Tributary Flow Research Articles

Geomorphology of the Liera catchment (Dolomites, NE Italy): understanding landscape response to an extreme event

ABSTRACT Geomorphological field surveys and mapping have been carried out in a catchment of the Dolomites (eastern Italian Alps) as part of a research project aiming at the assessment of sediment availability for mass wasting in mountain environments. The study area is the Liera catchment which was severely affected by a high-intensity, regional-scale storm named ‘Vaia’ (27–30 October 2018), which induced relevant morphological changes, caused a major flood in the main stream and triggered debris flows in many tributaries. This contribution gives a snapshot of the present-day state of the study area to improve the understanding of such a landscape by characterizing the processes that control its geomorphological spatio-temporal dynamics and evolution.

A hybrid deep learning model based on feature capture of water level influencing factors and prediction error correction for water level prediction of cascade hydropower stations under multiple time scales

The operating conditions of large cascade hydropower stations are complex. Improving the water level prediction accuracy of large cascade hydropower stations is significant for flood control, shipping, irrigation, etc. A new hybrid model based on a refined deep residual shrinkage network and an optimized gated recurrent unit – long term memory network (GRU-LSTM) model is proposed for water level prediction at different time scales. First, to make the input data in the form of a feature map so the model can capture the weight characteristics of each influencing factor when the water level changes, the water level, flow rate, and hydroelectric power plant output data are constructed as high-dimensional feature inputs. To reduce the prediction error caused by downstream tributary backwater jacking, downstream tributary flow is added to the input data. At the same time, a semisoft threshold function with an adjustable function is inserted into the model to improve feature recognition accuracy, reduce deviation, and eliminate the noise of the original hydrological data. Second, an error weight correction function is used to adjust the error between the predicted water level and the observed water level so that the model can automatically adjust the weights of each influencing factor according to the evaluation results of water level prediction. In this process, the parameters of LSTM are optimized using the Archimedes optimization algorithm, and the output results of the LSTM and GRU networks are weighted to obtain a more accurate water level prediction. The proposed model achieves good accuracy and efficiency in downstream water level prediction of the Xiangjiaba Hydropower Station, outperforms existing hydrodynamic and artificial intelligence methods, and has robust scalability in flood forecasting and urban rainwater forecasting.

Two-dimensional mathematical modeling of 2013 and 2020 Amur River floods

Predicting river flooding of the territory where people live and engage in economic activities is urgent. The most problematic area in the Russian Far East is the territory through which the Amur River and its tributaries flow. The article considers the calculations of two Amur River floods: 2013 – catastrophic flood and 2020 – low flood. The simulation was carried out using a system of two-dimensional Saint-Venant equations using the Stream 2D CUDA program. The solution of the system of equations by numerical methods is based on the original author’s methodology. Channel depth maps and WordDEMTM (Airbus Defense and Space, Intelligence) data at 24 m resolution were used as a digital elevation model. Calculations of river floods in 2013 and 2020 were performed on a built-in and calibrated mathematical model, which matches the observational data well.

Age of Information in Multihop Connections With Tributary Traffic and No Preemption

Age of Information (AoI) has gained significant attention from the research community because of its applications to Internet of Things (IoT) monitoring and control. In this work, we treat multihop connections over queuing networks with tributary flows and non-preemptive service: packets cannot be discarded because they are utilized for other system objectives, such as data analytics. Without preemption, the key tool for optimizing AoI is then the scheduling policy between the different data flows at each intermediate node. This is the subject of our analysis, along with the impact of packet erasure on the age. We derive upper and lower bounds for the average AoI considering several queuing policies in arbitrary network topologies, and present the results in different scenarios. Network topology, tributary traffic load, and link characteristics such as packet erasure generate complex trade-offs, which affect the optimal operation point and the age performance. The scheduling strategy at each node can also affect performance and fairness among users, particularly at critical bottleneck links, which have a significant impact on the overall performance of the whole network.

Analysis of Meanders and Bends of Lesser Zab River from Dalga VViilllage to Darbandi Rania

This study investigates the meanders of the Lesser Zab River in the study area, in terms of morphometric characteristics such as )length, width, direction, shape, area and symmetry of the meanders( and their distribution along the main river in the river valley through explaining the forcing factors in the creation of such shapes such as slope, geological structure, transported materials, flow of tributaries into the main river and tectonic activity in terms of geomorphic actions such as (carving, removal, transportation and sedimentation(, with the influence of human factors. Also, the phases of meanders development from north to south in the river valley are discussed. Furthermore, differences and dissimilarities of such formation can be seen between the periods 1972-2021; this is reflected in morphometric characteristics and geomorphic actions in all parts of the river basin. This research relies on various research methods such as deductive method, numerical methods and cartographic methods; using (ArcGIS.version.10.8), with the use of digital elevation model (DEM12.5m), to conduct detailed field work by the researcher. In the study area, 17 bends and meanders in the river have been identified, of which 7 bends were bends and 10 were meandering with the percent of meandering reaching (1.58), and the bend of Kewiya has the highest rate of twist, which reached (5.4). At the same time, the value of symmetry in the bend of Bekhre village is completely symmetric, because the value of each side (X) and (Y) is 49. For example, the length of the river for each of the years (2020,1984 and 2021) consecutively reached (32 km, 32.876 km, 31.7٢7 km), These changes will affect the size of human activities in the study area such as )distribution of human settlements, agricultural activities, poultry farms, fish ponds and industrial activities).

Seismic characterization of a landslide dam failure hazard chain: Insights into flow dynamics and implications for warning

Landslide dam failure hazard chains (i.e., landslide dam breaches → outburst debris flow → river blocking) are common in alpine valley regions worldwide, and they pose a great threat to human safety and infrastructure. However, the formation and dynamic processes of cascading hazards are still poorly understood, which limits our ability to recognize warning signals for this multi-hazard chain. We conducted 12 large-scale field tests on the multi-hazard chain induced by landslide dam failure, measuring the flow dynamics and the resulting seismic signals. The results showed that river blockage caused by a dam-breaching debris-flow underwent stages of injection and initial deposition, river damming and equilibration, during which the evolution of seismic signals can help interpret the physical processes and mechanisms involved. The radiated energy level resulting from the dam breaching and the debris flow increased with the diameter, speed and volume of the fluid-particles mixture; while the frequency of the seismic data increased with the speed of the fluid-mixture particles but decreased with the diameter of the particles. Greater tributary inflow discharge or dam height generally resulted in larger and more destructive outburst debris flows, characterized by greater seismic energy and a wider frequency domain, resulting in a greater degree of obstruction within the receiving channel. We also show that the seismic technique employed is an efficient means of detecting and characterizing landslide dam failure hazard chains, providing downstream warnings of a river blockage by estimating the critical blockage conditions, such as the tributary flow velocity, sediment concentration, and kinetic energy. This study provides a scientific perspective for understanding the dynamic signatures of the entire hazard chain evolutionary process and it highlights opportunities to use seismic data for multi-hazard chain research and warning.

A Geochemical and Mineralogical Study of the Sediments Transported through Wadi Al-Qassab and Wadi Al-Murr, South Mosul City, Northern Iraq

The Wadi Al-Qassab and Wadi Al-Murr are the main valleys in the west of the town of Qaiyarah, extending almost parallel in the northwest-southeast direction and descending from the topographically high areas located to the west towards the Tigris River in the east. Wadi Al-Qassab extends in the area sandwiched between the mountains (Attshan, Nuegett and Eklayan) in the north of the valley and the mountains (Jawan, Najmah and Qaiyarah) south of the valley which represents anticlines. While Wadi Al-Murr extends to the south of the mountains (Najmah and Qaiyarah). These two valleys are active during the rainy season due to the wide catchment area, especially for Wadi Al-Qassab, which several seasonal tributaries flow. The structural situation reflected by the Qaiyarah and Najma anticlines helps reveal many types of rocks belonging to the Fat'ha and Injana formations, as well as the sediments that cover the area mainly derived from the rocks of these two formations. The two valleys' sediments were classified as sand and gravelly sand that will contribute to the groundwater recharge during the rainy season. The average mineral compositions of the sediments (according to X-ray data and chemical composition of major and minor oxides) in the valleys of Al-Murr and Al-Qassab were estimated to be silicate minerals (such as quartz, clay minerals and feldspar minerals) estimated at 62.78% and 59.89%, carbonate minerals (main calcite) 26.14% and 31.97%, the evaporite minerals that included gypsum mineral 5.46% and 2.87% and halite 0.62% and 0.36%, in addition to the iron oxide phases of 4.69% and 4.41%, respectively. Most of the trace elements have been associated with clay minerals, either in the form of substitution and/or adsorption, and some of them are maybe as resistant minerals inherited from the source rocks from which they were derived. Chemical analysis shows that there are no significant indicators of hydrocarbon pollutions that may enrich the area with some organometallic compounds in valley sediments due to the emitted refinery gases and fine hydrocarbon particles.

Hydropeaking impairs upstream salmonid spawning habitats in a restored Danube tributary

AbstractHydropower is considered an important form of renewable energy, often involving hydropeaking. While the effects of hydropeaking on aquatic communities in areas downstream the dam are well understood, there is a lack of studies investigating potential impacts on tributaries located further upstream. In this study, we tested the effects of hydropeaking operations on upstream tributaries in a restored area of the Danube River, with a focus on the periods of backlog and release of water (up‐ramping and down‐ramping, respectively) during the filling and release of the reservoir. We used brown trout egg and larval mortality, linked to hydraulic, sedimentary and physiochemical changes in spawning grounds as an indicator. We compared hydropeaking‐affected versus non‐affected sites in upstream tributaries using HydroEcoSedimentary Tools (HESTs) loaded with clean gravels and brown trout eggs. Egg and larval mortalities were significantly higher in the hydropeaking‐affected site with more than 80% egg mortality and almost 100% larval mortality compared to values of 55–63% and 80–85%, respectively, in non‐affected sites. Spawning ground quality was significantly altered in the hydropeaking‐affected site, where the highest mortalities were observed. Overall, duration of time periods with flow velocities close to zero were a key variable, potentially decreasing oxygen supply for eggs and larvae. Such periods of close to zero flow velocities were driven by backlog periods during the filling of the reservoir, revealing that such events can severely impair ecological integrity of spawning sites in tributaries upstream of dams by slowing the flows in upstream tributaries. Such altered processes can reduce fish population recruitment and need to be considered in future restoration projects.

Regional Imbalance in the Levels of Development in Bagalkot District- Karnataka: A Spatial Analysis

After independence India has made remarkable progress in the socio-economic status of the people. But the attainment of this has spread highly uneven among the urban and rural areas. Regional imbalances are common phenomenon in the world, which occurred across different continents, countries and regions in different extent and India is not exception in this context. This phenomenon spread among inter-regions, inter-states and intra-states n India. This resulted into uneven development in the country. This process of imbalance is not exception in Bagalkot district. There are three major rivers namely the Krishna, the Malaprabha and the Ghataprabha and their tributaries flow in the study area and play important role in the development of the district. However, the study reveals that there exists a wide imbalance in the level of socio-economic development in the region. In view of this, an attempt has been made in this research work to evaluate and compares temporal growth and spatial pattern of disparities in the levels of socio-economic development at block level in Bagalkot district. Correlation coefficient technique has been applied to understand the correlation between different factors which are responsible for widening the regional imbalance. To analyses the regional imbalance of six taluks of Bagalkot district, 23 social, economic and demographic indicators have been considered. The present paper is based on secondary information based on which the socio-economic imbalance among the taluks of the district is made with the help of composite development index for two time of point i.e. 1997 and 2017 data. It has been observed that the social indicator values varied from 11 to 27. The study period witnessed Bagalkot, Badami, Hunagund and Jamkhandi are the three taluks which represent high social development, whereas low (< 11) social development was observed in Bilagi taluk. The outstanding causes for this backwardness are are, less number of education institutes, communication centers, adult education centers, health centers, family planning centers, recreational centers etc. The observed values of economic development are ranging between 19 and 35. It had been observed in only two taluks viz Bilagi and Hungund were found in high economic development, and low economic development was recorded in Jamakhandi taluk. Bagalkot, Mudhol and Badami taluks registered under relatively developed range. Lastly to understand the overall development, the observed values of socio-economic, economic and infrastructure indicators are added and derived a separate composite index.

Evaluation of water resources changes of the Mountain Dniester in 20th century following the RCP8.5 scenario and based on the “climate-runoff” model

The relevance of the research consists in the need for evaluating the water resources changes of the Dniester due to global warming. The mountain part of the Dniester Basin is a zone of the river's runoff formation that determines its water content. The subject of research includes a process of climate changes and their impact on the water resources of the Mountain Dniester’s catchments. The research focuses on determining the water resources changes under current and possible future climatic conditions represented by climatic scenarios.
 The research aims at evaluating the water resources changes of the mountain part of the Dniester’s catchment area at the present and in the future by the mid-21 st century (2021-2050) based on the “climate-runoff” model using meteorological observations data (up to 2018 inclusive) and scenario data (averaged data based on 14 mathematical models of the CORDEX project, RCP8.5 scenario).
 During the research the resources of humidification, heat (heat equivalent) and water content for modern (1989-2018) and scenario (RCP8.5, 2021-2050) climatic conditions based on application of the "climate-runoff" model were evaluated. The theoretical basis for estimating the natural (undisturbed by water management) annual runoff in this model is represented by the water-heat balance equation. The meteorological characteristics (average monthly air temperatures and precipitation) serve as input data. The runoff calculated using the water-heat balance equation is called a climatic runoff. One of the peculiarities of the research consists in the use of the vertical zoning law with respect to distribution of runoff and climatic factors of its formation. During the comparative analysis the dependence of annual runoff norms on height of the Mountain Dniester’s terrain specified in modern regulatory documents served as a basic dependence. Such dependence reflects an altitude-dependant distribution of runoff for the climatic conditions that preceded the significant impact of global warming on air temperature (until 1989).
 The analysis of the dependences of average long-term values of the annual runoff depending on the terrain altitude showed that the runoff changes for two studied periods (before and after 1989) are within ±12,3%. The analysis of the graphs of chronological course of annual water flow of the mountain tributaries of the Dniester made it possible to confirm the absence of statistically significant trends in their fluctuations.
 According to the RCP8.5 climate scenario over the period of 2021-2050 and following the results of calculations based on the “climate-runoff” model, the dependences of the average long-term altitude-related values of climatic factors and climatic runoff were retrieved. It was found that the effects of global warming decrease with increasing altitude. In the foothills (up to 200 m) the annual precipitation decreases (up to 11%), the maximum possible evaporation increases (up to 17%) and water resources decrease (up to 46%). Heat resources cease to increase and water resources cease to reduce at the altitudes over 800 m. The average deviation of the scenario and baseline values for precipitation over the estimated period will amount to 2.41% for precipitation, 5.79% for maximum possible evaporation and 8.87% for water resources. Thus, reduction of water resources in the mountainous part of the Dniester by the mid-21 st century will be insignificant. When evaluating the current state of water resources of the Mountain Dniester no significant changes were discovered, thereby not contradicting the other authors’ data.

Development of a Physically Based Sediment Transport Model for Green Bay, Lake Michigan

AbstractGreen Bay is the largest freshwater estuarine system on earth, drains one‐third of the Lake Michigan basin and delivers one‐third of the lake's phosphorus load. Southern Green Bay is a designated area of concern due to ecosystem degradation that includes eutrophication, harmful algal blooms, hypoxia, lost or altered habitat, and reduced water quality. While marine estuaries are subject to tidal influence and saltwater intrusion, this freshwater estuary is subject to lake intrusion of freshwater with different quality parameters. Understanding the simultaneous effects of tributary flows and lake intrusions is crucial to comprehend the dynamics of freshwater estuaries. A single hydrodynamic, wind‐wave, and sediment transport model was developed for the lake and its estuary. This approach provides fine resolution in the estuary and simulates directly the combined effects of tributary flows and lake intrusions. The approach overcomes open‐boundary limitations of nested models, and of whole‐lake models that lack sufficient resolution or wind‐wave and sediment transport simulation. The model confirms findings of previous studies and demonstrates how the circulation, thermal regime, wave action, and sediment transport in the estuary depend on meteorological forcing, tributary flows, and lake intrusions. The stage is set to apply this approach to study biogeochemical processes in lakes and estuaries.

Long-term analysis of road salt loading and transport in a rural drinking water reservoir watershed

Chloride exports from the widespread application of road salt serve as a primary contribution to water body salinity in cold climate regions. Road salt pollution is a concern in drinking water supplies due to the relationship between chloride concentration and water corrosivity. In the Northeastern U.S., researchers and water quality managers are interested in better understanding how management practices can mitigate the negative effects of road salt pollution. This study uses regression-based chloride load estimates from LOADEST to produce mass balances and analyze transport flow-paths to the Wachusett Reservoir from a predominantly rural watershed. A chloride mass balance for 2000 through 2019 revealed that reservoir and watershed export only recently reached a level similar to estimated inputs from road salt (11,200 ton/yr). Results from hydrograph and load separation techniques show that average loading (4300 ± 1300 ton/yr) and discharge from baseflow (3.2 ± 0.9 m3/s) contributed approximately 74% and 65% of the total loading (5800 ± 1800 ton/yr) and discharge (4.93 ± 1.50 m3/s), respectively from water years 2001 through 2019. Approximately 40% of the total annual tributary load (30% baseflow; 10% runoff) occurred in the spring (March–May) and is attributed to elevated baseflow conditions from snowmelt. As indicated by a baseflow chloride index, baseflow concentrations are 14% greater than the total concentrations measured in the tributaries. Therefore, the baseflow-dominated tributary chloride loading is due to a combination of greater discharge and chloride concentration in baseflow as compared to direct surface runoff. However, a long-term trend analysis suggests a slightly increased fraction of chloride loading via overland flow in several reservoir tributaries, potentially indicative of late 20th century land development. This study offers a unique monitoring approach for management authorities to better assess road salt pollution in water systems. The decadal response of the reservoir system reflects the slow-moving nature of the baseflow-dominated chloride loading and suggests that measurable water quality improvements will only be realized with a sustained long-term decrease in the amount of road salt applied.

Large‐Scale Particle Image Velocimetry Reveals Pulsing of Incoming Flow at a Stream Confluence

AbstractDespite widespread recognition that confluences are characterized by complex hydrodynamic conditions, few studies have mapped in detail spatial patterns of flow at confluences and variation in these patterns over time. Recent developments in large‐scale particle image velocimetry (LSPIV) have created novel opportunities to explore the spatial and temporal dynamics of flow patterns at confluences. This study uses LSPIV to map two‐dimensional flow structure at the water surface at a confluence and to examine variation in this structure over time. Results show that flow within the confluence is characterized by a large region of flow stagnation at the junction apex, a region of low velocities at the downstream junction corner, and a region of merging of the two flows along a mixing interface within the center of the confluence. Interaction between the incoming flows varies over time in the form of episodic pulsing in which one of the two tributary flows first decelerates and then subsequently accelerates into the confluence. The cause of this pulsing remains uncertain, but it may reflect unsteadiness in the water‐surface pressure‐gradient field as the two flows compete for space within the confluence. No large‐scale vortices are evident within the mixing interface for the particular flow conditions documented in this study, but such vortices do occur along the margins of the stagnation zone where shearing action between fast‐moving and slow‐moving fluid is strong. The results of the study provide insight into the time‐dependent dynamics of the spatial structure of flow at stream confluences.

Correlation Between Precipitation Index and Energy Generation in Hydroelectric Plants

A recent water crisis that befell over several states in Brazil negatively affected hydroelectric plants energy production once rainfall regime exerts a major influence in predominantly hydraulic power systems. This paper analyses the correlation between power generation and data collected from tributary flow, reservoir level, standardized precipitation index (SPI) on hydroelectric plants located in the Sao Francisco river basin. The analysis is performed by Pearsons Coefficient of Correlation, for a period of 28 years that includes the dry season, and for the dry season separately. The results showed weak and moderate correlation coefficients between SPI and generation for both analyzed periods with slightly higher correlations in the last years when a decrease in power generation is observed. The correlations found between the affluent flow, reservoir level, and the generation were influenced by the reservoir characteristics, and were slightly higher than those of the dry periods.

Long term hydrological and environmental monitoring of the Stryi River using remote sensing data and GIS technologies


 
 
 The proposed research sets the task of conducting monitoring aimed at determining the horizontal displacements of the channel of the Stryi River the largest right-bank tributary of the Dniester River. For this purpose, the river was zoned according to morphometric and hydrological characteristics. Three parts were identified, namely highland, piedmont and lowland ones, which radically vary in the nature of the flow and the amount of the displacement. The main research purpose consists in analyzing the impact of anthropogenic factors on the hydrological regime of the Stryi River, as well as studying the effect of the Ukrainian Carpathian Foredeep (UCF) and the Stryi Deep on the mode of horizontal displacements. The research object is processes occurring within the Stryi River channel. Considering main natural factors affecting the channel’s horizontal displacements, special attention is paid to the geological and sedimentological structures located in the region where the Stryi River and its tributaries flow; among the anthropogenic factors, deforestation and the extraction of building materials from the river channel are highlighted. Topographic, geological, soil maps and satellite images of various periods uploaded into ArcGIS software allowed us to monitor displacements observed for as long as 140 years ago. To monitoring the Stryi River channel displacements, such materials as topographic maps scaled 1: 75000 (Austrian period – 1874), 1: 100000 (Polish period – 1933, Soviet period – 1990); satellite images of Sentinel-2 (2019 and 2020 (after the flood)); a map of Quaternary sediments and a soil map scaled 1: 200000 were used. The Stryi River flows between two structures, i.e. the Skybovi Carpathians and the UCF. The right-bank tributaries (Bystrytsia, Limnitsia, Stryi, etc.), which begin in the Carpathians, cross the outer and inner boundaries of the UCF and are characterized by the stable river channel in its mountainous part, multi-braided in its piedmont part, as well as perennial and significant meandering within the Pre-Carpathian region. Lithological deposits have a significant impact at the mouth of the Stryi River. According to the research study results, displacements of up to 1,350m are measured in this area. The research includes an analysis of the influence of geological and sedimentological structures on the Stryi River displacement and the nature of its flow. It has been established that deforestation in the river basin, as well as unauthorized extraction of gravel materials, creates a significant environmental problem in this region. The results of monitoring of the channel deformation processes should be taken into account when solving problems related to river channel processes, namely the construction of hydraulic structures, the design of power transmission networks crossing rivers, the development of gas pipelines, the identification of hazardous flooding zones, the determination of consequences of destruction after floods, the establishment of boundaries of water protection zones, the management of recreational activities, monitoring of border lands and the establishment of an interstate border along rivers.
 
 

Changing River Network Synchrony Modulates Projected Increases in High Flows

AbstractProjections of change in high‐flow extremes with global warming vary widely among, and within, large midlatitude river basins. The spatial variability of these changes is attributable to multiple causes. One possible and little‐studied cause of changes in high‐flow extremes is a change in the synchrony of mainstem and tributary streamflow during high‐flow extremes at the mainstem‐tributary confluence. We examined reconstructed and simulated naturalized daily streamflow at confluences on the Columbia River in western North America, quantifying changes in synchrony in future streamflow projections and estimating the impact of these changes on high‐flow extremes. In the Columbia River basin, projected flow regimes across colder tributaries initially diverge with warming as they respond to climate change at different rates, leading to a general decrease in synchrony, and lower high‐flow extremes, relative to a scenario with no changes in synchrony. Where future warming is sufficiently large to cause most subbasins upstream from a confluence to transition toward a rain‐dominated, warm regime, the decreasing trend in synchrony reverses itself. At one confluence with a major tributary (the Willamette River), where the mainstem and tributary flow regimes are initially very different, warming increases synchrony and, therefore, high‐flow magnitudes. These results may be generalizable to the class of large rivers with large contributions to flood risk from the snow (i.e., cold) regime, but that also receive considerable discharge from tributaries that drain warmer basins.

An inverse design method for determining the optimal tributary flow into a main stream in a rainstorm period

Abstract To ensure water quality at the control cross-section of main streams (CCMS) in a rainstorm period, an inverse design method was proposed to determine the optimal discharge flow of tributary rivers. The design variables are tributary discharges and the target variables are the required concentrations of chemical oxygen demand (COD), dissolved oxygen (DO) and ammonia nitrogen (NH3-N) at CCMS. The relationship between target variables and design variables was identified using an artificial neural network (ANN). The database was obtained by Environmental Fluid Dynamics Code (EFDC) and the optimal tributary discharges were obtained by a genetic algorithm (GA) coupled with well trained ANN. The results showed the following results: (a) The relative prediction errors of ANN are mostly less than 5%. (b) When the inlet flow rate is 0 m3/s, 30 m3/s, 50 m3/s, 100 m3/s and 200 m3/s, the optimization total discharges of tributaries are 5.7 m3/s, 12.5 m3/s, 18.6 m3/s, 33.4 m3/s and 61.8 m3/s, respectively. (c) Most of optimization plans entirely satisfy the water quality requirements at CCMS except a few plans, in which the relative errors between optimized results and required values of COD and DO are less than 0.4% and 0.1%, respectively. The study showed that the inverse design method is efficient for determining the optimal discharges of multiple tributaries.

Sedimentary geochemistry of the Weihe River sediments, Central China: implications for provenance and weathering

Modern river sediments sampled from the Weihe River, Central China, were analyzed in regard to facies, grain size, major and trace element, and rare earth element (REE). The main aim of the study was to investigate source rock provenance and paleoweathering intensity. Grain-size and outcrop analyses indicate that sediments from the Weihe River are predominantly slit (< 62 μm) and sand (62 μm to 2000 μm). Major and trace element concentrations show inverse correlations with SiO2 content and grain size. Silty sediments are enriched in REE relative to upper continental crust (UCC), whereas sandy sediments tend to be depleted. UCC-normalized REE distribution fingerprints indicate that the silt sediments are mainly derived from the Loess Plateau, while sandy sediments are mainly sourced from the Qinling Mountains. Discrimination functions and La/Th ratio and Hf abundance discrimination diagram also show that silty sediments are mainly derived from quartzose sediments, the main components of Loess Plateau, while sandy sediments are mainly derived from felsic igneous source, the main components of Qinling Mountains in the region where tributaries flow. The chemical index of alteration (CIA), plagioclase index of alteration(PIA), and chemical index of weathering (CIW) suggest that Weihe River sediments are immature and have experienced relatively minor chemical weathering. This work has an important bearing on the general understanding of the role that source rock characteristics and weathering regime have on the formation of clastic sediments in modern rivers and provides a critical baseline for which future work on the Weihe River sediments can be evaluated against.

Lake Erie tributary nutrient trend evaluation: Normalizing concentrations and loads to reduce flow variability

Establishing tributary load (i.e., the mass exported over a period of time) targets to reduce anthropogenic nutrient inputs to receiving waters — and thus eutrophication — is a common mitigation strategy in freshwater and coastal ecosystems. However, detecting and quantifying trends can be difficult because annual precipitation strongly influences tributary flow (e.g., average daily stream discharge). This may obscure trends as wet years tend to produce high tributary loads despite management activities to reduce nutrient export, and dry years typically generate low loads, even without management of nutrients. Furthermore, flow and nutrient concentrations are often correlated. Earlier efforts to reduce the effect of flow variability on tributary nutrient assessment were limited by computational and methodological constraints, until the weighted regressions on time, discharge, and season (WRTDS) method was introduced in 2010. Here we use WRTDS to assess nutrient concentration and load changes from 1982 to 2018 in three tributaries to the western basin of Lake Erie, of the Laurentian Great Lakes. Generally, trends revealed by flow-normalization do not contradict those of non-normalized metrics; however flow-normalization made the patterns more perceptible than in non-normalized metrics and reduced the influence of a particularly wet or dry period at the end of records on long-term trend analysis. We demonstrate that using WRTDS for flow-normalization removed the noise arising from annual precipitation variability and makes tributary nutrient trend evaluation more straightforward.

Spatiotemporally varying inter-relationships between mainstem riverbed elevation and tributary sediment supply since the last interglacial in the upper Ara River, central Japan

The dynamics of sediment transport processes over millennial time scales in mountain river valleys remain poorly understood, limiting our overall understanding of sediment routing through river basins. Here, we reconstruct changes of the mainstem riverbed elevation, tributary sediment supply processes, and their inter-relationships since the last interglacial in the upper Ara River valley, central Japan. Aggradation of the mainstem river valley began before 100–95 ka and terminated by 41–40 ka. Then, the elevation of the mainstem floodplain remained stable until ~15 ka. Lateral erosion by the mainstem river, and intermittent periods of incision, continued until 5 ka, after which the mainstem river began actively incising. Aggradation of the mainstem riverbed before 41–40 ka elevated tributary junctions, decreasing the slopes of tributaries. Using reconstructed slope changes, and assuming sediment transport by debris flow in tributaries with slopes steeper than 8% and by traction in shallower tributaries, we classified the tributaries into three types: Type-A, with sediment supply by debris flow since the last interglacial; Type-B, with sediment supply by traction during the last glacial period and afterwards by debris flow; and Type-C, with sediment supply by traction since the last interglacial. Based on the relation between relief ratio and drainage area, we subdivided Type-C tributaries into those that plotted along (Type-C1) or markedly below (Type-C2) the regression line of the mainstem river and Type-A and -B tributaries. During aggradation of the mainstem river, sediments supplied by debris flow from Type-A and -B tributaries accumulated around junctions, interfingering with mainstem deposits. During this period, the junctions of Type-C1 tributaries were elevated almost synchronously with mainstem aggradation, while the junctions of Type-C2 tributaries were blocked by mainstem river deposits, forming blocked-valley lakes. Around 30 ka, Type-A and -B tributaries formed fans around their junctions that were subsequently truncated by lateral erosion by the mainstem river during the late glacial period and early Holocene, forming toe-cut terraces. Tributary deposits that had accumulated around the junctions were then reworked while maintaining a dynamic equilibrium state with the mainstem river. We infer that the responses of tributary landforms and sediment supply processes to the changing elevation of the mainstem riverbed during glacial and interglacial cycles varied depending on the drainage area and relief of each tributary. Considering the river basin as a whole, however, tributary deposits stabilized the elevation of the mainstem floodplain.