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Baseflow plays a crucial role in sustaining the alpine ecosystem during rainless or cold periods. Despite its importance, information on how and why baseflow has changed in the source region of the Yangtze River (SRYR) is sparse. In our study, statistical analysis and the elastic coefficient method were used to identify the dynamic characteristics of baseflow and the underlying causes. The results show that monthly baseflow contributed 62–97% of runoff with a mean value of 75%, and they followed remarkable increasing trends from 1957 to 2020. The contributions of precipitation, temperature, evapotranspiration, and ecological conservation programs (ECPs) on baseflow variations were 86, 53, −15, and −24%, respectively. However, their contributions differed across months. During the warm months of May to September, precipitation played a dominant role, followed by evapotranspiration. In contrast, during other colder months, temperature was dominant; meanwhile, the effect of precipitation was almost absent. Moreover, climatic change had a hysteretic effect on baseflow variation, with a maximum lag time of 10 months. Our results highlighted critical roles of both precipitation and temperature, and indicated that climate change, rather than ECPs, dominated the variation in baseflow in the SRYR. HIGHLIGHTS Monthly baseflow contributed 62–97% of runoff with a mean value of 75%.; Contributions of precipitation, temperature, evapotranspiration, and ecological conservation to the increasing baseflow were 86, 53, −15, and −24%, respectively.; During warm months, precipitation played a dominant role, while during colder months, the impact of temperature was dominant.; Climatic change had a hysteretic effect on baseflow variation.;

Study region: Poyang Lake Plain at the south bank of the middle Yangtze River Study focus: The dynamics of the groundwater budget, prominently driven by the surface water-groundwater interaction, present significant challenges for water resources and the eco-environment in extensive river-lake-floodplain systems. This research utilizes a groundwater flow model through the application of the MODFLOW-NWT numerical simulator, aiming to explore the patterns of exchange between surface water and groundwater due to intensive seasonal lake inundation, and its consequential impact on the annual and seasonal groundwater storage within the vast Poyang Lake floodplain, China. New hydrological insights for the region: Simulation results indicate that the change in groundwater storage during the dry year (i.e., –24.96×107 m3/yr in 2022) has decreased by 186.35×107 m3 compared to the wet year (i.e., 161.38×107 m3/yr in 2020). The contribution of surface water infiltration is approximately 45 % of the regional groundwater budget during wet seasons, and groundwater discharge into surface waterbodies accounts for over 60 % of the groundwater budget during dry seasons. The lake infiltration during wet years is approximately 3 times that in dry years, and the flow of infiltrated lake water into plain aquifers is approximately 5 times that in dry years. The present study contributes significant knowledge regarding the impact of intensifying seasonal inundation on variations in regional groundwater budget in large lake-aquifer system.

β-galactosidase, as a safe and nontoxic enzyme preparation, has been not only widely used in food industry and medical fields, but also has great application potential in biotechnology fields, such as enzyme engineering and protein engineering. Microbial fermentation, as a mainstream production method of β-galactosidase, still has some problems including long fermentation time and low extraction rate. While using the heterologous expression system of engineering bacteria to produce β-galactosidase shows the advantages of high expression quantity and low cost. This paper focuses on the gene source, expression host bacteria, expression methods of β-galactosidase heterologous expression system and its application value, to be aimed at providing scientific basis and theoretical reference for the development and utilization of novel β-galactosidase products.

This work aimed to explore low-intensity ultrasound-assisted adaptive laboratory evolution (US-ALE) of Bacillus velezensis and fermentation performance of mutant strains were investigated by nitrogen transformation metabolism. Results showed ultrasound accelerated the process of adaptive evolution and enhanced cell dry weight, amylase and protease activity of mutant strains, accompanied with the improved transformation abilities of NO–3-N to NH4+-N. Compared with original strain, the total peptide-N, peptide-N (

Study region: The Poyang Lake, which is located on the south bank of the middle-lower Yangtze River basin. The lake is the largest freshwater lake in China, and also a typical floodplain lake in the world. Study focus: The spatiotemporal heterogeneity of inundation dynamics of large floodplain lake system has not been paid enough attention. Based on the reconstructed high spatial and temporal resolution inundation dataset using the image fusion model and multi-source remote sensing data, this study systematically analyzed the spatiotemporal heterogeneity of inundation dynamics in the Poyang Lake- floodplain system. New hydrological insights for the region: It is found that within the same floodplain lake, the inundated area and inundation frequency in different regions of the lake (the main lake region and the adjacent floodplain region) can have asynchronous intra-annual fluctuation and opposite inter-annual change trend. This is highly related to the hydrological complexity of the lake: the relative impacts of catchment inflow and the Yangtze River varies in different regions across the lake. The stage-area relationship at the central station along the flow direction of the lake has the highest linear correlation, which might provide more accurate estimates of lake surface/volume. In addition, this study highlights the importance of reconstructed high spatial-temporal resolution of remote sensing data for the accurate assessment of inundation dynamics in floodplain lakes. All the results enrich the understanding of complex hydrological regime of large floodplain lakes and are valuable for the practice of water resources management and ecological conservation in such lakes.

Water changing conditions of a lake will affect the physical and hydrological conditions and ecology of the lake and groundwater. The unique "river-lake phase" transition of the Poyang Lake complicates the surface water-groundwater exchange process in the area. Therefore, this study uses Visual MODFLOW to build a 3D numerical model of groundwater transient flow and uses the LAK3 module to realize the dynamic simulation of the lake water area by inputting the runoff from five rivers into the lake and the Poyang Lake into the Yangtze River. The RMSE between the simulated and measured values of lake water level is 0.225 m, and between the simulated and measured values of groundwater level is 0.571 m. The month-on-month ratio variation of the Poyang Lake area simulated by the model ranges from −41% to 83%, consistent with the remote sensing images. This model reduces the constraint of lakes as boundary conditions, can effectively depict the frequently-changing water level and lake area, and accurately simulate the response of groundwater flow field and surface water-groundwater interaction relationship to the height dynamics of lake water. During the dry season, the lake is mainly recharged by groundwater, with an exchange flux ranging from 2.03×107 to 10.58×107 m3/mon. During the wet season, the lake water discharges into groundwater with an exchange flux ranging from 2.04×107 to 16.53×107 m3/mon, with the average groundwater level rise in the lake region and surrounding areas by 2~3 m compared to the dry season. The groundwater flows from the lake region to the surrounding areas. This study contributes an effective numerical simulation method for areas with dramatic changes in surface water bodies. The results can provide a basis for future water resources management and environmental assessment in the Poyang Lake Plain.

Canola (Brassica napus) is an important broadacre crop, produced under high nitrogen (N) fertilizer application. Modern canola varieties are developed under high N rates but the impacts on root-associated microbiomes of different varieties are unknown. We studied eight canola varieties spanning historical Canadian spring canola development at two sites under high and low N fertility and characterized bacterial and fungal microbiomes in the root and rhizosphere using amplicon sequencing. Environmental conditions and the resulting canola varietal responses strongly affected the root-associated bacterial and fungal microbiomes. Microbes regulated by N fertility in each canola variety were mainly Gammaproteobacteria, Bacteroidia, Actinobacteria, Sordariomycetes, Dothideomycetes, and Agaricomycetes classes. Differentially abundant (DA) microbial taxa showed that N more strongly enriched bacteria in the roots and fungi in the rhizosphere. Each variety had its specific pattern of DA amplicon sequence variants (ASVs) responding to soil N availability, and the profile of DA-ASVs in paired canola varieties were also altered by soil N availability, especially bacteria in the rhizosphere. The yield was strongly associated with a subset of microbial taxa, mainly from Proteobacteria, Actinobacteriota, and Ascomycota. These variety-dependent responses to N and links to yield performance make the root-associated microbiome a promising target for improving the agronomic performance of canola by manipulating microorganisms tailored to soil fertility and plant genotype.

The local deformation behavior and dynamic recrystallization of a shock compressed Mg-1Zn alloy was investigated through EBSD and TEM. Since dislocation slipping and twinning were locally suppressed during high strain-rate deformation, a more flexible kinking deformation was activated to adjusted local orientation and facilitate slipping and twinning within the kinks. Meanwhile, due to the slow heat dissipation that resulted in a local temperature elevating, the kink bands were evolved into deformation bands with recrystallized nano-grains. Such a finding provides a new perspective for kinking-facilitated nanocrystallization in Mg alloys and other anisotropic metallic materials.

The Mott insulator provides an excellent foundation for exploring a wide range of strongly correlated physical phenomena, such as high-temperature superconductivity, quantum spin liquid, and colossal magnetoresistance. A Mott insulator with the simplest degree of freedom is an ideal and highly desirable system for studying the fundamental physics of Mottness. In this study, we have unambiguously identified such an anticipated Mott insulator in a van der Waals layered compound Nb_{3}Cl_{8}. In the high-temperature phase, where interlayer coupling is negligible, density functional theory calculations for the monolayer of Nb_{3}Cl_{8} suggest a half-filled flat band at the Fermi level, whereas angle-resolved photoemission spectroscopy experiments observe a large gap. This observation is perfectly reproduced by dynamical mean-field theory calculations considering strong electron correlations, indicating a correlation-driven Mott insulator state. Since this half-filled band derived from a single 2a_{1} orbital is isolated from all other bands, the monolayer of Nb_{3}Cl_{8} is an ideal realization of the celebrated single-band Hubbard model. Upon decreasing the temperature, the bulk system undergoes a phase transition, where structural changes significantly enhance the interlayer coupling. This results in a bonding-antibonding splitting in the Hubbard bands, while the Mott gap remains dominant. Our discovery provides a simple and seminal model system for investigating Mott physics and other emerging correlated states.

Enzyme catalyzed plastein reactions refer to the process of catalyzing concentrated protein hydrolysate into protein analogues by protease under suitable conditions. Enzyme catalyzed plastein reactions can not only make up for the defects of natural protein in the amino acid composition, improve protein functionality and the flavor of protein hydrolysates, and provide new protein sources for scientific research and production, but also the products obtained by this method have high bioavailability, and no side effects, so it has received extensive attention from the scientific community and has been gradually applied to the food industry. This article introduces the mechanism, influencing factors, product characteristics and applications of enzyme catalyzed plastein reactions in the food field, in order to provide new methods for the improvement of food quality and new ways for the development of new foods.

The effects of power ultrasound (US) pretreatment on the preparation of soy protein isolate hydrolysate (SPIH) prepared at the same degree of hydrolysis (DH) of 12 % were measured. Cylindrical power ultrasound was modified into mono-frequency (20, 28, 35, 40, 50 kHz) ultrasonic cup coupled with an agitator to make it applicable for high density SPI (soy protein isolate) solutions (14 %, w/v). A comparative study of the alterations of the hydrolysates molecular weight, hydrophobics, antioxidants and functional properties change as well as their relation were explored. The results showed that under the same DH, ultrasound pretreatment decelerated the degradation of protein molecular mass and the decrease rate of the degradation lessened with the increase of ultrasonic frequency. Meanwhile, the pretreatments improved the hydrophobics and antioxidants properties of SPIH. Both surface hydrophobicity (H0) and relative hydrophobicity (RH) of the pretreated groups increased with the decrease of ultrasonic frequency. Lowest frequency (20 kHz) ultrasound pretreatment had the most improved emulsifying properties and water holding capacities, although decrease in the viscosity and solubility were found. Most of these alterations were correspondence toward the change in hydrophobics properties and molecular mass. In conclusion, the frequency selection of ultrasound pretreatment is essential for the alteration of SPIH functional qualities prepared at the same DH.

As blockchain technology plays an increasingly important role in the Internet of Vehicles, how to further enhance the data consensus between the areas of the Internet of Vehicles has become a key issue in blockchain design. The traditional blockchain-based vehicle networking consensus mechanism adopts the double-layer PBFT architecture, through the grouping of nodes for first intra-group consensus, and then global consensus. To further reduce delay, we propose a CRMWSL-PBFT algorithm (C-PBFT) for vehicle networking. Firstly, in order to ensure the security of RSU nodes in the network of vehicles and reduce the probability of malicious nodes participating in the consensus, we propose to calculate the reputation of RSU nodes based on multi-weighted subjective logic (CRMWSL) model. Secondly, in order to ensure the efficiency of blockchain data consensus, we improve the consensus protocol of traditional double-layer PBFT, change the election method of the committee and the PBFT consensus process, and improve throughput by reducing the number of consensus nodes. For the committee, we combine the credibility value and hash method to ensure the credibility of nodes, but also to ensure a certain degree of election randomness. For the PBFT consensus process, the regional committee consensus is carried out first, and then the regional master node carries out the global consensus. Through experimental comparison, we show that the C-PBFT significantly reduces consensus time, network overhead, and is scalable for Internet of Vehicles.

Low-lethality ultrasound technology has received more and more attention in regulating microorganisms of fermentation industry. Herein, two representative Ames tester strains TA97a and TA98 as model organisms were used to explore the effects of ultrasound on insertion-deletion (InDel) polymorphisms of microbial DNA and its underlying mechanisms. Results revealed that a promotion was observed in the reversion mutation of TA98 upon sonication. Sequencing results from 1752 TA98 revertants showed that there was a total of 127 InDels, of which the InDels unique to ultrasound were 36 more than that of the control. Compared with the control, ultrasound-mediated InDels of DNA displayed additional −29 bp deletion and +7 ∼ +43 bp insertions of direct repeat sequences. Combined with the analysis of transcriptomics and prediction of secondary structure of single-stranded DNA from InDels core region (No. 832 ∼ 915 bp) in hisD3052 gene of TA98 strain, ultrasound-mediated “thermal breathing” mechanism was proposed based on the formation of DNA hairpin structure with micro-homologous sequence. This finding implied that low-intensity ultrasound is expected to be developed a new low-lethal mutagenic technology for continuous mutagenesis.

Study region: The Poyang Lake watershed is located on the south bank of the middle and lower reaches of the Yangtze River in China. It has been hit by frequent floods in past few decades. Study focus: Lake-reservoir groups (LRG) are important in extreme hydrologic event mitigation in watersheds. This study used runoff-weighted model to quantify the influence of LRG on the flood mitigation in Poyang Lake based on weekly observations of GF-1 and Sentinel-1. New hydrological insights for the region: The weekly water storage volume of LRG in the Poyang Lake watershed showed a unimodal trend of increasing (April-September) first and then decreasing (October-March) from 2016 to 2020. The runoff-weighted model has a better effect on the calculation of detained flood volume and residence time of retained flood. The average annual total detained flood volume of LRG were 4.39 × 108 m3, 5.06 × 108 m3, 1.64 × 108 m3, 0.54 × 108 m3, and 0.15 × 108 m3 in the Xiushui, Ganjiang, Fuhe, Xinjiang, and Raohe basins, respectively, among which Xiushui and Ganjiang basins contributed the most to flood detention. The residence time of retained flood by LRG in the five basins are long during the dry season (October to March) but short during the wet season (April to September), and they are generally longer than those in the natural state with no reservoir. The delay days of the LRG to flood peaks were about 12, 7, 13, 22, and 26 d for each basin, respectively.

Corn gluten meal is a major by-product of corn wet-milling process in the starch industry. The low water solubility and deficiency of essential amino acids of corn gluten meal limits its application in the food industry, while corn polypeptides after enzymatic hydrolysis can greatly improve its functions and biological activities, it is one of the high value-added utilization methods. This review encompasses the studies reported to date on the main preparation methods of corn polypeptides, and also describes its bioactivities including antioxidant, antiglycemia, antihypertensive, hepatoprotective, pointing out the existing problems and future development prospects. The paper is of great significance for food enterprises to utilize corn gluten meal efficiently to develop bioactive peptides and improve economic benefits of the industry.

Hydrological connectivity plays a major role in solving water resource and eco-environmental problems. However, this phenomenon has not been afforded the attention it deserves. The detailed analysis of connectivity in river systems could provide considerable insight into the structural and functional attributes of riverine landscapes. The current study used a graph theory approach and associated connectivity indicators to explore the characteristics and evolution of river systems and hydrological connectivity in a large catchment (Poyang Lake, China). The results revealed that the structure of the river system tended to be complex during 1990–2020, characterized by a dynamic evolution of tributaries in certain northern areas. Both river density and complexity exhibited an increasing trend by up to 15%, with the change rate after 2000 approximately twice as high as that of the preceding period. Overall, human activities across the catchment were more likely to play a key role in leading to significant changes in the quantity, morphometric, and structural characteristics of the river system. Additionally, the functional connectivity analysis indicated that the index of connectivity (IC) in the downstream catchment was stronger than that of the upstream vegetation areas, suggesting a strong contribution to the runoff sediment transport (r = 0.6–0.7). This study highlights the spatial and temporal evolution of both structural and functional connectivity in the large Poyang Lake catchment. The findings of this work will benefit future water resource management and applications by providing a strategy for protecting the surface hydrology and mass transport of large river basins under climate and land use changes.

This study outlines a framework for examining potential impacts of future climate change in Poyang Lake water levels using linked models. The catchment hydrological model (WATLAC) was used to simulate river runoffs from a baseline period (1986–2005) and near-future (2020–2035) climate scenarios based on eight global climate models (GCMs). Outputs from the hydrological model combined with the Yangtze River's effects were fed into a lake water-level model, developing in the back-propagation neural network. Model projections indicate that spring–summer water levels of Poyang Lake are expected to increase by 5–25%, and autumn–winter water levels are likely to be lower and decrease by 5–30%, relative to the baseline period. This amounts to higher lake water levels by as much as 2 m in flood seasons and lower water levels in dry seasons in the range of 0.1–1.3 m, indicating that the lake may be wet-get-wetter and dry-get-drier. The probability of occurrence for both the extreme high and low water levels may exhibit obviously increasing trends by up to 5% more than at present, indicating an increased risk in the severity of lake floods and droughts. Projected changes also include possible shifts in the timing and magnitude of the lake water levels.

Information service platforms or management information systems of various institutions or sectors of enterprises are gradually interconnected to form a multi-domain environment. A multi-domain environment is convenient for managers to supervise and manage systems, and for users to access data across domains and systems. However, given the complex multi-domain environment and many users, the traditional or enhanced role-based access control (RBAC) model still faces some challenges. It is necessary to address issues such as role naming conflicts, platform–domain management conflicts, inter-domain management conflicts, and cross-domain sharing difficulties. For the above problems, a role-based access control model for inter-system cross-domain in multi-domain environment (RBAC-IC) is proposed. This paper formally defines the model, divides roles into abstract roles and specific roles, and designs the operating process of the access control model. The model has four characteristics: support role name repetition, platform–domain isolation management, inter-domain isolation management, and fine-grained cross-domain sharing. By establishing security violation formulas for security analysis, it is finally shown that RBAC-IC can operate safely.

In order to comprehensively analyze the dynamic response of full-depth asphalt pavement under moving load, a three-dimensional model of pavement structure and dynamic load moving zone are established based on ABAQUS finite element software. Based on the time history curves of different structures, the stress-strain states at the bottom of each structural layer in different structures under moving load are analyzed. The results show that the stress, strain, and shear stress of the middle layer of full-depth pavement are smaller than those of semirigid base pavement, and rutting is closely related to the deformation of this layer. The dynamic response results of the same structure at different speeds are similar, but the increase of the maximum speed will increase the shear stress at the bottom of the layer, and the road is more prone to longitudinal crack.

Poyang Lake, the largest freshwater lake in China, is featured with high-frequency fluctuations and unique seasonal changes in water level and inundation areas, which plays a substantial part in regulating the runoff of the Yangtze River and maintaining the ecological balance of the region. Frequent observations enable more effectively reflecting the water budgets and related driving force of Poyang Lake. This study first utilized the Sentinel-1 SAR data and cloud-free Sentinel-2 images in conjugation with lake bathymetry to reconstruct the time series of the water inundation area and storage of Poyang Lake from 2017 to 2020. Further, a simple and straightforward method, named the Fitting Curves of each Block and Total area (FCoBT), is developed to reconstruct the complete inundation area of Poyang Lake from partially cloud-free Sentinel-2 images to densify the original time series. This method takes full advantage of the significant characteristics on the strong correlations of the block areas (one small part of lake area) varying with the complete lake areas, with a mean R2 and ρ value of 0.94 and 0.98, respectively. The complete inundation area of Poyang Lake can be reconstructed from 113 scenes of partially cloudless Sentinel-2 images acquired from 2017 to 2020 by using the FCoBT. After integrating the Sentinel-1 and Sentinel-2 images, a maximum of 13 measurements are available within one month, with the temporal intervals of 2–3 days. Results show that our reconstructed time series of water inundation area can finely depict significant seasonal fluctuation (wet season: from April to September, dry season: from October to the next March) and inter-annual variations (larger areas: 2017 and 2020, smaller areas: 2018 and 2019) of Poyang Lake during 2017–2020. Similar to the area change, the water storage of Poyang Lake also shows evident seasonal variation and inter-annual fluctuation, reaching the peaks in July and the lowest stages during November to February. This study cannot only provide an efficient and feasible remote sensing means of constructing long-term observations for highly variable lakes at high spatial–temporal resolutions, but also greatly refine our understanding on the intra-annual and inter-annual variations of Poyang Lake.

This study aims at preparing the Maillard reaction products of protein hydrolysate from grass carp (Ctenopharyngodon idella) bone and identifying its characteristic flavour compounds. Meanwhile, bioactivities and amino acids composition of hydrolysates and its Maillard reaction products were compared with the thermal degradation reaction as one positive control. Single factor experiment was applied to optimize the enzymolysis parameters of grass carp bone protein using flavourzyme, under which the highest degree of hydrolysis (40.1%) was obtained. According to the response surface methodology, the top predicted value (70.45%) of degree of graft of Maillard reaction was obtained with initial pH of 7.07, temperature of 118.33°C, and time of 1.75 h. Moreover, the results of Maillard reaction products illustrated a significant increase in DPPH radical scavenging activity (p

Sweep frequency ultrasound- (SFU-) assisted alkali extraction was conducted to increase the yield and content of heat-sensitive protein of walnut meal under a relatively mild condition. The physicochemical and structural characteristics of the proteins obtained by SFU-assisted alkali extraction and the conventional alkali extraction were compared. It was found that the optimal parameters for the SFU-assisted extraction were the solid-liquid ratio of 1 : 12, pH value of 9, initial temperature of 25°C, ultrasonic frequency of 28 kHz, sweep frequency amplitude of 1.5 kHz, sweep frequency cycle of 100 ms, duty ratio of 77%, and ultrasonic time of 90 min. Under this condition, a vast improvement in the walnut protein yield (34.9%) and the walnut protein content (9.8%) was observed. Such improvement was due to the structural changes of the sonicated protein; e.g., SFU decreased the intermolecular/intramolecular hydrogen bond force of proteins and, therefore, caused more order secondary structures and more loosen microstructures. This helped to improve the thermoplastic and solubility of the heat-sensitivity protein. Thus, SFU treatment could be an effective auxiliary technology in the alkali extraction of heat-sensitivity walnut protein. It might also be a promising technology for the extraction of heat-sensitivity protein from other agricultural by-products.

Seasonal variations in local catchments and connected rivers lead to complex hydrological behaviours in river-lake systems. Poyang Lake is a seasonally dynamic lake with frequent low levels in spring and autumn, which may be triggered by the local catchment and Yangtze River. Based on two typical years, a hydrodynamic model combined with long term hydrological observations was applied to quantify the spatiotemporal impacts of the local catchment and Yangtze River on spring and autumn low water levels in Poyang Lake. As a first attempt, this study explored the spatial differences of the two influences. Simulation results showed that the contributions of the catchment and the Yangtze River were approximately 70% and 30% in spring 1963, and 5% and 95% in autumn 2006, respectively. The area of catchment influence was mainly distributed in channels and southern floodplains, with relatively uniform water levels. The area impacted by the Yangtze River mainly spanned from the northern portion of the waterway to the central lake, with strong spatial variability. This study focused on two typical years; however, the results can be extended to explain common hydrological phenomena and improve future strategies of water resource management in this river-lake system.

Variations in a lake area constitute an important indicator of the modifications of the lake hydrology. This paper explores the inter-annual variations of the Poyang Lake area during the dry seasons occurring within the 1961 to 2010 period and further quantifies the severity of dryness recently endured during the 2000s. A physically based hydrodynamic model of Poyang Lake established the relation between the lake area and lake level. The lake area was calculated using the observed lake water level. Results indicated the average lake area in the dry seasons was 1,015 km2. There was a considerable inter-annual variation of the minimum lake area that varied from 702.8 km2 to 1,259.7 km2. Poyang Lake experienced the most severe dryness in the 2000s, resulting in an average lake area during 2001 to 2010 of 124 km2 less than that of the preceding period. During the dry seasons, the catchment of the river discharge is likely the primary cause of the changes in lake area. This study evaluated the inter-annual variations of the Poyang Lake over a period of 50 years. Our results may provide support for an integrated management of the lake-catchment system, securing the water supply.

Groundwater plays an important role in supplying water to vegetation in floodplain wetlands. Exploring the effect of water table depth (WTD) on vegetation transpiration is essential to increasing understanding of interactions among vegetation, soil water, and groundwater. In this study, a HYDRUS-1D model was used to simulate the water uptake of two typical vegetation communities, Artemisia capillaris and Phragmites australis, in a floodplain wetland (Poyang Lake wetland, China). Vegetation transpiration was compared for two distinct hydrological conditions: high water table (2012) and low water table (2013). Results showed that vegetation transpiration in the main growth stage (July–October) was significantly influenced by WTD. Under high water table conditions, transpiration of A. capillaris and P. australis communities in the main growth stage totaled 334 and 735 mm, respectively, accounting for over 90% of the potential transpiration. Under low water table conditions, they decreased to 203 and 510 mm, respectively, due to water stress, accounting for merely 55% of the potential transpiration. Scenario simulations found different linear relationships between WTD and the ratio of groundwater contribution to vegetation transpiration. An increase of 1 m in WTD in the main growth stage may reduce the ratio by approximately 25%.

The biochemical processes and associated water quality in many lakes mainly depend on their transport behaviors. Most existing methodologies for investigating transport behaviors are based on physically based numerical models. The pollutant transport trajectory and residence time of Poyang Lake are thought to have important implications for the steadily deteriorating water quality and the associated rapid environmental changes during the flood period. This study used a hydrodynamic model (MIKE 21) in conjunction with transport and particle-tracking sub-models to provide comprehensive investigation of transport behaviors in Poyang Lake. Model simulations reveal that the lake’s prevailing water flow patterns cause a unique transport trajectory that primarily develops from the catchment river mouths to the downstream area along the lake’s main flow channels, similar to a river-transport behavior. Particle tracking results show that the mean residence time of the lake is 89 days during July–September. The effect of the Yangtze River (the effluent of the lake) on the residence time is stronger than that of the catchment river inflows. The current study represents a first attempt to use a combined model approach to provide insights into the transport behaviors for a large river–lake system, given proposals to manage the pollutant inputs both directly to the lake and catchment rivers.

Poyang lake floodplains are hydrologically complex and dynamic systems which exhibit dramatic intra-annual wetting and drying. The flow regime of the Yangtze River was previously known to play an important role in affecting Poyang Lake and its extremely productive floodplains (river−lake relationship). The recent severe declines and recessions in the lake are closely linked to the changed river−lake relationship, resulting in significant hydrological, ecological, and economic problems. This study aims to examine the spatiotemporal heterogeneity of the floodplain hydrodynamic behaviors with respect to impacts of the changed river−lake relationship, characterized by the lake water level, inundation area, and inundation duration based on a floodplain hydrodynamic model of Poyang Lake, and to further quantify the severity of dryness recently endured since 2000. Simulation results show that, in general, the current modified river−lake relationship is more likely to affect the hydrological seasonality of the floodplain system since 2000, relative to the flooding and drying cycles during past decades (1953−2000). The present hydrodynamic behaviors suffered significant change due to the greatest interference from the altered river−lake relationship, particularly for the falling period in October. On average, the floodplain water level and inundation duration decreased by 6 m and 12 days during October, respectively. Additionally, the highest monthly shrinkage rate in floodplain inundation shifted from the period of October−November to September−October, with the mean inundation area decreasing by around 50%, demonstrating an advanced and prolonged dry condition. The spatial responses of the hydrodynamics in the low-slope floodplains are most likely to be affected by the dynamic river−lake relationship, as expected. This study assessed the effects of the altered river−lake relationship on the hydrological regime of the Poyang Lake floodplains in terms of spatiotemporal distributions and changing processes for the periodic inundated behavior, which can support the relevant study of the subsequent ecological effects on the wetlands.

Understanding natural flows in porous media with low Reynolds number (Re) has significant implications for both science and engineering. However, knowledge and experimental gaps remain regarding such natural flows. In this context, we designed a sand column-based laboratory filtration experiment to investigate flow characteristics in porous media with low Re. Four media were considered including two silts (silt-I and silt-II), one silty sand, and one medium sand. Results show that constant hydraulic head is presumed to be an important factor that affects flow regime in porous media. In general, the flow approaches Darcian at a constant hydraulic head of ~170 cm, whereas it becomes non-Darcian at a constant hydraulic head of ~230 cm. The type of media determines the Re range that delimitates between Darcy and non-Darcy flows. Specifically, the transition appears at 0.015 < Re < 0.020 for medium sand and 0.000027 < Re < 0.000029 for silt-II, respectively. In the condition of constant hydraulic heads, the breakdown of Darcy’s law may occur at very low Re values (Re→0). Media dependent Re ranges are probably needed to describe the beginning of non-Darcy flows, rather than 1 to 10 or other value for all media. Findings in this study can offer insights into calculation and simulation of flows in low-permeability reservoirs, pumping process of foundation pit excavation, and other non-Darcy flows in low-permeability media.

Most biochemical processes and associated water quality in lakes depends on their flushing abilities. The main objective of this study was to investigate the transport time scale in a large floodplain lake, Poyang Lake (China). A 2D hydrodynamic model (MIKE 21) was combined with dye tracer simulations to determine residence and travel times of the lake for various water level variation periods. The results indicate that Poyang Lake exhibits strong but spatially heterogeneous residence times that vary with its highly seasonal water level dynamics. Generally, the average residence times are less than 10 days along the lake’s main flow channels due to the prevailing northward flow pattern; whereas approximately 30 days were estimated during high water level conditions in the summer. The local topographically controlled flow patterns substantially increase the residence time in some bays with high spatial values of six months to one year during all water level variation periods. Depending on changes in the water level regime, the travel times from the pollution sources to the lake outlet during the high and falling water level periods (up to 32 days) are four times greater than those under the rising and low water level periods (approximately seven days).

Although changes in water temperature influence the rates of many ecosystem processes in lakes, knowledge of the water temperature regime for large floodplain lake systems subjected to multiple stressors has received little attention. The coupled models can serve to derive more knowledge on the water temperature impact on lake ecosystems. For this purpose, we used a physically-based hydrodynamic model coupled with a transport model to examine the spatial and temporal behavior and primary causal factors of water temperature within the floodplain of Poyang Lake that is representative of shallow and large lakes in China. Model performance is assessed through comparison with field observations and remote sensing data. The daily water temperature variations within Poyang Lake were reproduced reasonably well by the hydrodynamic model, with the root mean square errors of 1.5–1.9 °C. The modeling results indicate that the water temperature exhibits distinct spatial and temporal variability. The mean seasonal water temperatures vary substantially from 29.1 °C in summer to 7.7 °C in winter, with the highest value in August and the lowest value in January. Although the degree of spatial variability differed considerably between seasons, the water temperature generally decreases from the shallow floodplains to the main flow channels of the lake. As expected, the lake water temperature is primarily affected by the air temperature, solar radiation, wind speed and the inflow temperature, whereas other factors such as cloud cover, relative humidity, precipitation, evaporation and lake topography may play a complementary role in influencing temperature. The current work presents a first attempt to use a coupled model approach, which is therefore a useful tool to investigate the water temperature behavior and its major causal factors for a large floodplain lake system. It would have implications for improving the understanding of Poyang Lake water temperature and supporting planning and management of the lake, its water quality and ecosystem functioning.