Hainburg, compared to total plastic loads of <14.3 t a-1 in Aschach and <41.6 t a-1 in Hainburg. Consequently, plastic loads were doubled to tripled within the Austrian section of the Danube River. The study contributes valuable insights into the complex nature of plastic transport in river systems, emphasizing comprehensive spatial, temporal and discharge-dependent assessments for characterizing and managing plastic pollution. It suggests that rivers can function as sources, pathways and sinks of plastic pollution, contingent upon hydro-morphological conditions. This underscores the need for longitudinal, basin-wide assessments to accurately understand plastic transport dynamics. [ABSTRACT FROM AUTHOR]

Plastic pollution in aquatic environments is a growing concern, with rivers recognized as major pathways. However, rivers themselves are also subject to pollution. Hence, understanding riverine plastic transport dynamics is essential for mitigating environmental impacts. Although plastic-related research focus has shifted from marine environments towards rivers, challenges remain in standardizing methods for monitoring and integrating spatio-temporal variabilities of riverine plastic occurrence into flux determination. This study addresses these challenges by adopting established methods from sediment research. Utilizing data from a net-based cross-sectional multi-point approach, it examines spatio-temporal and discharge-dependent variations. It comprehensively analyzes the complex dynamics of plastic transport in the Danube River, contrasting an impounded section near Aschach, Austria, with a free-flowing reach near Hainburg, Austria. The paper emphasizes the significance of applying these methodologies for accurate flux determination and underscores the risks of neglecting them. By incorporating average microplastic particle weights, we aim to overcome limitations in prior methodologies that solely emphasize qualitative aspects or rely on item numbers. Spatial distribution analysis revealed a pronounced stratification at low flow and a more variable distribution in the free-flowing section, attributed to higher turbulence. As discharge increased, vertical mixing occurred, along with distinct lateral patterns displaying increased concentrations toward the riverbanks. Encountering plastic particles throughout the river profile underscores their properties of both suspended and floating matter, emphasizing the importance of hydro-morphology and multi-point cross-sectional measurement approaches. Microplastic loads were calculated to be

The Narva River has its source in Lake Peipsi and flows into the Gulf of Finland [...]

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Water quality indices use biological, chemical, and physical data and information to classify the condition of surface waters, ultimately contributing to their management. We used multicollinearity and principal components analyses to develop the Revised Iranian Water Quality Index (RIWQI) as an indicator of agricultural and urban effects in the Karun River Basin of southwestern Iran. Seasonal sampling and analysis of water quality parameters from 54 sites across 18 rivers of the Karun River Basin include fecal coliform, total dissolved solid, phosphate, biological and chemical oxygen demand, nitrate, dissolved oxygen saturation, turbidity, pH, and water temperature. This study updates the previous version of Iranian Water Quality Index (IWQI) by differentially weighting individual variables, refining the main sub-indices, adding phosphate (PO4−), biological oxygen demand (BOD), chemical oxygen demand (COD), and temperature (T), and improving the aggregation calculation. Sensitivity testing of the RIWQI resulted in a mean value for discrimination efficiency (DE) > 85.6%, the highest of other indices calculated with the same dataset. [ABSTRACT FROM AUTHOR]

Recent advances in instruments are transforming our capabilities to better understand, monitor, and model river systems. The present paper illustrates such capabilities by providing new insights into unsteady flows captured with a Horizontal Acoustic Current Profiler (HADCP) integrated at an operational index-velocity gaging station. The illustrations demonstrate that the high-resolution stage and velocity measurements directly acquired during flood wave propagation reveal the intricate interplay among flow variables that are essential for better supporting judicious decision making for river management, flooding, sediment transport, and stream ecology. The paper confirms that the index-velocity method better captures the unsteady flow dynamics in comparison with the stage-discharge monitoring approach. At a time when the intensity and frequency of floods is continuously increasing, a better understanding of the critical features of flood waves during extreme events and the possibility of capturing more accurately their dynamics in real time is of special socio-economic significance. [ABSTRACT FROM AUTHOR]

Discharge monitoring stations are often costly and difficult to install, operate, and maintain, especially in small streams. The purpose of this study was to evaluate a low-cost method for remotely monitoring streamflow in small-scale watersheds to provide continuous discharge measurements across multiple sites and flow conditions. Within the Upper Poteau River Watershed (UPRW) in Arkansas, 12 sites were selected at bridge crossings near the outflow of HUC-12 or HUC-14 subwatersheds. A HOBO water level logger was deployed at each site to obtain continuous stage records, and HOBO barometric pressure transducers were installed within 16 km of each sample site to account for fluctuations in atmospheric pressure. SonTek-IQ acoustic Doppler instruments were deployed to measure discharge during high-flow events, and roving discharge monitoring stations were installed at each site to allow easy rotation of the SonTek-IQ instruments among sites between flood events. Once the roving discharge monitoring stations were installed at each site, one or more SonTek-IQ instruments could be rotated among sites to capture high-flow discharge measurements; therefore, a Son-Tek-IQ instrument was not required for every site of interest. The high-flow data captured during SonTek-IQ deployment, and baseflow discharge measurements collected on a monthly basis, were used to develop rating curves with a combination of simple linear regression, LOESS regression, and Manning's equation. The rating curves well represented the measured flows, with Nash-Sutcliffe efficiencies ranging between 0.87 and 0.98. This method provides an opportunity to collect continuous records of flow across multiple, remote, small-scale watersheds, and in conjunction with constituent concentrations and load estimations, can be used to calibrate and validate watershed models. [ABSTRACT FROM AUTHOR]

The power‐law rating curve has been used extensively in hydraulic practice and hydrology. It is given by Q(h)=a(h−c)b, where Q is discharge, h is water elevation, a, b, and c are unknown parameters. We propose a novel extension of the power‐law rating curve, referred to as the generalized power‐law rating curve. It is constructed by linking the physics of open channel flow to a model of the form Q(h)=a(h−c)f(h). The function f(h) is referred to as the power‐law exponent and it depends on the water elevation. The proposed model and the power‐law model are fitted within the framework of Bayesian hierarchical models. By exploring the properties of the proposed rating curve and its power‐law exponent, we find that cross‐sectional shapes that are likely to be found in nature are such that the power‐law exponent f(h) will usually be in the interval [1.0,2.67]. This fact is utilized for the construction of prior densities for the model parameters. An efficient Markov chain Monte Carlo sampling scheme, that utilizes the lognormal distributional assumption at the data level and Gaussian assumption at the latent level, is proposed for the two models. The two statistical models were applied to four datasets. In the case of three datasets the generalized power‐law rating curve gave a better fit than the power‐law rating curve while in the fourth case the two models fitted equally well and the generalized power‐law rating curve mimicked the power‐law rating curve. We developed an R package, bdrc, for fitting the power‐law and generalized power‐law rating curve models. It is available on CRAN. [ABSTRACT FROM AUTHOR]

This document discusses the challenges of estimating water discharge in the Narva River, which flows through Estonia and Russia. The two countries use different techniques for discharge estimation, leading to data inconsistencies when reporting to the Helsinki Commission. Additionally, the river's unique "backwater effect" further complicates the accuracy of discharge calculations. The NARVAWATMAN project, funded by the European Union, aimed to analyze existing techniques, conduct field measurements, and provide recommendations for harmonized discharge estimation in the future. [Extracted from the article]

A timely and cost-effective method of creating inundation maps could assist first responders in allocating resources and personnel in the event of a flood or in preparation of a future disaster. The Height Above Nearest Drainage (HAND) model could be implemented into an on-the-fly flood mapping application for a Canada-wide service. The HAND model requires water level (m) data inputs while many sources of hydrological data in Canada only provide discharge (m3/sec) data. Synthetic rating curves (SRCs), created using river geometry/characteristics and the Manning's formula, could be utilized to provide an approximate water level given a discharge input. A challenge with creating SRCs includes representing how multiple different land covers will slow impact flow due to texture and bulky features (i.e., smooth asphalt versus rocky river channel); this relates to the roughness coefficient (n). In our study, two methods of representing multiple n values were experimented with (a weighted method and a minimum-median method) and were compared to using a fixed n method. A custom ArcGIS tool, Canadian Estimator of Ratings Curves using HAND and Discharge (CERC-HAND-D), was developed to create SRCs using all three methods. Control data were sourced from gauge stations across Canada in the form of rating curves. Results indicate that in areas with medium to medium–high river gradients (S > 0.002 m/m) or with river reaches under 5 km, the CERC-HAND-D tool creates more accurate SRCs (NRMSE = 3.7–8.8%, Percent Bias = −7.8%—9.4%), with the minimum-median method being the preferred n method. [ABSTRACT FROM AUTHOR]

Understanding suspended sediment dynamics and their driving factors is essential for effective watershed management. In this study, the spatiotemporal patterns of suspended sediment were identified for 11 sub‐watersheds of the Goodwin Creek, Mississippi, USA, for the period 1982–2002 using wavelet transforms. The continuous wavelet transform (CWT) results of streamflow time series showed that a near‐continuous annual periodicity influenced all stations over the study period, yet an overall decline occurred in wavelet spectral power of sediment load during the 1990s. This decline in sediment load is a result of the indirect effect of decreased cultivation on reducing the rate of peak flow and thus fluvial erosion processes. The CWTs of fine sediment (clays and silts) concentration (FSC) time series showed that factors other than land‐use (e.g., ponds, ephemeral gullies, and bed composition) better explain the variations in FSC. A comparison of CWTs of FSC at two stations with different bed composition in their channels showed that sandy channels are less responsive to erosion control measures compared to gravely channels indicating that they are major sources of sediment. A change in phase relationship between flow and FSC for the gravel‐dominated channel was associated with the transition in upland land‐use indicating a change in sediment supply mechanisms. The CWTs of sand concentrations reflected the spatiotemporal impact of bank materials, the growth cycle of riparian vegetation, and in‐channel sand availability on sand dynamics. While CWT‐based analysis is sensitive to input conditions, the method is able to provide valuable outcomes for distinguishing patterns in complex temporal datasets. Key Points: An overall decline in fine sediment load occurred across all time scales during the period of land‐use change and in‐channel stabilizationStreambed composition and the locations of ponds and upland sediment sources explain the spatiotemporal patterns of suspended finesThe spatiotemporal patterns of sand dynamics reflect both the state of channel stability and the availability of in‐channel sand [ABSTRACT FROM AUTHOR]

Elevated turbidity (Tn) and suspended sediment concentrations (SSC) during and following flood events can degrade water supply quality and aquatic ecosystem integrity. Streams draining glacially conditioned mountainous terrain, such as those in the Catskill Mountains of New York State, are particularly susceptible to high levels of Tn and SSC sourced from erosional contact with glacial‐related sediment. This study forwards a novel approach to evaluate the effectiveness of stream restoration best management practices (BMPs) meant to reduce stream Tn and SSC, and demonstrates the approach within the Stony Clove sub‐basin of the Catskills, a water supply source for New York City. The proposed approach is designed to isolate BMP effects from natural trends in Tn and SSC caused by trends in discharge and shifts in average Tn or SSC per unit discharge (Q) following large flood events. We develop Dynamic Linear Models (DLMs) to quantify how Tn‐Q and SSC‐Q relationships change over time at monitoring stations upstream and downstream of BMPs within the Stony Clove and in three other sub‐basins without BMPs, providing observational evidence of BMP effectiveness. A process‐based model, the River Erosion Model, is then developed to simulate natural, hydrology‐driven SSC‐Q dynamics in the Stony Clove sub‐basin (absent of BMP effects). We use DLMs to compare the modelled and observed SSC‐Q dynamics and isolate the influence of the BMPs. Results suggest that observed reductions in SSC and Tn in the Stony Clove sub‐basin have been driven by a combination of declining streamflow and the installed BMPs, confirming the utility of the BMPs for the monitored hydrologic conditions. [ABSTRACT FROM AUTHOR]

The Logan River watershed, located in Northern Utah, USA, consists of a relatively pristine, mountainous area that drains to a lower elevation, valley area influenced by both urban development and agriculture. The Logan River Observatory has been collecting aquatic (streamflow and water quality) and climate data throughout the Logan River watershed since 2014. While streamflow measurements are commonly made at the outlets of research watersheds, the Logan River watershed consists of diverse hydrologic, topographic, and geologic settings that require a detailed understanding of streamflow variability over time at many locations. Here, we illustrate: (a) the importance of collecting streamflow time series throughout complex watersheds, and (b) how simple flow balances can provide much needed hydrologic insight into the locations and timing of gains and losses over reaches to guide future investigations. [ABSTRACT FROM AUTHOR]

Variation in fluvial suspended sediment-discharge behavior is generally thought to be the product of changes in processes governing the delivery of sediment and water to the channel. The objective of this study was to infer sediment supply dynamics from the response of suspended sediment behavior to antecedent hydrologic factors. The Salinas River (California) is seasonally active, moderately sized, and potentially susceptible to lasting impacts of hydrologic event history because of aridity, high discharge variability, and in-channel terminating flows. Forty-five years of suspended sediment data from the lower Salinas and 80. years of hydrologic data were used to construct hydrologic descriptors of basin preconditioning and to test the effects of these preconditions on suspended sediment behavior. Hydrologic precondition factors - including change in mean daily discharge and increasing elapsed time since the last moderate discharge event (~. 10-20 times mean discharge (Qmean)) - were found to have significant positive effects on discharge-corrected, fine suspended-sediment concentrations. Conversely, increased elapsed time since the last low discharge event (~. 0.1-0.4 times Qmean), and the sum of low flow conditions over interannual time scales were found to cause significant negative trends in fine suspended sediment concentration residuals. Suspended sand concentrations are suppressed by increased elapsed time after threshold discharges of ~. 0.1-2 and 5-100 times Qmean, and increased low to no flow days over time scales from 1 to 2000. days. Current and previous year water yield and precipitation magnitudes correlate positively with sand concentration. Addition of fine sediment from lower Salinas hillslope or channel sources on the rising limb of the hydrograph is the major mechanism behind an overall positive hysteretic pattern, which was forensically supported by the annual occurrence of in-channel suspended sediment deposition by early season, channel terminating flows and by the flushing function of moderate hydrologic events found in this study. The importance of hillslope and/or channel fine sediment contributions proximal to the lower Salinas are further highlighted by the lack of control exerted by upper subbasin water provenance on fine suspended sediment concentration, while sand behavior is differentiated by upper basin water provenance. Investigation of suspension of bed-sized sediment showed that the channel bed could exert significant effects on fine and sand-sized suspended sediment dynamics, but this mediation for fine sediment was most likely small in terms of decadal-scale sediment budgets. The magnitude of the effects of hydrologic variables on sediment dynamics remains uncertain, but the factors identified here may play a significant role in water quality, if not long-term sediment flux to the ocean. © 2014 Elsevier B.V.

The importance of discharge measurements is fully acknowledged in many research fields, mostly in hydrology. Numerous measurement devices and various overflow structures have been proposed for discharge measurements; however, their use is based on calibrated simple stage discharge relationships that may cause significant errors when unsteady flow conditions occur. This issue is quite common because of rainfall and runoff temporal variability that inhibits the achievement of the steady state. Although this issue has already been experimentally investigated, it seems that a physically based line of approach has not been attempted before. In this paper, unsteady stage discharge relationships on a theoretical basis are derived for the most common shapes of weirs. According to previous experimental investigations, a transposition of the simple (steady-state) rating curve occurs, with higher input discharges than those under steady state, when the water level rises, and with lower input discharges, when the water level falls. The corresponding time to equilibrium is also studied and two different applications are performed. Finally, when the outflow process is unsteady, an error analysis quantitatively shows that using simple rating curves may determine high errors in discharge measurements, which decrease more and more at the attaining of the steady state, where no transposition of the rating curve occurs. Triangular weirs result more sensitive to the unsteadiness than rectangular weirs, which in turn result more sensitive than the sharp crested orifices. The suggested procedure could be relevant to improve the accuracy in the discharge estimate, as it could be demonstrated by comparing the discharges derived by the proposed procedure and the ones provided by the application of hydrodynamic and rainfall-runoff models. [ABSTRACT FROM AUTHOR]

Abstract Design, operation and management of water resource projects are influenced by the amount of discharge passing through the stream. Discharge at the gauging site is generally estimated by developing single-valued simple rating curves. However, in case of unsteady flows, hysteresis affect is introduced in the stage discharge relationship and as such single-valued rating curves are no longer valid for such situations. The present paper presents a simple spreadsheet-based optimization approach for modelling the hysteresis-affected discharge rating curves. Generalized reduced gradient (GRG) technique has been reported as a reliable tool for handling optimization problems; therefore, in the present paper, it has been applied to estimate discharge for two sites with hysteresis affect based on Jones formula. Comparison of results shows that discharge estimated by GRG technique is as efficient as genetic algorithm and the goodness-of-fit criteria shows that the rating curves obtained by using Jones formula fit the observed data better than single-valued simple rating curves for both the sites considered in the present study. Application of spreadsheet-based GRG optimization technique could prove very helpful to the hydrometric offices.

ABSTRACT Calibration process is usually time demanding and as much streamflow information as possible in rainfall-runoff models. Nevertheless, from a practical point of view, the available information is measurement of water level, which is essential to design rating curves. This manuscript proposes a set of joint calibration of hydrological model parameters with a range of rating curves, developed for the main channel of the catchment in a crowded urban area. As an alternative of free calibration, the simulations were carried out based on a list of proficient parameters. Four streamflow gauging stations were analysed and used to subdivide the basin. The hourly lumped rainfall-runoff model GR4H was applied to four critical flash flood events to create a rank of Nash-Sutcliffe efficiency criteria (NSE) applying the best set of parameters. The results indicated that the hydrological model errors were compensated by hydraulics errors and they presented an equifinality in the process.

Abstract Long term and high resolution data on water discharge, suspended particulate matter (SPM) and contaminant concentrations in rivers are required for a better understanding of particulate transfers from the continental areas to the seas. The aim of this study was to provide a novel estimation of annual fluxes of SPM and related pollutants in the Rhône River from Lake Geneva to the Mediterranean Sea by combining high frequency or time-integrative monitoring and novel relations between SPM concentration (Cs) and water discharge (Q). At six stations of the Rhône Sediment Observatory (OSR), SPM fluxes were calculated over the 2000–2016 period by combining observational data and Cs - Q relations. Monthly average concentrations of mercury (Hg) and PCB 180 were obtained by analysis of SPM samples collected in time integrative particle traps between 2011 and 2016. These pollutants were selected because of the well documented contamination of the Rhône watershed by these substances. Inter-annual fluxes at the Rhône River outlet averaged 6.6 Mt. yr−1 for SPM, 572 kg yr−1 for Hg and 14 kg yr−1 for PCB 180. The Isère and Durance tributaries were found to be the main contributors of SPM fluxes. Annual SPM budgets were not balanced, suggesting deposition, remobilization of bottom sediments and/or contributions from non-monitored tributaries. The SPM sampled at the outlet was more contaminated than the combined SPM inputs from the monitored tributaries, suggesting that intermediate sources of contamination were not captured in the budget. Graphical abstract Unlabelled Image Highlights • Original methodology for annual river flux calculation with continuous monitoring • Assessment of two-segment Cs-Q relations for the Rhône River and its tributaries • New estimations of annual SPM, Hg and PCB 180 fluxes and budget • SPM at outlet more contaminated than SPM inputs from monitored tributaries [ABSTRACT FROM AUTHOR]

Highlights • Assessed the performance of rating curve methods at a non-ideal gauging station. • Stage-discharge rating curve method is more reliable for monitoring steady flows. • Index-velocity rating improves the accuracy of monitoring unsteady flows. • Event-based sampling protocols enable the capture of unsteady flow propagation. • Accounting for dynamic effects and flow features is required for improved accuracy. Abstract The paper presents various aspects of monitoring streamflows with stage-discharge (HQRC) and index-velocity (IVRC) based ratings at a non-ideal gaging station with emphasis on their reliance during fast-varying unsteady flows. For this purpose, the paper analyzes data obtained from customized experiments whereby the flow phases are tracked as they develop during flow transitions. The analysis compares discharges obtained from HQRC and IVRC ratings with those directly measured with Acoustic Doppler Current Profilers (ADCP) and a flowmeter set in the housing of the turbines that release the flow in the downstream channel. It is found that during steady flows, both HQRC and IVRC methods perform within the widely accepted ±5% thresholds recommended for streamflow gaging despite that the site considerably deviates from the guidelines for gaging site selection. For unsteady flows, the performance of the IVRC is considerably better than HQRC. Attempts are made to complement the typical statistical analysis used for assessing the quality of discharge estimates provided by the ratings with insights into flow characteristics that deteriorate the quality of the flow estimates passing through the stations. [ABSTRACT FROM AUTHOR]

We explored the stability of the rating curves at six streamflow gauging sites in the state of Iowa, USA, to examine temporal variability of their stage–discharge relationships. The analyzed sites have up to 10 years of rating and shift records. Rating curve shifts reflect the alteration of channel geometry caused by scouring and sediment deposition. We studied how rating shifts are connected to the occurrence of flood events and drought periods over time. We found that most rating curve changes take place during spring and summer, which are the seasons with more precipitation in Iowa. We quantified stability in terms of standard deviation of stages for a continuous range of discharges in a rating curve, and show that most of the sites exhibit greater standard stage deviation for discharge–flood ratios smaller than 1, while for larger discharge–flood ratios, the deviation decreases. In stable rating curves, the stage deviation tends to decrease as discharge increases. Non-stable rating curves exhibit large stage deviation in the stage–discharge relationship throughout all stages.

Highlights • The proposed method generates the rating curves in the natural and artificial open channels. • Present method does not need any calibration. • Rating curve could be estimated based on only a single pair of information of stage and discharge i.e. H , Q . • Multi-objective optimization uses for determining the proposed relationship. Abstract The stage-discharge relationship is one of the frequently used methods for continuous river flow measurement. In the management of water resources and flood control, the accuracy of the rating curve is a key priority. Various methods have been proposed for estimating the stage-discharge curves in open channels, including the model of Ahmadi et al. (2017) in which the rating curve was identified by utilizing the information of discharge at a referenced water level. In the present study, a novel approach was taken to improve that model by modifying its basic assumptions and employing multi-objective optimization. To this end, multivariate relationships were presented to determine the actual mean velocity in the flow cross-section. The unknown exponents of the proposed relationships were obtained by using the second version of the Strength Pareto Evolutionary Algorithm (SPEA2), and the appropriate equation was selected by applying the TOPSIS (Technique for Order Preferences by Similarity to an Ideal Solution) approach. The validity of the proposed method was assessed across 6 artificial and 6 natural hydraulic cross-sections. Results showed a close agreement between the estimated and observed data. In the next step, the results of the proposed method were compared with those of the previous model using the Mann-Whitney U test. The results demonstrated that the proposed model was more efficient than the previous one. [ABSTRACT FROM AUTHOR]

Highlights • Critical of current oversimplified description using power functions. • Develops two methods for the automatic calculation of rating curves. • Data approximation methods are used, global polynomial and spline approximation. • A rating curve for any time in the past or present can be calculated. • Where data is scattered or loopy, a rating envelope can be calculated. Abstract Traditional methods for the calculation of rating curves from measurements of water level and discharge are criticised as being limited and complicated to implement, such that manual methods are still often used. Two methods for automatic computation are developed using least-squares approximation, one based on polynomials and the other on piecewise-continuous splines. Computational problems are investigated and procedures recommended to overcome them. Both methods are found to work well and once the parameters for a gauging station have been determined, rating data can be processed automatically. For some streams, ephemeral changes of resistance may be important, evidenced by scattered or loopy data. For such cases, the approximation methods can be used to generate a rating envelope as well, allowing the routine calculation also of maximum and minimum expected flows. Criticism is made of current shift curve practices. Finally, the approximation methods allow the specification of weights for the data points, enabling the filtering of data, especially decreasing the importance of points with age and allowing the computation of a rating curve for any time in the past or present. [ABSTRACT FROM AUTHOR]

The aim of this study is to investigate the scaling exponent properties of mountainous river flow fluctuations by detrended fluctuation analysis (DFA). Streamflow data were collected continuously using Fluvial Acoustic Tomography System (FATS), which is a novel system for measuring continuous streamflow at high-frequency scales. The results revealed that river discharge fluctuations have two scaling regimes and scaling break. In contrast to the Ranting Curve method (RC), the small-scale exponent detected by the FATS is estimated to be 1.02 ± 0.42% less than that estimated by RC. More importantly, the crossover times evaluated from the FATS delayed approximately by 42 ± 21 hr ≈ 2–3 days than their counterparts estimated by RC. The power spectral density analysis assists our findings. We found that scaling characteristics information evaluated for a river using flux data obtained by RC approach might not be accurately detected, because this classical method assumes that flow in river is steady and depends on constructing a relationship between discharge and water level, while the discharge obtained by the FATS decomposes velocity and depth into two ratings according to the continuity equation. Generally, this work highlights the performance of FATS as a powerful and effective approach for continuous streamflow measurements at high-frequency levels. [ABSTRACT FROM AUTHOR]

One approach for performing uncertainty assessment in flood inundation modeling is to use an ensemble of models with different conceptualizations, parameters, and initial and boundary conditions that capture the factors contributing to uncertainty. However, the high computational expense of many hydraulic models renders their use impractical for ensemble forecasting. To address this challenge, we developed a rating curve library method for flood inundation forecasting. This method involves pre-running a hydraulic model using multiple inflows and extracting rating curves, which prescribe a relation between streamflow and stage at various cross sections along a river reach. For a given streamflow, flood stage at each cross section is interpolated from the pre-computed rating curve library to delineate flood inundation depths and extents at a lower computational cost. In this article, we describe the workflow for our rating curve library method and the Rating Curve based Automatic Flood Forecasting ( RCAFF) software that automates this workflow. We also investigate the feasibility of using this method to transform ensemble streamflow forecasts into local, probabilistic flood inundation delineations for the Onion and Shoal Creeks in Austin, Texas. While our results show water surface elevations from RCAFF are comparable to those from the hydraulic models, the ensemble streamflow forecasts used as inputs to RCAFF are the largest source of uncertainty in predicting observed floods. [ABSTRACT FROM AUTHOR]

Natural streams are characterized by variation in cross-section geometry, bed-slope, bed roughness, hydraulic slope, etc., along their channels resulting from several interacting features of the riverine system including the effects of discharge changes, geologic context, sediment load, etc. Quantitative and qualitative assessment of river flow dynamics requires sufficient knowledge of hydraulics and these geophysical variables. Average flow condition theory expressed as “At-A-Station” hydraulic geometry (AHG) relations are site-specific power-functions, relating the mean stream channel forms (i.e. water depth, top-width, flow velocity, and flow area) to discharge, have been studied since 50s. Establishing robust AHG relations requires pre-assessment of data quality by means of uncertainty analysis. Our paper introduces a recursive data filtering procedure to find both random and systematic errors in streamflow and river-survey data that can be used to produce robust and informative AHG relations. The method is first verified on synthetic data and then by experiments over: (1) real discharge-stage ratings provided by daily streamflow records of U.S. Geological Survey/National Water Information System dataset (USGS/NWIS), and (2) field river survey measurement data from USGS/NWIS. This produces robust AHG relations at 4472 monitoring stations across the U.S. [ABSTRACT FROM AUTHOR]

Discharge hydrograph estimation during floods, in rivers with torrential regime, is often based on the use of rating curves extrapolated from very low stage-discharge measurements. To get a more reliable estimation, a reverse flow routing problem is solved using water level data measured in two gauged stations several kilometers from each other. Validation of the previous analysis carried out on the flood event of February 2016 at the Europa Bridge and Castiglione Scalo sections of the Crati River (Cosenza, Italy) is based on the use of 'soft' discharge measurement data and the comparison of the water level data computed in the downstream gauged section by three different hydraulic models with the 'hard' available water level measures. Results confirm that the 1D diffusive model provides more reliable results than the 1D complete one and no significant improvement is gained by the use of a more computationally demanding 2D model. [ABSTRACT FROM AUTHOR]

Having a river basin as the study site, it is of fundamental importance to comprehend the sediment dynamics of river systems, in order to diagnose and understand them, aiming to carry out predictions. The observance of the sediment supply carried by the river systems is related to the erosion, transport and deposition, through rainfall and dynamic land use and cover in hillside environments. The Purus River basin is part of this context, the study area of this paper and it is located in the Amazon biome. This study aims to start the first steps to understand the suspended sediment dynamics of that basin, because of its expressive environmental variations. For this purpose was considered the sediment present in the river systems as an indicator which can be understood and used in order to support soil and water conservation measures in the Purus River basin, distinguishing the natural dynamics and anthropogenic dynamics. Thus, this study has the objective of evaluating the suspended sediments discharge in the Purus River basin, in order to collaborate with action planning and watershed management, with the objective of generating knowledge about the suspended sediment dynamics of that spring. [ABSTRACT FROM PUBLISHER]

The accuracy of river flow data is very important for most hydrological studies. Even so, the uncertainty of these data is often neglected. The uncertainty can be significant since the flow is rarely measured directly, but rather indirectly through pre-defined functions of the river stage to discharge relationship or rating-curves. The uncertainty is even more prevalent when the rating curve is extrapolated beyond the available stage-discharge pairs (or gaugings) that form the basis for the rating curve. In an on-going case-study, a hybrid modeling technique is utilized to produce synthetic gaugings for the extrapolation of a rating curve. The control at the gauging-station is at a bed-rock drop where the hydraulic conditions is known to be demanding, especially at high flows. The hybrid modeling is a combination of an original approach to physical modeling and a 3-dimensional Reynolds-averaged Navier-Stokes model of the same geometry. The physical modeling makes use of large-scale computer numerical control (CNC) milling technique in a plastic foam material to provide a high-detail geometry from a point cloud. A combination of survey techniques including terrestrial and aerial laser-scans, sonar and total station point measurements are used to produce the necessary detail in the geometry. This paper describes the on-going research project, and presents temporary results of the hybrid modeling. [ABSTRACT FROM AUTHOR]

The present study investigates the spatio-temporal variability of riverine sediment fluxes to the Gulf of Lions, one of the most extensive shelf regions in the Mediterranean Sea. Small coastal rivers compete here with the Rhone River, nowadays the largest Mediterranean river in terms of water discharge. Our scientific objectives were to investigate the major controls of riverine sediment yields (SY) in this area and to quantify the role of the small coastal rivers, largely ignored in previous studies, in the total sediment budgets. Another objective concerned the source identification of the Rhone sediments with regard to the major tributary contributions, and to test whether the sediment fluxes are in equilibrium in the basin. For the calculation of representative long-term fluxes, we used a Simplified Rating Curve Approach (SiRCA) which could be validated by high resolution monitoring and existing literature data. An overall of 13 drainage basins could be distinguished, covering about 86% of the study area (6 coastal rivers, the Rhone River, and 6 of its tributaries). Representative SY range from 19 to 151 t km −2 yr −1 in the investigated drainage basins. Despite their smaller basin areas and more torrential discharge regimes, SY of the coastal rivers were generally lower compared to SY of the Rhone River and its tributaries. Confrontation with the lithological, morphological and hydroclimatic basin characteristics indicate that lithology exerts the dominant control on SY in the study region. In particular, the existence of erodible sedimentary rocks in the headwater regions yields high SY. Peak values of 135 and 151 t km −2 yr −1 were observed for the Isere and Durance tributaries of the Rhone River, where badlands exist. The coastal rivers contribute on average only to slightly more than 5% of the long-term sediment inputs to the Gulf of Lions. During individual years however, their contribution can strongly increase (up to 27% in 2011). Their contribution is generally important during late spring and autumn, when flash-floods are frequent (up to 90% of the monthly sediment discharge). Summing the various tributary contributions of the Rhone River produces a sediment budget that is close to the sediment export at the river mouth. This indicates that at spatial scales, the average sediment fluxes are equilibrated in the basin. About 40% of the Rhone sediments originate from the Isere and Durance tributaries. However, fully closure of the budgets requires high SY in the lowermost basin parts. Omitting in our calculations only a few years with exceptional flooding considerably reduce these values. Trend analyses show at the same time that the sediment fluxes from the Saone and Isere tributaries decreased during the study period. At temporal scales, sediment transport from upstream to downstream was therefore not in equilibrium and the remobilisation of older sediments from the downstream basin parts may have been important. [ABSTRACT FROM AUTHOR]

The honey-bees mating programming (HBMP) algorithm is introduced as a novel tool for predicting suspended sediment concentration for the Mad River catchment near Arcata, USA. The paper also applies gene expression programming (GEP) as a comparison and shows that these two approaches can the produce transparent, nonlinear relationships between the independent and dependent variables. Some modifications have been made to the HBMP algorithm to improve its capability and efficiency. The results achieved from this method and GEP are compared with two different sediment rating curves based on regression techniques. The findings show that the results from both the HBMP and GEP methods are promising and outperform the results obtained from the sediment rating curves.Editor D. Koutsoyiannis; Associate editor L. See [ABSTRACT FROM AUTHOR]

This pilot study explores the potential of using low-resolution (0.2 points/m2) airborne laser scanning (ALS)-derived elevation data to model stream rating curves. Rating curves, which allow the functional translation of stream water depth into discharge, making them integral to water resource monitoring efforts, were modeled using a physics-based approach that captures basic geometric measurements to establish flow resistance due to implicit channel roughness. We tested synthetically thinned high-resolution (more than 2 points/m2) ALS data as a proxy for low-resolution data at a point density equivalent to that obtained within most national-scale ALS strategies. Our results show that the errors incurred due to the effect of low-resolution versus high-resolution ALS data were less than those due to flow measurement and empirical rating curve fitting uncertainties. As such, although there likely are scale and technical limitations to consider, it is theoretically possible to generate rating curves in a river network from ALS data of the resolution anticipated within national-scale ALS schemes (at least for rivers with relatively simple geometries). This is promising, since generating rating curves from ALS scans would greatly enhance our ability to monitor streamflow by simplifying the overall effort required. [ABSTRACT FROM AUTHOR]

We monitor bedload transport and water discharge at six stations in two forested headwater streams of the Columbia Mountains, Canada. The nested monitoring network is designed to examine the effects of channel bed texture, and the influence of alluvial (i.e. step pools and riffle pools) and semialluvial morphologies (i.e. boulder cascades and forced step pools) on bedload entrainment and transport. Results indicate that dynamics of bedload entrainment are influenced by differences in flow resistance attributable to morphology. Scaled fractional analysis shows that in reaches with high form resistance most bedload transport occurs in partial mobility fashion relative to the available bed material, while calibers finer than 16 mm attain full mobility during bankfull flows. Equal mobility transport for a wider range of grain sizes is achieved in reaches exhibiting reduced form resistance. Our findings confirm that the Shields value for mobilization of the median surface grain size depends on channel gradient and relative submergence; however, we also find that these relations vary considerably for cobble and gravel bed channels due to proportionality between dimensionless shear stress and grain size. Exponents of bedload rating curves across sites correlate most with the D90s of the mobile bed, however, where grain effects are controlled (i.e. along individual streams), differences in form resistance across morphologies exert a primary control on bedload transport dynamics. Application of empirical formulae developed for use in steep alpine channels present variable success in predicting transport rates in forested snowmelt streams. Formulae that explicitly account for reductions in mobile bed area and high morphological resistance associated with woody debris provide the best approximation to observed empirical data. Copyright © 2014 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

Since the 1970s, there has been both continuing and growing interest in developing accurate estimates of the annual fluvial transport (fluxes and loads) of suspended sediment and sediment-associated chemical constituents. This study provides an evaluation of the effects of manual sample numbers (from 4 to 12 year−1) and sample scheduling (random-based, calendar-based and hydrology-based) on the precision, bias and accuracy of annual suspended sediment flux estimates. The evaluation is based on data from selected US Geological Survey daily suspended sediment stations in the USA and covers basins ranging in area from just over 900 km2 to nearly 2 million km2 and annual suspended sediment fluxes ranging from about 4 Kt year−1 to about 200 Mt year−1. The results appear to indicate that there is a scale effect for random-based and calendar-based sampling schemes, with larger sample numbers required as basin size decreases. All the sampling schemes evaluated display some level of positive (overestimates) or negative (underestimates) bias. The study further indicates that hydrology-based sampling schemes are likely to generate the most accurate annual suspended sediment flux estimates with the fewest number of samples, regardless of basin size. This type of scheme seems most appropriate when the determination of suspended sediment concentrations, sediment-associated chemical concentrations, annual suspended sediment and annual suspended sediment-associated chemical fluxes only represent a few of the parameters of interest in multidisciplinary, multiparameter monitoring programmes. The results are just as applicable to the calibration of autosamplers/suspended sediment surrogates currently used to measure/estimate suspended sediment concentrations and ultimately, annual suspended sediment fluxes, because manual samples are required to adjust the sample data/measurements generated by these techniques so that they provide depth-integrated and cross-sectionally representative data. Published 2014. This article is a U.S. Government work and is in the public domain in the USA. [ABSTRACT FROM AUTHOR]

An empirical framework for assisting with water quality management is proposed that relies on open-source hydrologic data. Such data are measured periodically at fixed water stations and commonly available in time-series form. To fully exploit the data, we suggest that observations from multiple stations should be combined into a single long-panel data set, and an econometric model developed to estimate upstream management effects on downstream water quality. Selection of the model's functional form and explanatory variables would be informed by rating curves, and idiosyncrasies across and within stations handled in an error term by testing contemporary correlation, serial correlation, and heteroskedasticity. Our proposed approach is illustrated with an application to the Nakdong River basin in South Korea. Three alternative policies to achieve downstream BOD level targets are evaluated: upstream water treatment, greater dam discharge, and development of a new water source. Upstream water treatment directly cuts off incoming pollutants, thereby presenting the smallest variation in its downstream effects on BOD levels. Treatment is advantageous when reliability of water quality is a primary concern. Dam discharge is a flexible tool, and may be used strategically during a low-flow season. We consider development of a new water corridor from an extant dam as our third policy option. This turns out to be the most cost-effective way for securing lower BOD levels in the downstream target city. Even though we consider a relatively simple watershed to illustrate the usefulness of our approach, it can be adapted easily to analyze more complex upstream-downstream issues. [ABSTRACT FROM AUTHOR]

Fluvial sediment loads are frequently calculated with rating curves fit to measured sediment transport rates. Rating curves are often treated as statistical representations in which the fitted parameters have little or no physical meaning. Such models, however, may produce large errors when extrapolation is needed, and they provide no insight into the sediment transport process. It is shown that log-linear least squares, the usual method for fitting rating curves, does not generally produce physically meaningful parameter values. In addition, it cannot accommodate data that include zero-transport samples. Alternative fitting methods based nonlinear least squares and on maximum likelihood parameter estimation are described and evaluated. The maximum likelihood approach is shown to fit synthetic data better than linear or nonlinear least squares, and to perform well with data that include zero-transport samples. In contrast, nonlinear least squares methods produce large errors in the parameter estimates when zero-transport samples are present or when the variance structure of the data is incorrectly specified. Analyses with fractional bedload data from a mountain stream suggest that bedload transport rates are gamma distributed, that the arrivals of bedload particles in a sampler conform to a Poisson distribution, and that the variance of nonzero samples can be expressed as a power function of the mean. Preliminary physical interpretations of variations in the rating curve parameters fit to fractional bedload data with the maximum likelihood method are proposed, and their relation to some previous interpretations of rating curve parameters are briefly discussed. [ABSTRACT FROM AUTHOR]

• Rating curves are constructed for two major bifurcations of the Dutch Rhine river. • Rating curves at bifurcations can show a large water balance error between them. • Water balance errors are reduced if considering it in rating curve construction. • Rating curves with improved water balance closure are physically constrained. • It is recommended to specifically gauge at bifurcations and confluences. Accurate discharge records are essential for flood frequency analyses, hydraulic model calibration and flood forecasting. Discharge records are often obtained via a transformation of water levels to discharges using a rating curve. For accurate rating curves, a physical basis is important, particularly in the extrapolation domain towards extreme discharges. In this study, physical processes and constraints are incorporated in a rating curve model: water balance closure at a bifurcation and bed level degradation. The aim is to assess the effect of incorporating these physical processes and constraints for rating curves at two bifurcations of the Rhine river in the Netherlands. Intermittent gaugings are available for a 31 year period at these bifurcations. Bayesian inference and Markov Chain Monte Carlo sampling is used to estimate the posterior distributions of the rating curves. If rating curves are constructed independently, they show a large water balance error at bifurcations of up to 10%. Incorporating bed level degradation is required for accurate rating curves as it reduces the residual errors by up to 50%. If explicitly accounting for water balance closure, the water balance error can be reduced to 1%, while residual errors remain equally small. As water balance closure is a physical constraint at a river bifurcation, the rating curves that account for water balance closure are expected to be more physically realistic. Therefore, it is recommended to specifically gauge at river bifurcations and confluences, such that the constraint of water balance closure can be used to improve the accuracy of rating curves and discharge records. [ABSTRACT FROM AUTHOR]

Abstract: Variation in fluvial suspended sediment–discharge behavior is generally thought to be the product of changes in processes governing the delivery of sediment and water to the channel. The objective of this study was to infer sediment supply dynamics from the response of suspended sediment behavior to antecedent hydrologic factors. The Salinas River (California) is seasonally active, moderately sized, and potentially susceptible to lasting impacts of hydrologic event history because of aridity, high discharge variability, and in-channel terminating flows. Forty-five years of suspended sediment data from the lower Salinas and 80years of hydrologic data were used to construct hydrologic descriptors of basin preconditioning and to test the effects of these preconditions on suspended sediment behavior. Hydrologic precondition factors — including change in mean daily discharge and increasing elapsed time since the last moderate discharge event (~10–20 times mean discharge (Qmean )) — were found to have significant positive effects on discharge-corrected, fine suspended-sediment concentrations. Conversely, increased elapsed time since the last low discharge event (~0.1–0.4 times Qmean ), and the sum of low flow conditions over interannual time scales were found to cause significant negative trends in fine suspended sediment concentration residuals. Suspended sand concentrations are suppressed by increased elapsed time after threshold discharges of ~0.1–2 and 5–100 times Qmean , and increased low to no flow days over time scales from 1 to 2000days. Current and previous year water yield and precipitation magnitudes correlate positively with sand concentration. Addition of fine sediment from lower Salinas hillslope or channel sources on the rising limb of the hydrograph is the major mechanism behind an overall positive hysteretic pattern, which was forensically supported by the annual occurrence of in-channel suspended sediment deposition by early season, channel terminating flows and by the flushing function of moderate hydrologic events found in this study. The importance of hillslope and/or channel fine sediment contributions proximal to the lower Salinas are further highlighted by the lack of control exerted by upper subbasin water provenance on fine suspended sediment concentration, while sand behavior is differentiated by upper basin water provenance. Investigation of suspension of bed-sized sediment showed that the channel bed could exert significant effects on fine and sand-sized suspended sediment dynamics, but this mediation for fine sediment was most likely small in terms of decadal-scale sediment budgets. The magnitude of the effects of hydrologic variables on sediment dynamics remains uncertain, but the factors identified here may play a significant role in water quality, if not long-term sediment flux to the ocean. [Copyright &y& Elsevier]

Highlights: [•] A novel Bayesian framework for the analysis of hydrometric rating curves. [•] A versatile rating curve equation, based on piecewise compound power functions. [•] Identification of the hydraulic controls and specification of priors. [•] Quantification of the individual uncertainty of each gauging. [•] Verification of the hydraulic meaning of the resulting curve and uncertainty envelope. [Copyright &y& Elsevier]

Highlights: [•] We test and validate an improved discharge-concentration rating curve. [•] Sediment fluxes may be calculated from infrequent and degraded concentration data. [•] The number of concentration data matters more than the sampling frequency. [•] We provide an application for some of the major French rivers. [ABSTRACT FROM AUTHOR]