Lower Yangtze River Research Articles

The Foraging Window for Greater White-Fronted Geese (Anser albifrons) Is Consistent with the Growth Stage of Carex

Food resources are key limiting factors for migratory waterbirds, and the foraging strategies adopted by herbivorous waterbirds are affected by food availability in wetland habitats. The greater white-fronted goose (Anser albifrons) is mainly dependent on Carex in the lower and middle Yangtze River floodplain. Exploring the relationship between the growth conditions of Carex and the foraging strategies adopted by wintering greater white-fronted geese has important ecological implications for habitat protection and management. In this study, scan sampling and focal animal sampling were used to record the foraging behaviors of greater white-fronted geese wintering at Shengjin Lake, and the plant height and water content of Carex were surveyed simultaneously. The relationship between plant characteristics and foraging behaviors was tested using a linear regression equation. The results showed that Carex had two growth periods at Shengjin Lake, and the pecking rate and foraging time budget of greater white-fronted geese were higher during these two periods. Plant characteristics were positively correlated with goose foraging behaviors. The strategic adjustment of the foraging behaviors adopted by wintering greater white-fronted geese was consistent with the growth stage of Carex, which is the optimal foraging window for greater white-fronted geese. During the foraging windows, geese changed their foraging strategies to obtain more energy in order to guarantee successful wintering and migration.

Region-dependent meteorological conditions for the winter cold hazards with and without precipitation in China

Cold hazard is one of the major meteorological disasters in winter. However, the meteorological conditions for the cold hazard events vary significantly with both the feature of the event and the region of occurrence. This study divides winter cold hazard events in China into three categories based on the daily gridded dataset of cold hazards from November 1980 to March 2020: events without wintry precipitation (hazardous low temperature, abrupt temperature drop, and/or freezing), with wintry precipitation only (hazardous sleet and/or snowstorm), and with both. The region-dependent multivariate meteorological conditions for each category of cold hazards are investigated using ERA5 reanalysis data. Results show that the surface air temperature (T2m) and its anomaly (T2m_anom) are lower than climatology during cold hazards. But the difference in T2m among provinces exceeds 30 °C, and even for the same province, the difference among different categories of cold hazards exceeds 10 °C. The region- and category-dependent differences of T2m_anom and daily temperature drop (∆T24) are also large, about 5 °C and 2 °C d−1, respectively. The Multivariate Empirical Orthogonal Function analysis has further been applied to not only the abovementioned temperature-related variables but also the precipitation-related variables (i.e., daily accumulated total precipitation, daily accumulated snowfall, and daily mean snow depth) in the middle and lower Yangtze River region, which reveals the event-mean state and spatial–temporal coupling evolution during the progression of the event for the selected key meteorological variables. The meteorological conditions for cold hazards put forward by this study could provide region-dependent and category-dependent reference for the prediction and warning of cold hazards.

Screening of Heat-Tolerant Indica Rice Varieties in the Middle and Lower Yangtze River

Rice growth is constantly challenged by severe environmental conditions, especially high-temperature stress, brought about by global warming. How to increase rice yields is a current issue in many countries. By analyzing the meteorological data from Anhui Province over the past 60 years, the frequency and level of high-temperature damage were comprehensively analyzed. On this basis, five indica rice varieties with strong high-temperature tolerance, relatively high yield and stable yield were selected by laboratory-simulated high-temperature and field high-temperature experiments: Longliangyou Huazan (LLYHZ), 9you-6 (9Y-6), Longliangyou-1988 (LLY-1988), Fengliangyou-4 (FLY-4) and Huanghuazan (HHZ). These are suitable for planting in the middle and lower reaches of the Yangtze River. This study provides a theoretical reference and scientific basis for the study of rice tolerance to high-temperature stress.

The relative importance of antecedent soil moisture and precipitation in flood generation in the middle and lower Yangtze River basin

Abstract. Floods have caused severe environmental and socioeconomic losses worldwide in human history and are projected to exacerbate due to climate change. Many floods are caused by heavy rainfall with highly saturated soil; however, the relative importance of rainfall and antecedent soil moisture and how it changes from place to place has not been fully understood. Here we examined annual floods from more than 200 hydrological stations in the middle and lower Yangtze River basin. Our results indicate that the dominant factor in flood generation shifts from rainfall to antecedent soil moisture with the increase in watershed area. The ratio of the relative importance of antecedent soil moisture and daily rainfall (SPR) is positively correlated with topographic wetness index and has a negative correlation with the magnitude of annual floods. This linkage between watershed characteristics that are easy to measure and the dominant flood-generation mechanism provides a framework to quantitatively estimate potential flood risk in ungauged watersheds in the middle and lower Yangtze River basin.

Changes of total and artificial water bodies in inland China over the past three decades

• A New China’s artificial water bodies (WBs) dataset from 1987 to 2020 is developed. • The total area of WB in inland China increased by 38.8% from1987 to 2020. • The artificial area of WB in inland China increased by 32.3% from1987 to 2020. • Climate change dominates the WB increasing in the western basins of China. • Most WB changes are controlled by dam construction in the eastern basins of China. As an important surface water resource that can be directly used, water bodies (WBs) have a non-negligible impact on human life, production and maintaining ecological balance. Over the past few decades, how many WB have changed to different degrees due to climate change, dam construction and other factors? Using the high-resolution WB mask dataset and dam point data, the study distinguished artificial and natural WBs, calculated their spatiotemporal changes, and quantified climatic and human contributions in 17 basins in inland China during 1987–2020. The results show WBs exhibited a spatial pattern of contraction in the northeast and expansion in the southwest in inland China. The total, artificial and natural area of inland WBs in China increased by 38.8%, 32.3%, 40.8% from 1987 to 2020, respectively. In the western basins of China such as Inland rivers in Northern Tibet (61%), Upper Yellow River (61%), Upper Yangtze River (52%), Inland rivers in Xinjiang (51%), climate change dominates the increase of WBs. While in the eastern basins such as the Middle and Lower Yangtze River (60.84%), Lower Yangtze River (60.53%), and Songhua basins (52.66%), dam construction is the main reason for the area change in WBs. The analysis of the spatiotemporal evolution of WBs in inland China in the past three decades and the quantification of climate and human contributions are of great significance for the rational development and sustainable use of water resources.

Living Status and Perspective of the Silver Carp (Hypophthalmichthys molitrix) in the Lower Reach of the Yangtze River: Insights from Population Distribution, Age Structure, and Habitat Preference Analyses

Using systemic, periodic surveys from 2015 to 2019, population distribution, speculated age and habitat preference were analyzed to assess the living status for the Silver Carp (Hypophthalmichthys molitrix) in the lower Yangtze River. Small Silver Carps became more temporarily abundant in spring and autumn, and the catch per unit effort (CPUE) fluctuated yearly. Spatially, going from Anqing (AQ) to Changshu (CS), Silver Carps in the 200 mm standard length(SL) group became less abundant, whereas those in the 400–600 mm and >600 mm SL groups steadily increased. According to the Von Bertalanffy growth equation, the Silver Carp exhibits isometric growth, and the inflection point of SL and body weight (BW) were 564.01mm and 2948.31g, respectively, with a growth characteristic index (φ) of 5.0655. The fish dominant age range was 0+ to 5 years, reflecting the young age composition of the fish. Furthermore, the habitat survey findings revealed that the Silver Carp has the different preference on habitat selection in different life history. Juvenile Silver Carps were comparatively staying in the lower Yangtze River, where there exists a relatively stable bifurcated river. Adult fishes were mostly found in the CS and Nantong(NT) section where the river is wide and the food is rich. When compared with the historical survey data, it was found that the Silver Carp live in the AQ through NT section. The living status and perspective of the Silver Carp in the lower reach of the Yangtze River were clarified, and future work should be more concerned with the strengthening of conservation and the restoration of adequate habitat.

Three-Dimensional Mineral Prospectivity Modeling for Delineation of Deep-Seated Skarn-Type Mineralization in Xuancheng–Magushan Area, China

The Middle–Lower Yangtze River Metallogenic Belt is an important copper and iron polymetallic metallogenic belt in China. Today’s economic development is inseparable from the support of metal mineral resources. With the continuous exploitation of shallow and easily identifiable mines in China, the prospecting work of deep and hidden mines is very important. Mineral prospectivity modeling (MPM) is an important means to improve the efficiency of mineral exploration. With the increase in resource demands and exploration difficulty, the traditional 2DMPM is often difficult to use to reflect the information of deep mineral deposits. More large-scale deposits are needed to carry out 3DMPM research. With the rise of artificial intelligence, the combination of machine learning and geological big data has become a hot issue in the field of 3DMPM. In this paper, a case study of 3DMPM is carried out based on the Xuancheng–Magushan area’s actual data. Two machine learning methods, the random forest and the logistic regression, are selected for comparison. The results show that the 3DMPM based on random forest method performs better than the logistic regression method. It can better characterize the corresponding relationship between the geological structure combination and the metallogenic distribution, and the accuracy in the test set reaches 96.63%. This means that the random forest model could provide more effective and accurate support for integrating predictive data during 3DMPM. Finally, five prospecting targets with good metallogenic potential are delineated in the deep area of the Xuancheng–Magushan area for future exploration.

Perfluoroalkyl acids in representative edible aquatic species from the lower Yangtze River: Occurrence, distribution, sources, and health risk.

Perfluoroalkyl acid (PFAA) exposure poses a potential hazard to wildlife and humans. Food consumption is one of the main routes of PFAA exposure for the general population, with aquatic organisms being the major contributors. To evaluate the risk of coastal residents' intake of wild aquatic organisms, 14 PFAAs were detected in crucian carp and oriental river prawn from 18 sampling sites from the lower reaches of Yangtze River. The total PFAA (∑PFAA) concentrations ranged from 5.9 to 51.3ng/g wet weight (ww) in the muscle of crucian carp and river prawn, suggesting the potential risk to human and wildlife. Perfluorooctanesulfonate (PFOS), perfluorooctanoic acid (PFOA) and long-chain PFAAs (C≥10) were the main pollutants in the tissues of crucian carp and river prawn, which are known for their higher bioaccumulation capacity. The ∑PFAA concentration in all the samples showed an increasing trend from upstream to downstream and was higher in the south bank, owing to population density, prevailing winds, background pollution and industrial emission. Principal component analysis-multiple linear regression and Pearson correlation analysis showed that WWTP effluent, industrial pollution and surface runoff ware the main sources of PFAAs in the aquatic organisms and industrial pollution highest contributor, suggesting better regulation is needed to manage them. The assessment of risk to human health and wild life suggested a low risk for most residents of cities along the Yangtze River except for resident of Nantong, where frequent consumption of wild aquatic organisms may cause potential risk to human health, especially for traditional eaters and middle-aged people.

Amplification of non-stationary drought to heatwave duration and intensity in eastern China: Spatiotemporal pattern and causes

Amplifying the frequency and loss of weather and hydrological extremes under climate warming have aroused increasing human concerns in recent decades and it is particularly the case for compound drought-heatwave (CDH) events. The drought index based on the hypothesis of non-stationarity is of great significance for the study of CDH events. Here we presented spatiotemporal patterns of CDH, general heatwaves (GHW, he heatwave that does not occur in dry months) and relevant circulation backgrounds in eastern China. We found that heatwaves are starting earlier and ending later and later. While, the termination date of heatwaves in southern China is late than those in northern China. Significant increases since the 1980 s were detected in the frequency, duration, and intensity of heatwaves and the frequency of CDH events in eastern China. Besides, heatwaves were observed mainly in the middle and lower Yangtze River basin and in the Sichuan Basin as well. Most areas of eastern China were dominated by higher occurrence probability of CDHs in July and the probability was as high as 0.49. The duration and intensity of the CDHs were 0.28 days longer and 11.14℃ higher than GHWs. Further examinations show that the western Pacific subtropical high (WPSH) has a significant influence on the occurrence of heatwaves. The average position of the WPSH is shifted westward and its intensity is relatively stronger, thus favoring the occurrence of heatwave events. The occurrence of compound events in eastern China cannot be separated from the influence of large-scale circulation and atmospheric changes.

Reduced basal and increased topdressing fertilizer rate combined with straw incorporation improves rice yield stability and soil organic carbon sequestration in a rice-wheat system.

Fertilizer management is vital for sustainable agriculture under climate change. Reduced basal and increased topdressing fertilizer rate (RBIT) has been reported to improve the yield of in–season rice or wheat. However, the effect of RBIT on rice and wheat yield stability and soil organic carbon (SOC) sequestration potential is unknown, especially when combined with straw incorporation. Here, we report the effect of RBIT with/without straw incorporation on crop yields, yield stability, SOC stock, and SOC fractions in the lower Yangtze River rice–wheat system region over nine years. RBIT with/without straw incorporation significantly increased nine–year average and annual rice yields but not wheat yields. Compared with conventional fertilization (CF), RBIT did not significantly affect wheat or rice yield stability, but combined with straw incorporation, it increased the sustainable yield index (SYI) of wheat and rice by 7.6 and 12.8%, respectively. RBIT produced a higher C sequestration rate (0.20 Mg C ha−1 year−1) than CF (0.06 Mg ha−1 year−1) in the 0–20 cm layer due to higher root C input and lower C mineralization rate, and RBIT in combination with straw incorporation produced the highest C sequestration rate (0.47 Mg ha−1 year−1). Long–term RBIT had a greater positive effect on silt+clay (0.053 mm)–associated C, microbial biomass C (MBC), dissolved organic C, and hot water organic C in the surface layer (0–10 cm) than in the subsurface layer (10–20 cm). In particular, the increases in SOC pools and mean weight diameter (MWD) of soil aggregates were greater when RBIT was combined with straw incorporation. Correlation analysis indicated that topsoil SOC fractions and MWD were positively correlated with the SYI of wheat and rice. Our findings suggest that the long–term application of RBIT combined with straw incorporation contributed to improving the sustainability of rice production and SOC sequestration in a rice–wheat system.

Improved maps of surface water bodies, large dams, reservoirs, and lakes in China

Abstract. Data and knowledge of surface water bodies (SWB), including large lakes and reservoirs (surface water areas > 1 km2), are critical for the management and sustainability of water resources. However, the existing global or national dam datasets have large georeferenced coordinate offsets for many reservoirs, and some datasets have not reported reservoirs and lakes separately. In this study, we generated China's surface water bodies, Large Dams, Reservoirs, and Lakes (China-LDRL) dataset by analyzing all available Landsat imagery in 2019 (19 338 images) in Google Earth Engine and very-high spatial resolution imagery in Google Earth Pro. There were ∼ 3.52 × 106 yearlong SWB polygons in China for 2019, only 0.01 × 106 of them (0.43 %) were of large size (> 1 km2). The areas of these large SWB polygons accounted for 83.54 % of the total 214.92 × 103 km2 yearlong surface water area (SWA) in China. We identified 2418 large dams, including 624 off-stream dams and 1794 on-stream dams, 2194 large reservoirs (16.35 × 103 km2), and 3051 large lakes (73.38 × 103 km2). In general, most of the dams and reservoirs in China were distributed in South China, East China, and Northeast China, whereas most of lakes were located in West China, the lower Yangtze River basin, and Northeast China. The provision of the reliable, accurate China-LDRL dataset on large reservoirs/dams and lakes will enhance our understanding of water resources management and water security in China. The China-LDRL dataset is publicly available at https://doi.org/10.6084/m9.figshare.16964656.v3 (Wang et al., 2021b).

Knowledge-driven based three-dimensional prospectivity modeling of Fe–Cu skarn deposits; a case study of the Fanchang volcanic basin, anhui province, Eastern China

Mineral exploration at depth is becoming increasingly important as a result of the decades of discovery and mining of surficial or near-surface mineralization, leading to targeting of deeper-seated mineralization and mineral systems. The numerous challenges posed by this transition to deeper exploration can be partly overcome by the application of 3D prospectivity modeling. This study provides an outline of this type of prospectivity modeling and focuses on the under-explored Fanchang volcanic basin, an area prospective for skarn-type Fe–Cu mineralization within the Middle–Lower Yangtze River Metallogenic belt (MLYRB) of eastern China. The approach used utilizes a 3D geological model of the Fanchang volcanic basin that enables the identification and extraction of favorable elements for mineralization using 3D spatial and mathematical morphology analysis methods. A 3D distance field method was also used to obtain distance field information for the favorable ore-forming factors delineated during this study. The limited exploration to date in the study area means that there is a lack of specific information (e.g., location, size, grade) for the mineralization in this region. As such, knowledge-driven Index Overlay with Multi-Class (IOMC), Technique for Order Preference by Similarity to an Ideal Solution (TOPSIS), and Fuzzy Comprehensive Evaluation (FCE) approaches were used to generate 3D prospectivity models for the Fanchang volcanic basin. The resulting weight coefficients relating to favorable ore-forming factors were quantified using an Analytic Hierarchy Process (AHP) approach, yielding random consistency ratio (CR) values of 0.0125. These are all less than a value of 0.1, which would indicate inconsistencies between the matrix values and values for the entirety of the hierarchy, indicating that our calculated weighting coefficients are precise and accurate. Comparison of the 3D prospectivity modeling results of the three methods using a prediction area (P–A) plot indicates that 88% of the known mineralization and mineralized occurrences within the basin were located within an area of only 12% of the study area considered prospective during modeling using the IOMC method. In comparison, TOPSIS and FCE modeling positively identified 82% (18% of the study area) and 91% (9% of the study area) of the mineralization in the study area, respectively. These results indicate that these approaches are viable tools for exploration targeting in relatively unexplored areas without specific orebody size, location, and grade data, and the FCE method appears more efficient and reliable than the other two methods in predicting locations to explore for Fe–Cu skarn mineralization. The approaches outlined during this study are widely applicable for exploration for other mineralizing systems in under-explored regions elsewhere and the specific high prospectivity targets identified during this study and the links between exploration indicators and high prospectivity regions also provide key areas and insights for both future modeling and mineral exploration within the Fanchang volcanic basin and the wider MLYRB.

Genesis of Chaoshan skarn Au deposit, Tongling, eastern China: Insights from mineral geochemistry

Skarn Au deposits are particularly developed along Middle and Lower Yangtze River region, eastern China, but gold behavior and genesis of the skarn Au deposits remain unclear. Whole-rock geochemical, sulfur isotopic and in-situ mineralogical data from the mineralized alteration stages of Chaoshan skarn Au deposit in Tongling region are systemically investigated to reveal Au distribution and precipitation, and useful information for ore-forming process. The altered rocks and ores in the Chaoshan deposit have total REE contents of 7.81–226 ppm and show LREE enrichment patterns with weak negative to positive Eu (δEu = 0.71–2.24) anomalies. Electron probe microanalysis results indicate that garnet and pyroxene of the Chaoshan deposit are grossular-andradite and diopside-hedenbergite series, respectively. In situ elemental compositions of the euhedral pyrite analyzed show that invisible Au is mainly of lattice-bound Au+ in As-bearing pyrite. The studied pyrite samples also have high Co/Ni (mainly >1) and Se/Tl (>10) ratios, highly variable Pb and As contents, low Se content (<5.00 ppm), low Tl/Pb and Sb/Pb ratios, and relatively consistent sulfur isotopic compositions (5.0–8.3 ‰). The distinctly geochemical characteristics indicate that the Chaoshan skarn Au mineralization was likely derived from a magmatic-hydrothermal system. A comprehensive discriminant analysis shows that the Au precipitation and enrichment of the Chaoshan deposit are a result of boiling-induced trace element fractionation resulted from fluid boiling during the skarn formation process.

Waterway carrying capacity assessment: Model development and application in the lower Yangtze River, China

With rapid socioeconomic development, extra demands have been placed on the waterway sustainable exploration, which are closely related to river ecological protection, flood control and comprehensive utilization of water resources. Therefore, it is theoretically and practically relevant to investigate the waterway carrying capacity (WCC) under multi-objective coordination. Based on a hierarchical indicators system framework of WCC which including four subsystems (i.e., economic-demand system, flood-control system, water-supply system and ecological-protection system), we propose a fuzzy comprehensive evaluation model of WCC, which covers a flow module, a sediment module, an ecological module and a comprehensive analysis module. This model integrates two assessment methods of comprehensive index evaluation and fuzzy-pattern recognition with analytic hierarchy process (AHP). Determining weights by the AHP method can avoid the subjectivity and errors caused by weighing a large number of indicators, while the combined two methods have a complementarity of function to more objectively reflect the carrying capacity level of different layers. The WCC of the lower Yangtze River from Hukou to Nanjing reaches was assessed, and the results suggested that the carrying capacity states of waterway are generally on a downward trajectory with the increase of waterway scale, and the carrying capacity levels of waterway for the built (in 2015) and planning scales (in 2030) are in the state of bearable or critical bearable. In a certain future period, the exploitable thresholds of channel scales in the sections from Hukou-Anqing, Anqing-Wuhu and Wuhu-Nanjing reaches are estimated to be 8.0 × 200 × 1050 m, 8.0 × 200 × 1050 m and 10.5 × 500 × 1050 m, respectively. The evaluation results are generally consistent with exiting studies, thus the proposed model is effective to identify the threshold of waterway exploitation under the restriction of multiple factors. This research can provide a reference for the evaluation of WCC in the sustainable development of similar inland waterways.

Two alloying technology from the Muyushan site (Anhui Province, China): evidence for tin bronze and arsenic bronze smelting in the lower Yangtze River ca. 1100BC ~ 500 BC

Two alloying technology from the Muyushan site (Anhui Province, China): evidence for tin bronze and arsenic bronze smelting in the lower Yangtze River ca. 1100BC ~ 500 BC

The lower Yangtze River and Aegean Sea in the third millennium BC: parallel cradles of civilizations

The lower Yangtze River and Aegean Sea in the third millennium BC: parallel cradles of civilizations

REE and cathodoluminescence features of scheelites from the Tongshankou Cu–Mo deposit in Eastern China

The Tongshankou porphyry-/skarn-type Cu–Mo deposit is located in the Edong ore district, the largest district of the Middle–Lower Yangtze River Metallogenic Belt (MLYRMB) in Eastern China. From the ore-causative granodiorite porphyry and skarn at Tongshankou, three types of scheelite are recognized (Sch1 to Sch3): Sch1-subhedral–anhedral, occurring in the chalcopyrite ores within the porphyry; Sch2-granular, occurring inside garnet in the endoskarn and Sch3-subhedral–anhedral, occurring in calcite veins in the exoskarn. Sch2 and Sch3 have different internal texture according to CL images: Sch2-Dark core and bright rim, with the heterogeneous dark core; Sch3-Dark core and narrow dark rim, showing patches of different brightness in core. In addition, three REE types have been differentiated: 1) REE-Type1: LREE-enriched, HREE-depleted, and negative Eu anomalies patterns (Sch1), which is related to the porphyry system; 2) REE-Type2: No apparent fractionation between LREE and HREE, with positive Eu anomalies (Sch2), which is related to the endoskarn; 3) REE-Type3: Higher LREE and lower HREE with extremely positive Eu anomalies (Sch3), which is related to the exoskarn. The negative MoO3 vs. WO3 correlation for the Tongshankou scheelites suggests Mo-W substitution in the scheelite crystal lattice. No humped pattern (MREEs-enriched) of REE, lower Na content and the lack of correlation between Na and REE at Tongshankou excluded the Na substitute into the Ca site. The positive correlation with Nb and REE for Sch 1 and 3, suggests equation [2] and [3] should be more plausible mechanism to generate the Tongshankou scheelite REE patterns.

How Frequently Will the Persistent Heavy Rainfall over the Middle and Lower Yangtze River Basin in Summer 2020 Happen under Global Warming?

How Frequently Will the Persistent Heavy Rainfall over the Middle and Lower Yangtze River Basin in Summer 2020 Happen under Global Warming?

The Impact of the Three Gorges Reservoir on Water Exchange Between the Yangtze River and Poyang Lake

The Three Gorges Reservoir (TGR) operation has profoundly altered the hydrological regimes and ecosystem in the middle and lower Yangtze River basin. Its impacts on the river flow regime, sedimentation, lake level decline, and biodiversity have been extensively studied. However, the quantitative influence of the TGR on the downstream water exchange between the Yangtze River and Poyang Lake is lacking attention. In this study, we developed a machine learning model to investigate the river–lake water exchange variations under the TGR operation in typical hydrological years, compared with the natural scenario (i.e., no TGR). The results show that the machine learning model could provide a fast and accurate approach to identify the long-distance impact of reservoirs. The operation of the TGR has significant effects on the water exchange between the Yangtze River and Poyang Lake in the impounding period, with a 10,000 m³/s decrease in reservoir discharge approximately causing a 4,000 m³/s decrease in river–lake water exchange in the dry year and a decrease of 6,000 m³/s and 8,000 m³/s in reservoir discharge causing an increase of 4,000 m³/s and 6,000 m³/s in the normal year and the wet year, respectively. The TGR effect varies with different hydrological conditions of the river and lake, showing longer time range (from May to October) and greater degree (1.5 times the change rate in other years) in the wet year. The TGR operation is beneficial to the water maintenance of the lake in the dry year and flood control in the lake area in the wet year. This study provides a constructive approach and valuable information for decision making in water resource management and ecosystem protection in large river–lake systems.

Temporal and Spatial Characteristics of River Water Quality and Its Influence Factors in the TAIHU Basin Plains, Lower Yangtze River, China

Water quality pollution has been a serious problem in the Taihu Basin plains, which is a highly urbanized area in China. This study aims to detect the interannual and seasonal changes and spatial patterns of water quality in this region. Based on cluster analysis, Moran’s I, and standard deviational ellipses, the site clusters, spatial heterogeneity of water quality characteristics and identified polluted regions were clarified. Results showed that (1) water quality improved since 2002, and nutrient concentrations were lower in summer and autumn than in winter and spring. (2) The monitoring sites were divided into six clusters according to the water quality during the period from 2010 to 2014. Water quality worsened from Cluster 1 to Cluster 4. Cluster 1 sites were mostly distributed beside the Yangtze River and Taihu Lake. Cluster 4 sites were mainly located along the southeast border near Shanghai, while the remaining sites were separately distributed in the main cities. (3) A polluted region of both total nitrogen (TN) and total phosphorus (TP) was present in the southeastern part of the study area near the border from 2010 to 2014. In addition, polluted regions were most likely to form near the junctions of main cities. (4) Anthropogenic factors had greater impacts on water quality than natural factors. More attention should be given to water quality protection around impervious surface areas due to the greatest considerable effect.