The application of two‐dimensional hydrodynamic models for underwater archaeological finds from the Vistula River in Warsaw,Poland

Low water levels occurring on the Warsaw section of the Vistula River during droughts in 2012 and 2015 stirred considerable interest by exposing parts of the riverbed. The river's low flow discharge created favourable conditions for archaeologists who, from the river's bottom, managed to salvage sculptures, architectural artefacts, and military accessories dating back to the middle of the 17th century. Literature shows that archaeological finds at the bottom of a major lowland river are unique and are attributed to very specific hydrological and geological conditions. Embankments and works meant to regulate the channel of the Vistula River in Warsaw narrowed the channel and accelerated the erosion of the river's bottom. A comparison of rating curves created between 1919 and 2015 shows that the river's bottom had lowered by 225 cm. The diameter of sediment particles that could be moved at maximum shear stress has been calculated using the Meyer–Peter and Muller formula. According to the calculated shear stress corresponding to the highest historical flood of 1844 particles smaller than 0.05 m were transported down the river, and it is true that artefacts of that size had not been collected at the site. Taking into consideration the very specific geological and hydrological conditions, we believe that finding so many 17th century artefacts with a well‐documented history at a site at the bottom of major lowland river with intensive channel processes is indeed unique. Additionally, it is the first time that results of hydrodynamic modelling have been successfully used for archaeological survey to define the critical shear stress and the smallest diameter of artefacts, which could remain stable on a river's bottom.     

Hydraulic visibility: Using satellite altimetry to parameterize a hydraulic model of an ungauged reach of a braided river

What hydraulic information can be gained from remotely sensed observations of a river's surface? In this study, we analyze the relationship between river bed undulations and water surfaces for an ungauged reach of the Xingu River, a first‐order tributary of the Amazon river. This braided reach is crosscut more than 10 times by a ENVISAT (ENVironmental SATellite) track that extends over 100 km. Rating curves based on a modeled discharge series and altimetric measurements are used, including the zero‐flow depth Z ₀ parameter, which describes river's bathymetry. River widths are determined from JERS (Japanese Earth Ressources Satellite) images. Hydrodynamic laws predict that irregularities in the geometry of a river bed produce spatial and temporal variations in the water level, as well as in its slope. Observation of these changes is a goal of the Surface Water and Ocean Topography satellite mission, which has a final objective of determining river discharge. First, the concept of hydraulic visibility is introduced, and the seasonality of water surface slope is highlighted along with different flow regimes and reach behaviors. Then, we propose a new single‐thread effective hydraulic approach for modeling braided rivers flows, based on the observation scales of current satellite altimetry. The effective hydraulic model is able to reproduce water surface elevations derived by satellite altimetry, and it shows that hydrodynamical signatures are more visible in areas where the river bed morphology varies significantly and for reaches with strong downstream control. The results of this study suggest that longitudinal variations of the slope might be an interesting criteria for the analysis of river segmentation into elementary reaches for the Surface Water Ocean Topography mission that will provide continuous measurements of the water surface elevations, the slopes, and the reach widths.     

防止河道泥沙淤积的最小生态环境需水量

水土流失问题是生态系统面临的重要问题. 对于多沙河道来说,必须维持一定的生态环境需水量用于输沙,以保证河道生态平衡. 本文以多沙河流为研究对象,以输沙动力学理论为基础,分析了河流输沙能力和水流挟沙能力,在此基础上提出了河道在不冲不淤的临界状态下河流最小流量的计算方法,此为防止河道泥沙淤积的最小生态环境需水量. 通过实际算例,本文还说明了所提出的计算方法的应用,以期为多沙河道水资源合理配置及生态平衡维护提供科学依据.     

Assessments of Potential Spatial‐temporal Variations in Phosphorus Distribution and Fractionation in River Bed Sediments

Sediment characteristics influence the distribution and bioavailability of phosphorus (P) in river sediments. In this study, we analyzed different P fractions in the sediments of the Bronx River, New York City, NY, using sequential extraction. The results showed that the average P pool rank order was HCl?P > NaOH?P > NaHCO₃?P > residue?P, and their relative proportions were 3.7: 2.0: 1.4: 1 in sediments collected in 2006, while HCl?P > NaOH?P > residue?P > NaHCO₃?P, with their relative proportions of 27.8:6.2:2.7:1 in the sediments obtained in 2007. The strong correlation between microbial P and organic P (OP), along with the changes in microbial P over time indicate that most of the OP in the river bed sediments is potentially bioavailable. The sediment transport, deposition, assimilation, the exchange of P between sediments and water columns, the land use changes, raw sewer discharge, gas spill, construction, fertilizer application, etc., as well as the hydro‐climatic changes could result in the spatial and temporal variations in P bioavailability in the river bed sediments. The estimations of P pools and their bioavailability in river bed sediments could help determine the spatial and temporal variations in P transport and impacts of land use on water quality, in turn, help regulate P in the river's watershed.     

Channel mobility drives a diverse stratigraphic architecture in the dryland Mojave River (California,USA)

The links between flood frequency and rates of channel migration are poorly defined in the ephemeral rivers typical of arid regions. Exploring these links in desert fluvial landscapes would augment our understanding of watershed biogeochemistry and river morphogenesis on early Earth (i.e. prior to the greening of landmasses). Accordingly, we analyse the Mojave River (California), one of the largest watercourses in the Great Basin of the western United States. We integrate discharge records with channel-migration rates derived from dynamic time-warping analysis and chronologically calibrated subsidence rates, thereby constraining the river's formative conditions. Our results reveal a slight downstream decrease in bankfull discharge on the Mojave River, rather than the downstream increase typically exhibited by perennial streams. Yet, the number of days per year during which the channel experiences bankfull or higher stages is roughly maintained along the river's length. Analysis of historical peak flood records suggests that the incidence of channel-formative events responds to modulation in watershed runoff due to the precipitation in the river's headwaters over decades to centuries. Our integrated analysis finally suggests that, while maintaining hydraulic geometries that are fully comparable with many other rivers worldwide, ephemeral desert rivers akin to the Mojave are capable of generating a surprisingly wide range of depositional geometries in the stratigraphic record. © 2020 John Wiley & Sons, Ltd.     

基于熵值环境基尼系数法的平原河网区污染物总量分配

为制定科学合理的水污染物总量控制方案,以典型平原河网地区——张家港市为例,构建与人口、资源、经济和水污染物承受能力相协调的单因子环境基尼系数模型,并通过贡献系数判断引起不公平的主要污染物分配单元.利用熵值—环境基尼系数最小化模型,确定张家港市各乡镇基于多元公平性原则的氨氮总量分配方案.结果表明:在水污染物总量分配过程中,污染物削减比例的大小和污染物现状排放量之间并不具有一致性,最终的分配方案要综合考虑多方因素确定.本研究构建的熵值—环境基尼系数最小化模型综合考虑了研究区域社会、经济、资源等多种客观因素,对于平原河网地区,由于其特殊的地理位置和自然条件,人口、资源等分布相对比较均匀,故基于该模型所得到的分配方案充分表现了多元公平性原则,更公平合理.     

Estimating river discharge from very high‐resolution satellite data: a case study in the Yangtze River,China

The measurement of river discharge is necessary for understanding many water‐related issues. Traditionally, river discharge is estimated by measuring water stage and converting the measurement to discharge by using a stage–discharge rating curve. Our proposed method for the first time couples the measurement of water‐surface width with river width–stage and stage–discharge rating curves by using very high‐resolution satellite data. We used it to estimate the discharge in the Yangtze (Changjiang) River as a case study. The discharges estimated at four stations from five QuickBird‐2 images matched the ground observation data very well, demonstrating that the proposed approach can be regarded as ancillary to traditional field measurement methods or other remote methods to estimate river discharge. Copyright © 2004 John Wiley & Sons, Ltd.     

Estimation of river discharge from non-trapezoidal open channel using QuickBird-2 satellite imagery/Utilisation des images satellites de Quickbird-2 pour le calcul des débits fluviaux en chenaux ouverts non-trapézoïdaux

Abstract

Abstract River discharge is traditionally acquired by measuring water stage and then converting the water stage to discharge by using a stage–discharge rating curve. The possibility of monitoring river discharge by satellite has not been adequately studied hitherto, because of the difficulty in making sufficiently precise measurements of the water surface. Since the successful launch of commercial satellites with very-high-resolution sensors, it has become possible to derive ground information from satellite data. To determine river discharge in a non-trapezoidal open channel, an efficient approach has been developed that uses mainly satellite data. The method, which focuses on the measurement of surface water width coupled with river width–stage and ?remote? stage–discharge rating curves, was applied to the Yangtze River (Changjiang) and an accurate estimate of river discharge was obtained. The method can be regarded as ancillary to traditional field measurement methods or other remote sensing methods.     

Stream flow characterization and feature detection using a discrete wavelet transform

An exploration of the wavelet transform as applied to daily river discharge records demonstrates its strong potential for quantifying stream flow variability. Both periodic and non-periodic features are detected equally, and their locations in time preserved. Wavelet scalograms often reveal structures that are obscure in raw discharge data. Integration of transform magnitude vectors over time yields wavelet spectra that reflect the characteristic time-scales of a river's flow, which in turn are controlled by the hydroclimatic regime. For example, snowmelt rivers in Colorado possess maximum wavelet spectral energy at time-scales on the order of 4 months owing to sustained high summer flows; Hawaiian streams display high energies at time-scales of a few days, reflecting the domination of brief rainstorm events. Wavelet spectral analyses of daily discharge records for 91 rivers in the US and on tropical islands indicate that this is a simple and robust way to characterize stream flow variability. Wavelet spectral shape is controlled by the distribution of event time-scales, which in turn reflects the timing, variability and often the mechanism of water delivery to the river. Five hydroclimatic regions, listed here in order of decreasing seasonality and increasing pulsatory nature, are described from the wavelet spectral analysis: (a) western snowmelt, (b) north-eastern snowmelt, (c) mid-central humid, (d) south-western arid and (e) ‘rainstorm island’. Spectral shape is qualitatively diagnostic for three of these regions. While more work is needed to establish the use of wavelets for hydrograph analysis, our results suggest that river flows may be effectively classified into distinct hydroclimatic categories using this approach. © 1998 John Wiley & Sons, Ltd.     

Assessment of the Present State and Future Fate of River Saraswati,India: Water Quality Indices and Forecast Models as Diagnostic and Management Tools

Water quality assessment is key to the conservation and management of rivers. River Saraswati, a distributary of the river Ganga, serves as a lifeline to many villages in the district Hooghly in West Bengal, India. As the river is gradually dying due to diverse man-made pollution, ten water quality parameters in two sampling spots (PR-1 and PR-2) in the river are monitored month-wise from March 2017 to February 2020,  and these are compared with those from a reference pond. The water quality index (WQI) is determined for the two riverine spots and the reference pond based on the Canadian Council of Ministers of Environment WQI (CCMEWQI) and weighted arithmetic WQI, respectively. In addition to actual observations, three different forecasting methods, exponential smoothing, autoregressive integrated moving average, and artificial neural network, are used to predict WQI for the next two years. This study indicates that free CO₂, dissolved oxygen, and turbidity are the key parameters to evaluate this river's anthropogenic stress and health. The actual and forecasted results reflect the precipitous degradation of CCMEWQI in PR-2. Therefore, the immediate intervention of all stakeholders is required to adopt an integrated and comprehensive river management plan to save the river from utter obliteration.     

Optimized reservoir operation to balance human and riverine ecosystem needs: model development,and a case study for the Tanghe reservoir,Tang river basin,China

Reservoirs impose many negative impacts on riverine ecosystems. To balance human and ecosystem needs, we propose a reservoir operation method that combines reservoir operating rule curves with the regulated minimum water release policy to meet the environmental flow requirements of riverine ecosystems. Based on the relative positions of the reservoir and the water intakes, we consider three scenarios: water used for human needs (including industrial, domestic and agricultural) is directly withdrawn from (1) the reservoir; (2) both reservoirs and downstream river channels and (3) downstream river. The proposed method offers two advantages over traditional methods: First, it can be applied to finding the optimal reservoir operating rule curves with the consideration of environmental flow requirement, which is beneficial to the sustainable water uses. Second, it avoids a problem with traditional approaches, which prescribe the minimum environmental flow requirements as the regulated minimum environmental flow releases from reservoirs, implicitly giving lower priority to the riverine ecosystem. Our method instead determines the optimal regulated minimum releases of water to sustain environmental flows while more effectively balancing human and ecosystem needs. To demonstrate practical use of the model, we present a case study for operation of the Tanghe reservoir in China's Tang river basin for the three above‐mentioned scenarios. The results demonstrate that this approach will help the reservoir's managers satisfy both human and environmental requirements. Copyright © 2009 John Wiley & Sons, Ltd.     

Principles of regional estimation of infiltration groundwater recharge based on geohydrological models

Principles of estimation of infiltration groundwater recharge based on modeling the formation of water balance on the land surface and in the vadose zone are considered. The application of such models for regional discharge evaluation involves zoning of the territory by a set of meteorological, landscape, geological, soil, and hydrogeological factors. The reliability of the obtained estimates of water balance components, including infiltration recharge, should be assessed by correlating the calculated and measured river runoff characteristics for drainage basins within which the water-bearing section in the zone of active water exchange is completely drained. The application of such approach is illustrated by calculations for southwestern Moscow Artesian Basin.     

Seasonal variation of river and tide energy in the Yangtze estuary,China

In many large estuaries there are significant variations in flow conditions due to the interaction between tide (with spring–neap changes) and river discharge (with wet–dry seasons), which is key to understanding the evolution of the morphology and the resultant equilibrium state. To explore whether there exists an equilibrium state, and what might control such a state in such a dynamic environment, both numerical and analytical methods have been used to investigate the relative importance of tide and river contributions to the work done locally and globally over a wide range of discharge conditions in the Yangtze estuary. In particular, we have quantified the contributions from the tidal flow, the river flow and the tide–river interaction in terms of energy and its dissipation under different river discharge conditions. Model results suggest that there is a state of minimum tidal work for the case representing the wet season, when river and tide are doing uniform work locally and minimum work globally, within the bi‐directional tidal reach for tide and along the whole estuary for river. We also observe that the system is not optimized for other conditions (peak discharge and low flows during the dry season), but the system would tend to do the minimum work possible given the constraints on the system (e.g. imposed forcing conditions and available sediment supply). Results, therefore, are consistent with the use of these two energetic optimization principles, and the proposed method could be applicable to other alluvial estuaries. Copyright © 2015 John Wiley & Sons, Ltd.     

Bed-roughness investigation for a 2-D model calibration： the San Martin case study at Lower Parana

This paper illustrates how the acoustic Doppler current profiler （ADCP） and single-beam echo-sounder （SBES） recordings can be used for the calibration of existing software to assist in generalizing the morphodynamic processes in large rivers at key sites such as bifi.trcations and confluences. Calibration of the MIKE21C numerical model by the Danish Hydraulic Institute at the 25-km-long reach of Lower Paran~ near Rosario （Argentina） is presented. This reach includes two downstream confluences and two bifurcations. The model simulates a 2-D depth-averaged flow velocity and the related sediment fluxes to predict the bifurcation morphodynamics that affects the Paranh waterway. To investigate the river channel bathymetry, roughness, flow discharge allocation at bifurcations, suspended sediment concentration and grain size distributions, several instruments were used. These instruments included two ADCPs by Teledyne RDI working at frequencies of 600 and 1,200 kHz, a Sontek ADCP working at a frequency of 1,000 kHz and a SBES. The method to assess suspended sediment concentration and grain size distributions has been previously described. This paper focuses primarily on investigating dune morphology （by means of SBES depth measurements） and friction velocity （by means of ADCP profiling） to determine the river channel bed-roughness. The 2-D model results agree with observed values of bed-roughness, flow velocity and suspended sediment concentration distributions at the investigated sections, known data of water slope and total load of bed sediment are in good agreement with model results.     

Two solution methods for dynamic game in reservoir operation

During the last decade, a number of models have been developed to consider the conflict in dynamic reservoir operation. Most of these models are discrete dynamic models which are developed based on game theory. In this study, a continuous model of dynamic game and its corresponding solutions are developed for reservoir operation. Two solution methods are used to solve the model of continuous dynamic game, namely the Ricatti equations and collocation methods. The Ricatti equations method is a closed form solution, requiring less computational efforts compared with discrete models. The collocation solution method applies Newton's method or a quasi-Newton method to find the problem solution. These approaches are able to generate operating policies for dynamic reservoir operation. The Zayandeh-Rud river basin in central Iran is used as a case study and the results are compared with alternative water allocation models. The results show that the proposed solution methods are quite capable of providing appropriate reservoir operating policies, while requiring rather short computational times due to continuous formulation of state and decision variables. Reliability indices are used to compare the overall performance of the proposed models. Based on the results from this study, the collocation method leads to improved values of the reliability indices for total reservoir system and utility satisfaction of water users, compared to the Ricatti equations method. This is attributed to the flexible structure of the collocation model. When compared to alternative water allocation models, lower values of reliability indices are achieved by the collocation method.     

Towards hydrological model calibration and validation: simulation of stable water isotopes using the isoWATFLOOD model

Calibration and validation of hydrological models is a challenge, particularly in remote regions that are minimally gauged. This paper develops a novel methodology for large‐scale (>1000 km²) hydrological model calibration and validation using stable water isotopes founded on the rigorous constraints imposed by the need to conserve both water mass and stable isotopes simultaneously. The isoWATFLOOD model is applied to five basins within the Fort Simpson, Northwest Territories region of northern Canada to simulate stream discharge and oxygen‐18 signals over a 3‐year period. The isotopic variation of river discharge, runoff components, and evaporative fractionation are successfully simulated on both a seasonal and continual basis over the watershed domain to demonstrate the application of isotope tracers to regional hydrologic calibration. The intended application of this research is to remote, large‐scale basins, showing promise for improving predictions in minimally gauged basins and climate change research where traditional, rigorous approaches to constraining parameter uncertainty may be impractical. This coupled isotope‐hydrological (i.e. iso‐hydrological) approach to modelling reduces the number of possible parameterizations, resulting in potentially more physically‐based hydrological predictions. isoWATFLOOD provides a tool for water resource managers and utilities to use operationally for water use, allocation, and runoff generation estimations. Copyright © 2012 John Wiley & Sons, Ltd.     

Monthly suspended sediment load prediction using artificial intelligence: testing of a new random subspace method

ABSTRACT

The predictive capability of a new artificial intelligence method, random subspace (RS), for the prediction of suspended sediment load in rivers was compared with commonly used methods: random forest (RF) and two support vector machine (SVM) models using a radial basis function kernel (SVM-RBF) and a normalized polynomial kernel (SVM-NPK). Using river discharge, rainfall and river stage data from the Haraz River, Iran, the results revealed: (a) the RS model provided a superior predictive accuracy (NSE = 0.83) to SVM-RBF (NSE = 0.80), SVM-NPK (NSE = 0.78) and RF (NSE = 0.68), corresponding to very good, good, satisfactory and unsatisfactory accuracies in load prediction; (b) the RBF kernel outperformed the NPK kernel; (c) the predictive capability was most sensitive to gamma and epsilon in SVM models, maximum depth of a tree and the number of features in RF models, classifier type, number of trees and subspace size in RS models; and (d) suspended sediment loads were most closely correlated with river discharge (PCC = 0.76). Overall, the results show that RS models have great potential in data poor watersheds, such as that studied here, to produce strong predictions of suspended load based on monthly records of river discharge, rainfall depth and river stage alone.     

A stochastic conflict resolution model for water quality management in reservoir–river systems

In this paper, optimal operating rules for water quality management in reservoir–river systems are developed using a methodology combining a water quality simulation model and a stochastic GA-based conflict resolution technique. As different decision-makers and stakeholders are involved in the water quality management in reservoir–river systems, a new stochastic form of the Nash bargaining theory is used to resolve the existing conflict of interests related to water supply to different demands, allocated water quality and waste load allocation in downstream river. The expected value of the Nash product is considered as the objective function of the model which can incorporate the inherent uncertainty of reservoir inflow. A water quality simulation model is also developed to simulate the thermal stratification cycle in the reservoir, the quality of releases from different outlets as well as the temporal and spatial variation of the pollutants in the downstream river. In this study, a Varying Chromosome Length Genetic Algorithm (VLGA), which has computational advantages comparing to other alternative models, is used. VLGA provides a good initial solution for Simple Genetic Algorithms and comparing to Stochastic Dynamic Programming (SDP) reduces the number of state transitions checked in each stage. The proposed model, which is called Stochastic Varying Chromosome Length Genetic Algorithm with water Quality constraints (SVLGAQ), is applied to the Ghomrud Reservoir–River system in the central part of Iran. The results show, the proposed model for reservoir operation and waste load allocation can reduce the salinity of the allocated water demands as well as the salinity build-up in the reservoir.     

A Study on Confined Flow of Ground Water Through a Tunnel

Confined flow of ground water through a tunnel, which might be encountered in tunneling under the bottom of a sea or river, is numerically analyzed by a reductive finite element method formulated in our research. That is, the rate and potential distribution of the confined flow of ground water through an opening are obtained in connection with the permeability of rock masses, the thickness of covered ground, the location of impermeable bedrock, and other variables. In addition, flow through an opening in the ground with highly permeable masses and discharge of ground water through a tunnel in grouted masses are illustrated, and some useful results for the practical application of tunneling work are obtained.     

Insights into agricultural influences and weathering processes from major ion patterns

Karst areas and their catchments pose a great challenge for protection because fast conduit flow results in low natural attenuation of anthropogenic contaminants. Studies of the hydrochemistry of karst sources and river solutes are an important tool for securing and managing water resources. A study of the geochemical downriver evolution of the Wiesent River and its tributaries, located in a typical karst terrain, revealed unexpected downstream decreases of nitrate with maximum mean values of 30 mg/L at the source to minimum values of 18 mg/L near the river mouth. This trend persisted over the length of the river even though increased agricultural activities are evident in the downstream section of the catchment. This pattern is caused by fertilizer inputs via diffusive and fast conduits flow from karst lithology in the upstream area that may have reached the river's source even from beyond the hydrological catchment boundaries. Further downstream, these influences became diluted by tributary inputs that drain subcatchments dominated by claystone and sandstone lithologies that increased potassium and sulphate concentrations. Our findings indicate that bedrock geology remains the dominant control on the major ion chemistry of the Wiesent River and that agricultural influences are strongest near the headwaters despite increased land use further downstream, due to long‐term storage and accumulation in karst aquifers. This feature may not be unique to the Wiesent River system, as carbonates cover significant portions of the Earth's surface and subsequent work in other river systems could establish whether such patterns are ubiquitous worldwide.