Xitiaoxi River Research Articles

A Framework for Characterizing Spatio-Temporal Variation of Turbidity and Drivers in the Navigable and Turbid River: A Case Study of Xitiaoxi River

Turbidity, as a key indicator of water quality linked to underwater light attenuation, is crucial for evaluating water quality. Control in high-turbidity water environments plays a critical role in navigable rivers. For this purpose, our study proposed a framework for analyzing the spatio-temporal variation of turbidity and its driving factors in a navigable and turbid river using in situ measurement data, satellite data, socioeconomic data, a power index function model, and correlation analysis. The results show that the proposed model is feasible for quantitative turbidity monitoring of the Xitiaoxi River. Its upstream turbidity is lower than downstream, with seasonal averages for spring, summer, autumn, and winter of 93.9, 111.3, 113.5, and 120.9 NTU, respectively. Furthermore, the turbidity in the middle and lower reaches of the Xitiaoxi River continuously increased before 2005 and began to decline after 2005 due to the policy of mining moratorium. This trend is especially noticeable at monitoring points along the main stream of the Xitiaoxi River, such as downstream of the Xitiaoxi River (S1), Gangkou station (S2), middle reaches of the Xitiaoxi River (S4), Hengtangcun station (S6), upper stream of the Xitiaoxi River (S7), and Huxi River (S8). Mining and shipping have significantly contributed to the turbidity of the target river. This framework offers a practical approach for assessing the environmental impacts of both natural and anthropogenic factors, thereby providing valuable insights for river management practices.

Unraveling the response of water quality and microbial community to lake water backflowing in one typical estuary of Lake Taihu, China.

To investigate the effect of lake water backflowing on the aquatic ecosystem in the estuary, surface water samples in the backflowing and unbackflowing areas were collected from one typical estuary of Lake Taihu, Xitiaoxi River. 16S rRNA sequencing and redundancy analysis were conducted to quantitatively elucidate the correlation between microbial community and water quality parameters. Results indicated lake water backflowing would affect the relative distribution of nitrogen species and increase the concentration of total nitrogen (TN) and nitrate, especially in the outlets of municipal sewage and agricultural drainage. For backflowing areas, more frequent water exchange could lower the seasonal fluctuation of the abundance and diversity of microbial community. RDA results showed crucial water quality parameters that greatly influence bacterial community were total organic carbon (TOC), total dissolved solids (TDS), salinity (SAL), ammonia, nitrate, TN for backflowing areas, and TOC, TDS, SAL, ammonia, TN without nitrate for unbackflowing areas. Verrucomicrobia, Proteobacteria, Microcystis, and Arcobacter were dominant with 27.7%, 15.7%, 30.5%, and 25.7% contribution to the overall water quality in backflowing areas. Chloroflexi, Verrucomicrobia, Flavobacterium, and Nostocaceae were dominant with 25.0%, 18.4%, 22.3%, and 11.4% contribution to the overall water quality in unbackflowing areas. And lake water backflowing might mainly affect the amino acid and carbohydrate metabolism based on the metabolism function prediction. A better understanding of the spatiotemporal changes in water quality parameters and microbial community was obtained from this research to comprehensively assess the effect of lake water backflowing on the estuarine ecosystem.

Climate change increased the compound extreme precipitation-flood events in a representative watershed of the Yangtze River Delta, China

A compound perspective on hydrological extreme events is of paramount significance as it may lead to damages with larger losses. In this study, an integrated framework, based on downscaled climate variables and hydrological model, i.e. the Soil and Water Assessment Tool, was applied to generate extreme precipitation (Rx1day) and extreme streamflow (Sx1day) series under historical and future climate conditions. Then the potential impacts of climate change for univariate and bivariate joint frequency of extreme precipitation and flood in Xitiaoxi River Basin (XRB), a representative watershed of the Yangtze River Delta, are detected. The compound risk of extreme precipitation and flood under different levels of joint return period for historical and projected periods is estimated by copula‐based two-dimensional approaches. The Rx1day and Sx1day under future scenarios changed by − 0.4% to 11.7% and 0.7% to 20.4%, respectively, compared to historical period based on univariate frequency analysis, indicating the increasing magnitude of the flood in the future. Climate change with different emission scenarios all have a driving effect on the rising coactivity of extreme precipitation and flood under compound flooding frequency analysis. In addition, the enhancement of climate change to extreme events is more apparent for extremes with higher return period and under the periods of 2080s. Moreover, the flood frequency designs are deduced by bivariate joint distribution are safer than that by univariate distribution. This study may provide actionable insights to formulate the planning scheme of flood control and disaster reduction under the changing environment.

Calculation of instream ecological water requirements under runoff variation conditions: Taking Xitiaoxi River in Taihu Lake Basin as an example

Calculation of instream ecological water requirements under runoff variation conditions: Taking Xitiaoxi River in Taihu Lake Basin as an example

Spatial Distribution and Environmental Significance of Phosphorus Fractions in River Sediments and Its Influencing Factor from Hongze and Tiaoxi Watersheds, Eastern China.

This study explored the spatial distribution of phosphorus fractions in river sediments and analyzed the relationship between different phosphorus fractions and their environmental influence on the sediments within different watersheds in Eastern China. River sediments from two inflow watersheds (Hongze and Tiaoxi) to Hongze and Taihu Lake in Eastern China were analyzed by the sequential extraction procedure. Five fractions of sedimentary phosphorus, including freely sorbed phosphorus (NH4Cl-P), redox-sensitive phosphorus (BD-P), bound phosphorus metal oxide (NaOH-P), bound phosphorus calcium (HCl-P), and residual phosphorus (Res-P) were all analyzed. The orders of rankings for the P fractions of the rivers Anhe and Suihe were HCl-P > NaOH-P > BD-P > NH4Cl-P and HCl-P > BD-P > NaOH-P > NH4Cl-P, respectively. For the rank order of the Hongze watershed, HCl-P was higher while the NH4Cl-P contents were significantly lower. The rank order for the Dongtiaoxi River was NaOH-P > HCl-P > BD-P > NH4Cl-P, and that of Xitiaoxi River was NaOH-P > BD-P > HCl-P > NH4Cl-P. Compared with the phosphorus forms of the Tiaoxi watershed, NaOH-P contents were significantly higher compared to HCl-P, which was significantly higher in the Hongze watershed. In comparison, NH4Cl-P contents were significantly lower in both. Variations may be attributed to differential discharge of the P form in the watershed due to land-use changes and urban river ambient conditions.

Individual and combined impacts of future land-use and climate conditions on extreme hydrological events in a representative basin of the Yangtze River Delta, China

Land use/cover changes (LUCC) as well as climate change have the potential to significantly alter the characteristics of extreme hydrological events under changing environments. This study evaluates the individual and combined impacts that LUCC and climate change have on extreme hydrological events using Soil and Water Assessment Tool (SWAT) applied in the Xitiaoxi River Basin (XRB). Two future land-use conditions, projected by CA-Markov model, and 21 climate scenarios, downscaled from three general circulation models, are considered. The results show that urban area would expand dramatically from 4.4% to 12.63%, which mainly occupy the forest-grass and agriculture land. The LUCC will decrease low flow index as well as increase high flow index, annual maximum 1-day and 5-day streamflow. Extreme precipitation indices all exhibit trends toward an increase in future occurrence. Furthermore, in testing the response of extreme hydrological events to climate change, most extreme hydrological indices are predicted to become greater than they were throughout the 1970s. The combined effects of LUCC and climate change would increase all extreme hydrological indices. Moreover, the climate change would contribute >50% of these hydrological impacts. These findings indicate that the XRB will experience more severe extreme hydrological events in both flooding and drought due to climate and land-use change. It is advised that disaster mitigation measures must be updated accordingly to respond to this changing situation.

Spatial hydrological responses to land use and land cover changes in a typical catchment of the Yangtze River Delta region

This study assessed the individual and combined effects of land-use and land-cover changes (LUCCs) on spatial hydrological responses by using an integrated approach involving the Soil and Water Assessment Tool (SWAT) and geographically weighted regression (GWR) models in the Xitiaoxi River Basin (XRB). The LUCCs and their spatial patterns from 1985 to 2008 were evaluated in the XRB. The hydrological processes during the period from 1980–2015 were then generated by the SWAT model under the 1985 and 2008 land-use scenarios. GWR models were constructed to quantify the spatial impacts of LUCCs at the sub-basin scale. The results showed that the predominant trend of land-use conversion was between forest-grass land and agricultural land, and the diminishing portion of forest-grass land (25.93 km2) and agricultural land (46.77 km2) contributed to the expansion of urban land during the period 1985–2008. Moreover, the urban area increased from 5.6% to 17.05%, and the change ratio progressed towards the centre of the XRB. These changes in land use caused the average annual water yield and surface runoff to increase by 1.09% and 11.87%, respectively, and the average annual evapotranspiration (ET), percolation and baseflow to decrease by 0.73%, 16.53% and 17.26%, respectively. In addition, the results of the GWR models indicated that the responses of each hydrological component exhibited spatial differences. The comprehensive land-use intensification index (La), selected to reflect the combined effects of LUCCs, was positively correlated with water yield and surface runoff but negatively correlated with ET, percolation and baseflow. La had a greater effect on water yield, surface runoff, percolation and baseflow in rural areas than in the urbanized region. The combined effects of LUCCs in certain local areas increased water yield and surface runoff by up to 13.7% and 114.2%, respectively. The local coefficient indicated that rural regions might be exposed to greater effects of LUCCs. The results of this study could be useful to understand the effects of LUCCs on the spatial patterns of each hydrological component and to help improve flood control and water resource management.

Transcriptomic analysis of zebrafish (Danio rerio) embryos to assess integrated biotoxicity of Xitiaoxi River waters

Assessing the toxicity posed by mixtures of unknown chemicals to aquatic organisms is challenging. In this study, water samples from six cross-sections along the Xitiaoxi River Basin (XRB) were monthly or bimonthly collected in 2014. The year-period physiochemical parameters as well as one-month-water sample based acute biotoxicity tests showed that the river water quality of the year was generally in a good status. High performance liquid chromatography (HPLC) screening based on one-month-water samples suggested that the organic pollutants might be non-to-moderately-polar chemicals in very low concentrations. One-month-water sample based RNA-seq was performed to measure the mRNA differential expression profile of zebrafish larvae to furtherly explore the potential bioeffect and the spatial water quality change of the river. Result indicated that the number of deferentially expressed genes (DEGs) tended to increase along the downstream direction of the river. Gene ontology (GO) enrichment analysis implied that the key pollutants might mainly be the function disruptors of biological processes. Principle components analysis (PCA) combining with transcripts and one-month-water sample based physiochemical parameters indicated that the pollution might be similar at TP, DP and CTB sites while pollution homology existed on some extent between YBQ and JW sites. Although the water quality of the river had a complex time-space alternation during the year, and the one-month-data based RNA-seq could not reflex the whole year-water quality of a watershed, the gene expression profile via RNA-seq provided an alternative way for assessing integrated biotoxicity of surface water, and it was relatively fit for early-warning of water quality of a watershed with unobservable acute toxicity. However, the identification of detail toxicants and the links between DEGs and pollution level as well as physiological-biochemical toxicity needed further investigation.

Spatial Distributions of Transferable Nitrogen Forms and Influencing Factors in Sediments from Inflow Rivers in Different Lake Basins

It is necessary to investigate the distribution of nitrogen forms in river sediments to recognize the water environment quality. In this study, ion exchangeable form nitrogen(IEF-N), weak acid extractable form nitrogen (WAEF-N), strong alkali extractable form nitrogen (SAEF-N) and strong oxidation extractable form nitrogen (SOEF-N) in sediments were obtained by means of sequential extraction procedures.We analyzed the spatial variations of nitrogen forms in sediments from Taihu watershed (Dongtiaoxi River and Xitiaoxi River) and Hongzehu watershed (Anhe River and Suihe River), and expounded the influence factors of nitrogen form distribution. The results showed that the physicochemical properties of sediments from different watersheds varied in space. The concentrations of total nitrogen and nitrogen fractions also showed obvious changes in river sediments. As a whole, the concentrations of total nitrogen and transferable nitrogen in Taihu rivers were higher than those in Hongzehu rivers, but the former showed smaller spatial changes. Sediments from Taihu rivers showed the different concentration order of total nitrogen and transferable nitrogen comparing with those from Hongzehu rivers. The former followed the order of SOEF-N > SAEF-N > IEF-N > WAEF-N, and the latter followed the order of SOEF-N > SAEF-N > WAEF-N > IEF-N.The spatial varitions of transferable nitrogen fractions in Hongzehu rivers were prominent, which was associated with nitrogen sources. The spatial distributions of transferable nitrogen in sediments were obviously affected by their physicochemical properties, especially for organic matter and grain size.

Estimating parameters of the variable infiltration capacity model using ant colony optimization.

Because hydrological models are so important for addressing environmental problems, parameter calibration is a fundamental task for applying them. A broadly used method for obtaining model parameters for the past 20 years is the evolutionary algorithm. This approach can estimate a set of unknown model parameters by simulating the evolution process. The ant colony optimization (ACO) algorithm is a type of evolutionary algorithm that has shown a strong ability in tackling combinatorial problems and is suitable for hydrological model calibration. In this study, an ACO based on the grid partitioning strategy was applied to the parameter calibration of the variable infiltration capacity (VIC) model for the Upper Heihe River basin and Xitiaoxi River basin, China. The shuffled complex evolution (SCE-UA) algorithm was used to test the applicability of the ACO. The results show that ACO is capable of model calibration of the VIC model; the Nash-Sutcliffe coefficient of efficiency is 0.62 and 0.81 in calibration and 0.65 and 0.86 in validation for the Upper Heihe River basin and Xitiaoxi River basin respectively, which are similar to the SCE-UA results. Despite the encouraging results obtained thus far, further studies could still be performed on the parameter optimization of an ACO to enlarge its applicability to more distributed hydrological models.

Water nutrient status and its controlling factors in the inflow tributaries of Xitiaoxi River, upper reaches of Lake Taihu basin

In order to investigate the differences of nutrient status of tributaries in Lake Taihu basin and the impact of land use on water quality,ten tributaries of Xitiaoxi River were chosen. Total phosphorus( TP),particle phosphorus( PP),total nitrogen( TN),ammonia nitrogen( NH+4-N),nitrate( NO-3-N),chemical oxygen demand( COD) values of tributary waters were 0. 033-0. 205,0. 007-0. 104,2. 014-5. 921,0. 021-1. 659,1. 082-3. 415 and 6. 5-18. 5 mg / L,respectively. The concentration of nutrients and COD had a significant temporal variation in the following orders: dry season normal season wet season. The tributaries were polluted at various levels. TN concentrations of waters were high in some tributaries. The tributaries can be divided into four categories according to the clustering analysis on nutrient parameters. Fluxes of nutrients and COD showed from high to low amount in the order: wet season normal season dry season,which indicated that they were mainly controlled by discharge. Land use was the most important factor affecting water quality in tributaries of Xitiaoxi River. Cultivated land,residential area had a positive impact on water quality,while there were negative correlation between water quality and the forestland,grassland. In wet season and dry season,cultivated land and forestland had the most important impact on nutrients and COD,while in normal season,residential land and forestland had the most remarkably important influence on TP and TN,respectively.

Researches on Temporal and Spatial Changes of Suspended Sediment Nutrients and Source Contributions in Xitiaoxi River, China

Xitiaoxi River is the main discharge river of Taihu Lake. It is important to research changes of suspended sediment nutrients and their provenances for the water environment management. This paper analyzes temporal and spatial variations of nutrients in suspended sediments (SS) and establishes the geochemical model to quantify the proportions of SS sources with geochemical parameters in different reaches. The results show that the contents of SS and its nutrients of the downstream are significantly higher than the upstream and midstream. The contents of nutrients in SS in dry season are higher than in wet season. The C/N and IP/OP ratios of SS can effectively reflect the material source types in the different reaches, which are associated with land use types. Woodland is relatively higher contribution to SS in the upstream, arable lands become a major contributor to SS in the midstream, while urban land is the highest contribution to SS in the downstream. Seasonal changes also affect the contributions of land use to SS. Woodland and urban land show more contributions to SS in wet season than in dry season, whereas arable land and bank sediment show the higher proportions for SS source.

Comparative Researches on the Provenances of Suspended Sediments in Different Reaches of Dongtiaoxi and Xitiaoxi Watershed

Dongtiaoxi and Xitiaoxi river are the two main discharge rivers of Taihu Lake. It is important to research the provenances of suspended sediments (SS) and the difference of the provenances. This paper establishes the geochemical model to quantify the proportions of SS sources with geochemical parameters, and then analyzes the contribution differences of the sources to SS in the basins and its reasons. The results show that the contribution of woodland is highest in the upper reaches of both Dongtiaoxi and Xitiaoxi basin, but the contribution of arable land has more differences. Arable land becomes a major contributor to the midstream of Dongtiaoxi and Xitiaoxi basin, while the contributions of woodland and urban land are larger in Dongtiaoxi basin. The SS contribution of urban land is highest in the downstream of Dongtiaoxi and Xitiaoxi basin, while the contribution of arable land is larger in Dongtiaoxi basin. During wet season and dry season, the differences of the sources contribution variations in Dongtiaoxi basin are not obvious, while that in Xitiaoxi basin are significantly obvious, that is the SS contributions of woodland and urban land in wet season are significantly higher than in dry season, while the contributions of arable land and bank sediment are on the contrary.

Inferring land use and land cover impact on stream water quality using a Bayesian hierarchical modeling approach in the Xitiaoxi River Watershed, China

Lake eutrophication has become a very serious environmental problem in China. If water pollution is to be controlled and ultimately eliminated, it is essential to understand how human activities affect surface water quality. A recently developed technique using the Bayesian hierarchical linear regression model revealed the effects of land use and land cover (LULC) on stream water quality at a watershed scale. Six LULC categories combined with watershed characteristics, including size, slope, and permeability were the variables that were studied. The pollutants of concern were nutrient concentrations of total nitrogen (TN) and total phosphorus (TP), common pollutants found in eutrophication. The monthly monitoring data at 41 sites in the Xitiaoxi Watershed, China during 2009–2010 were used for model demonstration. The results showed that the relationships between LULC and stream water quality are so complicated that the effects are varied over large areas. The models suggested that urban and agricultural land are important sources of TN and TP concentrations, while rural residential land is one of the major sources of TN. Certain agricultural practices (excessive fertilizer application) result in greater concentrations of nutrients in paddy fields, artificial grasslands, and artificial woodlands. This study suggests that Bayesian hierarchical modeling is a powerful tool for examining the complicated relationships between land use and water quality on different scales, and for developing land use and water management policies.

Spatial Distribution in Forest Soil Nutrients and its Relationship with Ecological Factors on the up Stream of Taihu Lake Basin

To examine the role of the forest in non-point source pollution control in the Taihu lake region, the soil profile nutrients including nitrate, hydrolyze nitrogen(HN), available phosphorus(AP), total nitrogen(TN), total phosphorus(TP) concentration of 26 forest sample plots along the Xitiaoxi River from upstream to downstream were measured through July to August 2009, the relationship between vegetation type and topographic factors and soil nutrients was analyzed. results show that: (1) All of five soil nutrients concentration decreased with increasing soil depth; (2) Soil nutrients of different soil depth is intermediate variability, the coefficient of variation of AP, TN, HN, TP were increased with the increasing of soil depth, and the coefficient of variation of nitrate was decreased with the increasing of soil depth. (3)Soil HN content under plots with an average tree height above 10m was significantly higher than plots with an average tree height less than 10m; (4) Soil AP, HN, TN, TP content was first decreased and then increased with the increasing of elevation. .In summary, the soil nutrients of different soil depth was found to be closely related to vegetation type, community age, structure, fertilization and topographic features in the upstream of Taihu lake basin.

Hydrological response to urbanization at different spatio-temporal scales simulated by coupling of CLUE-S and the SWAT model in the Yangtze River Delta region

Summary The Main objective of the study is to understand and quantify the hydrological responses of land use and land cover changes. The Yangtze River Delta is one of the most developed regions in China with the rapid development of urbanization which serves as an excellent case study site for understanding the hydrological response to urbanization and land use change. The Xitiaoxi River basin, one of the main upstream rivers to the Taihu Lake in the Yangtze River Delta, was selected to perform the study. The urban area in the basin increased from 37.8 km 2 in 1985 to 105 km 2 in 2008. SWAT model, which makes direct use of land cover and land use data in simulating streamflow, provides as a useful tool for performing such studies and is therefore used in this study. The results showed that (1) the expansion of urban areas had a slight influence on the simulated annual streamflow and evapotranspiration (ET) as far as the whole catchment is concerned; (2) surface runoff and baseflow were found more sensitive to urbanization, which had increased by 11.3% and declined by 11.2%, respectively; (3) changes in streamflow, evapotranspiration and surface runoff were more pronounced during the wet season (from May to August), while baseflow and lateral flow had a slight seasonal variation; (4) the model simulated peak discharge increased 1.6–4.3% and flood volume increased 0.7–2.3% for the selected storm rainfall events at the entire basin level, and the change rate was larger for smaller flood events than for larger events; (5) spatially, changes of hydrological fluxes were more remarkable in the suburban basin which had a relative larger increase in urbanization than in rural sub-basins; and (6) analysis of future scenarios showed the impacts of urbanization on hydrological fluxes would be more obvious with growth in impervious areas from 15% to 30%. In conclusion, the urbanization would have a slight impact on annual water yield, but a remarkable impact was found on surface runoff, peak discharge and flood volume especially in suburban basins in the study area. The study suggested that more attention must be paid for flood mitigation and water resources management in planning future urban development in the region.

太湖西苕溪流域水文序列突变检测比较和分析研究

探索流域水文变点可发现其水文演变规律，为水资源的可持续利用提供科学指导。本文以太湖流域的重要水源西苕溪流域为研究对象，在5%显著性水平下，采用Mann-Kendall、Pettitt、滑动T检验、Yamamoto、差积曲线–秩检验联合识别法等分析和比较了1972~2010年流域降水和径流的变点。结果表明：西苕溪流域降水和径流的变点均发生在1999年，该结果为进一步甄别气候变化和人类活动的贡献率提供了研究基础。 The change-point analysis of hydrological time series would help to find the evolution of hydrological processes and provide the scientific guidance for sustainable utilization of water resources. As the crucial headwaters of Taihu Lake basin, Xitiaoxi River basin was chosen as the study case. Under the significance level 5%, Mann-Kendall, Pettitt, Moving T test, Yamamoto and the residual mass curve combined rank test methods were applied to compare and analyze the change-point of precipitation and streamflow from 1972 to 2010 in the basin. It is found that the change-point of precipitation and streamflow time series both happened at the year 1999 in Xitiaoxi River basin. The result would provide the basis for the further studies on identification for the impact of climate change and human activities on hydrological processes.

Response of streamflow to climate change and human activity in Xitiaoxi river basin in China

AbstractIn recent years, the Xitiaoxi river basin in China has experienced intensified human activity, including city expansion and increased water demand. Climate change also has influenced streamflow. Assessing the impact of climate variability and human activity on hydrological processes is important for water resources planning and management and for the sustainable development of eco‐environmental systems. The non‐parametric Mann–Kendall test was employed to detect the trends of climatic and hydrological variables. The Mann–Kendall–Sneyers test and the moving t‐test were used to locate any abrupt change of annual streamflow. A runoff model, driven by precipitation and potential evapotranspiration, was employed to assess the impact of climate change on streamflow. A significant downward trend was detected for annual streamflow from 1975 to 2009, and an abrupt change occurred in 1999, which was consistent with the change detected by the double mass curve test between streamflow and precipitation. The annual precipitation decreased slightly, but upward trends of annual mean temperature and potential evapotranspiration were significant. The annual streamflow during the period 1999–2009 decreased by 26.19% compared with the reference stage, 1975–1998. Climate change was estimated to be responsible for 42.8% of the total reduction in annual streamflow, and human activity accounted for 57.2%. Copyright © 2012 John Wiley & Sons, Ltd.

Relationships between the Seasonal Variations of Macroinvertebrates, and Land Uses for Biomonitoring in the Xitiaoxi River Watershed, China

AbstractThe impacts of differences in watershed land uses, and differences in seasonality on benthic macroinvertebrate communities, were evaluated in 12 stream sites within the Xitiaoxi River watershed, China, from April 2009 to January 2010. The composition of macroinvertebrate community differed significantly among three land use types. Forested sites were characterized by high taxa richness, diversity and the benthic‐index of biotic integrity (B‐IBI), while farmland and urban disturbed stream sites presented contrary patterns. The percentage of urban land use, conductivity, dissolved oxygen, ammonia nitrogen and total phosphorus were the major drivers for the variations. The land use related water quality stress gradients of the four sampling seasons were determined by means of four independent Principal Component Analyses. The responses of macroinvertebrate community metrics, to anthropogenic stressors, were explored using Spearman Rank Correlation analyses. All the selected metrics, including total numbers of taxa, numbers of Ephemeroptera, Plecoptera and Trichoptera taxa, percentage of non‐insect abundance, percentage of scrapers abundance, Pielou’s evenness index, Simpson diversity index, and the Benthic Index of Biotic Integrity were correlated significantly with environmental gradients (PC1) in autumn. In other seasons such correlations were less pronounced. Our results imply that autumn is the optimal time to sample macroinvertebrate communities, and to conduct water quality biomonitoring in this subtropical watershed. (© 2012 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)

Water Yield of Xitiaoxi River Basin Based on InVEST Modeling

Abstract: Water yield calculation and mapping are of great importance to water resource planning and management and hydropower station construction. A water yield model based on InVEST was employed to estimate water runoff in the Xitiaoxi River basin. The data included land use and land cover, average annual precipitation and potential evapotranspiration, soil depth, and plant available water content. In order to test model accuracy the natural runoff of Xitiaoxi River was estimated based on linear regression relation of rainfall—runoff in a ‘reference period’. After repeated validation, when the Z value was 6.5 the water yield was 8.30 E+8 m3 and this was a smaller difference with natural runoff. From the distribution of water yield, south and southwestern areas of the watershed had higher water yield volumes per hectare.