River Segments Research Articles

How many measurements are required to construct an accurate sand budget in a large river? Insights from analyses of signal and noise

AbstractMorphological change in river channels is frequently evaluated in the context of mass balance sediment budgets. In a closed sediment budget, measurements of sediment influx and efflux are coupled with measured changes in channel topography to provide both spatial and temporal resolution, and independent estimates of the mass balance. For sediment budgets constructed over long river segments (~102 channel widths or greater) and long periods (~2 years or longer), spatial and temporal accumulation of measurement uncertainty, compounded by inadequate sampling frequency or spatial coverage, may produce indeterminate results. The degree of indeterminacy may be evaluated in the context of a signal‐to‐noise ratio (SNR), which is a function of the magnitude of the mass balance and the magnitudes of potential systematic uncertainties associated with measurements and incomplete sampling. We report on a closed sand budget consisting of measurements of flux and two morphological surveys for a 50‐km segment of a large river over a 3‐year period. Accurate reporting of the magnitude and sign of the change in sand storage was only possible by using state‐of‐the‐art techniques with high temporal frequency and large spatial extent. Together, a sand flux and morphological mass balance revealed that sand evacuation was temporally concentrated (~100% of mass change occurred during 19% of the study period) and highly localized (70% of mass change occurred in 12% of the study segment). A SNR analysis revealed that uncertainty resulting from undersampling may approach or exceed that caused by measurement uncertainty and that daily sampling of suspended‐sand concentration or repeat mapping of at least 50% of the river segment was required to determine the sand budget with SNR > 1. The approach used here to analyze sand budget uncertainty is especially applicable to other river systems with large temporal variability in sediment transport and large spatial variability in erosion and deposition. © 2018 John Wiley & Sons, Ltd.

Геоинформационное картографирование геолого-геоморфологического строения долины р. Катунь (Горный Алтай) на основе морфометрических показателей

The types of geological and geomorphological structure of the Katun valley are distinguished in the work. For this, a method of geoinformation mapping using morphometric indicators of the valley’s width and meandering of the channel was developed. The morphometric parameter of the valley’s width was calculated as the total area of terraces. As the morphometric parameters of the channel’s meandering, the angles of the river segments’ deviation relative to each other were calculated. Conjugated analysis of these morphometric indicators enabled identifying 18 morphotypes. These morphotypes according to the geological and geomorphological structure of the valley were combined into 4 classes. Separation of the Katun valley in certain classes and morphotypes is due to the different geological history of these sites during the Quaternary period. The most important reasons predetermining the modern variety of geological and geomorphological types of the valley are neotectonic movements and exogenous phenomena (glaciers, dam lakes, landslides, etc.) naturally localized in the space from the upstream of the river to its exit into the foothills. The developed method can be applied for quantitative morphometric classification of the mountain rivers’ valleys in other regions.

Phosphorus retention along a typical urban landscape river with a series of rubber dams

Small dams are widely constructed in urban rivers as landscape engineering practice, which increasingly cause eutrophication problems. Phosphorus retention in dammed rivers is a critical factor driving eutrophication, but it is little known in urban landscape river systems controlled by small dams. In this study, we investigated the retention of different phosphorus species along an urban landscape river with 30 rubber dams. We found that 42.5% (7.69 metric tons/yr) of the total phosphorus (TP) was trapped within dams, of which total particulate phosphorus (TPP) retention load accounted for 81.5%. From first river segment BBF-4# to the segments further downstream, the TP retention rate sharply decreased from 47.6% to −8.3%-9.2%, and phosphorus was mainly retained in the uppermost segment of the dammed river. The retention rate of dissolved reactive phosphorus (86.3%) was higher than that of TPP (40.3%) because of biological uptake. Further, with a retention rate of −11.3%, the dammed river was a net source of dissolved organic phosphorus. Different hydrological regimes, due to seasonal events and dam management, greatly influenced phosphorus retention within the dammed river, resulting in higher retention loads in the rainy season than in the dry season, and very low retention loads in the snowmelt season, with 1.48, 0.55 and 0.06 t/month, respectively. Our findings imply that management practices should focus on reducing the phosphorus export from the upper watershed and improving the hydrodynamic conditions of the dammed urban landscape river with regard to eutrophication.

Water quality and pollution loading of a river segment affected by landfill leachate and domestic waste

ABSTRACT The Marikina River in the Philippines has been polluted by Payatas landfill leachate, and domestic and agricultural waste. This study monitored the water quality at five stations on the river and two stations on two creeks that discharge to the river to determine the effects of Payatas landfill and to estimate pollution loading. The dissolved oxygen (DO), chemical oxygen demand (COD) and other water quality parameters were compared with the Philippines Standards for river water classification. It was found that Payatas leachate has a significant influence on the DO and COD levels as well as other water quality parameters. Per capita pollution loading for Quezon City was found to be lower than for Europe and Japan. The effect of leachate is more significant during the dry season. It is recommended that a leachate collection system be established to prevent leachate form entering Payatas creek, and that the Patayas landfill be replaced with a modern landfill site, conforming to current best practice at another location. List of Abbreviation: BOD= Biological Oxygen Demand COD = Chemical Oxygen Demand DO = Dissolved Oxygen EC = Electrical Conductivity M1, M2, M3, M4, M5 = monitoring stations TDS = Total Dissolved Solids TSS = Total Suspended Solids

Utilizing non-traditional data sources for estimating channel seepage losses

Accurate streamflow data, which constitute the basic component in estimating seepage losses or gains in streamflow are in short supply in developing countries. The lack of either financial or technical resources, or both, and at times, the lack of understanding of the importance of accurate streamflow measurements in supporting modeling and water resources decision making process hinder the installation and proper maintenance of streamflow gauges. Therefore, the current study adopted the aim of demonstrating the feasibility of utilizing alternative streamflow data sources in hydrologic studies. In the current study, such sources included effluent from a large wastewater treatment plant as an inflow to the river segment under consideration while the outflow from the same river segment was taken to be the flow discharged into a dam reservoir as calculated from daily dam reservoir water balance. A water balance was established for a 48 km segment on the Zarqa River in Jordan with components covering the inputs of discharge from springs, and wastewater treatment plants and outputs such as direct evaporation, and surface withdrawals for irrigation purposes. Channel seepage was estimated as the difference between inputs and outputs of the river segment water balance. Final results demonstrated the feasibility of utilizing non-traditional data sources, whenever available, to conduct analysis that traditionally has not been possible.

Characterization of channel planform features and sinuosity indices in parts of Yamuna River flood plain using remote sensing and GIS techniques

River planform features and sinuosity are widely acknowledged as important geomorphological indices that control the channel hydraulics and stream power which determines the flow velocity and sediment supply to downstream reaches. Despite their significance, there has been little study about these indices in mighty Yamuna River for understanding the topographic control and hydraulic regime. This paper investigates the channel planform features and sinuosity by employing topographic map, digital elevation model (DEM), and satellite imageries to elucidate the morphological, sedimentological, and hydrological characteristics of the channel. Based on sinuosity index (varies between 1.02 and 1.41), the river segments are categorized into straight (segments 1, 3, 4, 5, 6), sinuous (segments 2, 7, 8, 9, and 11), and meandering (segment 10). The parameters analyzed to find out the influencing factors on sinuosity indicate geomorphological and anthropologic control in their development. Tectonic control of sinuosity in the studied stretch is ruled out as it is flowing through an alluvial plain with low rate of discharge.

Hydrological regime and climate interactively shape riparian vegetation composition along the Colorado River, Grand Canyon

AbstractQuestionsHow closely do riparian plant communities track hydrological and climatic variation in space, and how do interactions among hydrological and climatic filters influence success of flow management strategies?LocationGrand Canyon, Arizona, USA.MethodsMulti‐year vegetation surveys were conducted across three hydrological zones—active channel, active flood‐plain and inactive flood‐plain—within each of 42 sandbars that vary geographically in temperature and precipitation along a 400‐km river segment. Ecological niche models were used to estimate locally optimal conditions of maximum inundation duration, elevation above daily peak flow, mean annual precipitation and mean maximum and minimum temperature for 16 of the most abundant woody and 58 of the most abundant herbaceous plant species. These estimates were used to calculate CWM environmental preferences, which were used to determine how closely vegetation preferences tracked local variation in environmental factors, and to assess interactive responses of species and communities to variation in hydrology and climate.ResultsCommunities closely tracked hydrological variation across zones, but less so within zones. Communities tracked variation in minimum temperature more closely than maximum temperature or precipitation. At the species level, woody plants that were more abundant in wetter hydrological conditions were also more abundant in wetter climatic conditions, and vice versa. This relationship was even stronger at the community level, where there were significant negative relationships between CWM preferences of inundation duration and temperature for both woody and herbaceous vegetation.ConclusionsThe climate–hydrology linkages found in this system suggest that increasing temperatures and drought are likely to reduce the inundation tolerance of riparian vegetation within the Grand Canyon. Increasing the duration of high‐flow events would likely reduce the abundance of encroaching woody vegetation but could also reduce the resilience of remaining vegetation to heatwaves and drought. The reinforcing effects of climatic and hydrological filters are likely to generally result in greater sensitivity of species composition to environmental change than if those environmental filters acted independently. These results have implications for predicting resource responses to environmental change, as well as prescriptions for direct vegetation management to enhance resilience.

Bacterioplankton Community Structure in the Lancang River Basin and the Analysis of Its Driving Environmental Factors

In order to explore the bacterioplankton diversity community structure in the Lancang River basin, as well as to study the relationship between the bacterial diversity and environmental factors, MiSeq high-throughput sequencing was used to analyze and compare the bacterial diversity and community composition of samples in February 2017. Furthermore, Pearson correlation analysis and redundancy analysis (RDA) were used to identify the key environmental factors for the change of bacterial community structure in the natural river and reservoirs of the Lancang river. The results show that the ACE index and Shannon index of the natural river are higher than those of the reservoir, and the main environmental factors causing the diversity of planktonic bacteria in natural river and reservoir segments are water temperature (WT), dissolved oxygen (DO), turbidity (Tur), permanganate index, pH, and total nitrogen (TN). Overall, 26772 optimized reads were obtained from samples based on the high-throughput sequencing of the V3 and V4 region of the 16S rRNA gene. The bacterial species detected in these samples cover 45 phyla and 965 genera. Taxonomic assignment analysis indicated that Proteobacteria, Bacteroidetes, Firmicutes, and Actinobacteria are the abundant phyla. Among them, the Proteobacteria content is relatively rich, accounting for 36%-94% of the bacterial community. The predominant groups are α-Proteobacteria, β-Proteobacteria, and γ-Proteobacteria, at the genus level, with Proteobacteria ratios of 0.39%-21.56%, 0.39%-55.80% and 31.09%-99.18%, respectively. The environmental factors affecting the community structure of planktonic bacteria are different in natural river and reservoir. DO and Tur are the key environmental factors affecting the community structure of planktonic bacteria in the natural river, while the community structure of planktonic bacteria in reservoirs is mainly affected by WT, permanganate index, and TN.

Long‐Term Evolution of Sand Transport Through a River Network: Relative Influences of a Dam Versus Natural Changes in Grain Size From Sand Waves

AbstractTemporal and spatial nonuniformity in supplies of water and sand in a river network leads to sand transport that is in local disequilibrium with the upstream sand supply. In such river networks, sand is transported downstream as elongating waves in which coupled changes in grain size and transport occur. Depending on the magnitude of each sand‐supplying event and the interval between such events, changes in bed‐sand grain size associated with sand‐wave passage may more strongly regulate sand transport than do changes in water discharge. When sand transport is controlled more by episodic resupply of sand than by discharge, upstream dam construction may exacerbate or mitigate sand‐transport disequilibria, thus leading to complicated and difficult‐to‐predict patterns of deposition and erosion. We analyzed all historical sediment‐transport data and embarked on a 4‐year program of continuous sediment‐transport measurements to describe disequilibrium sand transport in a river network. Results indicate that sand transport in long river segments can evolve over ≥50‐year timescales following rare large sand‐supplying events. These natural changes in sand transport in distal downstream river segments can be larger than those caused by an upstream dam. Because there is no way to know a priori whether sand transport in a river has changed in response to changes in the upstream sand supply, contemporary continuous measurements of sand transport are required for accurate sand loads and budgeting. Analysis of only historical sediment‐transport measurements, as is common in the literature, may lead to incorrect conclusions with respect to current or future sediment‐transport conditions.

Water Quality Modeling For Pollutant Carrying Capacity Assessment Using Qual2Kw In Bedog River

Considering the abundance of potential pollutant sources along Bedog River, i.e. highly dense residential areas, agricultural lands, and industrial areas, this study aimed to quantitatively assess the Pollutant Load (PL) and Pollutant Carrying Capacity (PCC) of the river based on Chemical Oxygen Demand (COD) and Biological Oxygen Demand (BOD)parameters. The assessment employed a water quality modeling using Qual2Kw that provided not only the comprehensive values of PL and PCC but also the amount of PL that should be reduced to meet the PCC of every river segment. Water sampling and primary parameter measurement were conducted purposively in seven observation points, which included one point source and six non-point sources (river segments). River segments were determined according to the characteristics of land use and drainage system. Descriptive, graphic, and spatial analyses on water quality modeling show that the COD and BOD of Bedog River (2.24 km) indicates a small presence of PL compared to the river’s PCC. The PCC allows additional pollutant loads of 566.95 kg/day or 0.024 ton/hour BOD and 22,965.12 kg/day or 0.96 ton/hour COD. However, a high BOD in segments 3, 5, and 6 and a high COD in segment 5 imply the needs for PL reduction.

Flow Duration Curve from Satellite: Potential of a Lifetime SWOT Mission

A flow duration curve (FDC) provides a comprehensive description of the hydrological regime of a catchment and its knowledge is fundamental for many water-related applications (e.g., water management and supply, human and irrigation purposes, etc.). However, relying on historical streamflow records, FDCs are constrained to gauged stations and, thus, typically available for a small portion of the world’s rivers. The upcoming Surface Water and Ocean Topography satellite (SWOT; in orbit from 2021) will monitor, worldwide, all rivers larger than 100 m in width (with a goal to observe rivers as small as 50 m) for a period of at least three years, representing a potential groundbreaking source of hydrological data, especially in remote areas. This study refers to the 130 km stretch of the Po River (Northern Italy) to investigate SWOT potential in providing discharge estimation for the construction of FDCs. In particular, this work considers the mission lifetime (three years) and the three satellite orbits (i.e., 211, 489, 560) that will monitor the Po River. The aim is to test the ability to observe the river hydrological regime, which is, for this test case, synthetically reproduced by means of a quasi-2D hydraulic model. We consider different river segmentation lengths for discharge estimation and we build the FDCs at four gauging stations placed along the study area referring to available satellite overpasses (nearly 52 revisits within the mission lifetime). Discharge assessment is performed using the Manning equation, under the assumption of a trapezoidal section, known bathymetry, and roughness coefficient. SWOT observables (i.e., water level, water extent, etc.) are estimated by corrupting the values simulated with the quasi-2D model according to the mission requirements. Remotely-sensed FDCs are compared with those obtained with extended (e.g., 20–70 years) gauge datasets. Results highlight the potential of the mission to provide a realistic reconstruction of the flow regimes at different locations. Higher errors are obtained at the FDC tails, where very low or high flows have lower likelihood of being observed, or might not occur during the mission lifetime period. Among the tested discretizations, 20 km stretches provided the best performances, with root mean absolute errors, on average, lower than 13.3%.

Global river slope: A new geospatial dataset and global-scale analysis

A rivers’ longitudinal gradient (i.e. slope) is a key parameter in fluvial hydrology, hydraulics, and geomorphology. It affects a multitude of fluvial variables such as flow velocity and sediment transport. Limitations in river slope data, both its availability and accuracy, constrain the fidelity of fluvial modeling, particularly at larger or global scales. Traditional slope calculation algorithms cannot accurately predict river slopes as these are based on cell-by-cell calculation, which is only suitable for hillslopes and small mountainous streams. This paper presents a methodology for calculating global river slope and a procedure to upscale it for relatively coarse resolution, suitable for global scale modeling. The methodology is based on a simple principle of calculating slope from elevation depression over the length of a river segment, which is automated to allow global scale calculations. Version 1.0 of the Global River-Slope (GloRS) geospatial dataset is introduced and shown to be a step improvement over a previous product (NHDplus for the contiguous United States) and compares favorably to observed slope data collected from the literature. Statistical analysis of Earth’s continents and large basins highlights interesting spatial trends. A semi-empirical regression analysis between basin-average river slope and other basin-scale parameters show that terrain slope accounts for 67% of the variability in basin-average river slope, with average discharge, sediment load and basin temperature contributing additional improvements to global predictions of 3%, 4%, and 3%, respectively.

Integrating species-centric and geomorphic-centric views of interior least tern and piping plover habitat selection

The Federally endangered interior least tern (Sterna antillarum athalassos) and threatened piping plover (Charadrius melodus) nest on emergent sandbars in several braided rivers in the USA. Previous habitat selection and geomorphic investigations identified a relationship between channel width and nesting incidence. Species-centric analyses indicate selection for the widest available channels whereas geomorphic-centric analyses indicate the probability of species occurrence was higher in narrow channels that better supported suitable sandbar habitat. Given the disparate conclusions from each of these perspectives, we examined species use in relation to channel-width metrics across segments of the Platte, Niobrara, and Loup Rivers from both perspectives. We found the probability of nesting incidence increased with increased maximum unvegetated channel width in all river segments. However, maximum unvegetated width decreased with increased total channel width once total width exceeded 300 m in the central Platte River and 500 m in all other river segments as did the probability that the channel was free of permanently-vegetated islands. Channels within the Lower Platte, Loup and Niobrara River systems with total widths of 500–800 m appear to be both wide enough to have a high probability of nesting incidence and narrow enough to be free of vegetated islands. Actions that affect channels with total, bank-to-bank widths of <500 m and >800 m would likely have a small influence on species use while actions that change the width characteristics of 500–800 m channels could have a strong negative or positive influence on species use. Integrating species- and geomorphic-centric views into a single analysis provided a fuller picture of the relationship between species use and channel-width metrics.

Targeting lateral connectivity and morphodynamics in a large river‐floodplain system: The upper Rhine River

AbstractAs a consequence of historical damming and channelization, most large rivers are disconnected from their floodplains, which therefore endure severe deficits in fluvial dynamics. Regaining some degree of lateral connectivity can lead to improved geomorphological and biological interactions. Yet, it is necessary to take into account limitations posed by current uses and legislation. This study presents a methodological approach to the selection of a realistic restoration target for a heavily modified large river segment, the free‐flowing Upper Rhine River downstream of Iffezheim dam (France–Germany border), based on the analysis of the existing biogeomorphic deficits, constraints set by human uses, and previous restoration experiences. To achieve the selected restoration target, proposed scenarios include embankment removal, bank lowerings, and side channel widenings with the aim of increasing lateral hydrological connectivity and promoting morphodynamics (bank erosion in lateral channels) that allow for the renewal of floodplain habitats. Results from 2‐D hydraulic simulations allow for a sensitivity analysis, comparing the current situation with the proposed scenarios, through parameters such as shore length of side channels actively connected at both ends to the main channel (eupotamon), and shear stress as a proxy for initiation of gravel erosion. Outcomes indicate that the two proposed restoration scenarios would succeed in reconnecting side channels and in increasing areas prone to substrate erosion, while maintaining flood protection and the heaviest navigation use among European rivers. The presented approach aids in the assessment of potential large river restoration scenarios and, thus, in the discussion of water management strategies.

In-time source tracking of watershed loads of Taihu Lake Basin, China based on spatial relationship modeling.

Influent river carrying cumulative watershed load plays a significant role in promoting nuisance algal bloom in river-fed lake. It is most relevant to discern in-stream water quality exceedance and evaluate the spatial relationship between risk location and potential pollution sources. However, no comprehensive studies of source tracking in watershed based on management grid have been conducted for refined water quality management, particularly for plain terrain with complex river network. In this study, field investigations were implemented during 2014 in Taige Canal watershed of Taihu Lake Basin. A Geographical Information System (GIS)-based spatial relationship model was established to characterize the spatial relationships of "point (point-source location and monitoring site)-line (river segment)-plane (catchment)." As a practical exemplification, in-time source tracking was triggered on April 15, 2015 at Huangnianqiao station, where TN and TP concentration violated the water quality standard (TN 4.0mg/L, TP 0.15mg/L). Of the target grid cells, 53 and 46 were identified as crucial areas having high pollution intensity for TN and TP pollution, respectively. The estimated non-point source load in each grid cell could be apportioned into different source types based on spatial pollution-related entity objects. We found that the non-point source load derived from rural sewage and livestock and poultry breeding accounted for more than 80% of total TN or TP load than another source type of crop farming. The approach in this study would be of great benefit to local authorities for identifying the serious polluted regions and efficiently making environmental policies to reduce watershed load.

Benthic Macroinvertebrate Diversity in the Middle Doce River Basin, Brazil

This resource contains a checklist of the benthic macroinvertebrate community sampled biannually from 1999 to 2010 in eight natural lakes from the middle Rio Doce Valley lake system and eight river segments in the Piracicaba River basin (sub-basin of Doce river), Minas Gerais State, Brazil. Three of the lakes are located inside a protected state park and are surrounded by preserved vegetation (Atlantic Forest). The other five lakes are in private properties, surrounded by Eucalyptus plantations. The seven stretches of rivers have a distinct degree of anthropogenic impacts. Samples were collected with a kick net and fixed with formaldehyde solution. Four phyla were represented: Mollusca, Annelida, Arthropoda, and Platyhelminthes. For Insecta, 76 families were identified, one family was identified for Crustacea, and nine families were identified for Mollusca. This subproject belongs to the International Long-Term Ecological Research Project (ILTER—Programa de Pesquisas Ecológicas de Longa Duração—PELD) site 4.

Analisis Tingkat Pencemaran Air Sungai Yeh Sungi di Kabupaten Tabanan Dengan Menggunakan Indikator Biologis NVC Ikan dan Keragaman Jenis Makrozoobenthos

Water is a major component of life processes on earth, good quantity and quality of water is highly coveted by humans. River as one type of waters and become a living medium for aquatic organisms, to measure the level of water pollution one of them by using bioindicator method. Bioindicators are organisms that have biological responses that can indicate the entry of certain pollutants in the environment. The purpose of this research is to know river pollution based on Nutrition Value Coeficient (NVC) fish and Makrozoobenthos that live in it. The value of NVC (Nutrition Value Coefficient) of fish varies on each station in the downstream and upstream segments of the Yeh Sungi river, this illustrates that at each station and on different river segments shows different levels of pollution. Waters with clean categories up to the contaminated waters will be found larvae insect , insects and snails. So on headwaters with macrozoobenthos conditions like this describe the condition of clean waters up to be contaminated, so if associated with the value of NVC fish then the headwaters of Yeh Sungi including the contaminated waters category.

Water quality of Cisadane River based on watershed segmentation

The growth of population and industrialization combined with land development along river cause water pollution and environmental deterioration. Cisadane River is one of the river in Indonesia where urbanization, industrialization, and agricultural are extremely main sources of pollution. Cisadane River is an interesting case for investigating the effect of land use to water quality and comparing water quality in every river segment. The main objectives with this study were to examine if there is a correlation between land use and water quality in Cisadane River and there is a difference in water quality between the upstream section of Cisadane River compared with its downstream section. This study compared water quality with land use condition in each segment of river. Land use classification showed that river segment that has more undeveloped area has better water quality compared to river segment with developed area. in general, BOD and COD values have increased from upstream to downstream. However, BOD and COD values do not show a steady increase in each segment Water quality is closely related to the surrounding land use.Therefore, it can not be concluded that the water quality downstream is worse than in the upstream area.

Fulfilling spawning flow requirements for potamodromous cyprinids in a restored river segment

The Baixo Sabor hydroelectric scheme was recently constructed (began operating in 2015), blocking fish migration immediately at the river mouth. As a compensation measure for spawning habitat loss the Vilariça River which confluences with Sabor River, immediately downstream from the Baixo Sabor scheme, was chosen for rehabilitation site as an attempt to replace the spawning grounds lost in Sabor River for the potamodromous cyprinid Iberian barbel (Luciobarbus bocagei). Restoration activities included: placement of submerged weirs with fish ramps to increase the lotic/lentic sequence, bank reinforcement, boulder placement and river water profile increase. Water from the nearest reservoir was channeled underground to the lower Vilariça River in order to increase the water flow. The most appropriate volume of water was determined by means of a 1D model coupled with the CASiMiR to determine the weighted usable area for barbel spawners. Nine spawning grounds were identified. Fish migrations began in mid-April when water temperature increased (c. 16°C) and water flow decreased. Barbel tend to spawn in coarse substrate with shallow water and moderate current. Ontogenetic differences in habitat use were reported, with barbel juveniles preferring weaker currents and deeper zones when compared to spawners. Females also display different preferences, which are more apparent after spawning. Both life-stages exhibit the maximum habitat suitability at c. 1.5m3/s. The habitat model used in this study was able to accurately predict the occurrence of spawning grounds, representing, therefore, a valuable decision-making support tool for river managers.

A 10-Year Statistical Analysis of Heavy Metals in River and Sediment in Hengyang Segment, Xiangjiang River Basin, China

Heavy metal elements in water and surface sediments were characterized in Hengyang river segment in Xiangjiang River basin, one of China’s most important heavy metal control and treatment region. Data of heavy metal monitoring results in water and sediment for 10 years were acquired from an environmental monitoring program in the main channel of the studied area. Descriptive and exploratory statistical procedures were performed to reveal the characteristics of the sample distributions of heavy metal elements. The sample distributions of heavy metal elements were largely skewed right. Data censoring and too severe rounding in the water monitoring data were identified to have caused discretization in the sample distributions. Temporal and spatial characteristics of the data sets were addressed. The chromium (Cr) in the sediment possessed unique behavior, and this could be caused by a rapid deposition and releasing process.