Erhai Lake Research Articles

Climate-driven intensification of hypolimnetic deoxygenation in Lake Fuxian, a monomictic lake in south-western China, since the 1990s

In monomictic lakes, the potential intensification of hypolimnetic deoxygenation due to human activities and climate change threatens lake ecosystems and water quality. Understanding the trends and mechanisms of hypolimnetic deoxygenation would allow for the adaptive management of monomictic lakes. This study investigated the trends and drivers of hypolimnetic deoxygenation in Lake Fuxian (a monomictic lake in south-western China) over the past 150 years using paleolimnological evidence and historical records. Analysis of enrichment factors for molybdenum (Mo), uranium (U), and vanadium (V), and ratios of U/thorium (Th), pristane (Pr)/phytane (Ph), and total organic carbon (TOC)/total phosphorus (TP) in a dated sediment core indicated that the extent of hypolimnetic deoxygenation was relatively low before 1994 and increased substantially thereafter. Nutrient monitoring records and sediment n-alkane proxies indicated notable eutrophication of the lake since 1986 and a greater degree of human disturbance in the catchment between 1951 and 1967. Due to their asynchronous occurrence, eutrophication and catchment disturbance could not be the major drivers of hypolimnetic deoxygenation. Interestingly, climate records indicated that the local ambient temperature exhibited similar trends to that of hypolimnetic deoxygenation, including markedly higher temperatures after 1994. This implies that prolonged water column stratification due to climate warming could have promoted hypolimnetic deoxygenation by limiting oxygen exchange between the upper and lower water columns. In comparing the results with those of Lake Erhai, another monomictic lake with contrasting morphology and hydrology characteristics, we found that the low surface area/depth ratio and long water residence time in Lake Fuxian enable dissolved oxygen of the lake hypolimnion vulnerable to temperature over the lake.

Anthropogenic activities and environmental filtering have reshaped freshwater fish biodiversity patterns in China over the past 120 years

Over the past centuries, freshwater fish introductions and extinctions have been the major environmental and ecological crises in various water bodies in China. However, consequences of such crises on freshwater fish biodiversity in China remain only partially or locally studied. Furthermore, identifications of relatively sensitive areas along with stressors (i.e., environmental and anthropogenic drivers) influencing freshwater fish biodiversity patterns are still pending. Taxonomic, functional, and phylogenetic facets of biodiversity can well describe and evaluate the underlying processes affecting freshwater fish biodiversity patterns under different dimensionalities. Here we thus evaluated temporal changes in these facets of freshwater fish biodiversity as well as a new developed biodiversity index, multifaceted changes in fish biodiversity, for over a century at the basin level throughout China using both alpha and beta diversity approaches. We also identified the drivers influencing the changes in fish biodiversity patterns using random forest models. The results showed that fish assemblages in Northwest and Southwest China (e.g., Ili River basin, Tarim basin, and Erhai Lake basin) experienced extreme temporal and multifaceted changes in the facets of biodiversity compared with other regions, and environmental factors (e.g., net primary productivity, average annual precipitation, and unit area) largely drove these changes. Since fish faunas in over 80% of China's water bodies covering more than 80% of China's surface were currently undergoing taxonomic, functional, and phylogenetic homogenization, targeted conservation and management strategies should be proposed and implemented, especially for the areas with relatively high changes in biodiversity.

Coupling of light and nutrients affects Microcystis gas vesicle content at different depths

Abstract Lakes are important water resources for human beings, but Microcystis blooms pose a serious threat to drinking water security and aquatic ecosystems. Gas vesicles (GVs) are an important trigger for the occurrence of Microcystis blooms. To understand the effects of light and nutrients on GV content, the phytoplankton in Lake Erhai were investigated. The results showed that the average GV content in the surface water was higher than that in the deep water. The total nitrogen in water affected the GV content by limiting the protein content, and the content of GVs increased by 9.2 μm3/cell for each 1.0 pg/cell increase in the intracellular nitrogen content. Moreover, light and total phosphorus affected the GV content in deep water by limiting the energy supply, and the content of GVs increased by 52.4 μm3/cell for each 1.0 pg/cell increase in the intracellular phosphorus content. These results indicate that for lakes with low transparency, decreasing the total phosphorus concentration can reduce the GV content. Reducing the total nitrogen concentration can reduce the GV content and decrease the dominance of Microcystis in all lakes. This study provides useful information for the control of Microcystis.

Suspended phosphorus sustains algal blooms in a dissolved phosphorus-depleted lake

The expansion of algal bloom in surface waters is a global problem in the freshwater ecosystem. Differential reactivity of organic phosphorus (Po) compounds from organic debris, suspended particulate matter (SPM), and sediment towards hydrolysis can dictate the extent of supply often limited inorganic P (Pi) for algal growth, thereby controlling the extent of bloom. Here, we combined solution P-31 nuclear magnetic resonance (31P NMR), sequential extraction, enzymatic hydrolysis, and 16S rRNA measurements to characterize speciation and biogeochemical cycling of P in Lake Erhai, China. Lower ratios of diester-P/monoester-P in SPM in January (mean 0.09) and July (0.14) than that in April (0.29) reflected the higher degree of diester-P remineralization in cold and warm months. Both H2O-Pi and Po were significantly higher in SPM (mean 1580 mg ·kg−1 and 1618 mg ·kg−1) than those in sediment (mean 8 mg ·kg−1 and 387 mg ·kg−1). In addition, results from enzymatic hydrolysis experiments demonstrated that 61% Po in SPM and 58% in sediment in the H2O, NaHCO3, and NaOH extracts could be hydrolyzed. These results suggested that H2O-Pi and Po from SPM were the primarily bioavailable P sources for algae. Changes of Pi contents (particularly H2O-Pi) in algae and alkaline phosphatase activity (APA) during the observation periods were likely to be controlled by the strategies of P uptake and utilization of algae. P remobilization/remineralization from SPM likely resulted from algae and bacteria (e.g., Pseudomonas). Collectively, these results provide important insights that SPM P could sustain the algal blooms even if the dissolved P was depleted in the water column.

Water depth modulates the species richness–biomass relationship in submerged macrophytes

The effect of biodiversity on ecosystem productivity has been a controversial issue in ecological research. The species richness–productivity relationship is highly variable in natural ecosystems, with a positive relationship being one of the most commonly observed relationships. Previous regional studies from terrestrial ecosystems have demonstrated that environmental gradients can regulate the species richness–productivity relationship. However, how this relationship varies in freshwater ecosystems across spatial environment gradients remains unclear. In this study, we propose that the species richness–productivity relationship can be modulated by the water depth. Here, we surveyed the submerged macrophyte community structure by establishing 24 transects and 642 quadrats in Erhai Lake, Yunnan Plateau, China. Our findings highlight that the species richness–productivity relationship gradually changed from slightly positive to strongly positive as the environment became more light-limited with the increasing water depth, supporting the stress-gradient hypothesis. The results from this study provide new insights into the biodiversity–ecosystem functioning relationships and in managing lake macrophyte communities and productivity.

A Comprehensive Study of the Suitability of Urban Underground Spaces for Connection Development: A Case Study of the Erhai Lake Basin, China

Urban underground space (UUS) involves multiple stakeholders whose concerns span the entire life cycle of underground space. The government pays more attention to the social benefits of UUS to the region, developers pay more attention to the economic benefits brought by the development of UUS, and users pay more attention to the comfort level of UUS operation. This study used the analytic Hierarchy Process (AHP), government, developers, and users to construct a comprehensive evaluation index system of underground space development needs. Different from previous studies, considering the need for future connectivity development in the UUS circle, this paper proposes to comprehensively consider the impact of connectivity development on regional suitability through coupled AHP and cellular automata (CA). The results show that about 102.67 km2 (13.03%) underground area of Erhai Lake Basin is suitable for underground space development. Compared with the traditional evaluation method, the evaluation result of about 31.41 km2 (3.99%) area was improved, and the fragmentation problem between blocks was improved. This method is of great value to the comprehensive development of UUS in the Erhai Lake Basin and is helping to improve future underground space planning.

Water exchange unevenness alters the species dominance and community composition of submerged macrophytes in Erhai Lake and the potential mechanisms revealed by laboratory experiment

Water exchange unevenness (WEU) is defined as the coefficient of variation in water exchange intensity over time. Although its influence on aquatic plant characteristics has been recently investigated, there is limited understanding regarding the effects of this hydrodynamic change on submerged vegetation. This study investigated the impacts of WEU on the species dominance and community composition of submerged macrophytes in three bays with different WEU conditions in Erhai Lake, China. Subsequently, a laboratory experiment was conducted to elucidate the mechanisms underlying these effects. The field investigation showed that the dominance values of submerged macrophytes were influenced by WEU. As WEU decreased, the average dominance value decreased for Vallisneria natans (by 34.54 %), Myriophyllum spicatum (16.82 %), and Hydrilla verticillata (12.84 %); showed no significant change for Potamogeton lucens; and increased for Potamogeton maackianus (14.22 %) and Ceratophyllum demersum (17.52 %). The laboratory experiment showed that lower WEU markedly inhibited the growth of V. natans, slightly inhibited that of M. spicatum, and stimulated that of P. maackianus, consistent with the field observations. The inhibitory effect was attributed to a reduced concentration of carbon dioxide in the water; adaptive strategies, i.e., plant height, biomass allocation, and root traits, were more effective for M. spicatum than for V. natans. The stimulated growth of P. maackianus was attributed to increased dissolved oxygen concentration, which promoted root growth and nutrient uptake. Our results indicate that WEU has significant effects on the growth and community characteristics of submerged macrophytes.

Analysis on the Characteristics of Climate Change in Erhai Lake from 1956 to 2018

The Erhai Lake in Southwest China is not only an ecologically fragile area but also a vulnerable area from climate change. In order to deal with climate change, the characteristics of precipitation, temperature and evapotranspiration of Erhai Lake were investigated by trend analysis methods, periodicity analysis methods and abrupt change analysis methods. The results showed that: During the period 2006 to 2018, average precipitation and temperature in Dali Station changed by -10% and +0.76°C, respectively, compared with before 2006. It is expected that the variation of precipitation in the future is not significant. However, the trend of temperature change is consistent with the current situation and will show an increasing trend. Under the influence of temperature rise, evapotranspiration showed an obvious increasing trend and it will continue to increase with temperature rise in the future. The primary period for the changes of precipitation, temperature and evapotranspiration were 30a, 20~25a and 10~20a. The abrupt change points of precipitation and temperature were approximately 2005, while the abrupt change point of evapotranspiration in 1980s.

NSP variation on SWAT with high-resolution data: A case study

Abstract As a typical lake in the early stage of eutrophication, the non-point source pollution (NSP) in Erhai Lake was highly concerned. Since 2017, protection and rescue actions have been implemented in the Erhai Lake basin which significantly improved the water quality of Erhai Lake. But little attention has been paid to the interception effects of these actions on NSP. Based on high resolution datasets, including refinement land use/land cover (LU/LC) data, China Meteorological Assimilation Driving Database for the SWAT (CMADS), and Advanced Land Observing Satellite-1 (ALOS-12) data, the interception effects of ecological ponds newly built in 2018 on NSP was discussed with the support of the soil and water assessment (SWAT) model. These three high resolution datasets can meet the needs for simulating NSP by SWAT model, which was conductive to better reveal the interception effects of ecological ponds on NSP. Besides, the pollution load of shrubbery on Total nitrogen (TN)/Total phosphorous (TP), which has never been involved in similar research works in the Erhai Lake basin, was measured. Compared the temporal and spatial variations in TN/TP concentration before and after 2018, the interception effects of ecological ponds on NSP in the Erhai Lake basin were revealed by a sharp decrease in TN/TP concentration and a delayed presence of annual peak value about 1 month late in TN concentration before and after 2018. The interception intensity of NSP was determined by the number and volume of ecological ponds in each sub-basin and their corresponding upstream.

Effect and Mechanism of Rice-Pasture Rotation Systems on Yield Increase and Runoff Reduction under Different Fertilizer Treatments

This study investigated the effects of crop rotations and different ratios of dairy manure fertilizer on nitrogen loss and rice yield in the Erhai Lake basin. Two kinds of herbages were set in the rotation: Ryegrass (Lolium multiflorum cv.‘Tetragold’) (R) and Villose Vetch (Vicia villosa var. Glabresens) (V). The experiment involved two-year field tests with nine management treatments. The results showed that the rice-Vicia villosa rotation with 70% chemical and 30% dairy cattle manure fertilization increased rice yield significantly, while reducing nitrogen runoff losses and increasing microbial abundance with nitrification and nitrogen fixation. The microbial abundance varied among tested soils, with Alphaproteobacteria, Rhodopseudomonas, Rhizobiales, Bradyrhizobium, and Azotobacter Vinelandii being the highest in 70% chemical fertilizer + 30% manure rice Villose Vetch (R-V) to ameliorate plant growth and strengthen the efficiency of nutrient uptake, whereas that of Planctomycete was comparatively lower to promote long-term N stabilization in soil. The 70% F—30% M R-V treatment also significantly decreased nitrate reductase and ammonia monooxygenase enzyme activity, potentially improving fertilizer use efficiency, and reducing gaseous losses. The LEfSe analysis results indicated that 70% F—30% M R-V fertilizers significantly enhanced the abundances of metabolic genes related to energy and nitrogen. These findings suggested that appropriate agricultural management using rice-Vicia villosa rotation and 70% chemical + 30% dairy cattle manure fertilization can improve the soil quality and sustainability of agroecosystems.

Quantitative Assessment of Water Quality Improvement by Reducing External Loadings at Lake Erhai, Southwest China.

To quantitatively evaluate the effects on water quality improvement caused by reducing external loadings entering Lake Erhai through inflow rivers, a one-dimensional hydrodynamic and ecological model (DYRESM-CAEDYM) was set up to simulate the water quality and water level variations. The calibrated and validated model was used to conduct six scenarios for evaluating the water quality responses to different amounts of external loading reduction at Lake Erhai. The results show (1) the total nitrogen (TN) concentration of Lake Erhai will be higher than 0.5 mg/L without any watershed pollution control during April-November 2025, which cannot meet Grade II standard of the China Surface Water Environmental Quality Standards (GB3838-2002). (2) External loading reductions can significantly reduce the concentrations of nutrients and Chla at Lake Erhai. The effects of water quality improvement will be proportional to the reduction rate of external loading reductions. (3) Internal release might be an important source of pollution It needs to be seriously considered as well as external loading for mitigating the eutrophication at Lake Erhai in the future.

Floating Mat Formation Makes Zizania latifolia More Competitive under the Conditions of Continuous Significant Water Level Rise.

Water level rise is considered an environmental filter for the growth and reproduction of aquatic plants in lakes. Some emergent macrophytes can form floating mats, enabling them to escape from the negative effects of deep water. However, an understanding of which species can be uprooted and form floating mats easily and what factors affect these tendencies remains greatly elusive. We conducted an experiment to determine whether the monodominance of Zizania latifolia in the emergent vegetation community in Lake Erhai was related to its floating mat formation ability and to try to find the reasons for its floating mat formation ability during the continuous increase in water level over the past few decades. Our results showed that both the frequency and biomass proportion of Z. latifolia were greater among the plants on the floating mats. Furthermore, Z. latifolia was more likely to be uprooted than the other three previously dominant emergent species due to its smaller angle between the plant and the horizontal plane, rather than the root:shoot or volume:mass ratios. The dominance of Z. latifolia in the emergent community in Lake Erhai is due to its easier ability to become uprooted, allowing it to outperform other emergent species and become the single dominant emergent species under the environmental filter of deep water. The ability to uproot and form floating mats may be a competitive survival strategy for emergent species under the conditions of continuous significant water level rise.

Influence of Peat Soil Environment on Mechanical Properties of Cement-Soil and Its Mechanism

The influence of peat soil environment (PSE) on the mechanical properties of cement-soil in the area around Dianchi Lake and Erhai Lake in Yunnan Province has attracted much attention. This study explores the change law of cement-soil UCS in the PSE, and provides guidance for the development and sustained usage of peat soil foundation. The paper discusses the preparation of cement-soil samples by adding humic acid (HA) and cement to cohesive soil with low organic matter content (blending method) and soaking it in fulvic acid (FA) solution and deionized water (steeping method) to simulate the actual working environment of cement-soil. Unconfined compressive strength (UCS), acid consumption, ion leaching, scanning electron microscope (SEM), and X-ray diffraction (XRD) tests are carried out on cement-soil samples soaked for 90 days. The results show that HA can significantly reduce the UCS of cement-soil. FA can reduce the UCS of cement-soil when the content of HA is less than 18%. However, when the amount of HA is more than 18%, the UCS of cement-soil increases slightly. FA makes the deformation and failure type of cement-soil gradually change from brittle shear failure to plastic shear failure. FA reacts with the cement hydration products in the sample so that the cumulative acid consumption of the cement-soil sample continues to increase, and the dissolution of Ca2+, Mg2+, Al3+, and Fe3+ in the sample increases the ion concentration of the soaking solution. In addition, SEM and XRD show that HA can increase the macropores and connectivity of cement-soil, while FA fills part of the pores of the wetting layer. In the PSE, FA can strengthen the inner structure of HA particles and fill and cement the layers of cohesive particles, enhancing the construction of cement-soil with HA content greater than 18%, so that its UCS is relatively improved. However, when the amount of HA is less than 18%, there are more small pores in the cement-soil. The interaction between FA and HA in the cement-soil is weak. The influence of FA on cement-soil is mainly a weakening effect, and its UCS is relatively reduced.

Role of lake dissolved organic matter in cyanobacteria removal by cationic polyacrylamide flocculation and screen filtration

Prompt removal of densely accumulated cyanobacteria is a straightforward method to alleviate the harm of cyanobacterial blooms to lakes. In this study, a cyanobacteria harvesting ship based on flocculation and filtration was used for the removal of cyanobacteria in a bay of Dianchi Lake (Yunnan Province, China), in which the fate and influence of lake dissolved organic matter (DOM) were investigated. After flocculation with 1–3 mg/L cationic polyacrylamide (CPAM) and filtration with the 100-µm-pore-sized screens of a rotary drum filter (RDF), >90 % of cyanobacteria was removed and the DOM was slightly reduced from 7.83 mg/L to 4.61 ∼ 6.49 mg/L. Tryptophan protein-like and high molecular weight (MW) DOM was selectively removed, increasing the humification index and decreasing the biological index in the treated water. Lake DOM, especially the high MW fractions of lake DOM, played an important role in CPAM flocculation. Cyanobacteria could not be effectively flocculated in Milli-Q water while the removal efficiency increased to over 90 % when 1–3 mg/L high MW DOM of Dianchi Lake was added. Three lakes in Yunnan Province were also plagued by cyanobacterial blooms, including Erhai Lake, Qilu Lake, and Xingyun Lake. The high MW DOM (1.7–2.7 mg/L) in the lakes could also deduce the effective flocculation of cyanobacteria with CPAM. The flocculation mechanism could function by the interactions of quaternary ammonium groups of CPAM and carboxylate groups of high MW DOM that form net-like polyelectrolyte complexes (PECs), and coexisting cyanobacteria cells were encapsulated into the PECs, leading to the formation of large flocs under stirring conditions. In the lakes with high densities of cyanobacteria, there might be enough high-MW DOM to promote the flocculation of CPAM, and after flocculation-filtration treatment, both cyanobacteria and cyanobacteria-deprived DOM were effectively removed.

Effects of nitrogen input on N2O production and enzyme activity in Luoshijiang Wetland sediments, China

We examined the effects of nitrate (NO3--N) and ammonium (NH4+-N) input at different concentrations (0, 1, 5 and 25 mg·kg-1) on N2O production rate from the surface sediment (0-5 cm) of Luoshijiang Wetland, located upstream from Lake Erhai. The contribution of nitrification, denitrification, nitrifier denitrification, and other factors to the N2O production rate in sediments was studied by the inhibitor method. The relationships between N2O production and the activities of hydroxylamine (HyR), nitrate (NAR), nitric oxide (NOR), and nitrous oxide (NOS) reductases in sediments were analyzed. We found that NO3--N input significantly increased total N2O production rate (1.51-11.35 nmol·kg-1·h-1), which led to N2O release, whereas NH4+-N input decreased that (-0.80 to -0.54 nmol·kg-1·h-1), causing N2O absorption. NO3--N input did not change the dominant roles of nitrification and nitrifier denitrification in N2O production in sediments, but increased the contributions of these two factors to 69.5% and 56.5%, respectively. The NH4+-N input significantly changed N2O gene-ration process, and the nitrification and nitrifier denitrification changed from N2O release to uptake. There was a positive correlation between total N2O production rate and NO3--N input. NO3--N input significantly increased NOR activity and decreased NOS activity, thereby promoting N2O production. The total N2O production rate in sediments was negatively correlated with NH4+-N input. NH4+-N input significantly increased the activities of HyR and NOR, decreased NAR activity, and inhibited N2O production. Nitrogen inputs with different forms and concentrations changed the degree of contribution and mode of N2O production by affecting enzyme activities in sediments. NO3--N input significantly promoted N2O production, acting as a source of N2O, while NH4+-N input inhibited N2O production, resulting in an N2O sink.

Spatial non-stationarity of water conservation services and landscape patterns in Erhai Lake Basin, China

Understanding the relationship between water conservation service (WCS) and landscape patterns is important for ecosystem management and water resources regulation. However, existing studies on the relationship between water conservation services (WCS) and landscape pattern mainly focus on the impact of landscape composition on WCS, but ignore the spatial effects of landscape configuration. Taking the Erhai Lake Basin as an example, this study quantified the spatial and the temporal distribution of WCS and analyzed the changes in landscape composition and configuration from 1990 to 2020. Subsequently, the spatial non-stationarity between WCS and landscape pattern was discussed by using a geographically weighted regression model. The results showed that urban and forest landscapes increased by 3189.96% and 18.34%, while grassland, shrub, and cropland landscapes decreased by 21.30%, 20.65%, and 16.23%, respectively, from 1990 to 2020. The fragmentation degree of urban landscapes increased, while the fragmentation degree of other landscapes decreased. The fragmentation and the heterogeneity of the overall landscape decreased, while the aggregation increased. WCS increased by 15.82% from 1990 to 2020, it is mainly derived from forest landscape, which contributes more than 91% to WCS. The effects of landscape patterns on WCS were spatially heterogeneous. The mean patch density and largest patch index positively affected WCS in 66.80%–82.88% and 64.35%–72.42% of the regions, respectively, whereas the mean patch area negatively impacted WCS in 66.64%–82.41% of the regions. Decision makers can promote ecosystem management measures that are suitable for specific conditions based on the spatial differences of the effects of landscape patterns on WCS.

Identification of major environmental factors driving phytoplankton community succession before and after the regime shift of Erhai Lake, China

In lake ecosystems, regime shifts can induce changes in physical and biological components, particularly phytoplankton community structure, as well as across multiple trophic levels. Phytoplankton community succession may be driven by different environmental factors before and after regime shift; however, owing to the abruptness of the regime shift, long-term observations encompassing both periods are scarce, limiting our ability to identify the shift of key drivers of phytoplankton community succession. Here, an analysis was conducted based on long-term observations (involving phytoplankton community and environmental variables from 1997 to 2008) in Erhai Lake, a eutrophic lake in China that may have undergone a regime shift in 2001–2003. The dynamics of hydrochemical parameters and phytoplankton community composition indicated a distinct regime shift between 2001 and 2003. The phytoplankton community evolved over a decadal period toward community structure simplification, dominance of individual species, and homogenization of species composition. Prior to the regime shift (1997–2000), the eutrophic status of Erhai Lake was oligotrophic, and the phytoplankton community was characterized by high biodiversity and low biomass, with Cyanophyta, Bacillariophyta, and Cryptophyta being the dominant species. Nutrient concentrations had a significant limiting effect on phytoplankton, with total nitrogen concentration being the primary limiting factor. Following the regime shift (2005–2008), the phytoplankton community exhibited low biodiversity and high biomass, with the dominant taxa shifting to Cyanophyta, Chlorophyta, and Bacillariophyta. Light became the primary driver of phytoplankton community succession. Our study was based on long-term observations covering regime shifts in Erhai Lake, providing strong evidence that the phytoplankton community is influenced by nutrients in oligotrophic status. However, as nutrient concentrations increase, especially once the threshold is exceeded, species interactions may shift from competition for nutrients to competition for light. This implies that the resource competition theory, which integrates nutrient- and light-based approaches, provides an effective approach to predicting phytoplankton community succession, and that measures to improve underwater light environments should be considered as an additional option for nutrient load reduction in eutrophic lakes.

Developing a vine copula model to simulate and predict long serial lake water levels

Lake water level changes show randomness and the complexity of basin hydrological simulation and lake water level response. We constructed a vine copula model to simulate and predict lake water level that incorporated rolling decisions and real-time correction of prediction results. The model was applied to predict the long- and short-term water levels in Erhai Lake on the Yun-gui Plateau, southwest China. The results showed that (1) the predicted daily water levels (with ME=0.02~0.09, RMSE=0.02~0.024, NSE=0.99, and IA=0.99) were more accurate than the predicted monthly water levels (with the ME=0.039~0.444, RMSE=0.194~0.279, NSE=0.913~0.958, and IA=0.977~0.989), and the accuracy of the predictions improved as the number of variables increased. (2) The vine copula model outperformed the back-propagation neural network and support vector regression models, and, of the three model types, gave the best estimate of the nonlinear relationships between the predicted water level and climatic factors, especially in the wet season (May to October). (3) The prediction accuracy of the vine copula model was lower for small sample sizes and when there was a lack of runoff data. By improving the analysis of the model’s errors, the percentages of the relative errors of the prediction accuracy less than 5%, 10%, 15%, and 20% increased to 70%, 83%, 95%, and 98%, respectively.

Bottom-up and top-down effects on codetermination of the dominant phytoplankton functional groups in Lake Erhai

Bottom-up and top-down effects on codetermination of the dominant phytoplankton functional groups in Lake Erhai

Understanding stakeholder perceptions of environmental justice: a study of tourism in the Erhai Lake basin, Yunnan province, China

Understanding stakeholder perceptions of environmental justice: a study of tourism in the Erhai Lake basin, Yunnan province, China