Hanjiang River Research Articles

Spatial Association Network and Driving Factors of Agricultural Eco-Efficiency in the Hanjiang River Basin, China

Reducing agricultural emissions and promoting carbon sequestration are vital for China to achieve its dual carbon goals. Achieving the green transformation of agricultural watersheds requires a thorough understanding of the internal transmission relationships within the watersheds and the underlying spatial correlation structures. This paper used the SBM-3E model to calculate the agricultural ecological efficiency of 17 prefecture-level cities in the Hanjiang River Basin (HRB) from 2010 to 2020, taking agricultural carbon emissions and a comprehensive non-point source pollution index as the unexpected output. The Gravity model and social network analysis methods were used to analyze the evolution characteristics of the network structure of agricultural ecological efficiency, and the secondary assignment procedure method was used to identify the driving factors from the planting structure, water use structure, and resource endowment. First, from 2010 to 2020, the overall agricultural ecological efficiency in the HRB demonstrates a declining trend, with efficiency values of 12.15, 9.40, and 6.67 in the upper, middle, and lower reaches, respectively. Second, the spatial correlation network density of agricultural ecological efficiency in the HRB is 0.17, with a network efficiency of 0.89. The correlation among units within the basin is relatively low, but stability is high. Moreover, the individual network spillover absorption capacity exhibits heterogeneity, and the status of each subject within the watershed follows a “core-edge” structure. Third, total water consumption and corn cultivation have a positive impact on the agricultural ecological efficiency network in the HRB, whereas agricultural water use and rice cultivation negatively influence the network. We propose policy recommendations to facilitate the advancement of green development in China’s agricultural watersheds and the achievement of the dual carbon goals.

Reconstruction and characterization of droughts and floods in the Hanjiang River Basin, China, 1426–2017

Reconstruction and characterization of droughts and floods in the Hanjiang River Basin, China, 1426–2017

Downstream carbon transport and surface CO2 evasion in the Hanjiang River Network and their implications for regional carbon budget

Fluvial carbon fluxes have been increasingly recognized as important components of the global carbon budget. However, it is challenging to accurately quantify carbon fluxes in river networks; therefore, the role of carbon fluxes in the regional carbon budget remains poorly understood. The Hanjiang River Network (HRN) is located in a subtropical monsoon climate zone, and its material transport has a notable impact on the Changjiang River. In this study, it was hypothesized that the total fluvial carbon fluxes from the river network in the subtropical monsoon climate zone are dominated by vertical CO2 evasion and account for a large fraction of terrestrial net primary productivity (NPP) (e.g., 10 %) and fossil CO2 emissions (e.g., 30 %), which is roughly equivalent to the global average. Therefore, the downstream export of three carbon fractions and CO2 evasion were estimated in the HRN over the last two decades and the findings were compared with NPP and fossil CO2 emissions in the basin. The results suggest that approximately 2.14–6.02 Tg C year−1 (1 Tg = 1012 g) of carbon is exported in the HRN. Vertical CO2 evasion represents the largest destination at 1.22–5.34 Tg C year−1 or 68 % of the total fluvial carbon flux component, corresponding to 1.5 %–11 % of the fossil CO2 emissions. Downstream export of dissolved inorganic carbon is the second largest destination with a magnitude of 0.56–1.92 Tg C year−1. Downstream organic carbon export plays a relatively small role with a magnitude of 0.04–0.28 Tg C year−1. The findings also indicate that the offset of total fluvial carbon fluxes from terrestrial NPP is unexpectedly small (2.0 %–5.4 %). Data availability and the simplification of carbon processes introduced uncertainty; therefore, future research should incorporate a fuller representation of fluvial carbon processes and fractions to improve regional-scale carbon accounting.

Construction of precipitation index based on ensemble forecast and heavy precipitation forecast in the Hanjiang River Basin, China

Construction of precipitation index based on ensemble forecast and heavy precipitation forecast in the Hanjiang River Basin, China

Impact of inter-basin water diversion project operation on water quality variations of Hanjiang River, China

The impact of the operation of inter-basin water diversion projects on the integrity and stability of regional ecosystems cannot be ignored. In this study, water quality samplings were conducted monthly at 16 national monitoring sites in the mid-downstream of the Hanjiang River (HJR, the downstream of the water source of the South-to-North Water Diversion Project of China) over 3 years, covering seven physiochemical water quality indicators and six heavy metal elements. The water quality index (WQI) and multivariate statistical techniques were introduced to comprehensively evaluate water quality status and understand the corresponding driving factors of water quality variations. The heavy metal risks were evaluated using the Nemerow Pollution Index (Pn), the Heavy Metal Pollution Index (HPI), and the human health risk assessment model. The results showed that after the operation of the Middle Route of the South-to-North Water Diversion Project of China (MRSNWDPC), water quality in the mid-downstream of the HJR was generally at a “good” status, with the average WQI of 86.37, showing no water quality deterioration trends. The operation of the MRSNWDPC did significantly decrease the monthly flow in the HJR by about 4.05–74.27%, and the flow variation processes also became more stable than before. Most water quality indicators and WQIs have no correlations with the flow and water level changes. The human health risks of all heavy metal elements caused by dermal exposure and ingestion pathways increased over time. The average individual health risk caused by carcinogenic heavy metal Cr was the highest. Chromium is the major carcinogenic factor and should be a critical indicator to pay special attention to for water risk management in the HJR. This study provides a scientific reference for the water quality safety management of HJR under the influence of a water diversion project.

Water Quality Change Trend and Risk Analysis of Wuhan Hanjiang River Water Source

Hanjiang River is closely related to the middle route of the South-to-North Water Diversion Project, the Water Diversion Project from the Hanjiang River to the Wei River, and the Water Diversion Project in Northern Hubei. The Wuhan Hanjiang River water source is one of the important drinking water sources in China; its water quality safety is significant to living and production for millions of residents in Wuhan. Based on data from 2004 to 2021, the water quality variation trend and risk of Wuhan Hanjiang River water source were studied. The results showed that a certain gap existed between the concentrations of some pollutants such as total phosphorus, permanganate index, ammonia nitrogen, and correspondent water quality target, especially for the total phosphorus. The growth of algae in the water source was marginally limited by the concentrations of nitrogen, phosphorus, and silicon. When other factors remained unchanged, diatoms tended to grow rapidly when the water temperature was appropriate (6-12℃). The quality of water upstream had a great impact on the water quality of the Hanjiang water source. There may have been pollutants entering into the reach during the West Lake Water Plant and Zongguan Water Plant. There were differences in the temporal and spatial variation trend of concentrations between permanganate index, total nitrogen, total phosphorus, and ammonia nitrogen. Significant changes in the ratio of nitrogen and phosphorus in the water body will affect the population structure and quantity of planktonic algae and ultimately affect the safety of water quality. The water body in the water source area was generally in the state of medium nutrition to mild eutrophication, and middle eutrophication may have occurred in a few periods. In recent years, the nutritional level of the water source has been on the decline. It is necessary to make an in-depth investigation on the source, quantity, and change trend of pollutants in water sources in order to eliminate potential risks.

Pollution Characteristics and Risk Assessment of Antibiotics and Resistance Genes in Different Water Sources in the Wuhan Section of the Yangtze River

The distribution characteristics, correlations, and potential ecological risks of 13 antibiotics and 10 antibiotic resistance genes (ARGs) in 16 water sources in Wuhan were analyzed using solid-phase extraction-ultra-high performance liquid chromatography-tandem mass spectrometry (SPE-UPLC-MS/MS) and real-time quantitative PCR technology. The distribution characteristics and correlations and potential ecological risks of antibiotics and resistance genes in this region were analyzed. The results showed that a total of nine antibiotics were detected in the 16 water source samples, and the concentration range was ND-177.36 ng·L-1. The concentration distribution presented as follows:Tributary Jushui River<lower reaches of the main stream of the Yangtze River<upstream of the main stream of the Yangtze River<Tributary Hanjiang River<Tributary Sheshui River. The total absolute abundance of ARGs after the Yangtze River and Hanjiang River confluence was significantly higher than that before the confluence, and the average abundance of sulfa ARGs was significantly higher than that of the other three ARGs resistance genes (P<0.05). There was a significant positive correlation between sul1 and sul2, ermB, qnrS, tetW, and intI1 in ARGs (P<0.01), and the correlation coefficients were 0.768, 0.648, 0.824, 0.678, and 0.790, respectively. The correlation within the sulfonamide ARGs group was weak. Correlation of ARGs between groups. Four antibiotics, sulfamethoxazole, aureomycin, roxithromycin, and enrofloxacin, had a medium risk to aquatic sensitive organisms, and the proportion of each risk area in the ecological risk map was 9.0% (medium risk), 30.6% (low risk), and 60.4% (no risk). The combined ecological risk assessment (RQsum) of the 16 water sources indicated medium risk, and the RQsum (mean) of the rivers involved was 0.222 (Tributary Hanjiang River)<0.267 (main stream of the Yangtze River)<0.299 (other tributaries).

Study on Sedimentary Evolution of the Hanjiang River Delta during the Late Quaternary

In recent years, coastal areas have been threatened by many potential hazards due to global warming, glacier melting and sea level rise. Understanding their evolutionary history and development trends can help predict disasters and further reduce the corresponding losses. The Hanjiang River delta in the southeastern part of China is the second largest delta in Guangdong Province and has such challenges. Studying the sedimentary evolution and delta initiation of the Hanjiang Delta is beneficial for understanding the response of the Hanjiang Delta to present and future sea level and climate changes. In this research, we drilled a series of cores from the Hanjiang subaqueous delta, which contains information on the sedimentary environment, climate change and sea level change during the late Quaternary. Combined with previous research results and under the constraint of high-precision and high-resolution AMS14C and OSL, we carried out a multi-proxy analysis that included micropaleontology and grain size to obtain information on the sedimentary environment, sea level change and climate change. We then further discussed the initiation of the Hanjiang delta and its primary factors. The Quaternary sediments began depositing in the early Late Pleistocene (MIS5), and three sedimentary cycles can be recognized from bottom to top. The dating results also indicate that the first two cycles were formed during the late Pleistocene, while the last cycle was formed during the Holocene. The initiation of the Hanjiang Delta was indicated by a progradation in the process of a transition from estuary to a typical delta. At this time, the rate of delta progradation seaward was fast, and increasing amounts of sediments moved through the third line of islands into the sea. The barrier–lagoon system began to develop in the estuary of Hanjiang during this period. With the sequential construction of the delta, the lagoon was filled and covered by delta deposition, and the barrier bar moved to the sea; thus, the barrier-coast delta depositional model was established in the study area. Since the last glacial period (LGM), the Hanjiang River Delta and other river deltas in the region seem to have experienced similar evolutionary histories, including the filling of incised paleo-valleys and estuaries in the Early Holocene and deltaic progradation in the Middle to Late Holocene, controlled by sea level change.

Tourism Ecological Efficiency and Sustainable Development in the Hanjiang River Basin: A Super-Efficiency Slacks-Based Measure Model Study

The Hanjiang River is one of the major tributaries of the Yangtze River, and the Hanjiang River Basin serves as an important link connecting the western and eastern regions of China. As a significant tourist destination, the development of the tourism industry in the Hanjiang River Basin is of great significance for promoting local economic, social, and environmental sustainability. The study of the spatiotemporal evolution of the ecological efficiency of tourism in the Hanjiang River Basin is beneficial for optimizing the investment of tourism resource elements and promoting ecological protection and high-quality development in the area. In this paper, we used the Super-Efficiency Slacks-Based Measure Model to calculate the tourism ecological efficiency of 12 cities in the Hanjiang River Basin from 2010 to 2019 and measured its spatiotemporal evolution and spatial agglomeration using ArcGIS software. The results show that during the study period, the ecological efficiency of tourism in the Hanjiang River Basin presented a phased characteristic of first rising and then falling over time and a heterogeneity characteristic of decreasing in a downward-middle-upward staircase pattern spatially. In addition, the distribution of tourism ecological efficiency exhibited obvious spatial clustering and dependence, with significant low-level homogenization phenomena, which requires strengthening cooperation and coordination among neighboring cities to achieve more efficient resource utilization and higher-quality tourism product development.

Distribution and risk assessment of antibiotics under water level fluctuation in the riparian zone of the Hanjiang River

The riparian zone (RZ) is an important region connecting surface water and groundwater, and it has widely been acknowledged for its pollutant buffering capacity. However, the decontaminating effect of RZ on trace organic compounds such as antibiotics has received little attention. This study explored the distribution of 21 antibiotics and 4 sulfonamide metabolites in river water and groundwater in the lower reaches of the Hanjiang River. The diffusion and exchange of contaminants between the river and riverbanks under the influence of water conservancy projects (Xinglong Dam and the Yangtze-Hanjiang Water Diversion Project) were investigated. Macrolide antibiotics were prevalent in river water (62.5–100%) and groundwater samples (42.9–80.4%). Ofloxacin and chlortetracycline were detected with the highest concentrations in river water (12.2 ng L−1) and groundwater (9.3 ng L−1) respectively. Higher levels of antibiotics were observed in spring and winter than in other seasons. The river-groundwater interaction has a certain interception effect on antibiotics, especially near riverbanks. Redox sensitive element Fe2+ showed significantly positive correlations with some tetracycline and macrolide antibiotics (p < 0.05), and thus the migration mechanism between Fe2+ and antibiotics under the condition of redox change should be investigated further. Environmental risks posed by antibiotics were assessed for algae, daphnids, and fish in surface water and groundwater. Only clarithromycin and chlortetracycline presented a medium risk to algae (0.1 < RQ < 1), and the rest presented low risk (RQ < 0.1). Nevertheless, the risk range may be further extended by interactions between groundwater and surface water. Accurate understanding of antibiotic transport in RZ is critical for developing management strategies aimed at reducing the pollution load on the watershed.

Study on non-point source pollution characteristics under different spatial scales: a case study of Hanjiang River Basin, China.

In recent years, the research on non-point source (NPS) pollution has been deepening, but it is focused on the large-scale watershed or region. There are a few studies on the scales of small watershed and runoff plot, and it is even less to analyze the characteristics and mechanism of non-point source pollution in certain watershed by combining three different scales. Based on the combination of natural rainfall monitoring and MIKE model simulation, the Shaanxi section of Hanjiang River Basin in China was taken as an example to study the characteristics of NPS pollution at different spatial scales. The results showed that there was an obvious correlation between rainfall and runoff/sediment yield. The order of runoff yield/sediment yield per unit area was as follows: woodland > forested and grassy land > arable land. There was a significant relationship between the loss of total phosphorus and the sediment yield in the runoff plots. The total nitrogen pollution was serious, with an average concentration of 3.8mg/L. The nutrient loss was in the form of nitrate nitrogen, with an average proportion of 63.06%. For small watershed scale, the characteristics of rainfall runoff pollution generation were like runoff plot scale, both have obvious initial scour phenomenon. However, compared with runoff plot scale, the pollutant loss concentration increases with a strong lag. The MIKE model based on the coupling of hydrology, hydrodynamics, and pollution load had a strong applicability in the basin. The critical source areas of NPS pollution were identified, and five scenarios were laid out in the areas for the control of NPS pollution. Centralized livestock and poultry farming had the best reduction effect.

Exploring the impacts of climate change and human activities on future runoff variations at the seasonal scale

Most watersheds around the world have been changing their natural flow patterns because of the coupled effects of climate change and human activities. Understanding the quantitative impacts of projected climate and human factors on future runoff variations is essential for adaptability assessment of water resource management, especially at the seasonal scale where their intra-annual changes are detected. In this study, an extended Budyko framework that combines traditional elasticity and decomposition methods is developed to analyze future seasonal runoff variations. The upper reach of the Hanjiang River basin (UHRB) in China is used as a case study. The case results are quantified and compared with the monthly ABCD model using historical hydrometeorological observations over 1961–2020 and near-future climate projections over 2031–2060 from the multi-model ensemble of the Inter-Sectoral Impact Model Intercomparison Project (ISIMIP3b). We find that: (1) human activities including the operation of the Han-to-Wei inter-basin water transfer (IBWT) and reforestation projects have a substantial negative impact on runoff reduction in this region, accounting for a proportion of ∼70% in energy-limited seasons and ∼65% in water-limited seasons; and (2) the role of climate change projected by ISIMIP3b will intensify in energy-limited seasons, especially under the high-emission scenario with the increasing trend of effective precipitation,. Additionally, the performance of our extended Budyko framework is sufficiently robust to parameter disturbance experiments, indicating its applicability as an alternative for exploring future seasonal runoff variations.

Quantitative assessment methodology framework of the impact of global climate change on the aquatic habitat of warm-water fish species in rivers

Global climate change (GCC), with global warming as the main characteristic, has become a global issue widely concerned by people. GCC impacts the hydrological regime at the watershed scale and affects the hydrodynamic force and the habitat conditions of freshwater ecosystems at the river scale. The impact of GCC on water resources and the water cycle is a research hotspot. However, there are few studies on water environment ecology related to hydrology and the influence of changes in discharge and water temperature on warm-water fish habitats. This study proposes a quantitative assessment methodology framework for predicting and analyzing the impact of GCC on the warm-water fish habitat. This system integrates GCC, downscaling, hydrological, hydrodynamic, water temperature and habitat models and was applied to the middle and lower reaches of the Hanjiang River (MLHR), where there are four major Chinese carps resource reduction problems. The results showed that the calibration and validation of the statistical downscaling model (SDSM) and the hydrological, hydrodynamic, and water temperature models were carried out using the observed meteorological factors, discharge, water level, flow velocity and water temperature data. The change rule of the simulated value was in good agreement with the observed value, and the models and methods used in the quantitative assessment methodology framework were applicable and accurate. The rise of water temperature caused by GCC will ease the problem of low-temperature water in the MLHR, and the weighted usable area (WUA) for spawning of the four major Chinese carps will appear in advance. Meanwhile, the increase in future annual discharge will play a positive role in WUA. In general, the rise in confluence discharge and water temperature caused by GCC will increase WUA, which is beneficial to the spawning ground of four major Chinese carps.

Vegetation Dynamics and Their Response to Climate Changes and Human Activities: A Case Study in the Hanjiang River Basin, China

The Hanjiang River Basin (HJRB) is an important water conservation and ecological barrier area for the South–North Water Transfer Central Project. The quantitative analysis of regional differences in vegetation changes and their main drivers is important for the monitoring of the ecological environment of the basin and formulation of ecological protection measures. Based on MODIS13Q1 data from 2000 to 2020, spatiotemporal variation characteristics of vegetation in the HJRB were analyzed using Theil–Sen + Mann–Kendall, the Hurst index, and correlation analysis. Then, we detected the drivers using an optimal parameter geographic detector. The results showed that from 2000 to 2020, the average NDVI value increased from 0.651 to 0.737, with a spatial distribution pattern of “high in the northwest and low in the southeast”, and 88.68% of the study area showed an increase in vegetation cover, while 5.80% showed a significant degradation. The positive persistence of future vegetation changes is stronger than the negative. It may show a slowdown or degradation trend, among which the vegetation restoration along the Han River and urbanized areas need to be strengthened. The factor detector indicated that the main factors influencing vegetation change were topography and climate, for which the most influential variables, respectively, were elevation (0.1979), landform (0.1720), slope (0.1647), and soil type (0.1094), with weaker influence from human activity factors. The interaction test results showed that the interaction of various geographic factors enhanced the explanatory power of vegetation changes and showed mainly nonlinear and two-factor enhancements. The dominant factor varies between sub-basins; for example, the interaction between wind speed and land use conversion was the dominant factor in the middle reaches of the HJRB; the dominant factor in the lower reaches of the HJRB was expressed as the interaction between land use conversion and temperature. Finally, the effects of the range or category of different drivers on vegetation growth were systematically analyzed. The results of the study contribute to the understanding of the dynamic changes of vegetation based on a comprehensive consideration of the interaction of topography, climate, and human activities, taking into account the totality and variability of the geographical environment, and provide a reference for the ecological restoration and rational use of vegetation resources in the HJRB.

Characteristics and Driving Mechanism of Water Resources Trend Change in Hanjiang River Basin.

Studying the historical and future trends of water resources in a basin and explaining the causes of water resource changes is very important, which is key to the management of water resources in a basin. The Hanjiang River Basin is an important water supply source for southwestern Fujian and eastern Guangdong, but it has an uneven spatial and temporal distribution of water resources and an outstanding conflict between supply and demand. In this study, the SWAT model was used to simulate the conditions of the Hanjiang River Basin in the last 50 years, using long time series climate data to study the characteristics and driving mechanism of water resources trend change. The results show that the water resources in the basin have not increased significantly in the last 50 years, but evapotranspiration has increased significantly. The forecast results for water resources in the future are reduced. The water resource changes in the basin have been unevenly distributed in the last 50 years. Climate change has been the main factor in total water resource change in the basin, while the difference in water resource change trends within the basin is caused by land use. The key reason for the decrease in water resources in the Hanjiang River Basin is the significant increase in evapotranspiration due to the significant increase in temperature. If this situation continues, the available water resources in the basin will continue to decline. In fact, many basins around the world are currently likely to have such problems, such as the 2022 summer drought in the Danube River Basin in Europe and the Yangtze River Basin in China, so this article is informative and representative of future water resources management in the basin.

Water Environment Characteristics and Water Quality Assessment of Water Source of Diversion System of Project from Hanjiang to Weihe River

The water source of the water diversion project from the Hanjiang River to the Weihe River is one of the most important drinking water sources in China. Its water quality is related to the water safety of the long-distance water diversion system from the Hanjiang to Weihe Rivers. In order to explore the spatiotemporal change trend of the water environment characteristics of the water source area and analyze the key factors that have a greater impact on it, this study collected 9 types of water environment physical and chemical parameters from 10 water quality monitoring sections from 2017 to 2019; the water environment characteristics of the water source area of the water diversion system from the Hanjiang River to the Weihe River were analyzed and evaluated by using the variance analysis method, the hierarchical cluster analysis method and the water quality identification index evaluation method. The results were as follows. (1) There was spatiotemporal heterogeneity in a number of physical and chemical parameters in the water body of the water source. In terms of time, the concentrations of CODMn, COD, BOD5 and F- were higher in the flood season (July-October) than in the non-flood season (November-June). The concentrations of DO, TP and TN in the non-flood season were higher than those in the flood season. Spatially, the concentration of physical and chemical parameters of the water body in the Huangjinxia Reservoir area was higher than that in the Sanhekou Reservoir area. (2) The water quality of the water source area was good. The comprehensive water quality reached the Class II water quality standard of surface water environmental quality. Time showed that the comprehensive water quality in the non-flood season was better than that in the flood season. Spatially, the overall water quality of the tributaries was better than that of the mainstream. TN is a key indicator that affects water quality. (3) The spatial and temporal differences in water quality in water source areas are mainly affected by factors such as rainfall, temperature and human activities. This study can provide a scientific and data basis for related research on maintaining and improving the quality of the ecological environment of the water source areas of the Hanjiang to Weihe River Water Diversion System.

A Three-Parameter Hydrological Model for Monthly Runoff Simulation—A Case Study of Upper Hanjiang River Basin

Monthly hydrological models are useful tools for runoff simulation and prediction. This study proposes a three-parameter monthly hydrological model based on the proportionality hypothesis (TMPH) and applies to the Upper Hanjiang River Basin (UHRB) in China. Two major modules are involved in the TMPH: the actual evapotranspiration and runoff, in which the coupled water–energy balance equation and the proportionality hypothesis are used for calculation, respectively. It is worth mentioning that the proportionality hypothesis was extended to the partitioning of the available water into water loss and runoff at the monthly scale, which demonstrates that the ratio of runoff to its potential value is equal to the ratio of continuing water loss to its potential value. Results demonstrate that the TMPH model performs well when the NSE values are 0.79 and 0.83, and the KGE values are 0.86 and 0.78 for calibration period and validation period, respectively. The widely used two-parameter monthly water balance (TWBM) model and ABCD model are compared with the proposed model. Results show that TMPH performs better than TWBM model with NSE increased by 0.07 and 0.11, and KGE increased by 0.02 and 0.16, respectively, whereas the TMPH performs similarly as the ABCD model in the calibration period, and performs slightly better in the validation period, with NSE increased by 0.02, and KGE increased by 0.03. Sensitivity analysis show that the simulation result is most sensitive to parameter n, followed by SC and λ. In summary, the proposed model has strong applicability to the study area.

Medium-long-term prediction of water level based on an improved spatio-temporal attention mechanism for long short-term memory networks

River water level usually given by nonlinear and nonstationary time series and affected by numerous complex spatial and temporal factors. But not all input factors are positively correlated with flood forecasting, and uncorrelated inputs tend to bring a lot of noise, resulting in lower prediction accuracy. Attention mechanism is an effective solution to feature filter. This study presents a spatio-temporal attention LSTM (STA-LSTM). Meanwhile, attention visualization makes models interpretation providing the basis. In this work, the attention-weight matrix is generated independently by the spatial attention module and the temporal attention module to focus on the more valuable feature factors in time and space, respectively. Spatio-temporal attention is a combination of spatial attention and temporal attention to assign scores to input sequences. Forecasting the water level of Hanchuan in the next 6 h based on the observations in the past 6 h in the middle and lower reaches of the Hanjiang River, China. The experimental results indicate that the mean absolute error (MAE) of STA-LSTM is 0.74835, root mean square error (RMSE) is 0.90197, mean absolute percent error (MAPE) is 3.29924, and coefficient of determination (R2) is 0.94138. This study improves the accuracy of the water level prediction method, which makes it easier for decision-makers to plan evacuations in advance.

Plant Diversity and Quantitative Characteristics Of Wetland Community on the North Bank of Hanjiang River in Cheng GU, Shaanxi Province, China

Four water ecological surveys were carried out on the north bank of Hanjiang river in two seasons from 2020 to 2021. Based on the field wetland quadrat survey and literature data, the species diversity index was determined. The research showed that there are 360 species of wetland plants belonging to 108 families and 264 genera on the north bank of Hanjiang river, and the geographical composition of seed plants is at the genus level, mainly temperate distribution types, with 160 species. In the community species diversity index, the mean value of Patrick index was 18.80 ± 5.19. The mean Shannon Wiener diversity index was 2.15 ± 0.39. The mean value of Simpson dominance index was 0.81 ± 0.10. The average Pielou evenness index was 0.75 ± 0.10. The mean value of Margalef index was 3.44 ± 0.87. The Patrick index and Margalef index of the Bidens pilosa form were the lowest. The Shannon-Wiener diversity index，the Simpson index，and the Pielou index of the Potamogeton malaianus form were the lowest. The Patrick index of the Colocasia esculenta form was the highest,and the Pielou of the Sapium sebiferum form was the highest. The Shannon- Wiener diversity index and Simpson index of the Populus canadensis form group were the highest, and the Margalef index of the Flueggea virosa form was the highest. The research results provide basic data and scientific basis for the protection and restoration of wetland ecosystems and management of wetland resources in Yuan'an and similar areas. Bangladesh J. Bot. 51(4): 839-848, 2022 (December) Special

Sediment-isolated Comamonas terrigena strain HJ-2: a novel nitrate-dependent ferrous-oxidizing bacterium with multifunction on pollutant transformation.

Microbially driven Fe(II) oxidation is vital for Fe-cycling processes. In the present study, a novel strain of nitrate-dependent Fe-oxidizing bacteria (FOB) was isolated from the riparian zone sediment of the Hanjiang River, China. It was identified as Comamonas terrigena strain HJ-2. The strain HJ-2 oxidized 2.80mmol l-1 Fe(II) within 144h to form Fe(III)/Fe(II) complex on the cell surface using 1.63mmol l-1 nitrate as an electron acceptor. The formed nitrite from nitrate reduction chemically oxidized Fe(II). Surprisingly, this strain also reduced nitrilotriacetic iron to form 0.5mmol l-1 Fe(II) in 120h in anaerobic conditions primarily mediated by the NADH flavin oxidoreductase. Besides, the strain completely reduced 0.18mmol l-1 nitrobenzene to aniline in 24 days and 15.6 μmol l-1 arsenate to arsenite in 7 days due to the existence of nitro and arsenate reductases. However, the Fe(II) inhibited the reduction of nitrate, nitrobenzene, and arsenate, possibly due to the impeding of transport of the solutes through the membrane or the synthesis of the related enzymes. These results provide new knowledge about the Fe(II)-cycling and the fate of some pollutants in the riparian zone. It also informed that some bacteria have universal functions on elements and contaminants transformation.