Upstream Point Research Articles

Impact of desilting by excavation on water quality in a water reservoir in the municipality of Fernandópolis, SP

Desilting is an important job in restoring water reservoirs, but it disturbs the environment and has a potential impact on water resources. The objective of this work was to evaluate the impact of the desilting operation by excavation on the water quality of Córrego da Aldeia, Fernandópolis/SP. The experimental design was completely randomized in a 2x3x4 factorial scheme, in which the main factors were constituted by the runoff periods (with and without runoff), the secondary by the excavation periods (before, during and after excavation) and the tertiary by the points of monitoring (upstream points E1, E2 and E3 and downstream point S, in relation to the reservoir). Samples and analyzes of the physical, chemical and biological variables of the water were collected between July 2020 and March 2022. After that, analysis of variance of the isolated factors and their interaction was performed, followed by a mean comparison test. Through the results, it was observed that the work impacted the water quality in the concentration of ammonium and ammonia in 154.1% and 151.9%, respectively. The other qualitative water variables evaluated (water temperature, hydrogenionic potential, dissolved oxygen, electrical conductivity, total coliforms and Escherichia coli) were impacted due to climate and/or use and occupation of the soil around the collection points.

Emission Pattern of NORMs and 137Cs in the Sediments of the Gaz River and the Gorgan Bay, North Iran

Information on the distribution and emission patterns of natural and artificial radionuclides and their radiation level in the environment is very important for assessing the health effects of people living in a given region. In this study, the specific activity of radionuclides was measured using high purity germanium detector and a map of their distribution was drawn. The samples were collected from the Gaz River sediment in northern Iran, in the mountains of Golestan Province, and sediments on the middle and southern side of Gorgan Bay. The average of specific activities of 226Ra, 232Th, 40K, and 137Cs was 17.61, 35.91, 398.65, and 4.01 Bq/kg, respectively, which for natural radioactive nuclei are lower than the global average. The highest concentration of 40K was obtained in the sediments of the Gaz River estuary due to the use of potassium fertilizers for agriculture in this region. The highest concentration of 137Cs was obtained in the sediments of Gorgan Bay because 137Cs is injected both directly through the atmosphere and transfer by river water from upstream points to the Gorgan Bay. The diffusion pattern of 137Cs in the Gorgan Bay was exactly the opposite of 232Th and showed the tendency of 137Cs to precipitate in calm areas in the middle of the Bay.

Cross-waves and pulsating flows in the side-channel spillway – an experimental approach

Potentially hazardous side-channels of complex geometry need to be investigated using detailed hydraulic physical models. This study aims to analyse the cross-waves pattern and pulsating flow using a side-channel spillway physical model. This study compares the cross-waves pattern were measured using an experimental installation set to generate cross-waves on the surface (original series) with another structure that did not produce cross-waves (modified series). The results showed that the geometry of the left wall caused instability in flow patterns and secondary flows. The starting point of Q 2 discharge was detected by minor turbulence on the water surface near the left wall at a water depth of 3.3 m at the starting point of the wall, but with no overtopping. Cross-waves formed downstream at the right wall crosswise, lower than at the left wall. The height of the cross-wave increased substantially from Q 100 to Q 1000 discharges leading to overtoppings near the left wall at a water depths of 4.2 and 5.0 m at the starting point of the wall, and near the right wall at a water depths of 3.8 and 4.0 m at the upstream point of the wall. The modifications provided optimal hydraulic conditions, i.e. elimination of cross-waves and non-uniform flows. The Vedernikov and Montouri numbers showed that both original and modified series did not enter the area where the pulsating flow occurred. This indicated that both series were free from the pulsating flow.

Wall Shear Stress Associated with Stroke Occurrence and Mechanisms in Middle Cerebral Artery Atherosclerosis.

Various mechanisms are involved in the etiology of stroke caused by atherosclerosis of the middle cerebral artery (MCA). Here, we compared differences in plaque nature and hemodynamic parameters according to stroke mechanism in patients with MCA atherosclerosis. Consecutive patients with asymptomatic and symptomatic MCA atherosclerosis (≥50% stenosis) were enrolled. MCA plaque characteristics (location and plaque enhancement) and wall shear stress (WSS) were measured using high-resolution vessel wall and four-dimensional flow magnetic resonance imaging, respectively, at five points (initial, upstream, minimal lumen, downstream, and terminal). These parameters were compared between patients with asymptomatic and symptomatic MCA atherosclerosis with infarctions of different mechanisms (artery-to-artery embolism vs. local branch occlusion). In total, 110 patients (46 asymptomatic, 32 artery-to-artery embolisms, and 32 local branch occlusions) were investigated. Plaques were evenly distributed in the MCA of patients with asymptomatic MCA atherosclerosis, more commonly observed in the distal MCA of patients with artery-to-artery embolism, and in the middle MCA of patients with local branch occlusion. Maximum WSS and plaque enhancement were more prominent in the minimum lumen area of patients with asymptomatic MCA atherosclerosis or those with local branch occlusion, and were more prominent in the upstream area in those with artery-to-artery embolism. The elevated variability in the maximum WSS was related to stroke caused by artery-to-artery embolism. Stroke caused by artery-to-artery embolism was related to plaque enhancement and the highest maximum WSS at the upstream point of the plaque, and was associated with elevated variability of maximum WSS.

Impacts of an urban flood control infrastructure on the limnology and ichthyofauna of a basaltic Cuesta stream (southeast Brazil).

Strategies for flood control associated to extreme precipitation events in urban areas are urgent, in order to prevent not only material damages but also to avoid human losses. The construction of flood contention reservoirs ("piscinões") has become a common engineering intervention in urban and peri-urban areas. However, there is a lack of studies focused on the evaluation of environmental impacts of this type of construction. This study intended to verify the ecological effects of a retention reservoir built directly on the course of the Cascata stream, Botucatu (SP). Three sampling sites were selected, located upstream the reservoir, in the reservoir and downstream. Samplings were carried out in July (winter - dry) and November (late spring - rainy) 2020. In situ measurements were obtained through a multiparameter probe (temperature, pH, electrical conductivity, dissolved oxygen, total dissolved solids, and oxidation-reduction potential) and water samples were collected for laboratory determinations (nitrogen, total phosphorus, thermotolerant coliforms, and chlorophyll-a). For fish sampling, manual trawls, sieves and hand nets were used, with a sampling effort of 10 throws per artefact and site. Despite the small distance between the sampling points (~1,300 m) considerable changes in the limnological conditions and fish community structure were observed. The studied environment is originally a small river surrounded by riparian forest, but this characteristic was abruptly changed in the reservoir stretch, with the direct exposition of a much larger water surface to intense solar radiation and atmosphere exchanges. Consequently, as evidenced by the PCA analysis, there was a considerable (stream-reservoir increase) of temperature, dissolved oxygen and chlorophyll. However, this spatial trend was partially disturbed by an accidental sewage-pipe rupture (posteriorly fixed) adjacent to the first sampling point, due to a previous event of extreme precipitation, which resulted in increased values of nutrients, chlorophyll, conductivity and thermotolerant coliforms. Eleven fish species were collected (two non-native), belonging to seven families and five orders. The upstream reference point (despite not be pristine), was characterized by the predominance of native species, while the reservoir condition favored the development of large populations of the non-native species. Despite the urgency of effective actions to prevent floods in urban areas, construction of contention reservoirs directly on stream courses should be avoided, due to their negative ecological impacts.

UAV-Based Floodwater-Level Establishment for FEWS for Abrupt River Section Change in Imsan

Flood damage has been increasing owing to climate change; thus, a flood early-warning system (FEWS) has been established to evacuate residents safely in flood-prone areas. The FEWS is a fundamental nonstructural system that reduces human and material damage caused by floods. The damage can be minimized when appropriate settings are used. In general, the need for an early warning is determined using a water gauge installed on a bridge. If there is an abrupt change in the river section near the bridge, an alarm is issued based on the water-level gauge on the bridge. However, some areas may be more vulnerable to flooding than where the bridges exist. In these cases, vulnerable areas can be inundated by floods before a warning alarm is provided. The current study area of the Chogang-cheon River is such an area. Therefore, an unmanned aerial vehicle (UAV)-based remedy is proposed to overcome the discrepancy between the flooding water levels of the gauge location and the vulnerable area. First, spatial information about the river cross section was obtained through a UAV for the study area. As a result of Pix4D processing after river surveying by the UAV, a noticeable abrupt river width change section was confirmed, particularly upstream of the Gwangi Bridge in the middle of the Chogang-cheon River. Then, the level of the bridge and the upstream point of the bridge for the same flow rate were calculated using the Hydrologic Engineering Center River Analysis System (HEC-RAS) program. Through this remedy, the section of the river where flooding occurs first was defined, and an appropriate flood early-warning water level was appropriately estimated. The approach in this study can be widely applied to rivers where a FEWS is needed to determine where rivers change abruptly.

Spatio-seasonal patterns of the impact of wastewater treatment plant effluents on antibiotic resistance in river sediments

There is a growing concern about the risk of antibiotic resistance emergence and dissemination in the environment. Here, we evaluated the spatio-seasonal patterns of the impact of wastewater treatment plant (WWTP) effluents on antibiotic resistance in river sediments. To this purpose, sediment samples were collected in three river basins affected by WWTP effluents in wet (high-water period) and dry (low-water period) hydrological conditions at three locations: (i) upstream the WWTPs; (ii) WWTP effluent discharge points (effluent outfall); and (iii) downstream the WWTPs (500 m downriver from the effluent outfall). The absolute and relative abundances of 9 antibiotic resistance genes (ARGs), 3 mobile genetic element (MGE) genes, and 4 metal resistance genes (MRGs) were quantified in sediment samples, as well as a variety of physicochemical parameters, metal contents, and antibiotic concentrations in both sediment and water samples. In sediments, significantly higher relative abundances of most genes were observed in downstream vs. upstream sampling points. Seasonal changes (higher values in low-water vs. high-water period) were observed for both ARG absolute and relative abundances in sediment samples. Chemical data revealed the contribution of effluents from WWTPs as a source of antibiotic and metal contamination in river ecosystems. The observed positive correlations between ARG and MGE genes relative abundances point out to the role of horizontal gene transfer in antibiotic resistance dissemination. Monitoring plans that take into consideration spatio-temporal patterns must be implemented to properly assess the environmental fate of WWTP-related emerging contaminants in river ecosystems.

Effects of a single spanwise surface wire on a free-ended circular cylinder undergoing vortex-induced vibration in the lower synchronization range

This experimental study investigated the control induced by a spanwise surface wire on a rigid circular cylinder undergoing vortex-induced vibration (VIV) under the conditions of low mass damping in the lower synchronization branch. Being motivated by the idea of VIV-based energy harvesting from ocean and river flows, this elastically mounted cylinder was immersed in a water channel, leaving a free end at its bottom spanwise end, while the free water surface bounded its top. The cylinder was constrained to vibrate in the cross-stream direction. The wire diameter was 6.25 % of the cylinder diameter. Experimental research was conducted by attaching this large-scale wire along the span of the cylinder at various angular positions ranging from 0° to 180° (with respect to the most upstream point of the cylinder) at a fixed Reynolds number of 104(based on the cylinder diameter). Simultaneous to measuring the trajectory of the cylinder motion via a laser distance sensor, the instantaneous velocity field in the near wake of the cylinder was obtained using particle image velocimetry. Several VIV response categories were identified depending on the angular position of the wire, which led to the classification of distinct angular ranges for the wire application. Associated with the structural vibrations in these categories, different vortex-formation modes induced by the wire were revealed. For specific wire positions, decreases of up to 98 % and increases of up to 102 % were identified in the oscillation amplitude of the cylinder compared with the amplitude of the clean cylinder under similar conditions.

Investigation of pressure feedback technique to control ramp based SWBLI

Shock wave boundary layer interaction (SWBLI) and associated boundary layer separation create undesirable phenomena such as enhanced aero-thermodynamic loads, localized turbulent spots, unsteadiness, drag enhancement, pressure recovery losses in high-speed flow applications. It necessitates an investigation on the control of shock-induced boundary layer separation. Therefore, a pressure feedback technique (PFT) to control the boundary layer separation has been studied numerically on a two-dimensional flat plate and ramp configuration. PFT consists of a channel that drains fluid from the separated region and reintroduces it in the core flow under the influence of pressure difference. The effect of various freestream, wall, and geometric conditions on the separation controllability of the PFT is examined. It has been observed that PFT with injection located near the upstream influence point and suction at the ramp foot reduces the length of the separation bubble by 12.15%. Variation of injection location marginally affects the separation reduction capability of PFT, while the performance of PFT is greatly dependent on suction location. The parametric study noted that the optimum suction location, for which the separation size is minimum, shifts downstream with increasing freestream Mach number, wall temperature, and ramp angle. Again the optimum suction location shifts upstream as freestream stagnation temperature to wall temperature ratio increases. Reynolds number is seen to have no impact on the optimum suction location. Moreover, freestream stagnation temperature to wall temperature ratio, which is a governing parameter in SWBLI studies, is also a relevant factor in the mechanism of PFT. Finally, the present limited investigation revealed that the suction end of the PFT positioned between Xsu/L = 1.12 to 1.194 provides a minimum size of shock-induced separation for varying freestream and wall conditions.

Analysis of the Aggregate Strength Variation along Different Sections of the River Basin

Purpose: There is high demand of aggregates material in the construction industry of Nepal. Till date, river borne aggregate material fulfills major part of the demand. Among various rivers, Biring River is one of the major rivers in Province 1. The objective of this research was to analyze the strength of Aggregate variation along the selected section river basin with a case of Biring. Design/Methodology/Approach: The selected section of Biring River is about 20 Km of Arjundhara Municipality from which 6 sites along the river was selected on the basis of accessibility and deposition for aggregate sources. Lab Test for Physical properties and mechanical properties were conducted on that sample to evaluate their quality for the construction works. Also 18 cubes (3 each from 6 selected sites) were casted to evaluate their compressive strength variation. A linear relationship between the ACV, AIV and LAA value with longitudinal variation of river was established. Also the economic analysis of revenue collected by selling the aggregate of Biring River was done. Findings/Result: After conducting the lab test of physical properties of aggregate, Fineness Modulus, Water Absorption and Specific Gravity were found in the range of (7.16-7.49)%, (0.72-1.15)% and and (2.616-2.712) %. A linear equation for the longitudinal variation in the LAA, AIV and ACV value was established. For a longitudinal variation equation for LAA value y=-0.352x+37.41 ACV value an equation y=-0.212x+29.88 and AIV value an equation y=-0.0189x+27.15 where y = Value of LAA, AIV and ACV value and x = distance in km from upstream origin point. The average compressive strength for 7 and 28 days of all cubes were found to be within standard required. The economic contribution of revenue collected by selling the river bed materials as aggregate of Biring River on the total internal revenue of Arjundhara Municipality was found to be significant that is about 30.86%. Originality/Value: The study contributes that the aggregate material becomes more suitable in their hardness, toughness and strength on moving from upstream towards the downstream along the Biring river. The lower part of stream was assessed to have somewhat better quality of aggregates. Paper Type: Applied Research

Environmental impact of oil palm processing on some properties of the on-site soil in a growing city in Nigeria

Both natural and anthropogenic activities exert a great influence on soil conditions, with some being beneficial to soil health. This study was conducted to assess the impact of oil palm processing activities on selected soil properties in Iwo, Nigeria. Soil samples taken from upstream, mid-section, and downstream points along an oil palm mill dumpsite were compared against a control. Soil organic matter, bulk density, and soil moisture were determined using standard procedures, while soil structural stability was estimated using stability index. The soil organic matter was significantly higher at the oil palm mill relative to the control and reduced by 50.8 and 64.4% at the upstream and downstream relative to the mid-section, respectively. The bulk density did not differ significantly among the sampling points but increased at the upstream, mid-section, and downstream by 2.4–13.1% compared with the control. The soil moisture at field capacity was substantially higher at the site relative to the control, with the upstream having the highest value (0.94 m3m−3). The soil structural stability was superior at the mid-section and reduced by 57.0–76.2% at the upstream, downstream, and control points. In general, oil palm mill processing activities improved the on-site soil organic matter and its physical conditions.

Pervasiveness and characteristics of microplastics in surface water and sediment of the Buriganga River, Bangladesh

Microplastics (MPs) are an emerging environmental problem due to their all-around existence and extraordinary stability. A significant number of studies are found in recent literature on the occurrence, distribution, transport, and fate of the MPs in several environmental compartments. In this study, we have investigated the occurrence and characteristics of MPs in the surface water and sediment of the Buriganga river, located beside the mega-city of Dhaka in Bangladesh. In the Buriganga river, the concentration of MPs in the surface water was found from 4.33 ± 0.58 to 43.67 ± 0.58 items L−1, and in the sediment, MPs varied from 17.33 ± 1.53 to 133.67 ± 5.51 items kg−1 of dry sediment. Fragment-type MPs were predominant in the surface water and sediment, which was 72.7% and 85.5% respectively. The most abundant polymer type polypropylene (PP) was found -to be 46% in the surface water and 61% in the sediment sample. The next major category, polyethylene (PE) was found to be 26% and 21%, respectively. Polystyrene (PS), polyvinyl chloride (PVC), polyethylene terephthalate (PET), and polyamide (PA) were other commonly detected polymer types. The MPs were found to be contaminated by Pb, Cd, Cr, Zn, Cu, and Sn from Energy dispersive-X-ray fluorescence (ED-XRF) analysis. Tannery-induced Cr was detected in the highest concentrations in the MPs, which were 20.67 ± 1.66 mg kg−1 (in surface water) and 14.2 ± 1.25 mg kg−1 (in sediment). The pollution load index (PLI) of the MPs contamination in different sampling sites along the Buriganga river was found in the risk level category of I and II. The anthropogenic influence of the city area was reflected in the PLI values, which had an increasing trend from the upstream sampling points (1.00 ± 1.00, 1.00 ± 1.00) to the downstream sites (10.09 ± 1.00, 7.71 ± 3.60).

Evaluation of Surface Water Contamination by Leachate from Uncontrolled Landfills: A Case Study of Yenagoa Central Waste Dump, Nigeria

Recently, surface water pollution has generated grave concerns because of anthropogenic activities including inadequate management of waste. Therefore, this study is concerned with the evaluation of surface water contamination by leachate from uncontrolled landfill in Yenagoa Bayelsa State, Nigeria. Three surface water samples were taken from a stream adjacent to an uncontrolled landfill and analyzed. The Downstream point (SW 1) and Upstream points (SW 3) were taken 50 meters from the southernmost and northernmost ends of the landfill, while the Central point (SW 2) was also taken 50 meters from the central edge of the landfill. The parameters analyzed were, pH, EC, TDS, COD, BOD, TH,NH4+, SO42-, NO3-, Phosphate, Cd, Cr, Cu2+, Pb, Zn, Ca2+, Mg2+, Na+, Fe2+, K+, as well as Total coliform count using standard methods. The concentration of these parameters were compared with NSDWQ and WHO to ascertain their levels within the surface water. The surface water analysis across the Downstream point (SW 1) showed that parameters like pH, EC, TDS, TA, TH, Na, K, Fe, BOD, COD, Phosphate and Total Coliform Count, recorded 7.18, 2,450 μS/cm, 1,225 mg/l, 534.9 mg/l, 270 mg/l, 122.92 mg/l, 69.42 mg/l, 9.48 mg/l, 25 mg/l, 16 mg/l, 7.5 mg/l and 2.80 X 106 cfu/ml respectively. All these values except pH were above NSDWQ and WHO recommended values for potable water. When compared to samples from SW 2 and SW 3, SW 1 samples had higher concentration of parameters. However, some metals and heavy metals like Pb, Cu, Zn, Cd and Cr were below equipment detectable limits for all sampled locations. It was confirmed therefore that the Downstream point (SW 1), was the most contaminated among the three sampled surface water points, in this study. Pearson’s correlational analysis also confirmed that some parameters indicated unity. It was recommended that surface water sources around landfills should be properly monitored to curb water pollution.

The human–technical–environmental systems framework for sustainability analysis

The field of sustainability science has grown significantly over the past two decades in terms of both conceptual development and empirical research. Systems-focused analysis is critical to building generalizable knowledge in the field, yet much relevant research does not take a systems view. Systems-oriented analytical frameworks can help researchers conceptualize and analyze sustainability-relevant systems, but existing frameworks may lack access or utility outside a particular research tradition. In this article, we outline the human–technical–environmental (HTE) framework, which provides analysts from different disciplinary backgrounds and fields of study a common way to advance systems-focused research on sustainability issues. We detail a step-by-step guide for the application of the HTE framework through a matrix-based approach for identifying system components, studying interactions among system components, and examining interventions targeting components and/or their interactions for the purpose of advancing sustainability. We demonstrate the applicability of the HTE framework and the matrix-based approach through an analysis of an empirical case of coal-fired power plants and mercury pollution, which is relevant to large-scale sustainability transitions. Based on this analysis, we identify specific insights related to the applicability of upstream and downstream leverage points, connections between energy markets and the use of pollution control technologies, and the importance of institutions fitting both biophysical dynamics and socioeconomic and political dynamics. Further application of the HTE framework and the identification of insights can help develop systems-oriented analysis, and inform societal efforts to advance sustainability, as well as contribute to the formulation of empirically grounded middle-range theories related to sustainability systems and sustainability transitions. We conclude with a discussion of areas for further development and application of the HTE framework.

Scour at a Submerged Square Pile in Various Flow Depths under Steady Flow

Local scour around submerged piles in currents are common in coastal and offshore engineering. This paper studies the influences of the submergence ratio (flow depth to pile height) on local scour around a square pile in steady flow. Submergence ratio ranging from 1–4, as well as two unsubmerged tests, were tested with a 10 × 10 square pile of 20 cm height. The three-dimensional profiles were measured to study the scour and deposition characteristics. Results show that the maximum scour depth was always at the upstream corner points rather than at the symmetry center point of the pile. The temporal maximum scour depth achieved its equilibrium sate in less than 4 h for each test. The equilibrium scour depths at the upstream corner points were independent of the submergence ratio when the latter was larger than 1.5. These findings give meaningful reference to the numerical simulations and local scour depth protections in the submerged pile cases deeper than which the flow depth does not affect the equilibrium scour depth.

Temperature Modeling, a Key to Assessing Impact on Rivers Due to Urbanization and Climate Change

With widespread ongoing urbanization and as climate change continues, the importance of protecting the water quality of streams and lakes is intensifying. However, while many water quality constituents in lakes and rivers are of overall interest, water temperature is a ‘key’ variable as temperature influences mixing within a waterbody, influences the acceptability of the habitat for flora and fauna, and serves as a guide to the general health of a stream. To enable the assessment, a physics-based, deterministic hydraulic and heat-balance modeling procedure using the combination of MIKE SHE, MIKE HYDRO and ECO Lab is described to assess heat transfer magnitudes in portions of the Credit River, Ontario. Changes in instream temperature regimes are examined, including both frequency and spatial extent, providing insights into the impacts of urbanization in terms of seasonal temperature shifts arising from land use changes. For flow and temperature regimes, Nash–Sutcliffe model efficiency coefficient (NSE) values of 0.49 and 0.955 were achieved, respectively, for current threshold conditions. Durations of temperature increases from threshold levels indicate that land use changes from current agriculture conditions to urbanization may change stream water temperatures for 9% of the time by 1 °C, and 2% of the time by 2 °C for distances of 1000 m downstream, because of land use change from agriculture to low-density urbanization, and for 20% of the time by 1 °C, and 4% of the time by 2 °C at distances of 1000 m downstream with land use change to high-density urbanization. With climate change RCP 4.5 Scenario in 2050 (Base, for a Wet Year—2017), the continuous amount of time the stream water temperature remains at elevated temperatures of more than 3 °C (from 5000 m to 25,607 m from the most upstream point of Fletchers Creek) for a distance of 20,000 m is more than 13 h. These elevations in temperature may have serious implications for flora and fauna in the creek, particularly impacting the cold-water and mixed-water fish species.

Response of Runoff Yield to Land Use Changes in the Small Watershed of Core Area for 2022 Winter Olympic Games in Zhangjiakou City Based on SWAT Model

Based on an improved high-precision land use map, the SWAT model of the small watershed of the core area for the 2022 Winter Olympic Games in Zhangjiakou City was established. The model was set up, calibrated, and validated with data from 2017 to 2019. In comparison with the measured flow discharge, all the coefficient of determination values of the simulated results at the upstream, midstream, and downstream (outlet) points were larger than 0.80 in both calibration and validation periods, and the relevant Nash–Sutcliffe efficiency coefficient values were above 0.62. With the model, the response of runoff yield in the small watershed to the land use change before (2015) and after (2019) Olympic construction was simulated and analyzed. The runoff yield change was only −5.1% from 2015 to 2019, which was not statistically significant (p = 0.87 > 0.05). Through simulation of two extreme scenarios, two runoff yield change coefficients were introduced to explore the effects of land use change on runoff yield. The results revealed that the neutralization effects of the land use change from grassland to forest (with strong water conservation capacity) and residential and bare land (with poor water conservation capacity) were the main reasons for the insignificant change of runoff yield. The results of this research may provide some inspiration to the application of SWAT model in small watershed and some guidance to the vegetation restoration practices for water conservation. These results can promote understanding on the response of runoff yield to the land use changes towards two extreme directions of forest land and residential and barren land, and provide some guidance for the vegetation restoration practices in the small watersheds hosting major events.

Morphological Changes of Sharp Bends in Response to Three Gorges Project Operation at Different Discharges

Dam construction often changes downstream fluvial processes by reducing sediment supply. Taking Tiaoguan reach and Laijiapu reach of the lower Jingjiang Reach downstream of the Three Gorges Project as examples, three-dimensional flow velocity, sediment, and bed elevation were observed in the two bends for investigating the impact of flow structure and sediment transport of different discharges on sharp bend morphology. Results indicated that the flow structure and sediment transport process in curved channels depended upon the flow stages, which affected the patterns of erosion and deposition along the point bars and concave banks. Flow separation and development of secondary flow were depended on the shapes of point bars and flow depths nearby, and the strength of secondary flow increased with flow discharge. The high flow discharges, which had high sediment carrying capacity and stream power, provided the main driving force for erosion on upstream point bar, thus the type and duration of floods were crucial factors in the morphological evolution of meandering bends. The reduction of sediment supply should be responsible for erosion on the point bars, causing the flow to migrate toward the convex banks. In meandering rivers with reduced sediment supply, retreats (push inward) of inner (convex) banks dominated advances (pull inward) of outer (concave) banks. In addition, the formation and development of concave-bank bars might relate particularly to meander curvature. This study is expected to constitute a reference for bank protection and river management in meandering bends downstream of reservoirs.

An economical robust algorithm for solving 1D coupled Burgers’ equations in a semi-Lagrangian framework

In this study, we propose an efficient algorithm for solving one-dimensional coupled viscous Burgers’ equations. One of the main accomplishments of this study is to develop a stable high-order algorithm for the system of reaction–diffusion equations. The algorithm is “robust” because it is designed to prevent non-physical oscillations through an iteration procedure of a block Gauss-Seidel type. The other is to develop an efficient algorithm for the Cauchy problem. For this, we first find half of the upstream points by adopting a multi-step qth-order (q=2,3) error correction method. The algorithm is also “economical” in the sense that an interpolation strategy for finding the remaining upstream points is designed to dramatically reduce the high computational cost for solving the nonlinear Cauchy problem without damage to the order of accuracy. Three benchmark problems are simulated to investigate the accuracy and the superiority of the proposed method. It turns out that the proposed method numerically has the qth-order temporal and 4th-order spatial accuracies. In addition, the numerical experiments show that the proposed method is superior to the compared methods in the sense of the computational cost.

Phosphorus in soils and fluvial sediments from a Cerrado biome watershed under agricultural expansion.

Over the past decades, lands alongside Gurguéia River have witnessed rapid expansion of soybean agriculture which has increased soil degradation and affected nutrient concentration in sediment, especially phosphorus (P). The present study aimed to quantify the P concentration in soils under different land uses (i.e., croplands, grasslands, and cerrado) and fluvial sediments (suspended sediment, channel bank, and riverbed sediments), assessing pollution over the main watercourse in cerrado biome Gurguéia watershed, located in Piauí State, Brazil. In total, 136 compositesoil samples at a depth of 0-5cm, under different land uses, as well as 51 composite fluvial sediment samples were collected over the watershed. The land use change from native cerrado had resulted in an increase of total phosphorus (TP) whose concentration was higher in cropland areas, followed by suspended sediment, channel bank, and riverbed sediments. This high concentration in cropland areas resulted from phosphate fertilizer inputs. The transfer of phosphorus to water bodies was evidenced, since an increase of TP was observed in suspended sediment, channel bank and riverbed sediments. Mineralogical signatures in sediments were identified by X-ray diffraction analysis which showed the occurrence of kaolinite, illite, smectite, iron oxides, and other minerals in lesser proportions. The presence of 1:1 minerals was higher in riverbed sediments and downstream sampling points, while 2:1 minerals were present in higher proportions in suspended sediment and channel bank sediment, as well as at the upstream and middle sampling points. This finding shows that land use change from cerrado to cropland due to soybean agriculture expansion might increase P discharges from terrestrial to aquatic environments, with sediments being the major carrier of this element.