Tributary Sections Research Articles

Implications of Water Quality Index and Multivariate Statistics for Improved Environmental Regulation in the Irtysh River Basin (Kazakhstan)

The selection of sites for permanent environmental monitoring of natural water bodies should rely on corresponding source apportionment studies. Tools like the water quality index (WQI) assessment may support this objective. This study aims to analyze a decade-long dataset of measurements of 26 chemical components at 26 observation points within the Irtysh River Basin, aiming to identify priority zones for stricter environmental regulations. It was achieved through the WQI tool integrated with geoinformation systems (GISs) and multivariate statistical techniques. The findings highlighted that both upstream sections of tributaries (Oba and Bukhtarma rivers) and the mainstream of the basin are generally in good condition, with slight fluctuations observed during flooding periods. Areas in the basin experiencing significant impacts from mining and domestic wastewater treatment activities were identified. The rivers Glubochanka (GL) and Krasnoyarka (KR) consistently experienced marginal water quality throughout the observation period. Various contaminant sources were found to influence water quality. The impact of domestic wastewater treatment facilities was represented by twofold elevated concentrations of chemical oxygen demand, reaching 22.6 and 27.1 mg/L for the KR and GL rivers, respectively. Natural factors were indicated by consistent slight exceedings of recommended calcium levels at the KR and GL rivers. These exceedances were most pronounced during the cold seasons, with an average value equal to 96 mg/L. Mining operations introduced extremal concentrations of trace elements like copper, reaching 0.046–0.051 mg/L, which is higher than the threshold by 12–13 times; zinc, which peaked at 1.57–2.96 mg/L, exceeding the set limit by almost 50–100 times; and cadmium, peaking at levels surpassing 1000 times the safe limit, reaching 0.8 mg/L. The adverse impact of mining activities was evident in the Tikhaya, Ulba, and Breksa rivers, showing similar trends in trace element concentrations. Seasonal effects were also investigated. Ice cover formation during cold seasons led to oxygen depletion and the exclusion of pollutants into the stream when ice melted, worsening water quality. Conversely, flooding events led to contaminant dilution, partially improving the WQI during flood seasons. Principal component analysis and hierarchical cluster analysis indicated that local natural processes, mining activities, and domestic wastewater discharge were the predominant influences on water quality within the study area. These findings can serve as a basis for enhanced environmental regulation in light of updated ecological legislation in Kazakhstan, advocating for the establishment of a comprehensive monitoring network and the reinforcement of requirements governing contaminating activities.

A dataset of vector and coverage of river and lake surface water in Guangxi, Yunnan, Guizhou (China), and the ASEAN member states

Runoff plays an important role in the water cycle, and information on the distribution of rivers in a watershed is essential for water resources, ecology, environment as well as socio-economic activities in a certain region. The region involving Guangxi, Yunnan and Guizhou in China, and the ASEAN member states is known for cloudy rainfall and distinct mountainous terrain. A comparative analysis of existing river datasets highlights the insufficient characterization of river information in this unique region. To obtain more accurate river distribution data for assessing water resources and the ecological environments, we integrated in this paper the Eurasian continental river vector data (2010) and the ESA land classification data (2020). Following this, we employed an expansion and contraction buffer analysis method to address the issue of river discontinuity. And in this way, we produced a dataset of river surface water in Guangxi, Yunnan and Guizhou in China and the ASEAN member states. After further processing the ESA land classification data, we derived a vector dataset of lake surface water encompassing Guangxi, Yunnan, and Guizhou in China, along with the ASEAN member states. Finally, we calculated the coverage of river and lake surface water and compiled a coverage dataset with a resolution of 1km grid across Guangxi, Yunnan, Guizhou in China, and the ASEAN member states. Comparing with the HydroRIVERS dataset and our water remote sensing datasets (Global Surface water, Esri Land Cover, Dynamic World V1, GRWL), this dataset excels in characterizing the river system in the study area, and provides richer details than the input datasets, as evidenced by the following. This dataset can fill in gaps in the mountainous tributary sections of the Eurasian continent's river vector data from 2010, and effectively address the issue of discontinuous and missing rivers. The dataset can be used to provide basic prior data for water extraction in Guangxi, Guizhou, Yunnan and the ASEAN state members, and it holds great value in flood forecasting and water resources management. Moreover, it can also serve social and economic activities such as ecological preservation, transportation planning, agricultural irrigation and energy use.

Sediment Particle Size Composition in the Riparian Zone of the Three Gorges Reservoir

The riparian zone is a transitional zone of terrestrial ecosystems and aquatic ecosystems, which is one of the main sources of reservoir sediment and pollutants. The sediment loss has an increasing trend in the riparian zone of the Three Gorges Reservoir (TGR), which was closely related to sediment particle size composition change in the riparian zone, but its distribution and factors are still unclear. Hydrological conditions, sediment particle size composition and vegetation properties in the riparian zone were investigated in 3 mainstream and 8 tributary sections along the Yangtze River within the TGR across 450 km. On the one hand, both sediment sand content and median particle size (D50) showed a horizontal raising trend from the upstream to the dam region of the TGR at the mainstream and tributary sites. On the other hand, compared to the upper-middle mainstream and the tributaries of Longxi, Wu, Longxi, Pengxi, Daning, Tongzi rivers, the D50 was much higher in the lower altitudes of the riparian zone in the tributaries of Wubu, Ruxi, and Xiangxi and the mainstream in the lower reaches of the Yangtze River. With the raising of the riparian zone slope, D50 decreased in the mainstream riparian zone sites, while increased in the tributary riparian zone sites (p < 0.05). Besides, D50 was 2.3 times higher in the south aspect relative to the north aspect of the riparian zone in the TGR. No significant relationship was found between root biomass of a local dominate species-Cynodon Dactylon (Linn.) and D50. Hydrological and geographical variables could predict 64%–67% of the D50 variance, and thus could be regarded as the main predictor of D50 in the riparian zone of the TGR.

Geomorphological analysis of Tinto-B Vallis on Mars

This work analysis an 81 km long 1.85 km wide fluvial valley on Mars (at 2°55’ South and 111°53’ East) for the first time, located near to the so-called Palos carter and Tinto Vallis, called Tinto-B hereafter. The length of the valley is approximately 81 km, and the average width is ~1.85 km, depth ~250 m. The hypsometric curves were created in 5 different buffer sizes on the main valley and the biggest tributary valley. The tributary valley shows a youth stage in the geomorphological evolution opposite to the main valley, which shows a mature stage. The crater statistical analysis based age of the main valley (2.9 Ga) poorly correlates with the early wet period of the red planet, thus, formed somehow later than most Martian valleys. Using the model SIMWE (SIMulated Water Erosion), for the to identify the small-scaled tributary valley systems and the small-scaled erosional landforms showed area elevated drainage density. The highest density of the tributary sections is 29.02 km/km2 , and the average is 3.09 km/km2. Considering only the main valley 0.017 km/km2 would have been measured, suggesting dozen(s) early tributaries were heavily eroded.

Simulation-based assessment of the impact of fertiliser and herbicide application on freshwater ecosystems at the Three Gorges Reservoir in China

Dams have profound impacts on river ecosystems, amongst them inundation of land, altered dynamics of the water body or uprising reservoir backwaters influencing tributary or upstream river sections. Along the outstandingly ecologically important Yangtze River in China, the Three Gorges Reservoir (TGR) is the largest project, covering an area of 1080 km2. From the beginning, the dam-project came in for criticism on increasing environmental risks due to sub-merging former industrial and urban areas.We simulated dynamics of biotic and abiotic components of the TGR ecosystem (trophic guilds of aquatic organisms, hydrodynamics, nutrients), as well as the behaviour of the herbicidal substance propanil and its metabolites 3,4-Dichloroaniline (DCA) and 3,3′,4,4′-tetrachloroazoxybenzene (TCAB). A modelling environment, provided by the AQUATOX software, was adapted to the specific situation at a tributary reach to the Yangtze river ‘Daning River’. As the simulated food web contained several interconnected trophic levels, a significant biomagnification of metabolites was demonstrated by our simulation studies. In particular, newly emerging stagnant downstream sections of tributaries exhibited high probabilities due to accumulating pesticides from upstream sources.The common problem of algal blooms in the TGR-region was addressed by dose-response simulation experiments with essential nutrients. Impacts on structure and abundance of populations of aquatic organisms were shown. However, even high nutrient loads resulted in only slight changes of densities of organisms of all trophic levels. Nevertheless, the probabilities for large-scale algal blooms affecting drinking water quality were considered low because of high flow velocities and discharge rates towards the Yangtze River.We see high potential of simulation-based assessments that provide information for risk managers dealing with whole catchment areas. They are put in the position to differentiate the magnitude of impacts of various factors and decide about the most effective remediation measures.

Spatial Distribution of Carbon, Nitrogen and Phosphorus within Surface Sediments in the Lower Lancang River: Pollution Assessment Related to Dams

Surface sediment is one of the main sources of nutrients in overlying water environments, and these can also indirectly reflect the degree of eutrophication. In this paper, the spatial distribution characteristics of total organic carbon (TOC), total nitrogen (TN) and total phosphorus (TP) in the surface sediments of 11 sections in the lower Lancang River during flood season are analyzed, as well as the distribution of phosphorus in different forms. The main sources of TOC and its correlation with TN and TP are discussed and, finally, the pollution levels of the surface sediments are evaluated. The results show that the average content of TOC in the surface sediments of the lower Lancang River is 9003.75 mg/kg. The average TN content is 893.79 mg/kg, while the average TP content is 521.35 mg/kg. The TOC in the surface sediments of the lower Lancang River is derived mainly from algae and plankton in the river, and the TN and TP have similar sources. The total phosphorus in the surface sediments of the lower Lancang River is composed mainly of calcium-bound phosphorus (Ca-P). The evaluations of the organic pollution index and comprehensive pollution index show that the surface sediment pollution degree at the upper sections of the Nuozhadu and Jinghong Dams are more serious than those below the dams. Furthermore, the tributary sections are all slightly polluted, with the exception of the Mengyang River, which is considered moderately polluted.

Esker systems in the Gulf of Bothnia

Eskers, straight-to-sinuous ridges of waterlain sand and gravel, and their erosional meltwater channel counterparts are geomorphological imprints of the palaeo-glacial hydrological system. Esker networks hundreds of metres to hundreds of kilometres long are widespread features of Quaternary glaciations and are used to reconstruct regional and continental patterns of deglaciation. However, they have been less commonly reported from sedimentary marine environments. Esker systems from the southern Gulf of Bothnia are imaged with unprecedented clarity in new multibeam datasets which reveal a highly connected subglacial hydrological network and its relationship to an underlying drumlin field. Sinuous, elongate sediment ridges thread through a drumlin field which rises from about 80 to 50 m water depth in the southern Gulf of Bothnia (Fig. 1a–i). Individual ridge segments range from 4 km long and are c. 50–200 m wide and c. 2–20 m high. They connect into much longer esker chains over 15 km long, broken only by small gaps. The longer esker paths form a broadly dendritic network, with up to fourth-order ‘tributaries’, converging southward in the direction of ice-flow. Within tributary sections, localized braiding and anabranching occur; occasionally isolated distributaries do not reconnect to the main …

Analysis of channel evolution characteristics in the Hobq Desert reach of the Yellow River (1962–2000)

A series of problems, resulting from sediment deposition and channel silting, have occurred on the Hetao Plain as a result of changes to the Hobq Desert reach of the Yellow River. Therefore, improved research on channel evolution in this reach is vitally important. Using profile data from 80 channel cross-sections obtained in 1962, 1982, 1991 and 2000 from the Yellow River in the Hobq Desert, we showed that there was serious sediment deposition here (especially for the tributary section in the eastern desert) and that maximum sediment deposition occurred during 1982–1991. As sediment was deposited along the mobile channel, the channel trunk shrank and moved to the north. The characteristics of river channel evolution are dramatically different between the western and the eastern Hobq Desert reaches of the Yellow River, which include desert and the tributary sections, respectively. Erosion mainly occurred in the desert section, whereas sediment deposition occurred in the tributary section, with peak values at the mouths of on Yellow River tributaries. The desert section had a larger average erosion rate and smaller accumulation rate than the tributary section. The influences of tectonic movement and stream gradient on channel evolution in this fluvial reach were minimal. The sediment inputs from ten Yellow River tributaries (especially during flood seasons) have dominated channel evolution in these tributaries. The building of artificial levées has intensified sediment deposition in the channel, whereas the reduction of mainstream discharge (especially in the flood seasons), caused by the operation of reservoirs and water diversion activities (such as for agricultural irrigation), has further intensified the sediment deposition in the river channel.

Automated classification of debris-covered glaciers combining optical, SAR and topographic data in an object-based environment

Abstract Satellite imagery is increasingly used to monitor glacier area changes and create glacier inventories. Robust and efficient pixel-based band ratios have proven to be accurate for automatically delineating clean glacier ice, however such classifications are restricted on debris-covered ice due to its spectral similarity with surrounding terrain. Object-Based Image Analysis (OBIA) has emerged as a new analysis technique within remote sensing. It offers many advantages over pixel-based classification techniques due to the ability to work with multiple data sources and handle data contextually and hierarchically. By making use of OBIA capabilities we automatically classify clean ice and debris-covered ice in the challenging area surrounding Mount Manaslu in Nepal using optical (Landsat 8), topographic (void-filled SRTM) and SAR coherence (ALOS PALSAR) data. Clean ice was classified with a mean accuracy of 93% whilst debris-covered ice was classified with an accuracy of 83% when compared to manually corrected outlines, providing a total glacier accuracy of 91%. With further developments in the classification, steep tributary sections of ice could be contextually included, raising the accuracy to over 94%. One prominent advantage of OBIA is that it allows some post-processing and correction of the glacier outlines automatically, reducing the amount of manual correction needed. OBIA incorporating SAR coherence data is recommended for future mapping of debris-covered ice.

Sediment grain-size characteristics and its source implication in the Ningxia–Inner Mongolia sections on the upper reaches of the Yellow River

The Ningxia–Inner Mongolia (NIM) reaches of the Yellow River are characterized by a high sediment load, severe siltation, large channel migration, and frequent dike breaching, resulting in substantial social, economic, and environmental problems for residents along the river. Therefore, studies on the grain-size characteristics of sediments in the NIM reaches of the Yellow River and locating the primary sediment source areas are important for the prevention and mitigation of silt accumulation and the construction of water conservation facilities. In this study, 361 samples from the Yellow River and 178 samples from potential source areas were analyzed. Large grain sizes in the riverbed and floodplain materials were found in the desert sections and in sections containing 10 tributaries, respectively. The size of the riverbed and floodplain materials fluctuates relatively frequently in the tributary sections and is coarser at confluences of the tributaries with the Yellow River. The floodplain material is better sorted than the riverbed material, and the sorting coefficients (especially the former) fluctuate most widely in the tributaries sections. Two main fractions of the floodplain and most of the riverbed materials in the major river reaches are observed: 3.9–63μm and 63–250μm. The first fraction component of the riverbed material, 63–250μm, is found in the desert sections and part of the tributary sections, whereas the second fraction component (250–500μm) is found in some parts of the desert sections. The variations in the size characteristics of the riverbed and floodplain materials demonstrate that both materials are derived from lateral sources. The main sources of the riverbed materials are the Ulan Buh Desert and the Kubuqi Desert in the Wuhai-Zhonghexi reaches, and the main sources of the riverbed and floodplain materials are the 10 tributaries in the Zhonghexi-Lama Bay reaches. The riverbed and floodplain materials in the desert sections are deposited near the source and far from the source, respectively. Both types of sediments in the tributary sections are mainly deposited near their sources. Through wind and hydraulic sorting, the size of the riverbed material in the tributaries sections becomes finer in contrast to that in the desert sections, which suggests that coarse sediments have not been effectively carried downstream.

Distribution patterns of benthic diatoms during summer in the Niyang River, Tibet, China

The aim of this study was to investigate the distribution, density, community structure and biodiversity characteristics of benthic diatoms, and to analyze whether differences in species composition and abundance exist in different regions of the Niyang River, Tibet. Among the 157 taxa observed in 15 sampling sites in the main river and tributary, most were casual species (>100), the relative abundance of the genera Achnanthes and Fragilaria was 67% of the total relative abundance. Achnanthes minutissima was the most important species and dominated the whole river reaches (average relative abundance was 30%); the average diatom densities were 7.4 x 10(5) cell/cm(2) at all sites, and increased slowly from the upper section to downriver. The significant indicator taxa with higher relative abundance were Achnanthes biasolettiana (18.0%) and Fragilaria arcus (18.2%), Fragilaria capucina var. vaucheriae (31.2%), Fragilaria construens var. venter (11.3%) and Cymbella affinis (11.0%) in the upper, tributary and mid-river sections, respectively. Achnanthes minutissima was the most abundant species (56%) in the downriver section. Biodiversity indices showed a gradual decrease from the up-to down-river section, and dominant species were more abundant in the upper and mid-river sections than in the downriver section. A two-way indictor species analysis (TWINSPAN) of diatom composition clearly showed four different groups, namely the upper, mid, lower and tributary sections. Detrended correspondence analysis (DCA) supported the results of TWINSPAN, and the characteristics of site distribution and species composition in the Niyang River supported the spatial structure of diatom assemblages. This study indicates that bio-assessment programs utilizing benthic diatoms could clearly benefit lotic water with regional stratification.

Late Quaternary hydroclimatology of a hyper-arid Andean watershed: Climate change, floods, and hydrologic responses to the El Niño-Southern Oscillation in the Atacama Desert

Although certain characteristics of the El Niño-Southern Oscillation (ENSO) are well known on contemporary timescales, less is known about the magnitude–frequency relationships of this atmospheric phenomenon on longer timescales or its relationship to widespread flooding, especially in its core zone along the sub-tropical Andes where La Niña or El Niño episodes control regional hydroclimatology. Using a combination of stratigraphic evidence, geochronologic dating ( 14C and OSL), stable isotope analyses, and water geochemistry along the Rio Moquegua in the northern fringes of the Atacama Desert, we assemble a paleoflood chronology for mainstem and tributary sections for the past ca. 20 ka and ascertain the variation in ENSO frequency and magnitude. Because of the inherent watershed structure and regional hydroclimatology, mid-valley tributaries of the Rio Moquegua only flood during El Niño episodes and thus provide an important proxy of extreme El Niños while mainstem stratigraphy records both La Niña and El Niño episodes. El Niño floods appear to have been pronounced during the Late Pleistocene and up to at least the Younger Dryas (~ 12,000 cal yr BP) while stratigraphic evidence of large El Niño floods is lacking in tributary systems during the Mid-Holocene. Flood stratigraphy in a ~ 2 ka 7 m high terrace along the mainstem indicates an increased frequency and magnitude of large floods between ca. 700 and 1610 AD as compared to the period from ca. 160 BCE to 700 AD with “mega-Niños” occurring ca. 1330 AD and ca. 1650 AD. Water geochemistry and radiocarbon dating indicate that at least two major aquifers exist, with wells and springs in the mid-valley dating to 710 and 3100 14C yr BP, respectively, while water from a spring in the headwaters dates to 10,320 14C yr BP. This range in dates suggests that groundwater flow in the mid-valley is neither fossil water nor exclusively recharged from local precipitation while the older date for headwater sections suggests a more fossil groundwater source and lack of contemporary recharge. The 18O similarity between groundwater in the mid-valley and the regional meteoric water line (MWL) suggests a Pacific moisture source and the role of El Niño precipitation in recharging local aquifers. Thus, El Niños and Pacific-sourced moisture are an important component of the regional hydroclimatology and the variation in ENSO frequency and intensity has significant social and hydrologic repercussions in these hyper-arid settings.

Development of a 3D Hydrodynamic Model for Coastal Ecosystem Modelling. Application to the Plume of the Seine River (France)

A 3D (three dimensional) numerical hydrodynamical model has been developed as the basis for ecological modelling and long time simulations. A compromise between computation time reduction and the model capacity to simulate fine-scale physical processes has been looked for. The model is based on a separation between external and internal modes and the coupling between the two modes can be locally optional. The horizontal grid is rectangular with irregular meshes and cross sections of tributaries are respected. The vertical grid uses real depth coordinates and the vertical axis is split into several layers bounded by fixed horizontal levels irregularly distributed. Turbulence closure is based on a mixing length model that accounts for turbulence damping by density gradients. This model is applied to the ‘Baie de Seine’ and the Seine River plume is studied. The model is validated by numerous comparisons with measurements (tide, currents, salinity fields). The three-dimensional behaviour of the Seine plume has been studied and compared to theoretical study cases. In particular the importance of topography is enlightened as well as the diffusive role of tides and the small influence of the earth rotation in the near field of the plume. On the other hand winds are shown to control the plume structure.

El Niño floods and culture change: A late Holocene flood history for the Rio Moquegua, southern Peru

The 1997–1998 El Nino generated large floods throughout southern Peru, especially in inland locations along Rio Moquegua. Using remote sensing, hydraulic modeling, field surveying, and stratigraphic analyses, we estimate the magnitude and frequency of this flood and determine a late Holocene flood history for main- stem and tributary sections. Modeling indicates a peak discharge of 450 m3/s for the 1998 flood, with an estimated recurrence interval between 50 and 100 yr. Flood deposits for two large events, dated to A.D. 690 and A.D. 1300, respectively, exist in a small tributary system. Tiwanaku site abandonment (ca. A.D. 1000) predates the younger flood, indicating that stratigraphically recognizable El Nino–driven floods were not a causal mechanism for abandonment. Although possessing three flood units, main-stem alluvium is considerably younger (<320 14C yr B.P.) than tributary alluvium, evidencing the major channel widening and lateral reworking of the main stem.

Fine‐scale genetic structuring in endemic galaxiid fish populations of the Taieri River

Many of New Zealand's Galaxias species have declined in abundance this century. Some stream‐resident species are now restricted to sections of tributaries above waterfalls >3 m in height that act as barriers to the predatory brown trout (Salnto trutta). It has been suggested that these spatially isolated populations are also genetically isolated and as a result experience restricted gene flow. We used isozyme electrophoresis to test this hypothesis. Comparisons were made between and within tributaries at sites separated by waterfalls. Results from six polymorphic loci showed evidence of genetic heterogeneity among populations of G. anomalus and G. depressiceps from tributaries of the Taieri River system, South Island, New Zealand. In one instance, heterogeneity was found within a single tributary. This demonstrates that gene flow among populations is restricted and that waterfalls are likely to be a significant influence in controlling galaxiid population structure.