Taihu Lake Watershed Research Articles

Positive Impact of Environmental Governance Policies on Watershed Economy: A Case Study of the Taihu Lake Watershed

This paper seeks to investigate how environmental governance policies positively influence the regional economy within the context of the Taihu Lake Watershed. It will specifically delve into the practical measures taken for policy implementation and their resulting outcomes. This paper extensively examines the Taihu Lake Watershed through a comprehensive analysis of existing literature. It consolidates prior research focusing on how environmental governance policies affect the regional economy within watersheds. The study reveals that environmental governance policies have positively influenced the economy of the Taihu Lake Watershed. Policy implementation has not only advanced economic development but also enhanced public consciousness regarding environmental conservation, contributing to ecological system enhancement. Effective environmental governance policies can drive economic growth within watersheds, raise public consciousness regarding environmental preservation, and facilitate ecological system enhancements, thereby contributing positively to the sustainable development of watersheds. The insights derived from this research hold relevance for shaping environmental governance policies and economic development strategies in various regions. To further promote sustainable watershed development, it is crucial to optimize environmental governance policies, improve policy execution, foster collaboration between departments, and establish efficient benefit-sharing mechanisms.

Water crisis, environmental regulations and location dynamics of pollution-intensive industries in China: A study of the Taihu Lake watershed

Most existing studies on environmental regulations and the location dynamics of pollution-intensive industries regard new environmental procedures as an incremental development process, and neglect the influence of sudden changes in environmental regulations triggered by a pollution crisis. Using the drinking water crisis in the Taihu Lake Watershed (TLW) in 2007 as an example, this paper examines the spatial behavior of pollution-intensive firms across the TLW, and pays special attention to the regional differences in the effectiveness of enforcing environmental regulations. We find that the pollution haven hypothesis works efficiently in the short term after an unexpected pollution crisis because of the immediate strengthening of environmental regulations by local governments under pressure from the central government and the public. However, the effect of strict environmental policies was compromised by differences in the effectiveness of policy enforcement across the watershed. Specifically, when other regions (for example, Huzhou) were compared with Wuxi (the site of the crisis in the present study), these regions were found to be relatively insensitive to the effects of the pollution incidents and the environmental regulations that were triggered.

Deciphering the origins, composition and microbial fate of dissolved organic matter in agro-urban headwater streams

Landscape urbanization and intensive agriculture dramatically alter stream ecosystems, but it is little known how urban and agriculture land use change the quantity, quality and ultimate fate of dissolved organic matter (DOM) in stream ecosystems via nonpoint source pathways. Size-exclusion chromatography with fluorescence excitation-emission matrices, as well as absorbance and lignin biomarkers were applied to investigate the characteristics and microbial fate of DOM in 15 first-order agricultural, urban and forest headwater streams in Taihu Lake Watershed, a subtropical region of SE China. Results showed that both urban and agricultural land cover increased the amount of dissolved organic matter (DOC) with a lower C/N ratio, and that the majority of DOC was bound to terrestrial humic-like substances. Compared to forest-impacted headwater streams, the aromaticity and molecularity of OM were greatly decreased as the amounts of anthropogenic/aquagenic fulvic acid-like and protein-like DOM enriched in urban streams, and that of microbially soil-derived humic-like DOM and low molecular-weight substances (e.g., neutrals and acids) increased in agricultural streams, respectively. Human-influenced land use also influenced the seasonal variability of stream DOM biogeochemistry. Natural watersheds produced high DOC specific loads and concentrations only in the rainy season (high-flow period). Agricultural streams contributed a higher amount of terrestrial humic-like and protein-like fractions and urbanized watersheds had high values of autochthonous protein-like fractions only. Redundancy analysis (RDA) revealed that DOM quality (explainable variables: molecular source, 43.29%; molecular-weight, 29.74%) were the most prominent factor impacting microbial carbon processing, followed by inorganic nutrients (17.29%). A higher proportion of DOM from urban streams was eventually mineralized to carbon dioxide mainly due to the inefficient utilization of humic and nonhumic (e.g., protein, polysaccharides and lignin) substances as well as higher levels of inorganic nitrogen and phosphorus, whereas a significant fraction of DOM from agricultural and forest streams tended to enter microbial production and the recalcitrant-DOM pool due to the presence of less labile substrates. Our findings indicate that differences in stream-DOM and environmental properties due to urbanization and farming practices may influence stream microbial carbon processing and cause bottom-up changes in the fate of organic carbon moving through freshwater ecosystems.

Measuring the past 20 years of urban-rural land growth in flood-prone areas in the developed Taihu Lake watershed, China

There is growing interest in using the urban landscape for stormwater management studies, where land patterns and processes can be important controls for the sustainability of urban development and planning. This paper proposes an original index of Major Hazard Oriented Level (MHOL) and investigates the structure distribution, driving factors, and controlling suggestions of urban-rural land growth in flood-prone areas in the Taihu Lake watershed, China. The MHOL of incremental urban-rural land increased from M 31.51 during the years 1985–1995 to M 38.37 during the years 1995–2010 (M for medium structure distribution, and the number for high-hazard value). The index shows that urban-rural land was distributed uniformly in flood hazard levels and tended to move rapidly to high-hazard areas, where 72.68% of incremental urban-rural land was aggregated maximally in new urban districts along the Huning traffic line and the Yangtze River. Thus, the current accelerating growth of new urban districts could account for the ampliative exposure to high-hazard areas. New districts are driven by the powerful link between land financial benefits and political achievements for local governments and the past unsustainable process of “single objective” oriented planning. The correlation categorical analysis of the current development intensity and carrying capacity of hydrological ecosystems for sub-basins was used to determine four types of development areas and provide decision makers with indications on the future watershedscale subdivision of Major Function Oriented Zoning implemented by the Chinese government.

Nitrate reduction in groundwater and isotopic investigation of denitrification in integrated tree-grass riparian buffers in Taihu Lake watershed, eastern China

Riparian buffer strips can play an important role in reducing nitrate (NO₃⁻) contamination of groundwater from agricultural fields to the adjacent inland water system. Our objective was to investigate the temporal and spatial variation of NO₃⁻ concentrations and delta nitrogen (N) 15 (δ¹⁵N)-NO₃⁻ in groundwater at the integrated poplar-grass buffer strips with three different tree planting densities, and to assess in situ denitrification rate in riparian soils in Taihu Lake watershed of China under a subtropical climate. Nitrate concentrations and δ¹⁵N-NO₃⁻ values in groundwater were monitored along transects of piezometers installed from field edge to ditches at 5 m (16.4 ft) spacing in the integrated poplar-grass buffers. We found that groundwater NO₃⁻ concentrations declined by 67.5% to 88% while the δ¹⁵N-NO₃⁻ values enriched along the subsurface flow paths within the 15 m (49.2 ft) poplar-grass riparian buffers in Taihu Lake watershed throughout the year. Nitrate was removed more efficiently in spring and summer than in autumn and winter owing to vegetation uptake in the growing season combined with high denitrification rates due to higher groundwater table level and soil temperature. The isotopic enrichment factors for NO₃⁻ retention varied seasonally, with the highest absolute value in winter (−8.95‰) and lowest in summer (−4.53‰). The difference between poplar planting densities in buffers did not significantly affect their capacity to reduce groundwater NO₃⁻. Riparian soil denitrification rate was highly seasonal and significantly different in the different soil depths. Our results indicate that the upper soil layer (10 to 35 cm [3.9 to 13.8 in]) in the riparian zones were hot spots for denitrification, and denitrification was strongly influenced by hydrological conditions and soil temperature in the integrated poplar-grass buffers in the Taihu Lake watershed.

A simple approach to assess N load capacity of rice paddy fields in the southern Taihu Lake watershed.

High nitrogen (N) leaching from irrigated agricultural soils is the result of N input exceeding soil N load capacity (NLC). A simple approach was developed in this research to assess the NLC of paddy soils in the southern Taihu Lake watershed. Paddy soils were classified into four types (Submergenic, Illuvium, Gleyed, and Percogenic) and 28 soil samples representing all four types were collected from across the region. The NLC values of the paddy soils were assessed using a split-line model and the spatial variability of the NLC among various rice paddy soils in the region was also evaluated with Kriging analysis. Results showed the NLC of paddy soils were both soil type and background N content related. The critical N sorption values (NLC plus soil N background) of the Gleyed, Illuvium, Submergenic, and Percogenic paddy soil samples varied from 283.1 to 315.6 mg kg(-1), 203.0 to 270.2 mg kg(-1), 240.6 to 254.4 mg kg(-1), and 177.4 to 186.2 mg kg(-1), respectively. However, on average the NLC of paddy soils in the region was 80.3 mg kg(-1), and the corresponding environmental N load threshold was around 110 kg N ha(-1). Geo-statistic results showed that the NLCs were unevenly distributed throughout the rice paddy dominated areas of the southern Taihu Lake watershed. The NLC assessment approach and spatial distribution information provided helpful guidance to set an environmental N threshold for best N management and hence reduce degradation of water for the whole rice ecosystem.

Sediment and nutrient removal by integrated tree-grass riparian buffers in Taihu Lake watershed, eastern China

Loss of nitrogen (N) and phosphorus (P) from agricultural runoff is a leading cause of eutrophication in Taihu Lake, China. Riparian buffer strips can effectively remove sediment and nutrients from surface runoff. A field-scale study was conducted to assess the effectiveness of the integrated poplar (<i>Populus</i>)-grass buffer strips with different tree planting density in reducing sediment, N, and P from agricultural runoff during natural rainfall events in Taihu Lake watershed, eastern China. The experimental site consisted of four treatments, including a control plot with no buffer strip (T₀) and three poplar-grass buffer strips with different planting densities of 1,346 trees ha⁻¹ (T₁), 769 trees ha⁻¹ (T₂), and 577 trees ha⁻¹ (T₃) with planting spacing of 2 × 5 m (6.5 × 16.4 ft), 4 × 5 m (13.1 × 16.4 ft), and 6 × 5 m (19.7 × 16.4 ft), respectively. The integrated poplar-grass buffer strips significantly reduced runoff volume, sediment, total N, and total P masses by 49.3% to 61.6%, 78.7% to 90.2%, 57.2% to 71.5%, and 65.4% to 81.4%, respectively. With increasing poplar planting density in buffer strips, the canopy interception and maximum water storage capacity of litter layer increased, while the loss of sediments and nutrients from runoff decreased. There was significantly higher removal efficiency in buffer T₁ than that in buffers T₂ and T₃ for sediment, particle-bound N (PN), and particle-bound P (PP). There was no significant difference in removal efficiency for ammonium as N (NH₄-N), nitrate as N (NO₃-N), and phosphate P (PO₄-P) between buffers T₁ and T₂. According to different rainfall regimes, we found that the reduction in runoff volume, sediment, and nutrients load for buffers were higher under mild-long duration events (rainfall intensity class 2 to 4 mm h⁻¹ [0.078 to 0.15 in hr⁻¹]) and lower under intense-short duration events (rainfall intensity class 6 to 8 mm h⁻¹ [0.23 to 0.31 in hr⁻¹]). The removal efficiency of the buffers was negatively correlated with both precipitation and rainfall intensity, and the rainfall intensity had more effect on the removal efficiency than the precipitation. The results indicated that the impact of tree planting density on the effectiveness of buffer strips depended on the measured parameter. That is, the impact on sediment, PN, and PP was greater than that on the soluble N and P. The effect of tree planting density on the performance of buffer strips is mainly due to the interception of canopy and litter layer.

Tracing the Nitrate Sources of the Yili River in the Taihu Lake Watershed: A Dual Isotope Approach

As the third largest freshwater lake in China, Taihu Lake has experienced severe cyanobacterial blooms and associated water quality degradation in recent decades, threatening the human health and sustainable development of cities in the watershed. The Yili River is a main river of Taihu Lake, contributing about 30% of the total nitrogen load entering the lake. Tracing the nitrate sources of Yili River can inform the origin of eutrophication in Taihu Lake and provide hints for effective control measures. This paper explored the nitrate sources and cycling of the Yili River based on dual nitrogen (δ15N) and oxygen (δ18O) isotopic compositions. Water samples collected during both the wet and dry seasons from different parts of the Yili River permitted the analysis of the seasonal and spatial variations of nitrate concentrations and sources. Results indicated that the wet season has higher nitrate concentrations than the dry season despite the stronger dilution effects, suggesting a greater potential of cyanobacterial blooms in summer. The δ15N-NO3− values were in the range of 4.0‰–14.0‰ in the wet season and 4.8‰–16.9‰ in dry, while the equivalent values of δ18O were 0.5‰–17.8‰ and 3.5‰–15.6‰, respectively. The distribution of δ15N-NO3− and δ18O-NO3− indicated that sewage and manure as well as fertilizer and soil organic matter were the major nitrate sources of the Yili River. Atmospheric deposition was an important nitrate source in the upper part of Yili River but less so in the middle and lower reaches due to increasing anthropogenic contamination. Moreover, there was a positive relationship between δ18O-NO3− and δ15N-NO3− in the wet season, indicating a certain extent of denitrification. In contrast, the δ18O-δ15N relationship in the dry season was significantly negative, suggesting that the δ15N and δ18O values were determined by a mixing of different nitrate sources.

Differences of soil fertility in farmland occupation and supplement areas in the Taihu Lake watershed during 1985-2010.

Since the 1980s a series of farmland policies have been implemented in China to stabilize the balance of farmland quantity and quality against accelerating urbanization and industrialization processes. This paper aims to reveal differences of soil fertility in the farmland occupation area (FOA) and farmland supplement area (FSA). In 1985–2000 the decline of the FOA area was 181,000 ha, but the FSA rarely increased. In 2000–2010 the decline of the FOA area was 824,800 ha, but the FSA increased dramatically. The accelerating loss process is closely related to urbanization and industrialization of the locations. Most occupied farmland was still located in the areas with higher soil fertility. The FOA in 1985–2000 had higher soil fertility than the FSA, but the FSA in 2000–2010 significantly raised its soil fertility to close to the FOAs’ level. The rate of excellent-good levels of the FOA in 2000–2010 decreased from 46.13% to 37.61%; The development model shifts and farmland policies implementation are the chief driving factors behind AFOS changes. The TDBF policy and the main function zoning project should continue to play an effective role in balancing the farmland system.

Pollution Assessment of Rice Agriculture in the Taihu Lake Watershed Based on the Pollution Footprint: A Case Study of Changzhou City and Yixing City, China

Pollution Assessment of Rice Agriculture in the Taihu Lake Watershed Based on the Pollution Footprint: A Case Study of Changzhou City and Yixing City, China

Community structure of zoobenthos in spring and their application to bioassessment of water quality in Taihu Lake Watershed

The macrozoobenthic assemblages in 7 reservoirs,8 rivers,and 14 lakes of Taihu Lake Watershed w ere investigated in May,2010. Totally,57 species,belonging to 8 classes,representatives of 4 phyla,w ere collected. Of those,Insecta( 17 species) and Oligochaeta( 15 species) w ere the most abundant in species number. As a w hole,the zoobenthic assemblage in this w atershed w as predominated by Limnodrilus hoffmeisteri. According to cluster analysis( CA),there existed 10 community types in the selected 29 w ater bodies,15 of w hich w ere prevailed by L. hoffmeisteri and 5 of w hich by Bellamya aeruginosa. The mean density and biomass in the w hole basin w ere 2741. 2 ind / m2and 47. 2 g / m2,respectively. Oligochaeta was predominant in density( about 91%),and Bivalvia together w ith Gastropod contributed about 93% of the total biomass. Among the different w ater body types,there w ere marginally significant or conspicuous differences in density w ith the maximum for river and the minimum for reservoir,and in biomass w ith the maximum for lake and the minimum for reservoir. Meanw hile,the numerical composition of macrozoobenthic groups( i. e. at the taxonomic level of class) differed obviously betw een the w ater body types. Although Shannon-Weaver diversity index( H') w as conspicuously correlated w ith richness( species number,S),H'w as more strongly governed by evenness( J). H',J,and Margalef species richness( R) in lake and reservoir w ere all significantly higher than those in river,respectively,and S did marginally conspicuously. The density in lakes w ith practice of aquaculture w as significantly higher than in ones w ithout. The reverse w ere found for biomass,H',and J. According to BPI index and H',the most stations of lake and river w ere moderately or seriously polluted,and the most reservoirs w ere clear or slightly polluted based on Wright index.

Removal Effects on Nitrogen, Phosphorus and COD in Water Body of Shanghu Lake Ecological Wetland in Taihu Lake Watershed

Abstract Shanghu ecological lake wetland is mostly made up of woody plants. So far, its removal effects on nitrogen and phosphorus are unknown. The removal effects on TN, TP, AmmN and COD in wastewater of Shanghu lake wetland were studied from July, 2008 to May, 2009. The relationship between removal effects on pollutants and temperatures of water body was studied too.192 samples were collected from input point, output point, and 6 points in water body. The results show that the wetland has always a good removal effect on TN, TP and AmmN under different water temperature, the water temperature has influence on removal effects to various extents. First report to removal effects on nitrogen and phosphorus of Shanghu lake wetland and woody plants wetland in China.

Properties of phosphorus retention in sediments under different hydrological regimes: A laboratory-scale simulation study

Summary Excessive nutrient loading and changing hydrological regimes can significantly impact the ecological function of wetland ecosystems. Three wetland sediment samples collected from West Lake, Xiazhuhu Wetland and Baoyang River in the Taihu Lake Watershed, China, were compared to understand the P retention properties responding to hydrological regimes by using static column and steady-flow flume laboratory-scale experiments. Sediment in Xiazhuhu Wetland currently function as a P sink with equilibrium P concentration (EPC 0 ) values of 0.010 mg L −1 , while sediments from West Lake and Baoyang River, have EPC 0 values of 0.050 mg L −1 and 0.023 mg L −1 , respectively, and serve as an internal P source. The P retention by sediments ranged from 17.20 to 22.61 mg m −2 d −1 under 35-d static conditions, while sediment beds continuously fed by the simulated inflow water containing 2 mg L −1 P ranged from 59.20 to 171.93 mg m −2 d −1 . The P removal capacities by sediments were higher during the rainy season than the dry season when wetlands were subjected to excessive P input. Since the majority of external P stored in sediment is in the form of Al-P (e.g., for Xiazhuhu wetland), the application of alum to water column could potentially increase the P retention capacity of sediment.

Influence of land use/cover change on storm runoff—A case study of Xitiaoxi River Basin in upstream of Taihu Lake Watershed

Land use/cover change (LUCC) is one of the main boundary conditions which influence many hydrologic processes. In view of the importance of Taihu Lake Watershed in China and the urgency of discovering the impacts of LUCC on storm runoff, two flood events under five land cover scenarios in the Xitiaoxi River Basin of the upstream of Taihu Lake watershed were simulated by distributed hydrologic modeling system HEC-HMS. The influences of each land cover on storm runoff were discussed. It was concluded that under the same rainstorm the ascending order of runoff coefficient and peak flow produced by the 5 different land covers were woodland, shrub, grassland, arable land, and built-up land; the descending order of swelling time were woodland, shrub, grassland, arable land, and built-up land. Scenario of built-up land was the first to reach peak flow, then arable land, grassland, shrub, and woodland. There were close relationships between the runoff coefficients produced by the 5 different land covers. The degrees of impacts on runoff coefficient of land cover change modes were sorted by descending: woodland to built-up land, shrub to built-up land, grassland to built-up land, arable land to built-up land, woodland to arable land, shrub to arable land, arable land to grassland, shrub to grassland, grassland to arable land, and woodland to shrub. Urbanization will contribute to flood disaster, while forestation will mitigate flood disaster.

Controlling effects of forest belts on non-point source pollution of agricultural lands in Taihu Lake area, China

Taihu Lake area is one of the most developed areas in agricultural production. Application of fertilizers and pesticides in large quantities greatly aggravate environmental pollution of this area, and water pollution has worsened to an unbearable condition. Two sampling farms (respectively 1 hm2) under rape-rice rotation and wheat-rice rotation were selected as studied ecosystem and a 5-yr-old Poplar forest and 8-yr-old Metasequoia forest were chosen in the selected areas. By collecting samples of Nitrogen, Phosphorus in water, crops and underground of forest, the transfer and loss of N and P (main water pollutants) in faming ecosystem were studied, and the effects of forest belts on non-point source pollution of agricultural lands was analyzed. The results indicated that the transfer and loss of N and P vary with means of rotation, types of crops and the amount of fertilizer application. Buffering forest belts betweens farmlands and ditches can effectively stop and purify such elements as N and P in soil runoffs, thus controlling non-point source pollution of agricultural lands. When the width ratio of farmland to forest belt is 100 to 40, 50.05% losing N, 29.37% losing P can be absorbed by forest under rape-rice rotation and 30.98% N, 86.73% P can be absorbed by forest under wheat-rice rotation. When the width ratio of farmland to forest belt is 150 to 40, 33.37% losing N, 19.58% losing P can be absorbed by the forest under rape-rice rotation, and under wheat-rice rotation 20.65% lost N and 57.82% lost P can be absorbed. There is only some purification effect when the width ration of farmland to forest belt is 200 to 40. Based on model of buffering forest belts, the width ratio of farmland to forest is determined between 100 to 40 and 150 to 40, because it not only can purify water, but also occupy less farmland. It is suggested that Poplars, with the characteristics of fast-growing and high value, are suitable to be planted as shelter-forest in Taihu Lake Watershed.

Phosphorus Sorption and Desorption of Upland Soils in the Hilly Areas of Taihu Lake Watershed

旱地土壤中流失的磷是地表水体中磷的重要来源,本文通过模拟实验对比太湖地区丘陵旱地土壤和水稻土对磷的吸持解吸特征,结果表明虽然旱地土壤对磷的固定能力略高于水稻土,但由于旱地土壤的有效磷水平普遍高于水稻土,因而前者磷的吸持饱和度(DPS)要大大高于后者,这就决定了旱地土壤中的磷被淋溶或以溶解态随径流流失的风险和数量也显著高于水稻土.磷吸持饱和度是土壤磷素水平和土壤固磷能力的综合指标,更能反映土壤固相中的磷进入液相的难易程度,可以作为评价水-土界面磷迁移能力的重要指标.;Phosphate sorption isotherms were determined for representative upland and paddy soils in Taihu Lake watershed.P desorped from the soils were also studied by successive extractions with iron oxide-impregnated paper st rips.Although the averaged P sorption maxima of upland soils derived from Langmuir sorption plot was a lit tle higher than thatof paddy soils the po tential of P loss from upland soils to waterbodies was greater because upland soils usually had a much higher P level.The Deg ree of Phosphorus Saturation (DPS), an integrated expression of soil P level and soil sorption capacity, can give good estimate of the amountof P desorped from soils so it can be used as a reliable index to assess the potential of soil P loss via leaching or surface runoff.