Nansi Lake Basin Research Articles

Identification of groundwater nitrate sources and its human health risks in a typical agriculture-dominated watershed, North China.

Identifying nitrate sources and migratory pathways is crucial for controlling groundwater nitrate pollution in agricultural watersheds. This study collected 35 shallow groundwater samples in the Nansi Lake Basin (NLB) to identify groundwater nitrate sources and potential health risks. Results showed that NO3- concentration in 62.9% of groundwater samples exceeded the drinking water standard (50 mg/L). Hierarchical cluster analysis (HCA) was used to classify the sampling points into three groups based on hydrochemical and isotopic data. Groups A and C were situated in the eastern recharge and discharge regions of Nansi Lake, while Group B was located in the Yellow River floodplain west of the lake. Hydrochemical data and nitrate stable isotopes (δ15N-NO3- and δ18O-NO3-) indicated that elevated NO3- primarily originated from soil organic nitrogen (SON) in Group A, while manure and sewage (M&S) were the primary sources in Groups B and C samples. Microbial nitrification was identified as the primary nitrogen transformation process across all groups. The source apportionment results indicated that SON contributed approximately 40.1% in Group A, while M&S contributed about 53.9% and 81.2% in Groups B and C, respectively. The Human Health Risk Assessment (HHRA) model indicated significant non-carcinogenic risks for residents east of Nansi Lake, primarily through the oral pathway, with NO3- concentration identified as the most influential factor by sensitivity analysis. These findings provide new perspectives on identifying and handling groundwater nitrogen pollution in agriculture-dominated NLB and similar basins that require enhanced nitrogen contamination management.

Study on Non-Point Source Pollution Prevention and Control System in Nansi Lake Basin Based on System Dynamics Approach

Agriculture, as an important activity on which human beings depend for their livelihood, brings serious environmental problems while meeting the needs of human survival, among which agricultural non-point source (NPS) pollution is one of the most urgent environmental problems. This study quantitatively assessed the loading characteristics spatial and temporal evolution patterns of two agricultural NPS pollutants, chemical oxygen demand (COD) and ammonia nitrogen (NH3-N), from 2010 to 2020 in the Nansi Lake Basin as an example, and constructed a system dynamics (SD) simulation model to simulate and analyze agricultural NPS pollution under different development and treatment scenarios, based on an investigation of the regional prevention and control strategy of agricultural NPS pollution and the technological system. The results show that the current status of agricultural NPS pollution load in the Nansi Lake Basin is poor, and the level of pollution load is high, showing obvious geographical differences. In terms of temporal changes, the pollution loads of the two pollutants showed a decreasing trend from 2010 to 2020, among which the pollution load of NH3-N showed the largest change. Spatially, the spatial distribution of each type of pollutant has some similarities, with smaller pollution loads in Jining and Zaozhuang and relatively larger pollution loads in Heze and Ningyang. The main source of COD pollution in the Nansi Lake Basin is rural life, with an emission proportion of 52.85%, and the main sources of NH3-N pollution from agricultural NPS pollution in the area are rural life and livestock and poultry farming, with emission proportions of 47.55% and 35.36%, respectively. Under the status quo continuum scenario, the pollution load values for COD are consistently higher than those for NH3-N, so the relative impact of COD is greater. In this study, the principles and methods of SD in system science are adopted to deal with the agricultural NPS pollution of Nansi Lake Basin, and the evolution of its behavioral characteristics are simulated, forecasted, and predicted, and policy experiments are conducted, with a view to providing references for the prevention and control of agricultural NPS pollution in Nansi Lake Basin and further research.

Industrial fluoride emissions and their spatial characteristics in the Nansi Lake Basin, Eastern China.

Excessive fluoride emissions threaten ecological stability and human health. Previous studies have noted that industrial sources could be significant. However, quantifying industrial fluoride emissions has not been yet reported. In this study, both bottom-up and top-down approaches were used to estimate the fluoride emissions in the Nansi Lake Basin. Global and local spatial autocorrelation were adopted to reveal the spatial agglomeration effects. The fluoride emissions calculated by the bottom-up approach were larger than those calculated by the top-down method. The highest fluoride input mainly occurred in Zoucheng and Mudan. The highest fluoride emissions mainly occurred in Zoucheng and Rencheng using the bottom-up approach. The highest fluoride emissions mainly occurred in Zoucheng and Yanzhou using the top-down approach. Mining and washing of bituminous coal and anthracite (BAW) was the most significant source of fluoride input and emissions. A significant spatial agglomeration effect of fluoride emissions was found. These findings could provide a method for accurate industrial fluoride emission estimation, complement the critical data on the fluoride emissions of main industrial sectors, and provide a scientific basis for tracing fluoride sources.

Theory and practice of basin-wide floodwater utilization: typical implementing measures in China

Floodwater utilization (FU) helps alleviate water shortages in regions with uneven rainfall. This study focuses on basin-wide FU, considering diverse water infrastructure and the delicate balance between flood risks and water scarcity. FU measures including optimizing reservoir flood limited water level (FLWL), extending the use of flood detention areas, and compensatory use of channel capacities, were reviewed and exemplified by real-world applications in China. The proposed procedure for implementing FU involves assessing FU potential, selecting appropriate utilization methods, and conducting a comprehensive evaluation of the associated risks and benefits. Using the Nansi Lake basin in China, as a synthesis example, the current-level FU potential and FU rate are estimated to be 1.47 km3/yr and 65%. This FU value exceeds the theoretical potential, indicating the severe crowding out of ecological water uses. Multi-stage FLWL through raising the post-flood FLWL from 34.20 m to 34.35 m could increase the reservoir (the upper Nansi Lake) ability to refill by 19.1%. Appropriate control of the sluices of interconnected rivers could conserve up to 0.135 km3 of floodwater from a single flood event without increasing flood risk.

Multi-scenario simulation of land use/land cover change and water yield evaluation coupled with the GMOP-PLUS-InVEST model: A case study of the Nansi Lake Basin in China

Changes in land use/land cover (LULC) can impact water yield (WY) by altering the structural layout and functions of terrestrial ecosystems. Therefore, to ensure regional economic and ecosystem sustainability, it is critical to investigate the correlation between LULC change and WY. The GMOP-PLUS-InVEST (GPI) coupling model based on the gray multi-objective optimization model, the patch-generating land use simulation model, and the integrated valuation of ecosystem services and trade-offs model was used in this study. Establishing three different scenarios: business as usual (BAU), economic development scenario (ED), and ecological conservation scenario (EC) to predict the LULC distribution pattern in the Nansi Lake Basin (NLB) in 2035, and obtain the WY from 2000 to 2035. Getis-Ord Gi* and Anselin Local Moran's I were used to investigate the spatial–temporal features of WY at the grid scale. The results indicated that: (1) The dominant LULC types of the NLB were farmland and construction land. The primary transfer trend was construction land encroaching on farmland due to the acceleration of the urbanization process and policy intervention. (2) The results of the LULC simulation in the NLB in 2035 showed that the BAU had a continuous trend of change for nearly 20 years; Under the ED, the intensity of construction land encroachment on farmland was accelerating; Under the EC, an apparent increase in the proportion of ecological land could be seen, and the contradiction between construction land and farmland had eased, which was expected to be more in line with the policy and planning objectives. (3) LULC change had a significant effect on WY. From 2000 to 2035, WY of the NLB continued to increase, and in 2035, the WY under different scenarios was ED > EC > BAU. Spatially it always showed a high value distribution in the south and west in the NLB. The GPI coupling model can be used for LULC optimization and ecosystem service evaluation, providing ideas for rational planning of future LULC. Research results have significant reference significance for the formulation of LULC policies and the protection and restoration of ecological environment of the NLB.

Natural and anthropogenic factors regulating fluoride enrichment in groundwater of the Nansi Lake Basin, Northern China

Excess fluoride (F−) in groundwater can be hazardous to human health of local residents who rely upon it. Beside natural sources, anthropogenic input may be an additional source to be considered. Twenty surface water and 396 groundwater samples were collected from the Nansi Lake Basin, with hydrogeochemical and isotope techniques employed to clarify the spatial variability, source, and the natural and anthropogenic factors regulating the occurrence of high F− groundwater. The factors responsible for elevated F− levels in surface water and deep confined aquifers are discussed based on their hydraulic relationship. Also a conceptual model of F− enrichment with different aquifer systems is put forward based on the geomorphic units of the basin. The results show that F− concentration is between 0.1 and 6.9 mg/L in the west of Lake, while ranged from 0.03 to 1.74 mg/L in the east of Lake. The hydrogeological setting and lithology are the primary factor determining the provenance of high-fluoride groundwater in the basin. Fluoride mainly originated from the dissolution of fluorine-bearing minerals, and is affected by the alkaline groundwater environment, cation exchange, adsorption, and evaporation. The landforms on the east side of Nansi Lake are low hills and piedmont sedimentary plains, where the aquifers consist of karst fissure water and overlying porewater. High F− groundwater is not observed in this area due to its rapid flow and Ca2+-enriched hydrochemical characteristics. The anthropogenic input (such as fertilizer application on farms and illegal industrial pollutant discharge), contribute F− to groundwater in varying degrees, especially in the shallow aquifers east of the lake and in some parts west of the lake. This work is a clear example of how natural processes together with human activities can affect the chemical quality of groundwater, which is essential to safeguard the sustainable management of water resources in semi-arid areas.

Simulation of land use landscape pattern evolution from a multi-scenario simulation: a case study of Nansi Lake Basin in China.

Reasonable regulation of the total amount and layout of land resources is the significant cornerstone for releasing the potential of land resources. This study explored the spatial layout and evolution characteristics of the Nansi Lake Basin from the perspective of land use and simulated the spatial distribution pattern under multiple scenarios in 2035 with the Future Land Use Simulation model which more effectively reflected the process of land use change in the actual situation, revealing the land use change of the Nansi Lake Basin under the influence of different human activities. Analysis indicated that the simulation results obtained using the Future Land Use Simulation model strongly agree with reality. By 2035, the magnitude and spatial distribution of land use landscapes will change significantly under three scenarios. The findings provide a reference for the adjustment of land use planning in the Nansi Lake Basin.

Ecological function zoning of Nansi Lake Basin in China based on ecosystem service bundles.

Ecological function zoning is an essential means of scientific management of ecosystems. According to the characteristics of ecological function zoning, implementing zoning control is conducive to the governance and protection of the ecological environment and the maintenance of ecological sustainability. This study was conducted with the Nansi Lake Basin as the cross-section for 2018. The Integrated Valuation of Ecosystem Services and Trade-offs model was adopted to assess and measure five ecosystem services, including water yield, crop production, soil conservation, carbon storage and carbon sequestration, and habitat quality. The Self-Organizing Feature Maps neural network was applied to obtain the ecosystem service bundles, and then, the ecological function zones were divided. The results indicated that the overall spatial pattern of ecosystem services in the study zone showed a decreasing schema from east to west; There was a trade-off between supply services and support services and a synergy between supply services and regulatory services; according to the bundling results, the Nansi Lake Basin was divided into four ecological functional zones: the eastern ecological surplus zone, the central crop supply zone, the western ecological balance zone, and the lake habitat protection zone. The results showed that (1) the spatial distribution of various ecosystem services in the Nansi Lake Basin showed spatial heterogeneity and specific regional laws, showing a decreasing pattern from the east to the west as a whole, especially in soil conservation, carbon sequestration, and habitat quality. (2) According to the supply and spatial distribution of each ecosystem service, the Nansi Lake Basin was divided into four ecological functional zones: the eastern ecological surplus zone, the central crop supply zone, the western ecological balance zone, and the lake habitat protection zone. (3) For zone I, provisioning services and regulation services were in synergy. For zone II and zone III, the provisioning service had a trade-off relationship with the regulation service and the supporting service. For zone IV, supporting services were trade-offs not only with provisioning services but also with regulating services. In general, the trade-offs between ecosystem service in the Nansi Lake Basin were stronger than the synergies, and the overall benefits of ecosystem services were smaller. Relying on the perspective of the ecosystem service bundles, at the county level, this study provided an analysis of the trade-offs and synergies among ecosystem services in the Nansi Lake Basin, which helped formulate the management plan for the corresponding region and provided the appropriate recommendations for regional habitat conservation and restoration.

Sources and cycling processes of nitrogen revealed by stable isotopes and hydrochemistry in a typical agricultural lake basin

Increased exposure to nitrate has been reported in many arid and semi-arid areas where groundwater is used as the drinking water source, presenting a major public health threat. Groundwater nitrate pollution is becoming serious due to intensive agricultural activities in the Nansi Lake Basin, Shandong Province, Northern China, through which the trunk line of the South-to-North Water Diversion Project passes. This study characterized potential nitrogen pollution sources by combined analysis of hydrochemical components and stable nitrate isotopes (δ15N–NO3-, δ18O–NO3-); the contribution of different sources was estimated using the SIAR model. The results show groundwater nitrate contamination in the Nansi Lake Basin is widespread both west (NSW) and east (NSE) of the lake. Manure and sewage (M&S), soil nitrogen (SN), and chemical fertilizer (CF) are potential NO3−-N sources in the study area, with the order of contribution being M&S (78.38%) > SN (15.02%) > CF (6.60%) in areas west of the lake and M&S (59.40%) > SN (30.38%) > CF (10.22%) in areas east of the lake, indicating the significant impact of human activities. The relationship between d-excess and δ15N–NO3- suggests irrigation practices increase soil moisture, resulting in more N from 15N-depleted soils leaching into the groundwater, increasing the contribution of SN. The predominant processes of the nitrogen cycle in the basin are different in the NSW and NSE areas. In the upper-middle reaches of the NSW area, nitrification dominates the nitrogen cycle due to aerobic conditions and elevated salinity; however, denitrification occurs in local downstream aquifers at depths ranging from 10 to 50 m. In contrast, SN plays a bigger role in the NSE, where the mineralization of soil organic nitrogen is the predominant process, followed by nitrification of M&S and CF nitrogen sources due to rapid groundwater flow in the carbonate and metamorphic rock aquifers.

A Tiered Ecological Risk Assessment of Caffeine by Using Species Sensitivity Distribution Method in the Nansi Lake Basin.

Caffeine has been reported toxic to aquatic organisms, and it frequently occurs at relatively high concentrations in most of surface waters. However, it is difficult to control caffeine pollution because of the lack of Water Quality Criteria (WQC). In this study, species sensitivity distribution method and Log-normal model were applied to derive caffeine WQC as 83.7 ng/L. Meanwhile, concentrations of caffeine in the Nansi Lake basin were detected in 29 sampling sites, with the mean of 99.3 ng/L. The levels of caffeine in tributaries were higher than those in the lakes. In addition, a tied ecological risk assessment method was applied to assess the adverse effect of caffeine on aquatic system. The joint probability curve indicated that ecological risk might exist 3.1% of surface water in the study area, while 5% threshold (HC5) was set up to protect aquatic species. Generally, caffeine posted a low risk to aquatic organisms in the Nansi Lake basin.

Hydrochemical evolution characteristics, controlling factors, and high nitrate hazards of shallow groundwater in a typical agricultural area of Nansi Lake Basin, North China

Anthropogenic nitrate contamination in groundwater could not be neglected, which has been a global issue threatening public health, especially in agricultural fields where fertilizers were used intensively. The present study focused on evaluating the groundwater evolution process, quality, and associated health risks from nitrate pollution in Nansi Lake Basin (NLB), a typical intensive agricultural region of North China. For this purpose, fifty-two shallow groundwater samples were collected and analyzed major chemical parameters in June 2022. The groundwater samples are found to be mainly dominated by HCO3–Ca·Mg and SO4·Cl–Ca·Mg types. Water-rock interactions like minerals dissolution/precipitation and ion exchange were found to be the important processes influencing hydrochemistry. Nitrate content in groundwater fluctuated from 1.9 to 750.0 mg/L (average:148.7 mg/L), with about 75% of samples surprisingly exceeding the permissible limit (50 mg/L) set by the World Health Organization (WHO). Anthropogenic activities can be classified as excessive nitrogen fertilizer application, livestock manure, and industrial/domestic sewage, coupled with irrigation return flow, which brought significant hazards to human health. The calculation results of entropy weighted water quality index (EWQI) showed that about half of groundwater samples are unfit for drinking purposes. Most importantly, 88.5%, 88.5%, 73.1%, and 71.2% of the water samples had considerable NO3− health risks (HQ > 1) for infants, children, females, and males, respectively. It is suggested that the groundwater should be chemical and biological denitrification for nitrate removal before being used for drinking purposes. The findings of this work can help policymakers to solve groundwater pollution problems and ensure healthy drinking water in such intensive agricultural basins and other similar regions worldwide.

Spatial-Temporal Variation and Driving Factors of Ecological Vulnerability in Nansi Lake Basin, China.

Lake basins are one of the most significant areas of human-land interaction. It is essential for the region's ecological protection and high-quality development to assess their ecological vulnerability (EV) and analyze the key driving factors of EV. Considering the characteristics of the lake basin, we chose 17 indicators to evaluate the EV of the Nansi Lake Basin based on the "sensitivity-resilience-pressure" (SRP) model. Then, spatial principal component analysis (SPCA) and a transfer matrix were used to analyze the spatial-temporal variation characteristics of the EV. Moreover, the optimal parameters-based geographical detector (OPGD) was applied to investigate the factors influencing the spatial heterogeneity of the EV. The results indicated that the EV of the Nansi Lake Basin was characterized by a circling spatial structure, with low values distributed in the Nansi Lake and its surrounding areas, as well as high values concentrated in the northwest. The EV of the Nansi Lake Basin decreased from 2010 to 2020, indicating that the overall ecological pressure in the Nansi Lake Basin decreased. Climatic factors, land use type, and habitat quality were the primary factors that influenced the spatial heterogeneity of the EV in the basin. Our findings can serve as policy guidelines for ecological management and the sustainable development of the Nansi Lake Basin and also contribute to the EV assessment of lake basins.

Derivation of Water Quality Criteria for Carbamazepine and Ecological Risk Assessment in the Nansi Lake Basin.

Carbamazepine, as one of several pharmaceutical and personal care products, has gained much attention in recent years because of its continuous discharge in natural waters and toxicity to aquatic ecosystems. However, it is difficult to evaluate and manage carbamazepine pollution because of the lack of a rational and scientific Water Quality Criteria (WQC) of carbamazepine. In this study, the carbamazepine toxicity data of thirty-five aquatic species from eight taxonomic groups were selected, and the species sensitivity distribution (SSD) method was applied to derive the WQC for carbamazepine based on the Log-logistic model, which was 18.4 ng/L. Meanwhile, the occurrence and distribution of carbamazepine in the Nansi Lake basin was studied. Results showed that concentrations of carbamazepine in 29 sampling sites were in the range of 3.3 to 128.2 ng/L, with the mean of 17.3 ng/L. In general, the levels of carbamazepine in tributaries were higher than those in the lakes. In addition, qualitative and quantitative ecological risk assessment methods were applied to assess the adverse effect of carbamazepine on aquatic systems. The hazard quotient (HQ) method showed that there were 24 and 5 sampling sites, in which risk levels were low and moderate, respectively. The joint probability curve (JPC) method indicated that ecological risks might exist in 1.4% and 1.0% of surface water, while a 5% threshold and 1% threshold were set up to protect aquatic species, respectively. Generally, carbamazepine posed a low risk to the aquatic organisms in the Nansi Lake basin.

Growth in the Economic and Hydraulic Engineering Capacities Drives Water Quality Improvement in the Eastern Region of Nansi Lake, China

Knowledge of the extent of water pollution along a diversion channel is essential for ensuring the security and effectiveness of water diversion projects. Thus, identifying the trends in the water quality and the factors which influence the trends along a diverted river is a prerequisite to ensuring the safety of the water diversion. As an important control unit of the Eastern Route of the South to North Water Diversion Project, the hilly eastern region of Nansi Lake Basin (ENLB) suffers excess water pollution in the water transferred into Nansi Lake during the flood season. The comprehensive pollution index (CPI), the Mann-Kendall trend test and analysis of variances were used to characterize the spatiotemporal variation of water quality in the three main mountainous rivers of the ENLB. The contribution of different factors which influencing the variation of the water quality parameters may be explained using ridge regression analysis. The results showed that the CPI for the three major rivers decreased significantly from 2000 to 2012. The rivers had problems in compliance, and this was most noticeable in the Guangfu River. The main pollutants exceeding the water quality standards were the chemical oxygen demand and total phosphorus. The GDP per capita was the largest factor which influenced the changes in the regional water quality, with the average contribution being 30%. An increase in the water storage capacity was shown to have a positive effect on improving the water quality. The results provided a scientific basis for establishing a regional pollution control strategy and would give support to the planning of future water diversion projects.

基于格网的南四湖流域土地利用碳排放与其生态系统服务价值时空关系分析

基于格网的南四湖流域土地利用碳排放与其生态系统服务价值时空关系分析

An accuracy-improved flood risk and ecological risk assessment in an interconnected river–lake system based on a copula-coupled hydrodynamic risk assessment model

Understanding flood event-related risk in an interconnected river–lake system (IRLS) is a prerequisite for developing water resource management strategies and enhancing disaster resilience. Previous flood event-related risk assessments either hardly consider the context in which water diversion encounters flood events or hardly consider the physical process, stochastic analysis and multivariate interactions of flood event characteristics simultaneously, thereby resulting in a less reliable assessment of flood event-related risk. To resolve this limitation, a copula-coupled hydrodynamic risk assessment model (CHRAM) is proposed to characterize the physical, multivariate, and stochastic nature of risk, improving the accuracy of risk assessment. In this study, CHRAM is capable of accurately quantifying flood event-related risks (i.e., flood risk and ecological risk) of the Nansi Lake Basin in the flood season under the operation of the eastern route of the South-to-North Water Diversion Project in China. Our findings revealed that the total flood volume (Rsum) and duration (Td) of flood events were significantly sensitive characteristic indexes for flood risk and ecological risk. In addition, the security domains of flood risk (Rsum < 35 mm and Td < 23 d) and ecological risk (Rsum < 50 mm and Td < 27 d) were determined based on the analysis of the relationship between sensitive characteristic indexes and risk indicators. The results also showed that the impact of Td on flood risk, ecological risk and flood-ecological combined risk was 3–14 times greater than the impact of Rsum. The occurrence probability of flood-ecological combined risk was smaller than that of flood risk but greater than that of ecological risk, with the corresponding maximum risk probabilities of 11.2%, 36.5%, and 4.7%, respectively. This study extends the current knowledge about risk assessment in IRLS and is beneficial to instruct the management of projects for similar systems.

The response of net primary productivity to climate change and its impact on hydrology in a water-limited agricultural basin.

Climate change has remarkably altered growing-season vegetation growth, but the impacts of vegetation variability on the regional hydrological cycle remain poorly understood. Exploring the relationships between climate change, vegetation dynamics, and hydrologic factors would contribute to the sustainable management of ecosystems. Here, we investigated the response of vegetation dynamics to climate change and its impact on hydrologic factors in a traditional agricultural basin with limited water resources in China, Nansi Lake Basin (NLB). To this end, CASA (Carnegie-Ames-Stanford Approach) model and the SWAT (Soil and Water Assessment Tool) model were applied to simulate the net primary productivity (NPP), evapotranspiration (ET), and soil water in the growing season (April-October) from 2000 to 2016. Results showed that the mean growing-season NPP (NPPGS) exhibited an ascending trend at a rate of 2.93 g C/m2/year during the 17-year period. The intra-annual variation of NPPGS displayed two peaks in May and July, respectively. The first peak in May was accompanied by relative deficits in soil water, which might inhibit vegetation productivity. Precipitation was the principal climatic factor controlling NPPGS dynamics in the water-limited NLB. The positive influence of temperature on NPPGS was relatively weak, and even future warming could negatively affect ecosystem productivity in the south-central regions of the NLB. Furthermore, a strongly positive relationship between NPPGS and ET was detected, suggesting that increasing NPP in the future might stimulate the rise in ET and then exacerbate drought at the watershed scale. This study provides an integrated model for a comprehensive understanding of the interaction between vegetation, climate, and hydrological cycle, and highlights the importance of water-saving agriculture for future food security.

Land-use changes and ecosystem services under different scenarios in Nansi Lake Basin, China.

Ecosystem services (ESs) have been affected drastically by rapid urban sprawl and significant land-use changes (LUC) in Nansi Lake Basin (NLB) in China. Based on land-use data with a 30-m resolution from 1990 to 2015, we analyzed the process of LUC by atlas analysis and explored the impacts of LUC on ecological service value (ESV) under urban sprawl. The results showed that water area and buildup land increased significantly from 1990 to 2015. The area of cultivated land, forests, grassland, and unutilized land decreased. Land transfer mainly occurred between cultivated land, water area, and grassland. The total amount of land transfer was 4830.64 km2, and the average transfer rate is 185.79 km2/year in 26 years. The most obvious transfer occurred in period IV. The increased buildup land was mainly transferred from cultivated land. The total urban sprawl in the NLB was 1623.37 km2 in the past 26 years, with an average expansion rate of 62.44 km2/year, with the fastest sprawl in period IV. Tengzhou city was the most prominent area of expansion. Its ESV increased by 5.73 × 107 US$ with an increased rate of 2.21 × 106 US$/year. The annual total value of regulating and supporting services in the first-level ESs in the NLB accounted for 54.8 and 25.2% of the total ESV in all years, which were the primary types of ESs. Water area, forests, and cultivated land were the principal contributors to ESV changes. In conclusion, urban sprawl had a significant negative effect on ESV changes. Urban sprawl, water area, forests, and cultivated land were all sensitive factors for ESV changes.

南四湖流域关键生态系统服务的时空权衡关系

从多尺度科学地研究流域各生态系统服务间的权衡与协同关系，对流域实现经济发展与生态保护双重目标具有重要研究意义。运用InVEST模型模拟评估产水量、水质净化、土壤保持、碳存储、生物多样性维持和授粉等6类区域关键生态系统服务，并通过热点分析、相关分析和主成分分析，定量分析自改革开放以来（1980-2018年）这些生态系统服务的时空变化及其在不同尺度上的权衡关系。结果表明：（1）南四湖流域产水服务呈上升趋势，而水质净化、土壤保持、碳储存、生境质量、授粉等服务则总体呈下降趋势。（2）研究区东部林地和草地广布，是碳存储、生境质量和授粉服务的高值区，而建设用地分布的地区是产水量和土壤保持服务的高值区。（3）产水量与水质净化服务之间呈权衡关系，水质净化与生境质量、碳存储与授粉之间则存在较强的协同关系。（4）在子流域尺度上主要是存在着供给服务（产水量）与调节服务（水质净化和土壤保持）、供给服务（产水量）与支持服务（生境质量）之间的空间权衡关系；在县域尺度上，供给服务、调节服务与支持服务（产水量、水质净化、碳存储、生境质量和授粉）之间主要是空间协同关系，两个尺度之间具有较大差异。研究结果可为管理者在合适的空间尺度上制定相应的政策提供科学支撑，促进南四湖流域生态环境和社会经济协同发展。;It is important to create a win-win situation on both economic development and ecological protection. For better ecological management and protection in the future, it is essential to identify the trade-offs and synergies of multiple ecosystem services (ESs) at differently spatial scales. The relationships of ESs varied over time and spatial scales, it is important to study the spatio-temporal dynamics of relationships to realize the trends of ESs change and determine appropriate scale to manage. However, the spatio-temporal dynamics of ESs relationships in the Chinese large basin remain a challenge, as information on adaptable unit to ESs management is often insufficient. Therefore, the purpose of this research is to identify relationships of ESs on sub-watershed and county scales. Six key ESs in Nansihu Basin were selected to simulate and evaluate by InVEST (Integrated Valuation of Ecosystem Services and Tradeoffs) model since the reform and opening-up (1980-2018), which included water yield (WY), water purification (WP), sediment delivery ratio (SDR), carbon storage (CS), habitat quality (HQ), and crop pollination (CP). In this paper, the spatial distributions of six ESs were analyzed and the hotspots of each ES were identified by hot spot analysis in ArcGIS 10.2. Moreover, the spatial and temporal dynamics of relationships among six ESs were analyzed through correlation and principal component analyses via the correlation and principal component analyses. And further analyses were performed on different scales to the relations. The results displayed as follow:(1) in the Nansi Lake Basin, the WY was increasing from 1980 to 2018, while WP, SDR, CS, HQ and CP were decreasing during this periods. (2) The land use types in eastern basin were mainly forest and grassland, which possessed high levels of CS, HQ and CP. The areas with construction land suggested high levels of WY and SDR. (3) There was a significant trade-off relationship between WY and WP, as well as strongly synergetic relationships between WP and HQ, CS, CP occurred in the basin. (4) There was a great difference in relationships between sub-watershed and county scale. Trade-offs mainly occurred between the provisioning service (such as WY) vs the regulating services (such as WP and SDR) and provisioning service (such as WY) vs the supporting service (such as HQ) on sub-watershed scale. While on the county scale, there was a synergetic relationship between the provisioning service and regulating services vs supporting services (such as WY, WP, CS, HQ, CP). Our research provided an assessment framework to spatio-temporal dynamics of ESs relationships, which suggested that sub-watershed unit was suitable for ecological management. Based on the results of different spatial scales, this research provided scientific support for managers to formulate corresponding strategies at appropriate spatial scale and promote eco-economic coordinated development in the Nansihu Lake Basin.

Evaluation on sustainable utilization of water resources in Nansi Lake Basin

Based on the influencing factors of sustainable development by Bossel, the evaluation index system of sustainable utilization of water resources was constructed, which includes 18 indexes considering the development and utilization of water resources, social economy and ecological environment. The evaluation grade was classified into five levels: special, strong, intermediate, light and tiny. Because there were many fuzzy characteristics in this evaluation, this study was constructed an evaluation method of sustainable utilization of water resources based on the variable fuzzy sets model. Taking the Nansi Lake Basin in China as an example, the evaluation method was introduced in detail. The example showed that the evaluation index system constructed in this paper was reasonable and generalized, and the evaluation method was easy to understand, easy to operate and high credibility of the results. In addition, the evaluation results had a certain guiding significance for the sustainable development of water resources.