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The heterogeneity of geographic environments and vegetation types plays a crucial role in determining soil erosion patterns. Highlighting the influence of environmental factors and their gradient changes on soil erosion is key to effective control and management. In this study, conducted in the arid-hot valley area of the Jinsha River, one of the main sand-producing areas in the Yangtze River Basin, we considered the topographic factors and land cover and applied the Revised Universal Soil Loss Equation (RULSE) with geographic information system (GIS) was applied to quantify the contribution and change pattern of different factors to soil erosion in the arid-hot valleys. Then, the spatial and temporal patterns of soil erosion in 2000 and 2015 were analyzed, showing erosion amount of 1812.96 t/(km2·a) and 1965.98 t/(km2·a), respectively. The increase in erosion was attributed to the frequency of heavy rainfall events. In terms of spatial distribution, strong soil erosion has been mainly observed in arid-hot basins, such as Yuanmou and Huaping. The soil erosion modulus (SEM) was closely connected to topographical elements, increasing incrementally with slope. High soil erosion areas were predominantly distributed across slopes between 18° and 36°. In contrast, SEM decreased gradually with increasing altitude, with strong erosion occurring primarily below 2000 m. SEM for different land use types followed this order: bare land > cultivated land > grassland > forest > paddy land. Based on the relationship between vegetation cover and soil erosion, the area could be roughly divided into three types of area by vegetation coverage: erosion control areas (30% vegetation coverage), erosion-vegetation transition areas (30–70%), and vegetation control areas (>70%). These results provide an essential reference for assessing soil erosion patterns and implementation of ecological vegetation restoration measures in arid-hot valleys. • The tempo-spatial characteristics of soil erosion in arid- hot valley were analyzed. • The change threshold between topography and soil erosion were revealed. • The impact of climate change and land use changes on soil erosion were explored. • A method to divide the relationship between erosion and vegetation was proposed. [ABSTRACT FROM AUTHOR]

Motion of eggs has received increasing attention because they are different from inanimate particles in physical and biological properties (density, diameter and adhesiveness), which determines their motion mechanism. Settling and drifting experiments were conducted to measure and identify the transport mechanism of eggs of two sturgeon species, Siberian sturgeon and Amur sturgeon. The terminal settling velocities are 4.30 ± 0.19 cm s−1 and 4.85 ± 0.22 cm s−1 for adhesive and de-adhered Siberian sturgeon eggs, respectively, and 5.23 ± 0.16 cm s−1 and 5.46 ± 0.19 cm s−1 for adhesive and de-adhered Amur sturgeon eggs, respectively. Adhesiveness decreases the terminal settling velocity. Meanwhile, the terminal settling velocity increases with increasing fish egg size. We developed a formula for the drag coefficient of sturgeon eggs and verified it via drifting experiments. The drag coefficient of sturgeon eggs is mainly affected by adhesive force when the Reynolds number R e ≤ 700 and by inertial force when R e > 700. The results show that sturgeon eggs differ significantly from other solid particles in their behaviour and an exclusive formula is necessary. This further provides new insights into the movement of adhesive demersal eggs and supports numerical simulation of their transportation in natural rivers. [ABSTRACT FROM AUTHOR]

• We constructed a coupling model system of suitable habitats. • We simulated changes in nearshore vegetation biomass and habitat. • We considered the impact of natural and human activities on vegetation. • The growth of Zostera japonica was severely affected. Estuarine ecosystems are influenced by the combination of freshwater runoff and ocean tides, and the natural environment is intricate and complex, with special natural environmental conditions and biological habitat characteristics. The Yellow River is characterized by high sediment-bearing water flow, and the estuary forms a unique clear and turbid confluence. The Water and Sand Regulation (WSRS) from the Xiaolangdi Reservoir to the estuary and nearshore has had significant impacts on the environmental conditions of water, sediment and nutrients, further affecting the growth and development of vegetation in the nearshore zone. In recent years, more studies have focused on the effects of climate change and ocean tides on vegetation in the Yellow River Estuary; however, few studies have been conducted on the effects of the WSRS on klysmoeionion. In this study, we investigated the influence of water flow, sediment and nutrients on klysmoeionion based on long-term field monitoring and indoor control experiments; constructed a three-dimensional hydrodynamic water quality model to simulate the hydrodynamic characteristics, sediment transport patterns and nutrient salt distribution in the Yellow River Estuary under the combined influence of tides and riverine water and sediment; and further combined the growth competition model of typical vegetation (including the native species Zostera japonica and invasive species Spartina alterniflora) to construct a suitable habitat simulation model for typical vegetation communities in the Yellow River Estuary. Habitat and biomass changes in Z. japonica and S. alterniflora in the Yellow River Estuary were simulated under the influence of the WSRS and climate change. The results showed that the distribution of suitable habitats for Z. japonica and S. alterniflora in the Yellow River Estuary and offshore was characterized by a zonal distribution along both sides of the estuary, with an increasing trend of suitable habitat area from the estuary to both sides of the estuary; due to environmental conditions and inter- and intra-species competition, the biomass of Z. japonica and S. alterniflora was mainly distributed in the estuary and near the northern and southern shores, with the southern shore have the most distribution. In contrast, S. alterniflora was mainly distributed in the northern shore away from the estuary and in Laizhou Bay. During the WSRS period, the suitable habitat area of Z. japonica decreased by 25%, and the biomass decreased by 50%, while the suitable habitat and biomass of S. alterniflora were not significantly affected. The growth of Z. japonica was severely affected by the dual effects of global warming and the WSRS, while the biomass of S. alterniflora showed an increasing trend. The WSRS can further consider the growth pattern of vegetation to protect the resources of Z. japonica and to curb the expansion of the invasive S. alterniflora. [ABSTRACT FROM AUTHOR]

The relations between benthic macroinvertebrate communities and eco-factors usually are nonlinear and highly complex, and are often difficult to evaluate. In this study, canonical correlation analysis (CCA) and a generalized additive model (GAM) were applied to identify the key eco-factors that influence the community characteristics of benthic macroinvertebrates in a shallow water lake--Baiyangdian Lake. The water depth (H), water transparency (secchi disc depth, SD), concentration of chlorophyll-a (Chl-a), water temperature (T), concentration of dissolved oxygen (DO), oxidation and reduction potential (ORP), ammonium nitrogen (NH 4 -N) and nitrate nitrogen (NO 3 -N) in water, median particle diameter (D 50 ), ammonium nitrogen in the substrate (NH 4 -N soil ), and biomass of macrophytes, are the main eco-factors affecting the spatial distribution and structure of the benthic macroinvertebrate community in the shallow freshwater lake. This study is the first to introduce GAM to habitat suitability evaluation for benthic macroinvertebrates in large shallow lakes, and to use the Margalef index (d M ) instead of individual indicator species to indicate diversity variation. Five factors, including H, T, NH 4 -N soil , organic matter (OM) in the substrates, and the biomass of macrophytes, were selected in the optimal model by stepwise regression. The response curves generated by the GAM indicated that the diversity of benthic macroinvertebrates was negatively correlated with H and (NH 3 -N soil ) and was positively correlated with T and OM. The response curve showing the relation between taxa diversity and the biomass of macrophytes was unimodal. The current study examined the combined influence of multiple eco-factors on benthic macroinvertebrates, and increased understanding of relations between the benthic macroinvertebrate community and eco-factors in a shallow lake system. [ABSTRACT FROM AUTHOR]

Large shallow lakes play an important role in providing water for domestic supply and landscape irrigation, and maintaining a healthy ecosystem. A lake ecosystem possesses abundant aquatic plants and animals. Changes of the hydrological regime affect the water level, water quality, and species distribution. In this study, a two-dimensional hydrodynamic and water quality model is applied to a large shallow lake, Baiyangdian Lake. The model was established based on measured lake bed elevation, hydrological data, and water quality data. This model was validated for two water transfer events and wind-driven circulation in local areas was observed in the model results. Influences of water transfer and wind effects on water flow and distribution of ammonium and phosphate were then evaluated and discussed. A total of eighteen water transfer scenarios were simulated. The entire lake flow field and water transfer routes in the lake and nutrient distributions were analyzed under each water transfer scenario. The water transfer suggestions proposed in this paper are based on hydraulic characteristics of the lake and make up for deficiencies that previous did not consider the effects of flow transfers on the flow field of receiving. The environmental flow patterns and ecological restoration measures for Baiyangdian Lake are proposed based on the lake hydrodynamics and flow routes under different water transfer scenarios. [ABSTRACT FROM AUTHOR]

Hydraulic geometry (HG) is an important geomorphic concept that has played an indispensable role in hydrological analyses, physical studies of streams, ecosystem and aquatic habitat studies, and sedimentology research. More than 60 years after Leopold and Maddock (1953) first introduced the concept of HG, researchers have still not uncovered the physical principles underlying HG behavior. One impediment is the complexity of the natural river cross section. The current study presents a new way to simplify the cross section, namely, the hydraulic equivalent section, which is generalized from the cross section in the “gradually varied flow of an alluvial river” (GVFAR) and features hydrodynamic properties and bed-building laws similar to those of the GVFAR. Energy balance was used to derive the stage Z -discharge Q relationship in the GVFAR. The GVFAR in the Songhua River and the Yangtze River were selected as examples. The data, including measured discharge, river width, water stage, water depth, wet area, and cross section, were collected from the hydrological yearbooks of typical hydrological stations on the Songhua River and the Yangtze River from 1955 to 1987. The relationships between stage Z -discharge Q and cross-sectional area A -stage Z at various stations were analyzed, and “at-a-station hydraulic geometry” (AHG) relationships were obtained in power-law forms. Based on derived results and observational data analysis, the Z - Q and Z - A relationships of AHG were similar to rectangular weir flows, thus the cross section of the GVFAR was generalized as a compound rectangular, hydraulic equivalent cross section. As to bed-building characteristics, the bankfull discharge method and the stage-discharge-relation method were used to calculate the dominant variables of the alluvial river. This hydraulic equivalent section has the same Z - Q relation, Z - A relation, dominant discharge, dominant river width, and dominant water depth as the cross section in the GVFAR. With the hydraulic equivalent section, the relationships between the discharge and river width, river depth, and width-to-depth ratio are easier to depict in DHG analysis. Replacement of the cross section in the GVFAR with the hydraulic equivalent section is expected to promote further development of HG. [ABSTRACT FROM AUTHOR]

Excessive nutrient loads reduce ecosystem resilience, resulting in fundamental changes in ecosystem structure and function when exceeding a certain threshold. However, quantitative analysis of the processes by which nutrient loading affects ecosystem resilience requires further exploration. Food web stability is at the heart of ecosystem resilience. In this study, we simulated the dynamics of the food web under different phosphorus loads for Lake Baiyangdian using the PCLake model and calculated the food web stability. Our results showed that there was a good correspondence between the food web stability and ecosystem state response to phosphorus loads. This relationship confirmed that food web stability could be regarded as a signal for the state transition in a real lake ecosystem. Moreover, our estimates suggested that food web stability was influenced only by several functional groups and their interaction strength. Diatoms and zooplankton were the key functional groups that affected food web stability. Phosphorus loads alter the distribution of functional group biomass, which in turn affects energy delivery and, ultimately, the stability of the food web. Corresponding to functional groups, the interactions among zooplankton, diatoms and detritus had the greatest impact, and the interaction strength of the three was positively correlated with food web stability. Overall, our study explained that food-web stability was critical to characterize ecosystem resilience response to external disturbances and can be turned into a scientific tool for lake ecosystem management. • The PCLake model was a useful tool for bridging biotic information as a function of nutrient loads to food web stability. • Food web stability could be regarded as a signal for the state transition in a real lake ecosystem. • Diatoms and zooplankton were the key functional groups that affected food web stability. [ABSTRACT FROM AUTHOR]

The pattern of vegetation along the cross-section of macrophyte-dominated shallow waters is generally uneven, which affects water velocity and turbulence. This study examined the velocity and turbulence in the open channel with an uneven transverse distribution of vegetation in laboratory flume experiments. Two vegetation patterns were tested: emergent vegetation which covered part of the channel, and a symmetrical combination of submerged and emergent vegetation canopies along the lateral direction of the flume. The flow was measured using a three-dimensional Acoustic Doppler Velocimeter. The velocity and turbulence characteristics were analyzed under three vegetation densities and five discharge scenarios. Results showed that the longitudinal mean velocity changed with vegetation density and flow discharge when vegetation was unevenly distributed in a lateral direction. The strong variation in shear stress at the emergent vegetation–open water intersections and submerged–emergent vegetation intersections resulted in large-scale vortices at the interfaces. The formation processes of stem-scale turbulence and shear-scale turbulence under different vegetation scenarios were discussed. A turbulent kinetic energy model within partly obstructed vegetation canopies was established, which helped to identify the development of horizontal and vertical coherent vertices. • Flow and turbulence in unevenly distributed vegetated flows were analyzed. • The longitudinal velocity varied with vegetation density and input discharges. • Strong variations of shear stress at the interface resulted in large-scale vortices. • A turbulence model within a partly emergent vegetation canopy was established. [ABSTRACT FROM AUTHOR]

In order to evaluate the ecological influence of hydraulic projects, aquatic habitat suitability modeling was proposed. Compared with other environmental flow methods, this method, for the first time, integrated considering hydrology parameters and ecology attributes, quantitatively describing the relationships between species and habitat. Aquatic habitat suitability models began with one-dimensional physical habitat simulation model (PHABSIM) at micro-scale physical habitat. Afterwards, habitat suitability models for meso- and macro-scale were developed; eco-factors indicating physical habitat and water quality situation were included; two- and three-dimensional model were employed to provide the situation of eco-factors. Based on field survey or mathematical models, the state of habitat eco-factors can be obtained. By establishing habitat suitability evaluation criteria, the impact of aquatic habitats on the particular life stage of indicate species can be assessed, the effect of reservoir regulation mode and habitat restoration projections can be predicted. Here, we summarized aquatic habitat suitability models in different spatial scale, and the advantages and disadvantages of each model were analyzed and concluded. [ABSTRACT FROM AUTHOR]

For a long distance water transfer system, guaranteeing the safety of water transferred in a long open canal is a challenge. Potential pollution sources and locations are identified first. Bridges above the canal are considered as the typical location where pollution accidents could happen. Truck responses, road conditions, and human responses are the main factors resulting in sudden pollution accidents. A Bayesian Network model is developed to calculate the risk of water pollution and evaluate the effects of pollutants in water. The key causes (human judgment, truck condition) were determined to calculate the unfavorable accidental risk. Six types of hydraulic structures were included in this canal reach. MIKE 11, a one-dimensional hydrodynamic and water quality model, was used to simulate the fluid field and pollutants transportation process. The water quality situations of cyanide at four pollution loads (0.5 t, 5 t, 10 t, 20 t) were simulated. Emergent countermeasures and measures, including the management of diversion and check gate, have been proposed according to the calculate result. [ABSTRACT FROM AUTHOR]

• Bacterial communities and functional groups before/during/after WSR was analyzed. • Hydrodynamic change of WSR was the main cause to communities difference. • Anammox group became the main groups during WSR since the worse water quality. • The communities and functional groups of bacteria could gradually recover after WSR. Discharge containing large amount of sediment will cause a series of ecological effects on downstream river systems. To solve the siltation problem of Yellow River and Xiaolangdi reservoirs, water and sediment regulation has been carried out since 2000. To clarify the impact of the regulation on bacterial communities in the lower Yellow River, the composition of bacterial communities and functional groups in the riverbed and suspended sediment was analyzed by high-throughput sequencing and functional annotation of prokaryotic taxa method. The results showed that the overall diversity index of the Yellow River bacterial community was 3.014–7.045, and at a medium level compared to other large rivers in China. During the water and sediment regulation, the bacterial diversity index slightly decreased compared to the previous stage, while significantly increased at the post-stage of regulation, considering relatively small changes in chemical factors among three stages, it was thought that the The variation of bacterial community diversity was more influenced by the fluctuations of discharge, turbulent kinetic energy and sediment concentration. The relationship between suspended and riverbed samples to environmental factors also showed differences at three stages of regulation. During the regulation, increasing discharge and high velocity caused the ammoxidation related groups, such as nitrate and nitrite ammoxidation groups, to displace nitrification, nitrate reduction, and nitrate respiration groups, hence inhibit the water purification capabilities, while at the post-stage, the functional group of most sites recovered to similar level to the pre-stage. In summary, we reveal a characteristic pattern on how the microorganism in the high sediment river respond to the severe disturbance. [ABSTRACT FROM AUTHOR]

Summary To date, a wide range of models have been applied to evaluate aquatic habitat suitability. In this study, three models, including the expert knowledge-based preference curve model (PCM), data-driven fuzzy logic model (DDFL), and generalized additive model (GAM), are used on a common data set to compare their effectiveness and accuracy. The true skill statistic (TSS) and the area under the receiver operating characteristics curve (AUC) are used to evaluate the accuracy of the three models. The results indicate that the two data-based methods (DDFL and GAM) yield better accuracy than the expert knowledge-based PCM, and the GAM yields the best accuracy. There are minor differences in the suitable ranges of the physical habitat variables obtained from the three models. The hydraulic habitat suitability index (HHSI) calculated by the PCM is the largest, followed by the DDFL and then the GAM. The results illustrate that data-based models can describe habitat suitability more objectively and accurately when there are sufficient data. When field data are lacking, combining expertise with data-based models is recommended. When field data are difficult to obtain, an expert knowledge-based model can be used as a replacement for the data-based methods. [ABSTRACT FROM AUTHOR]

Summary The Chinese sturgeon is a type of large anadromous fish that migrates between the ocean and rivers. Because of the construction of dams, this sturgeon’s migration path has been cut off, and this species currently is on the verge of extinction. Simulating suitable environmental conditions for spawning followed by repairing or rebuilding its spawning grounds are effective ways to protect this species. Various habitat suitability models based on expert knowledge have been used to evaluate the suitability of spawning habitat. In this study, a two-dimensional hydraulic simulation is used to inform a habitat suitability model based on the generalized additive method (GAM). The GAM is based on real data. The values of water depth and velocity are calculated first via the hydrodynamic model and later applied in the GAM. The final habitat suitability model is validated using the catch per unit effort (CPUE d ) data of 1999 and 2003. The model results show that a velocity of 1.06–1.56 m/s and a depth of 13.33–20.33 m are highly suitable ranges for the Chinese sturgeon to spawn. The hydraulic habitat suitability indexes (HHSI) for seven discharges (4000; 9000; 12,000; 16,000; 20,000; 30,000; and 40,000 m 3 /s) are calculated to evaluate integrated habitat suitability. The results show that the integrated habitat suitability reaches its highest value at a discharge of 16,000 m 3 /s. This study is the first to apply a GAM to evaluate the suitability of spawning grounds for the Chinese sturgeon. The study provides a reference for the identification of potential spawning grounds in the entire basin. [ABSTRACT FROM AUTHOR]

To guarantee the security of water quality in water transfer channels, especially in open channels, analysis of potential emergent pollution sources in the water transfer process is critical. It is also indispensable for forewarnings and protection from emergent pollution accidents. Bridges above open channels with large amounts of truck traffic are the main locations where emergent accidents could occur. A Bayesian Network model, which consists of six root nodes and three middle layer nodes, was developed in this paper, and was employed to identify the possibility of potential pollution risk. Dianbei Bridge is reviewed as a typical bridge on an open channel of the Middle Route of the South to North Water Transfer Project where emergent traffic accidents could occur. Risk of water pollutions caused by leakage of pollutants into water is focused in this study. The risk for potential traffic accidents at the Dianbei Bridge implies a risk for water pollution in the canal. Based on survey data, statistical analysis, and domain specialist knowledge, a Bayesian Network model was established. The human factor of emergent accidents has been considered in this model. Additionally, this model has been employed to describe the probability of accidents and the risk level. The sensitive reasons for pollution accidents have been deduced. The case has also been simulated that sensitive factors are in a state of most likely to lead to accidents. [ABSTRACT FROM AUTHOR]

Summary The middle route of the South-to-North Water Transfer Project (MRP) will divert water to Beijing Tuancheng Lake from Taocha in the Danjiangkou reservoir located in the Hubei province of China. The MRP is composed of a long canal and complex hydraulic structures and will transfer water in open channel areas to provide drinking water for Beijing, Shijiazhuang and other cities under extremely strict water quality requirements. A large number of vehicular accidents, occurred on the many highway bridges across the main canal would cause significant water pollution in the main canal. To ensure that water quality is maintained during the diversion process, the effects of pollutants on water quality due to sudden pollution accidents were simulated and analyzed in this paper. The MIKE11 HD module was used to calculate the hydraulic characteristics of the 42-km Xishi-to-Beijuma River channel of the MRP. Six types of hydraulic structures, including inverted siphons, gates, highway bridges, culverts and tunnels, were included in this model. Based on the hydrodynamic model, the MIKE11 AD module, which is one-dimensional advection dispersion model, was built for TP, NH 3 -N, COD Mn and F. The validated results showed that the computed values agreed well with the measured values. In accordance with transportation data across the Dianbei Highway Bridge, the effects of traffic accidents on the bridge on water quality were analyzed. Based on simulated scenarios with three discharge rates (ranged from 12 m 3 /s to 17 m 3 /s, 40 m 3 /s, and 60 m 3 /s) and three pollution loading concentration levels (5 t, 10 t and 20 t) when trucks spill their contents (i.e., phosphate fertilizer, cyanide, oil and chromium solution) into the channel, emergency measures were proposed. Reasonable solutions to ensure the water quality with regard to the various types of pollutants were proposed, including treating polluted water, maintaining materials, and personnel reserves. [ABSTRACT FROM AUTHOR]

When simulating the habitat suitability for a species or a community, the selection of the habitat evaluation index is still a matter of debate. This study examined Chinese sturgeon spawning grounds in the Yangtze River as an example. The water level and velocity were simulated by a two-dimensional hydraulic model. Five methods, including a two-dimensional preference curve method, one- and two-dimensional expert knowledge-based fuzzy logic methods, and one- and two-dimensional data-driven fuzzy logic methods, were used to calculate the habitat suitability of Chinese sturgeon spawning grounds below the Gezhouba Dam. The data-driven fuzzy logic method used a training dataset and the nearest climbing algorithm to optimize fuzzy sets and fuzzy rules. The weighted usable area (WUA), hydraulic habitat suitability index (HHS) and the spatial distribution of suitable Chinese sturgeon spawning grounds at different discharges (4000 m 3 /s, 9000 m 3 /s, 12,000 m 3 /s, 16,000 m 3 /s, 20,000 m 3 /s, 30,000 m 3 /s, and 40,000 m 3 /s) were calculated. The performances of the habitat suitability models based on different methods were compared. There were few differences in the results regardless of the use of a preference curve method or a fuzzy logic method. For the data-driven fuzzy logic method, the quality of the training dataset is very important. Therefore, the data-driven fuzzy logic method is a good method when the amount and coverage (e.g., including very high and very low discharges) of the measured dataset are sufficient. However, conditions at different discharges can be taken into account comprehensively with the expert knowledge-based method when the available data are not sufficient. [ABSTRACT FROM AUTHOR]

Abstract: The Lancang–Mekong River is the most important international river in Southeast Asia. Where the river flows through China, it is called the Lancang River. The Lancang River basin has become the most abundant species resource and the most bio-diverse region of China and has significant potential as a source of hydropower. The construction of cascade hydropower dams on the main river has brought great economic benefit, but has also changed the river as a physical habitat. Many fishes, especially endemic species and those with economic value in this area, have been affected by these changes. An ESHIPPO-PPm model was established to evaluate the extinction risk of fish species in this area. Four endemic fish were evaluated, two of which (Tor sinensis, and Cosmochilus cardinalis) are classified as critical extinction risk. The habitat quality of T. sinensis, an endemic and economically important fish, was simulated using a habitat suitability index model. The habitat suitability index (HSI) model was developed by coupling a one-dimensional (1-D) hydraulic model with habitat suitability curves. Considering the spawning characteristics of the fish, habitat suitability curves were established for key factors influencing adult fish and spawning behavior of T. sinensis. A hydraulic model was developed to simulate and predict parameter of the physical habitat. Based on the simulated result of the HSI model, Weighted Usable Areas for adult (WUA d ) and spawning (WUA s ) were obtained. A Mann–Kendall test was used to analyze the variation trend of WUA s and WUA d before and after the construction of the Manwan dam. Abrupt change in WUA d and WUA s occurred during the dam construction and operation period, respectively. According to the simulation and analysis, habitat suitability has been changed during the construction and operation of Manwan Reservoir. For the spawning of T. sinensis (WUA s ), the dam has a visible influence on the minimal and medium level habitat, but little influence on the optimal habitat. For the adults habitat, the dam reduced the medium and optimal WUA d . Optimal discharge for spawning is much greater than for adult. Different discharges for maintaining different degrees of habitat quality are suggested. [Copyright &y& Elsevier]

The food web structure (FWS) and ecosystem functioning (EF) of lakes worldwide are impacted by multiple disturbances. The historical evolution of the FWS and EF are not well understood due to the lack of sufficient long-term records of biotic variations. This study reconstructed the food web models in the 1950s, 1980s, 1990s, 2000s, and 2010s for Baiyangdian Lake (BYDL), the largest shallow lake in northern China, using the Linear Inverse Modeling (LIM) and investigated EF in different periods. Our results confirmed that the FWS and EF of BYDL have undergone significant changes. The biomass of phytoplankton continuously increased, and the primary productivity of phytoplankton began to replace the primary productivity of submerged macrophytes in the 2000s and became the largest energy flow in the food web. Changes in the energy flow of primary producers are transmitted to high-trophic functional groups, which affects the diet composition of fish. Based on the ecological network analysis indices and food web stability indicators, it was concluded that after a turning point in the 1990s, the ecosystem showed initial stability and then gradually became unstable. Water level fluctuations and nutrient enrichment may be the key driving factors for changes in ecosystem state. Therefore, to maintain a good state of the ecosystem, we recommend implementing comprehensive management measures of hydrological management, nutrient-loading reduction, and biomanipulation. Furthermore, this study extended LIM to lake ecosystems, which may provide a new method for lake ecological environment management. • The long-term changes in food-web structure and ecosystem functioning were quantitatively assessed. • The food-web dynamics were influenced mainly by the primary producers. • A turning point occurred in the 1990s, a shift from macrophytes production to phytoplankton blooms. • Water level fluctuations and nutrient enrichments challenged the stable status. [ABSTRACT FROM AUTHOR]

The Dujiangyan Project is a World Cultural Heritage Site with relevance to water conservancy. It has been operated for more than 2,260 years and still plays an important role in irrigation, urban, and industrial water supply, flood control, and tourism. This paper discusses the hydraulic principles of the project, focusing on the reasons for the longevity of the project. In particular, two aspects of the project are reviewed; namely, the practical engineering design of the project and its outstanding historical significance and time-based maintenance. The project ingeniously used the topography of the terrain in the design of weir structures. The tasks of water diversion, irrigation, and flood control were achieved using a two-step approach. The first step was achieved by utilizing the shifting of streamlines and the bend of flow from the town of Guankou to Fish Mouth (a diversion embankment). The discharge of flow and sediment was further optimized by using the second step of combined control of Feishayan (a sediment and flow spillway) and Baopingkou (an irrigating gate). The bend of flow within the Inner River forces the surface water to flow into Baopingkou, whereas the bottom sediments and pebbles discharge from Feishayan. Dynasties throughout history attached great importance to the management and maintenance of the project. Retrofitting and time-based renovation prevented the abandonment of the project due to sediment accumulation and aging of building materials. Because the maintenance and operation costs were far lower than the economic, social, and ecological benefits the project had brought, the Dujiangyan Project was sustainable over the long term. The study of the engineering design and maintenance rules of the Dujiangyan Project has value for the design and construction of modern hydraulic projects. [ABSTRACT FROM AUTHOR]

Summary: The Gezhouba Dam and Three Gorges Project are the two largest hydraulic projects in the middle reach of the Yangtze River. Although these projects have yielded benefits to local communities by providing flood control, water supply, and safe navigation, they also have changed the physical habitat of the Yangtze River. As a consequence, aquatic organisms, including rare species and fishes with economic value, have been affected. The Yangtze River’s four major carp species (YFMCS)—black carp (Mylopharyngodon piceus), grass carp (Ctenop haryngodon idellus), silver carp (Hypoph thal michthys molitrix), and big-head carp (Aristichyths nobilis)—have significant importance to the fresh water fishery in China. According to field surveys, the percentage of the YFMCS in the total catch of fish from Tongting Lake has gradually reduced. The percentages were 22%, 14.1%, 11.84%, and 8.5% in 1963, 1980–1982, 1997, and 2002, respectively. These reductions in species population are mainly attributed to the loss of spawning ground caused by dam construction. Considering the spawning characteristics of the YFMCS, a habitat suitability index model (HSI) has been established. A one-dimensional (1-D) mathematical model was also developed to simulate and predict aspects of the physical habitat situation for the YFMCS. By coupling the habitat suitability curves and the 1-D mathematical model, a HSI model for the YFMCS was established. The HSI model was validated by comparing measured data with predictions from the model. These comparisons show that the computed results agree well with the measured results. The HSI model for the YFMCS is used to suggest a minimum instream flow and suitable daily discharge increase during the reproduction season for the carp species. The minimum discharge needed for the YFMCS in the middle reach of the Yangtze River is 3000m3/s. Different daily discharge increases are required for different initial discharges, too small or too large of an increase in daily discharge is not good for carps spawning. Therefore, adjusting reservoir operations to create reasonable water level fluctuations is a key method to improve the habitat suitability of carps spawning sites. [Copyright &y& Elsevier]

Since the construction of the Gezhouba Dam in the 1980s, the number of Chinese sturgeon in the Yangtze River has been rapidly declining. The Gezhouba Dam has cutoff the migration path of these sturgeon, resulting in an overall reduction of suitable sturgeon habitat. This paper describes a habitat suitability index model that is used to evaluate the impacts of the Gezhouba Dam and Three Gorges Project on Chinese sturgeon spawning sites. Based on research concerning the reproduction characteristics of Chinese sturgeon, ten major ecological factors that influence reproduction were analyzed, including: water temperature, velocity, water depth, substrate, suspended sediment concentration, and the amount of egg predatory fish. The suitability index (SI) curves based on these ten ecological factors were obtained, and a habitat suitability function was developed. A two-dimensional mathematical model was also created to simulate and predict physical habitat situation (such as hydraulic, sediment, and substrate) of the Chinese sturgeon. By coupling the habitat suitability function and a two-dimensional mathematical model, a habitat suitability index model for Chinese sturgeon was established. The habitat suitability index model was validated by comparing measured data with predictions from the model. These comparisons showed that the computed results agreed well with the measured results, and the high calculated habitat suitability index (HSI) corresponded to high measured quantity of eggs per unit (1000m3) discharge (CPUEd). The calculated habitat suitability index for Chinese sturgeon also showed that the habitat suitability index was better in 1999, before the impoundment of the Three Gorges Project, compared with the habitat suitability in 2003. Simulation results of different discharges from Gezhouba Dam predicted that flow discharges between 10,000 and 30,000m3/s were most suitable for sturgeon spawning. [Copyright &y& Elsevier]

• A quantitative method for evaluating response of estuarine ecosystem to hydrological variations was established. • The unity of hydrological and ecological data on time scale was realized. • Daily water and sediment fluxes into estuary explained 56% of change in fish. • Both low and high water and sediment fluxes limited the estuarine ecosystem. • Advancing the discharge time of dam to spring can benefit ecology. The water and sediment fluxes into the estuary from upstream highly influence the estuarine ecosystem. The lack of method to evaluate the impact of daily water and sediment fluxes on ecosystem has limited the ecological management of estuary. Therefore, it is important to find a quantitative method for analysing the response of estuarine ecosystem to daily water and sediment fluxes into the estuary. Based on long time sequenced data, we aim to determine the dynamic response of fish communities to the interannual and seasonal variations of water and sediment fluxes, providing a novel method for the regulation of water and sediment process in dammed rivers. We establish a functional regression model and improve Functional Linear Regression That is Interpretable (FLiRTI) method to quantify the dynamic response relationship between the annual catch per unit effort (CPUE) and the daily water and sediment fluxes into the Yellow River Estuary from 1980 to 2011. The results showed that the water and sediment fluxes into the estuary explained 56% of the variability in the CPUE. Low fluxes during the spawning period (April-May) and high fluxes during the dam discharge period (June-July) were not conducive to estuarine fisheries. By increasing freshwater inflow in spring to 3.1 or 4.3 billion m3, the cumulative effect on estuarine fish communities can be increased by 20% and 44%, respectively. We propose a functional regression method to quantify the response of estuarine fish communities to water and sediment fluxes into the estuary. We suggest that advancing the discharge time of dam to spring, a suitable spawning environment for fish can be provided, thus effectively increasing fish production in the estuary. This study overcomes the limitation of number of species as well as the disunity of hydrological and ecological data on time scale, providing new idea for estuarine ecology research. [ABSTRACT FROM AUTHOR]

Urbanization is an inevitable trend associated with social development that occurs preferentially in plain areas. Ecosystem services (ES) refer to the various benefits that human beings obtain from ecosystems. Competing priorities of economic development and ecological protection lead to conflicts in land use under conditions of urbanization, the root cause of which is an imbalance in the ES supply and demand. Whereas existing studies have mainly focused on the decline of ES supply capacities, an exploration of the extent to which the supply and demand of ES are matched and of their changing trends would be instructive and have practical implications. In this study, we examined changes in the temporal and spatial characteristics of the relationship between ES supply and demand in the Baiyangdian Basin in the North China Plain. We found that ES supply and demand were spatially distinctive. ES supply areas were concentrated in the western mountainous region, whereas ES demand areas were predominantly located in the eastern plain area. The main sources of ES surplus in the study area were woodland and grassland in mountainous areas, comprising 12% of the study region. Strict protection on these lands during the period 1980–2015 ensured a consistently high level of ES supply. In recent years, urbanization has been a major driver of increasing ES demand and decreasing ES surplus and is projected to accentuate the trend of declining ES surplus in the future. However, current policies remain focused on the protection of forests and grassland that predominate in mountainous areas, where urban expansion poses a lower threat compared with plain areas. We therefore recommend a policy emphasis on sustainable urban planning to mitigate ES degradation. • A method was proposed to consider both supply and demand of ecosystem services. • The supply and demand of ecosystem services for a plain area were estimated. • Urbanization highly decreased surplus of ecosystem services. • Sustainable city planning should be considered for future land use management. [ABSTRACT FROM AUTHOR]

Excessive nutrients inputs cause anthropogenic lake eutrophication worldwide. It is thus crucial to provide information on future trends of nutrient loading and its implications for the lake's trophic state. Here we quantified total phosphorus (TP) loading to the Lake Baiyangdian (BYD), the largest shallow lake in northern China, and assessed their future trend and the trophic state of the lake. The TP loading to the Lake BYD by rivers in 2015 was 276 ton, which was in a relatively low level in lakes from China. Based on the five shared socioeconomic pathways (SSPs), the TP loading to the Lake BYD in 2050 will increase only at the fragmentation scenario (SSP3) by an increment of 34.4%, in which the directly discharged animal manure become the main source. The lowest TP loading in 2050 is observed at the sustainability scenario (SSP1), in which sewage system will be the dominant contributor. At the sub-basin scale, compositions of river exported TP in rural areas will be more influenced by future socioeconomic developments than those in urban areas. The twenty years nutrient dynamics from clear or turbid state in the Lake BYD were simulated by the PCLake model to calculate the critical P loading (CPL). The results indicated that the CPL in the Lake BYD was 2.06 mg P m−2 d−1 for eutrophication and 0.84 mg P m−2 d−1 for oligotrophication. The only scenario in which Lake BYD will become eutrophic is SSP3, which should be avoided in the future development. To restore the lake water to the oligotrophic state, more efforts are necessary to reduce direct discharge of animal manure and increase the TP removal rates, especially in rural areas. [Display omitted] • Animal manure and sewage system will be the main contributors of P loadings. • Riverine P compositions will be changed greater in rural areas than in urban areas. • Fragmentation scenario (SSP3) should be avoided for future development. • The critical P loading in Lake Baiyangdian is 2.06 mg P m−2 d−1 for eutrophication. [ABSTRACT FROM AUTHOR]

The Yellow River (YR) is famous for its high sediment concentration. The Xiaolangdi dam (XLD), the most downstream dam on the mainstream of the YR, plays an integral role in siltation mitigation, flood defence, agriculture, and hydropower generation. To alleviate siltation of the Xiaolangdi Reservoir (XLDR) and riverbed uplift of the lower reaches of the YR and strengthen flood control safety downstream, the XLDR began to implement water-sediment regulation in 2002. Water-sediment regulation (WSR) has significantly changed the hydrological processes, erosion and deposition, and sediment transport in the downstream channel, and the downstream water environmental conditions have also changed. In this study, 10 sections in the Lower Yellow River (LYR, from the XLDR to the Lijin section) and 4 sections in the soft floodplain area were sampled in the field to analyse their surface sediment grain size composition and nutrient content. At the same time, data on the average annual median particle sizes (D 50) of channel sediments and suspended particles in 7 typical sections in the LYR from 2004 to 2015 were statistically analysed. The results show that the channel sediment grain size in the LYR decreased along the river course, and the D 50 ranged from 0.20 mm in the HYK section to 0.08 mm in the LJ section. Moreover the D 50 of the suspended sediment was less than 0.05 mm. The D 50 of the channel and suspended sediment were both ranked as follows: non-flood season > flood season > WSR period. After WSR, fine silt particles with diameters of 0.01–0.05 mm were deposited on the soft floodplain. The channel sediment size was mainly coarse particles with diameters of 0.05–0.20 mm due to channel erosion. The suspension of fine silt particles due to flood scouring led to the total organic carbon (TOC) and total nitrogen (TN) absorbed in the particles to also be resuspended in the water. As a result, the TOC and TN contents in the channel sediments decreased by approximately 40% after WSR. • The sediment grain size in the Lower Yellow River decreased along the river course. • The average median particle size of the channel and the suspended sediment in the Lower Yellow River over many years was in the following order: non-flood season > flood season > water-sediment regulation period. • The channel was scoured, and the beach area underwent deposition because of water-sediment regulation. • The regulation is conducive to the sediment transport in downstream during flooding season. • The Xiaolangdi water-sediment regulation resulted in a decrease of approximately 40% in the TOC and TN contents in the sediments in the Lower Yellow River. [ABSTRACT FROM AUTHOR]

• Bacterial community structure and diversity in Baiyangdian Lake were assessed. • Dominant bacteria in different habitats at different seasons were assessed. • Main functional groups were sulfur-oxidizing, sulfur-reducing, nitrifying and pollutant-degrading bacteria. • Main factors affecting bacterial community composition were pH, phosphorus and heavy metals. • Bacterial community composition, evenness and diversity varied more significantly with habitat. Benthic bacteria are drivers of aquatic ecosystem material circulation and energy flow, and are sensitive to environmental changes. In this study, a total of 79 sediment samples were collected from four representative habitat types (duck farm, fish farm, lotus pond and residential area) and one reference site (conservation district) of Baiyangdian Lake, North China, in three seasons (winter, spring and summer). The physical and chemical properties and the levels of contaminants in sediment were determined. Bacterial communities were studied by 16S rRNA high-throughput sequencing techniques. The result showed that, Proteobacteria, Chloroflexi, Bacteroidetes, Firmicutes and Actinobacteria were the dominant species at the phylum level in Baiyangdian. Sulfuricurvum, Thiobacillus Dechloromonas, Sulfurovum, Nitrospira and Desulfatiglans were the dominant species at the genus level. The dominant genus was different among different habitats. Proteobacteria exhibited the highest relative abundance in all seasons, and the relative abundance of dominant bacteria was highest in winter. The main functional group from the sampling sites were contamination tolerance bacteria, such as sulfur-oxidizing, sulfate-reducing and nitrifying bacteria. Sulfur-oxidizing bacteria were found mainly in duck farms and residential areas, whereas sulfate-reducing bacteria and nitrifying bacteria occurred in lotus ponds. Habitat type was the most important factor influencing the bacterial community composition, evenness and diversity. Sediment pH and the amount of active phosphorus played the most important role in the composition of the bacterial community, and the heavy metals (Zn, Mn and Cr) and organic pollutants (polycyclic aromatic hydrocarbons, PAH) also had moderate influence. As Baiyangdian Lake is the central of Xiong'an New Area, the water quality management has become the hottest topic. Plenty of researches about environmental variables and aquatic species were taken, but lacking report of bacteria. This study provide basic information of bacterial community composition in this area, and help to understand the response of the bacterial community to habitat and seasonal change, which provide a scientific basis for the recovery and reconstruction of the degraded ecosystem. [ABSTRACT FROM AUTHOR]

Increasingly, modern hydrological technologies are dynamically altering river water flow and drastically affecting river hydrogeochemical cycle regimes globally. The present study focused on the reservoir discharges of artificial floodwaters that influence spatiotemporal variations in the physicochemical and stable isotope compositions in the lower Yellow River (LYR) of China. The surface water samples were collected at the nine sites along the LYR during the pre-, inter-and post-flood periods. Then, the collected samples were analysed with the following standard method. The δD and δ18O slopes of the waterline clearly indicated that the prolonged reservoir water and different water flows impacted the hydrological cycle in the LYR regions compared to GMWL (global meteoric water line) and LMWL (local meteoric water line). The thermal stratification processes of the water in the largest reservoir slightly enriched the heavy isotopes, and physicochemical alteration was neglected. Statistical analysis of two-way ANOVA revealed that the p -values (p < 0.01, p < 0.05) were very strong for most of the variables between the periods, and the linear regression exhibited weak values (R2 = 0.253, R2 = 0.150) at the surface water temperature variations and suggested no significant influence of isotope composition. Overall, the Xiaolangdi reservoir water prolonged time rates, and artificial floodwater flow had a very small effect on the isotope composition; in particular, a large high turbidity concentration in the discharged artificial floodwaters was the only considerable ecological risk condition in the LYR. This kind of proper monitoring work is immensely important and prevents reservoirs from causing hydrological cycle impacts in the LYR and the adjacent coastal ecosystems. • The Xiaolangdi reservoir operation slightly altered the stable δD and δ18O isotope levels in the Lower Yellow River (LYR) surface water. • The stable δD and δ18O isotope values in the surface water strongly deviated from the GMWL and LMWL. • The river water low flow variation strongly changed the stable δD and δ18O isotope levels. • The turbidity concentrations of the artificial floodwater discharges were only a major threat in the LYR. • The Xiaolangdi reservoir operation has very little impact on the hydrological cycle of the LYR. [ABSTRACT FROM AUTHOR]

Variations in the flow regime lead to changes in the spatial and temporal distributions of nutrients entering the estuary area from the river, which causes corresponding changes in the trophic structure of the estuarine food web and ultimately affects the entire ecosystem. Therefore, studying the responses of estuarine food webs to changes in upstream water and sediment conditions is of great significance for protecting the biodiversity, stability, and functional integrity of estuarine ecosystems. This study focused on the world-famous sandy river, the Yellow River, and the south and north shores of the Yellow River estuary and selected sample areas with different environmental characteristics. Typical species were sampled and measured for carbon- and nitrogen-stable isotopes in the wet and dry seasons, respectively. Based on community indicators of stable isotopes, the trophic structure patterns of the aquatic ecosystem in the Yellow River estuary at different times and spaces were described. The results showed that the north shore area had greater trophic diversity and lower trophic redundancy than the south shore area. This kind of gap was more obvious in the wet season when water was abundant than in the dry season. The south shore area with lower aquatic productivity had greater reliance to input from terrestrial organic matter than the north shore area. The increase in terrestrial material input during the wet season increased the carbon-stable isotope value of the south shore food web and changed the basic food sources. The north shore food web, which did not depend on a single food source, had more abundant organic matter sources. The trophic diversity increased in the wet season, but the trophic redundancy was reduced. Our research suggests that the trophic structure patterns of estuarine ecosystems vary with the hydrological regime and environmental conditions, especially turbidity, which greatly affect the stability of estuarine ecosystems. • Trophic structure of Yellow River estuary food web varied with times and spaces. • North shore had greater trophic diversity and lower trophic redundancy. • South shore relied more on the input of terrestrial organic matter. • Increased terrestrial material during wet season changed estuarine trophic structure. • Trophic structure patterns of estuarine ecosystems vary with hydrological regime. [ABSTRACT FROM AUTHOR]

Dams intercept the river flow and reduce the water input of downstream lakes, which leads to the decreased water level and deteriorated water environment. Environmental water releases are becoming regular ways to maintain ecological water demand of lakes. This study was carried out to describe how natural submerged flexible vegetation altered velocity and generated turbulence under different water releases discharge scenarios. Natural Ceratophyllum demersum L. was collected from a large shallow lake, Baiyangdian Lake, China. Two vegetation densities were set in this flume experiments. The flow velocity was measured using particle image velocimetry (PIV) techniques and used to study the mean flow features (velocity and Reynolds stress) and distributions of vegetative drag and development length. The observed velocity profiles presented vertical stratification. The greatest gradient of velocity and shear stress appeared around the top of the canopy. The canopy drag of submerged flexible vegetation presented a parabolic vertical distribution, and smaller drag was generated by larger flows under the same density. The initial adjustment length of water flow was linearly correlated with the deflected height of flexible vegetation and was little affected by the vegetation density in the two studied densities. The most intense turbulence in the vegetation canopy appeared at its top, where the largest shear stress was also observed. Strong canopy-scale vortices on the top of the canopy were produced and penetrated closer to the bed in the cases of denser vegetation under small discharges (Cases 3.1–3.5); penetration was also restricted by canopy drag and was unable to reach the bed. • Drag of natural flexible vegetation canopy was vertically parabolic. • Initial adjustment length of flow was linear with the deflected height of vegetation. • The diffusion near the bed dominated the mass and momentum exchange within the vegetation canopy. [ABSTRACT FROM AUTHOR]

With stores that are more than 50 times greater than in terrestrial ecosystems, riverine and coastal ecosystems are the most important carbon (C) stocks worldwide, with most C stored in wetlands. Wetlands are, however, among the most threatened ecosystems worldwide, and face pressures from hydropower development, flow regime alteration, and land use/cover change (LUCC). Despite great efforts to protect and restore wetlands, anthropogenic drivers (e.g., land reclamation) still result in more C loss than gain in most cases. Of these, LUCC is driven by social and economic processes, and is a self-organizing, path-dependent phenomenon. Therefore, we proposed a land use management framework with which to analyze the spatial patterns in the drivers of LUCC, and then verified the strategy using two study areas in the lower reaches and delta of the Yellow River. The first step of the process was to analyze LUCC from historic land use/cover maps (from 1995 to 2015 for the lower river reaches and from 1970 to 2015 for the delta), and identified a suitable land use (waterbody) for the connections. We calibrated and validated the DINAMICA model using data for changes in C. We then set up different scenarios and created connections between high C patches. The simulation results showed that even slight modifications in the connections with water could trigger noticeable changes in the spatial patterns of C gain and loss, and that original hotspots of C loss could be converted to areas of C gain in some cases. Our findings highlight the need to consider both spatial patterns and drivers of LUCC when protecting wetlands and show that water-sediment regulation in the Yellow River should be coordinated with dynamic changes in the landscape in the lower reaches and delta. • Spatial patterns of C change were investigated. • Carbon storage was impacted by different drivers with time. • Tendency of land use to gain or lose C remained constant with time. • Connections was simulated to reduce C loss likelihood. [ABSTRACT FROM AUTHOR]

• The groundwater characterizes in estuaries' different macrophytes zones are significantly different. • The upward porewater flow causes the accumulation of shallow soil salt. • The shallow soil water-salt interactions affect macrophytes' habitat, which form band-shaped macrophytes zones. Tides and river water affect the groundwater vertical flow in the shallow soil in estuary areas, which in turn determines the ecological zonation of the salt marsh macrophytes. The groundwater vertical flow under the influence of the interaction of saltwater and freshwater is very complicated and includes upward porewater flow driven by evapotranspiration and downward groundwater drainage. In this study, in situ experiments were conducted to investigate the groundwater vertical flow direction and rate in four macrophytes zones of salt marsh macrophytes in the Yellow River Estuarine Nature Reserve. This study found that there are significant differences in groundwater vertical flow among these four macrophytes zones. (1) In the Bare flat zone, the downward drainage of groundwater and the upward porewater movement process frequently alternate. The processes of accumulation of and reduction in shallow soil salinity frequently alternate, and it is difficult for salt to accumulate continuously. (2) The Suaeda heteroptera Kitag. zone is mainly affected by tides. There are long periods of continuous porewater upward movement or groundwater downward drainage, and salinity in the shallow soils continues to accumulate or decrease during these periods. (3) In the Chinese tamarisk zone, the groundwater table is deep, and the moisture content of the shallow soil is low. The groundwater vertical flow is mainly an upward porewater process caused by evapotranspiration, and the shallow soil salinity accumulates gradually. (4) In the Staggered growth zone, the groundwater vertical flow characteristics of both the Bare flat zone and the Chinese tamarisk zone are evident. In general, in the salt marshes of the Yellow River Estuary, the tides and the Yellow River recharge affect the characteristics of the salt marsh groundwater. The salt marsh macrophytes are affected by the interactions of water and salt in the shallow soil, which form band-shaped macrophytes zones. [ABSTRACT FROM AUTHOR]

Both radial growth and canopy dynamics of trees play a critical role in terrestrial carbon cycle. Yet, it is still not very clear about how climate variability influences radial growth and canopy dynamics. To help bridge the knowledge gap in this field, we combined Tree Ring Width Index (TRWI, radial growth) and Normalized Difference Vegetation Index (NDVI, canopy dynamic), to quantify how forests responded to climatic variability across altitudinal gradients in Hengdaun Mountain, China. We applied TRWI of Pinus yunnanensis at nine sample sites and NDVI from 2000 AD to 2016 to analyze how these two indicators respond to temperature and precipitation. The results showed that the radial growth of P. yunnanensis was mainly limited by precipitation at low altitudes (≤1700 m). But the limited factor transformed into temperature at high altitudes (≥2200 m). NDVI presented significantly positive correlation with temperature and negative correlation with precipitation at annual scale. Relationship between TRWI and NDVI showed significantly positive correlation in July but negative correlation during dry season, indicating that both indicators had consistent response to climate during growing season, while the response was heterogeneous in dry season. Our comprehensive study helps to elucidate the unique contributions of foliar and radial growth to terrestrial carbon cycling and to explore the difference of these two indicators response to climate change. • Trends of TRWI and NDVI at temporal and spatial scale are analyzed. • Precipitation is the key influencing factor for vegetation growth in low altitude. • Temperature is the key influencing factors for vegetation growth in high altitude. • NDVI has increased from 2000 to 2016, and is larger at high altitude than low altitude. • Significantly correlation between TRWI and NDVI existed in wet-season and low altitude. [ABSTRACT FROM AUTHOR]

• Biomass was used as community descriptor rather than usual diversity indices. • Both individual effects and interactions of environmental variables were included. • Max biomass was found under conditions of 2.1 m deep water and 0.07 mg/L TP. Submerged macrophytes are widely distributed primary producer that play important roles in maintaining healthy aquatic ecosystems. Generally, the relationships between macrophytes and environmental factors are complicated, so nonlinear nonparametric models with relatively flexible structures are optimal for macrophyte habitat simulation. In this study, generalized additive model (GAM) was used to evaluate the response of the submerged macrophytes biomass to water environmental factors in the Baiyangdian Lake. Forward stepwise method was used to implement model optimization. Likelihood ratio test was used to determine whether adding a variable enhances the model performance. Four individual variables (water depth, transparency, total nitrogen, and total phosphorus) and two interaction terms (water depth × transparency and water depth × total phosphorus) were included in the optimal GAM. The optimal model explained 70.5% of the biomass variation with a relatively low residual deviance value (22.40). There was a significant correlation between the measured and predicted data (R2 = 0.716, p = 0.0004). The response lines generated by the model indicated that macrophyte biomass had a positive correlation with transparency but negative correlations with total nitrogen and nitrite nitrogen in water. The response patterns of macrophyte biomass to water depth and total phosphorus were unimodal. The biomass reached the maximum value when the water depth was about 2.1 m and the total phosphorus concentration was 0.07 mg/L. Water depth and transparency, which affect light availability, are critical physical variables affecting the conditions associated with the submerged macrophytes, and excess nitrite and phosphorus limiting macrophyte biomass. [ABSTRACT FROM AUTHOR]

• Spatio-temporal variation of a shallow lake benthic community was investigated. • Correlations between environmental variables and biotic metrics were determined. • Assemblages of disturbed habitat shifted to be less diverse and more tolerant. • Lestidae and Gammaridae were sensitive indicators for water pollution in the lake. Shallow lakes widely distributed in middle and lower reaches of watershed are easily multi-stressed by natural forces and human activities. Here, spatio-temporal variations of macroinvertebrate community and their influential variables in a typical large macrophyte-dominated shallow lake--Baiyangdian Lake were studied, using three-year in-situ observational data of spring, summer, and autumn. In total, ten environmental variables and five biological indices were measured for the six sites from each of the two habitat types, semi-natural habitat and disturbed habitat divided by their different exposures to human activities. Disturbed habitat had deeper mean water depth, lower mean transparency, and higher mean concentrations of DO, TN, NH 4 -N, NO 3 -N, and COD than that of semi-natural habitat regardless of seasons. Biological metrics indicate lower family-level richness but higher community tolerance level in disturbed habitat in spring and summer, but the results were close in autumn. The present of Lestidae and Gammaridae was a significant determination of semi-natural habitat. Redundancy analyses showed community temporal distribution was mainly driven by temperature, water depth, and pH that greatly influenced by natural forces, while spatial distribution was mainly driven by TN and transparency that greatly influenced by human activity. Regarding averaged data over the same year, season, and habitat, richness and Shannon-Weiner index had significant Pearson linear correlation with transparency (r = 0.521 and r = 0.541, p < 0.05, respectively), family biotic index significantly correlated with TP (r = 0.495, p < 0.05), and NO 3 -N (r = 0.592, p < 0.01), and percentage of tolerant individuals significantly correlated with pH (r = 0.667, p < 0.01), temperature (r = −0.640, p < 0.01) and NO 3 -N (r = 0.522, p < 0.05). Those variables are likely responsible for the major variations of community characteristics. High concentrations of nitrogen and phosphorus nutrients probably encourage the thriving of tolerate assemblage in the lake. Our results reveal that the macroinvertebrate community can shift to be more monotonous and pollution-tolerant under the stress of eutrophication and organic pollution. Disturbance and pollution, in general, can diminish the benefit of habitat-scale protection in certain location. [ABSTRACT FROM AUTHOR]

• During the growing season, common reed above-ground biomass is primarily controlled by water level. • Common reed suitable habitat area is primarily controlled by intern-annual water level fluctuation. • High water level can destroy the stable state of common reed habitat area and total biomass. • To maintain a suitable habitat area, the monthly mean lowest ecological water level of Baiyangdian Lake is at 6.7 m. Simulating of suitable habitat for the common reed (Phragmites australis) can provide theoretical support for water-resources managing of shallow lakes. Earlier research has focused on statistical models of shallow lakes and process-based dynamic models for coastal wetlands. However, process-based dynamic modeling for shallow lakes remains relatively incomplete, and the loss of biomass in unsuitable situations is seldom considered. This study established an occupied habitat model by coupling a cellular automaton with a modified logistic function. The cellular automaton was used to simulate the spatial diffusion of the reed. The logistic function was used to simulate the accumulation of biomass over time, and modified with the loss of biomass in unsuitable habitats. Both reed distribution and dynamic variations in reed growth can be simulated by this model. Water level was considered the most important factor in reed growth. In Baiyangdian Lake, China, the growing season is from April to October. The suitable habitat area (SHA) and aboveground biomass (AGB) of reeds were simulated using data from actual hydrological processes and hypothetical scenarios. Element contents and water consumption by transpiration were estimated on the basis of the AGB data. The results are as follows. (1) Water-level changes affected the habitat of the common reed. The SHA increased slightly (from 6.0 m) and then decreased with rising water level, reaching its maximum value at 6.7 m of the 90 % guarantee rate water level. SHA declined rapidly when the water level was higher than 7.5 m. (2) When the water level was maintained at 6.3–7.3 m, the water consumption for transpiration per unit AGB was lower than that for other water levels. (3) To maintain a higher water level for a suitable reed habitat area and to reduce water consumption per unit biomass transpiration, a reference value of 6.7 m can be regarded as the lowest ecological water level in Baiyangdian Lake. [ABSTRACT FROM AUTHOR]

• The NANI/NAPI methods and ECM model are integrated to quantitatively assess nutrient budgets. • Nutrient budgets were mainly from fertilizer application and livestock breeding. • The hotspots with low area ratio contributed about 50% of total nutrient budgets. • Around 2% of nutrient inputs was exported into rivers. Excessive nitrogen (N) and phosphorus (P) runoff from human activities results in degraded water quality. It is, therefore, crucial to quantitatively assess nutrient inputs over time and their impact on riverine nutrient exports. In this study, we estimated the long-term (1995–2015) nutrient inputs at the county scale by integrating Net Anthropogenic Nitrogen Input (NANI) and Net Anthropogenic Phosphorus Input (NAPI) methods, and nutrient exports into rivers by the Export Coefficient Model (ECM) for a semiarid plain basin, the Baiyangdian (BYD) Basin, China. The results showed that N and P input intensities in the year 2015 reached 18852 kg N km2 yr−1 and 2073 kg P km−2 yr−1, showing a 35% and 11% increase in comparison with 1995, respectively. About 60% of these nutrients were derived from fertilizer application. The multi-year averaged N and P exported to rivers was 548 kg N km−2 yr−1 and 79 kg P km−2 yr−1, respectively. Hotspots for nutrient budgets were found in the southeastern counties. Hotspots covered about 12% of the total land, but contributed by 38–52% of total nutrient budgets. The nutrient export ratios showed no significantly temporal variations, and only about 2.15–2.89% of NANI and NAPI were exported into rivers. The low nutrient export ratio was due to the low water discharge that limited the nutrient transportation in the semi-arid plain basin. As most of anthropogenic nutrient inputs were retained in the basin, their impacts on the pollution of soils and aquifers need to be considered and adequately addressed in the future. This study constructs the spatial quantitative nutrient budgets, which can provide effective information for region policy formulation. [ABSTRACT FROM AUTHOR]

For the management of eutrophic lakes, watershed nitrogen and phosphorus control is oriented to future water quality. Assessing future nutrient dynamics and the risk of lake eutrophication is necessary. However, current assessments often lack integrated consideration of socioeconomic and climatic factors, which reduces the reference value of the results. In this study, a typical large shallow lake Chaohu, which is highly influenced by human activities, was selected as the study area, and the current and future total nitrogen (TN) and total phosphorus (TP) loading in the basin were analysed using the improved MARINA model, and the risk of water bloom were assessed. The results showed that socioeconomic factors alone varied future TN and TP loading by −24% to 32% and −40% to 34%, respectively, under different development patterns. After considering the effect of increased precipitation, the changes of TN and TP loading became −10% to 163% and −29% to 108%, respectively. The effect on loading reduction under the sustainable development pattern was weakened (58% and 28% for TN and TP loading, respectively) and the increase in loading under the brutal development pattern was significantly amplified (409% and 215% for TN and TP loading, respectively). The adoption of active environmental policies remained an effective way of loading control. However, the risk of water bloom in local lake areas might persist due to factors such as urbanization. Timely and comprehensive assessments can provide managers with more information to identify key factors that contribute to the risk of water blooms and to develop diverse water quality improvement measures. The insights from our study are applicable to other watersheds around the world with similar socio-economic background and climatic conditions. • Analysis of the compounding effect of socio-economic and climatic factors on loading. • Complex impact of precipitation on loading under different development scenarios. • Improved MARINA model to enhance model accuracy and applicability. • Assessing the risk of future water bloom from a local perspective in the lake. [ABSTRACT FROM AUTHOR]

The age of tracer is a spatio-temporal scale, indicating the transition time of solute particles, which is helpful to monitor and manage the pollutant leakage accidents. In this study, an effective Lagrangian model for the age of tracer is developed based on the lattice Boltzmann method in 5 lattices. A tracer age problem in an asymmetrical circular reservoir is then employed as a benchmark test to verify this method. Then it is applied to computing the age of tracers under two different reservoir operation schemes in the Danjiangkou Reservoir, the drinking water source for the Middle Route of South-to-North Water Transfer Project. [ABSTRACT FROM AUTHOR]

The middle catchment of the Nu River is highly susceptible to debris flows. Differences in flow and substratum conditions among mainstem reaches correlate with debris flow depositions from lateral tributaries. We studied the impacts of debris flows on macroinvertebrates, especially responses in their diversity and assemblage structure to habitat modification at 22 sites in three habitats: barrier lakes and debris dams, formed by debris flow deposits barring the river, and unaffected mainstem sections. Unaffected mainstem sites supported the most diverse macroinvertebrate assemblage, with mean taxon richness, density and biomass 1.4, 1.1, and 23.6 times higher than those of debris dam sites, and 2.1, 4.2, and 7.4 times higher than those of barrier lake sites, respectively. Variance analysis revealed significant differences in diversity indices, and both taxonomic and functional feeding group composition among habitats. Although barrier lakes and debris dams had lower taxon richness, the two affected habitats contributed 17 and 16 exclusive taxa, respectively, to total taxon richness. Redundancy analysis identified habitats could be characterized by water temperature, electrical conductivity, flow velocity, and median particle size of substratum type. Significant differences in flow velocity and substratum median particle size among habitats were attributed to debris flows. Distinct assemblages within barrier lakes were associated with fine sediments. By altering habitat conditions, debris flows affect macroinvertebrate assemblages, reducing diversity locally in affected reaches, contributing to variation in diversity and assemblage structure throughout the catchment. Three genera ( Cricotopus sp., Pseudocloeon sp. and Monodiamesa sp.) are proposed as potential indicator taxa for unaffected mainstem, debris dam and barrier lake habitats, respectively. [ABSTRACT FROM AUTHOR]

Regional water cycles increasingly reflect the dual influences of natural and social processes, and are affected by global climate change and expanding human activities. Understanding how to maintain a healthy state of the water cycle has become an important proposition for sustainable development of human society. In this paper, natural-social attributes of the water cycle are synthesized and 19 evaluation indices are selected from four dimensions, i.e., water-based ecosystem integrity, water quality, water resource abundance and water resource use. A hierarchical water-cycle health evaluation system is established. An analytic hierarchy process is used to set the weight of the criteria layer and index layer, and the health threshold for each index is defined. Finally, a water-cycle health composite-index assessment model and fuzzy recognition model are constructed based on the comprehensive index method and fuzzy mathematics theory. The model is used to evaluate the state of health of the water cycle in Beijing during 2010–2014 and in the planning year (late 2014), considering the transfer of 1 billion m 3 of water by the South-to-North Water Diversion Project (SNWDP). The results show health scores for Beijing of 2.87, 3.10, 3.38, 3.11 and 3.02 during 2010–2014. The results of fuzzy recognition show that the sub-healthy grade accounted for 54%, 49%, 61% and 49% of the total score, and all years had a sub-healthy state. Results of the criteria layer analysis show that water ecosystem function, water quality and water use were all at the sub-healthy level and that water abundance was at the lowest, or sick, level. With the water transfer from the SNWDP, the health score of the water cycle in Beijing reached 4.04. The healthy grade accounted for 60% of the total score, and the water cycle system was generally in a healthy state. Beijing’s water cycle health level is expected to further improve with increasing water diversion from the SNWDP and industrial restructuring. [ABSTRACT FROM AUTHOR]

• Nutrient thresholds increase and then decrease from west to east. • For West Lake TP ≤ 0.05 mg/l, the nutrient load needs to be reduced by over 80 %. • Wide variation in thresholds under different management objectives. • Flow density and wind influence the spatial distribution of nutrient thresholds. Persistent eutrophication frequently causes toxic algal blooms, which is a serious threat to drinking water safety, food security, and public health. Nutrient thresholds, the maximum nutrient load that an aquatic ecosystem can absorb while meeting management objective, are key to avoiding and reducing blooms. The determination of thresholds relies on nutrient load-response curves. The spatial heterogeneity of large shallow lakes in terms of lake characteristics results in different curves shape among areas of the lake, which leads to spatial differences in thresholds. However, the spatial heterogeneity of thresholds is typically neglected; there are few methods to analyse the relationship between river loads and lake-specific area thresholds. Here, we proposed the Area Threshold Analysis Framework to analyse the spatial patterns of nutrient loads and thresholds in lakes. We first quantified the flow and load of the rivers entering the lake. The lake was then zoned and modelled to analyse area thresholds. Finally, an intuitive link between the nutrient loads of specific rivers and the thresholds of specific areas of the lake was established. The results showed a nonlinear without hysteresis response in all areas of Chaohu Lake; the nutrient loads and thresholds were highly variable in space, showing a trend of increasing and then decreasing from west to east. Flow density and wind might be important in influencing the spatial distribution of thresholds. The different effects of the wind and flow density on total phosphorus (TP) and chlorophyll a (Chl-a) lead to large differences in the thresholds with TP and Chl-a as management objectives, respectively. The large gap between nutrient loads and thresholds made it important for management to consider appropriate management goals to deal with unrealistic nutrient reductions. Achieving year-round Chl-a ≤ 30 µg/l in Chaohu Lake was easier than TP ≤ 0.05 mg/l, since for the latter, the Shiwuli, Paihe, and Nanfei river loads needed reductions of >80 %. In addition, for Area 1 and 2, it was more practical to first start meeting TP ≤ 0.05 mg/l for 2 or 3 seasons of the year than for 4 seasons. Overall, we developed a new framework for spatial threshold analysis and established an intuitive link between nutrient loads and thresholds in large shallow lakes. These results are valuable for understanding the threshold properties of spatially heterogeneous ecosystems in general and provide a reference for watershed nutrient management and ecological restoration of lakes. [ABSTRACT FROM AUTHOR]

• Scenarios were designed to test sediment impacts on flood propagation and flood risk during a flash flood event. • Constant sediment inflow from upstream had little effect on the water level at the peak discharge. • Flood risk increased after the peak discharge in cross-sections showing aggradation. • Sudden sediment inflows from debris flows greatly increased flood risk in the reach near the inflow point. • A framework was proposed to include sediment in flash flood risk assessment. Sediments seriously increase flood risk. The lack of sediment data, as well as uncertainty in sediment yield and transport modeling, hampers the incorporation of sediment into flood risk assessment/early-warning systems. In this study, we targeted a 10 km reach that experienced a flash flood with high sediment inflows in 2019 and simulated sediment impacts on flood propagation and flood risk using a 1D hydraulic model. Two sediment inflow types were considered: sudden inflow from a debris flow and constant inflow from upstream. For the former type, different inflow times before, during and after the peak discharge were tested; for the latter type, different sediment concentrations and medium grain sizes were tested in the scenario design. Our results showed that when sediments inflowed into the reach in a short time, they greatly increased the water level by up to 3.7 m in the reach near the inflow point (i.e., 500–700 m upstream and downstream of the point). When sediments constantly inflowed from upstream, they influenced the water level of the whole reach but raised the water level by up to 1.2 m in the cross-sections, which showed strong bed aggradation. Sudden sediment inflow influenced the reach near the inflow point and might increase its flood risk to the highest level, whenever it occurred before, during or after the peak discharge. Constant sediment inflow did not affect the flood risk of the peak discharge much but increased the risk afterwards when the sediment concentration was higher than 40 kg m−3. Cross-sections showing increased flood risk were characterized by decreasing bed slopes or increasing widths. In view of the impacts of different sediment inflow types on flood risk, we developed a method to identify potential sediment risk. Together with current risk assessment by water flow, we proposed a framework to incorporate sediment into flood risk assessment. [ABSTRACT FROM AUTHOR]

• Environmental drivers and characters of algal blooms in Dongting Lake were studied. • Algal bloom potential was low, but functional traits suggested toxic hazards. • NH 4 + was the key factor for phytoplankton biomass and toxigenicity. • Sensitivity of zooplankton to environmental factors inhibited phytoplankton control. • Warm winters may exacerbate algal bloom risk. Algal bloom (AB) risk assessment is critical for maintaining ecosystem health and human sustainability. Previous AB risk assessments have focused on the potential occurrence of ABs and related factors in the growing season, whereas their hazards, especially in the pre-growing season, have attracted less attention. Here, we performed a comprehensive AB risk assessment, including water trophic levels, phytoplankton biomass, functional trait-based assemblages, and related environmental factors, in the pre-growing season in Dongting Lake, China. Although mesotrophic water and low phytoplankton biomass suggested low AB potential, toxic taxa, which constituted 13.28% of the phytoplankton biomass, indicated non-negligible AB hazards. NH 4 + and water temperature were key factors affecting phytoplankton motility and toxicity. Our study establishes a new paradigm for quantitative AB risk assessment, including both potential AB occurrence and hazards. We emphasize the importance of phytoplankton functional traits for early AB warning and NH 4 + reduction for AB control in the pre-growing season. [Display omitted] [ABSTRACT FROM AUTHOR]

A new probabilistic conceptual model, named the Assessment Model of Human Impact on Runoff Based on Stationarity Hypothesis (AMHIRBSH), was developed to attribute runoff variations to human activities through evaluating the changes in the runoff–runoff relationship (i.e. that between runoff of different watersheds). The AMHIRBSH was then applied to the Baiyangdian drainage basin, North China. After applying the Mann-Kendall test for trend and the Pettitt test for breakpoint, the runoff over the Baiyangdian drainage basin was shown to have had a breakpoint in approximately 1979, which split the time series into a baseline period (pre-1979) and an altered period (post-1979). The runoff was greatly reduced between these two periods. The runoff–runoff relationship of the Wangkuai and Xidayang sub-watersheds was evaluated using a copula function which showed it to have a non-stationarity degree of 35.64%, likely induced by massive afforestation programmes. This method provides an innovative perspective for attributing runoff variations to human activities. [ABSTRACT FROM AUTHOR]

Land use classification is fundamental both for monitoring and predicting regional development patterns and for planning and regulating land use. This research proposed a joint probability-based classifier for land use classification of multispectral remote sensing data and applied it to the Lake Baiyangdian region of North China. This classifier, based on the vine copula method, was suitable for dealing with the uncertainties of land classification and its random variables that did not necessarily obey predefined distributions. Comparison of the results obtained using the proposed classifier with those derived using the widely used maximum likelihood classifier indicated that the accuracy of land use classification of multispectral remote sensing data was higher with the proposed classifier. Compared with the contingency matrix of the maximum likelihood classifier, that of the vine copula classifier showed an increase in the producer's (user's) accuracy of rural land (shallow water) of 29.4% (30.0%). The proposed classifier increased the shallow water area and significantly reduced the area of rural land. The main reason was the maximum likelihood classifier had poor classification performance, misclassifying pixels of shallow water as rural land. The findings of this study demonstrated that the vine copula classifier performs better than the traditional maximum likelihood classifier and that its application could promote full utilization of remotely sensed data. [ABSTRACT FROM AUTHOR]

• Multiple scales analysis method is effective for exploring vegetation coverage. • Precipitation is the main impact factor of vegetation growth. • The vegetation coverages around the CHSs were affected by their constructions. • It can be helpful for the sustainable ecosystem management in the DRR system. Along with the development of large-scale hydropower projects, many changes are arising both on the river channel and the ecosystems, which leads to the formation of a dam-reservoir-river system. The system is of significance to China due to the large-scale utilization of hydropower. However, such projects may cause significant impacts on local vegetation dynamics, which is of importance to local decision makers and water resources managers. In this research, the spatio-temporal variations of normalized difference vegetation index (NDVI) and climatic factors (CFs) under multiple time scales (i.e., annual, seasonal, and wet/dry periods) and the spatio-temporal pattern of the correlation of NDVI-CFs under the scales of annual and wet season were analyzed in the system by using the statistical methods. The response of NDVI to CFs in the basin was explored at the monthly scale. The main results indicated that from 1999 to 2013, the annual average NDVI had a significant overall upward trend. The distributions of the NDVI and its trend had the spatial and seasonal differences, with majority areas showing medium-high and high vegetation cover and a slight improvement in the grade of vegetation cover change of more than 40% of the total area. In the basin, temperature (T) and evapotranspiration (ET0) showed an upward trend, and precipitation (P) and the humidity index (HI) were the opposite. The corrections of NDVI-T and NDVI-ET0 were positive, and that of NDVI-P and NDVI-HI were negative. Also, the vegetation growth was mainly affected by the amount of P, and its time-lag period to the P was two months. In the scale of the eight cascade hydropower stations, the vegetation coverage and the correlation of NDVI-CFs around the Jinanqiao and Longkaikou hydropower stations were the best, and those near the Ludila and Guanyinyan were the worst, indicating that the vegetation coverage was affected by the cascade hydropower stations development. Therefore, the results may be beneficial for sustainable watershed ecosystem management in the system, as well as ecological development planning around the cascade hydropower stations. [ABSTRACT FROM AUTHOR]

This study investigates the relations between climate change and both runoff and sediment yield in watersheds and provides a scientific basis for water resources planning and design as well as watershed-scale soil and water conservation. The impact of climate change on runoff and sediment yield in a watershed does not occur in isolation, but is a synergistic process in which climate and vegetation jointly influence runoff and sediment yield. Previous studies have seldom addressed this synergistic effect. For this study, a regression model between climate factors (temperature and precipitation) and the Normalized Difference Vegetation Index (NDVI) was established using data from the Zhenjiangguan Watershed in China. By combining data on climate-driven changes in vegetation cover, the Soil and Water Assessment Tool (SWAT) model was built to simulate runoff and sediment yield in the watershed under two scenarios: changes in climate, and synergistic changes in climate and vegetation cover. The simulation results show that precipitation is the most sensitive factor affecting runoff and sediment yield; 10% change in annual precipitation can cause 10%–14% change in annual runoff and 17%–24% change in annual sediment yield. Temperature is also an important factor affecting runoff and sediment yield in the watershed. Each temperature increase of 0.7 °C can result in a decrease of 1.4%–2% in annual runoff and 2%–3.7% in annual sediment yield. This research reveals that accounting for synergetic change in vegetation has an impact on runoff and sediment yield results, and that the magnitude and nature of this influence vary among different combinations of temperature and precipitation changes. When temperature was kept constant, the effect of vegetation cover change caused by precipitation change on runoff and sediment yield was relatively small (only 0.9%–1.5% of the total change), and vegetation cover change inhibited the effects of precipitation change on runoff and sediment yield. When precipitation was kept constant, the effects of vegetation cover change caused by temperature change on runoff and sediment yield were relatively large (20%–30% of the total change), and vegetation cover change enhanced the effects of temperature change on runoff and sediment yield. This investigation considers the synergistic effects of climate and vegetation cover change, and thus further clarifies the extent to which climate change impacts water and ecological resources. Unlabelled Image • The laws of vegetation change due to climate change were investigated. • The distributed hydrological model and the vegetation change model were coupled. • The synergetic change and its impact on runoff and soil erosion were considered. • Vegetation synergetic change would influence runoff and erosion to a certain degree. [ABSTRACT FROM AUTHOR]

Climatic variation within a typical dry-valley area located in the southern Hengduan Mountains of China is studied, and the potential regional climate influences of large reservoirs in the area are discussed. Six meteorological stations near a reservoir are identified and classified into two categories (dry and non-dry valleys) to compare their level of climate change. Temperatures tended to increase since 1990 with a precipitation shift toward the dry season in both dry and non-dry valleys. Wavelet analysis shows that temperature and precipitation have significant variation with periods of 3.6 and 16.5 years, respectively. The standardized precipitation evapotranspiration index (SPEI) shows that dry valleys have multiple drought trends. Temperature in non-dry valleys changed more than that in dry valleys, but the variations of other indices in the two categories of valleys are not statistically different. The climatic variation of one station is in accordance with the reservoir filling, which is related to the orientation of the reservoir in the prevailing wind direction especially during summer. This study provides a profile of the climate change of dry valleys and documents the influence of large artificial reservoirs on regional climate. [ABSTRACT FROM AUTHOR]

Graphical abstract Highlights • 17 indicators were used to evaluate natural and social aspects of water cycle status. • A distributed hierarchical evaluation system was constructed for water cycle status. • A water resources carrying capacity model was applied based on water cycle status. • Water cycle status of the Beijing–Tianjin–Hebei region was scored as normal. • Approaches to sustainable development of regional water resources are discussed. Abstract Water cycles protect and maintain ecological environments, while enabling sustainable development of human societies. Various approaches have been proposed for maintaining optimal water cycles. This study developed an evaluation system based on both natural and social attributes of the water cycle. The system incorporated the four dimensions of water ecology, water quality, water quantity, and water use in a distributed hierarchical evaluation model. A water resources carrying capacity model was also constructed. Both models were evaluated using the Beijing–Tianjin–Hebei region as a case study. Statistical data from 13 prefecture-level cities were used to assess the water cycle status of this region. Overall, the water cycle status of the Beijing–Tianjin–Hebei region received a score of 3.33, indicating normal status (although this value varied throughout the region) and the standard deviation of the values was up to 0.48. Results suggested that although water use efficiency is close to ideal, insufficient water resources prevent the region from achieving an optimal regional water cycle. Feasible approaches to more sustainable water resource development within the Beijing–Tianjin–Hebei region include developing interregional cooperation, promoting population–industry relocation, and supplementing shortages with interbasin water transfers. [ABSTRACT FROM AUTHOR]

Highlights • Water for energy sector in China's two biggest megalopolises was analyzed. • Energy sector in Jing-Jin-Ji had 2.41 km3 of water withdrawal footprint in 2010. • Energy sector in Yangtze Delta had 9.59 km3 of water withdrawal footprint in 2010. • Water consumption footprint was 848.06 and 973.91million m3 respectively. • Jing-Jin-Ji had much larger external water footprint than Yangtze Delta. Abstract Using a consumption-based Multi-Regional Input-Output (MRIO) model, we investigate the distinctive characteristics, self-efficiency or external dependency, of energy demand's water footprint in China's two biggest and fastest developing megalopolises. We find that energy demand water footprint in the Jing-Jin-Ji and the Yangtze Delta amounted to 2.41 and 9.59 billion m³of water withdrawal respectively in 2010, of which 848.06 and 973.91 million m³was consumed. Among all energy products, electricity contributed the largest share to the energy sector's water footprint in both regions. The sectoral distribution of water footprint in the upstream supply chain differed by region. Most significantly, the agricultural sector accounted for more than 30% of water consumption footprint. In addition to water used locally, final energy demands in these two regions induced external water footprint beyond their administrative boundaries. The Jing-Jin-Ji region's energy sector had a smaller water footprint compared to the water-abundant Yangtze Delta region. However, external water footprint occupied a larger proportion in the former. Such divergence can be attributed to the distinctive water endowments and water-using technologies utilized in their respective energy sectors. Bespoke urban governance and policies tailored to local resource and technology portfolios are recommended for different urban agglomeration energy and water flows. [ABSTRACT FROM AUTHOR]