Yanhe Watershed Research Articles

Multidimensional multiscale complexity analysis of sediment dynamics in the Yanhe Watershed of the loess Plateau, China

The Yanhe Watershed, emblematic of the loess hilly-gully landscape and ecological fragility in China's Loess Plateau, has experienced significant soil erosion and extensive soil-water conservation measures. To elucidate sediment dynamics and identify influencing factors in this region from 1960 to 2020, a novel multidimensional multiscale complexity analysis (MMCA) method was developed, based on entropy and complexity perspectives. This method integrated the refined composite multiscale fuzzy entropy (RCMFE) with multidimensional complexity analysis, offering a nuanced evaluation of sediment complexity and its implications for water resource management and ecological restoration. The findings revealed two distinct stages of sediment complexity variations: 1971–1988 and 2000–present. During the first period, the operation of the Wangyao Reservoir predominantly influenced sediment dynamics, initially reducing sediment complexity through sediment interception but later increasing it during discharge phases, particularly at larger scales. After 2002, extensive vegetation restoration efforts significantly reduced sediment complexity but raised concerns about long-term ecosystem resilience. Over the past decade, urbanization and climate change have exacerbated sediment instability, especially over semi-annual scales. This study advocates for management strategies that prioritize ecosystem sustainability and address the challenges posed by climate change and urbanization, facilitating improved soil and water conservation efforts in the Yanhe Watershed and similar regions in the Loess Plateau.

Spatial and Temporal Heterogeneity of Eco-Environmental Quality in Yanhe Watershed (China) Using the Remote-Sensing-Based Ecological Index (RSEI)

The long-term impacts of climate change and human activities have resulted in the Yanhe watershed, a typical watershed in the Loess Plateau region, exhibiting a high degree of vulnerability and significant heterogeneity in ecological environmental quality. This has led to environmental degradation and complex socio-ecological challenges. Consequently, there is an urgent need to carry out research on the spatial and temporal differentiation patterns of ecological environment quality. By utilizing remote sensing data spanning 21 years, this study evaluated the evolutionary trends and consistency of ecological environment quality (EEQ) within the Yanhe watershed based on the remote-sensing-based ecological index (RSEI). Furthermore, it examined global and local spatial autocorrelation of the RSEI by constructing a hexagonal grid, thereby revealing the spatiotemporal characteristics of EEQ at different scales within the Yanhe watershed. The results were as follows: (1) The EEQ has exhibited an overall upward trend in the past two decades, while it has displayed significant fluctuations; (2) the Global Moran’s I values for the years 2000, 2010, and 2020 were 0.18, 0.32, and 0.21, respectively, indicating a presence of spatial autocorrelation within the RSEI; (3) the overall EEQ of the Yanhe watershed will continue to improve, although the ecological quality in certain areas remains unstable due to local natural conditions and human activities. This research not only contributes to the technical framework for analyzing the spatiotemporal heterogeneity of EEQ but also provides actionable insights for ecosystem restoration and sustainability within the Loess Plateau watershed. Our work advances the understanding of ecological dynamics in semi-arid regions and offers a model for assessing ecological quality in similar environmental contexts.

Hydrological complexity analysis using multiscale entropy: Methodological explorations and insights

Multiscale entropy is a popular and valuable methodology for analyzing hydrological complexity. However, some errors and limitations remain in its use and interpretation. This study identified three key issues, incorrect mapping of entropy values with frequency signals, an insufficient time scale range, and an unclear relationship between features in the multiscale entropy curve and hydrological interpretation. To address these issues, we focused on the sediment concentration and runoff in the Yanhe Watershed and conducted in-depth explorations using refined composite multiscale entropy (RCMFE) and three other methods, power spectrum density analysis, wavelet transform, and surrogate analysis.The results indicate that the entropy at each scale is influenced by signals with time scales equal to or greater than its own scale and that its variation is controlled by the overall signal dispersion. The RCMFE method demonstrated suitability for the complexity analysis of sediment and runoff sequences with short-length data. To effectively capture hydrological complexity, attention to the scale range issue is crucial, ensuring that the richness of complex features at larger scales in multiscale entropy curves is not overlooked. Interpretation of the local minima and maxima in the multiscale entropy curve is highlighted. Local minima signify high periodic patterns and predictability, whereas the first peak, typically occurring at approximately 2–3 months, is a valuable indicator of the overall complexity of the hydrological series. Linear characteristics were found to contribute significantly to the hydrological complexity, with stronger linear correlations resulting in an overall increase, lower local minima, and increased volatility in the multiscale entropy curve. The notable reduction in the hydrological complexity of the Yanhe Watershed calls for ecological sustainability and sustainable soil and water conservation efforts.

Spatial Correlation between Water Resources and Rural Settlements in the Yanhe Watershed Based on Bivariate Spatial Autocorrelation Methods

The production–living–ecological functions of rural settlements are closely tied to water resources, which are the primary influencing factors of the spatial characteristics of rural settlements. However, the specific relationship between water resources and the spatial characteristics of rural settlements remains unclear. Understanding the interrelationship between the two can better safeguard the ecological pattern of the basin and optimize the living environment of settlements. This study utilized multi-source data to calculate the water yield, water demand, and ecological surplus or deficit of water resources in the Yanhe watershed. We quantified the spatial characteristics of rural settlements and employed bivariate spatial autocorrelation methods to analyze the spatial correlation between water resources and the spatial distribution, scale, and boundary form of rural settlements in the Yanhe watershed. The results show the following: ➀ Seven sub-basins in the upper reaches exhibit a severe ecological deficit in water resources, with insufficient water resources to support the demands of regional socio-economic development. The middle and lower reaches have achieved a balance between water supply and demand. ➁ Rural settlements are most densely distributed in the middle reaches, with the smallest area scale, exhibiting a transitional spatial characteristic towards the upstream and downstream ends. ➂ The Moran’s I values of spatial aggregation and morphological index of rural settlements with respect to the ecological surplus or deficit of water resources are 0.36 and 0.50, respectively, indicating a strong positive correlation. The Moran’s I value of the area scale with respect to the ecological surplus or deficit of water resources is −0.60, indicating a significant negative correlation. This research has important practical significance for guiding the spatial layout of rural settlements in the Yanhe watershed and promoting their sustainable development.

An integrated watershed modelling framework to explore the covariation between sediment connectivity and soil erosion

AbstractQuantitative identification of the covariation between sediment connectivity and soil erosion can contribute to provide the key information for watershed sediment management. However, this covariation and its spatiotemporal response mechanisms are still unclear, especially whether this covariation can be used as a basis for identifying critical source areas of sediment in large‐scale ecological restored watersheds. In this study, an integrated methodology framework by the revised universal soil loss equation (RUSLE), index of connectivity (IC) and sediment delivery ratio (SDR) was proposed to visually assess the spatiotemporal characteristics of erosion and sediment yield processes in the Yanhe Watershed with large‐scale ecological restoration from 1985 to 2020 and to identify the covariation between sediment connectivity and erosion in subbasins. The soil erosion estimated by RUSLE has decreased by over 80% since 1985 owing to increased vegetation cover and the effective implementation of soil conservation measures, but the upper reaches still have high erosion intensity due to differences in specific controlling factors such as topographic conditions and land cover, requiring focused soil conservation practice. The IC results showed that as the vegetation restoration and soil conservation measures in the Yanhe Watershed varied from year to year, their spatial and temporal patterns had a strong influence on the distribution of sediment connectivity, and some local areas in the middle reaches showed local minima of IC in 1995, 1998 and 2010 mainly due to the implementation of long‐term ecological restoration project. The developed IC‐Erosion maps indicated that areas with high connectivity but low erosion accounted for over 60% of the total watershed area from 1985 to 1999, demonstrating a reverse correlation between sediment connectivity and erosion. Meanwhile, over 40% of the erosion occurred in a few areas (approximately 20%) with high connectivity and high erosion from 2000 to 2004, which can be characterized as the critical areas of erosion. The methods and results of this study provide ideas for separately defining both erosion and connectivity and quantifying bi‐variable erosion–connectivity classification, which can be easily viewed on a scatterplot.

Water resource security assessment and prediction in a changing natural and social environment: Case study of the Yanhe Watershed, China

Water security is the backbone of regional development. However, it is generally compromised by the increasing competition for water resources between natural and social systems, especially in areas with limited water resources. Sustainable water planning requires a comprehensive analysis of supply and demand patterns, which is difficult owing to scale mismatches in data and methodologies. This study investigated the dynamics and interrelationships of water supply and demand in a semi-arid watershed of the Loess Plateau, China, by developing a system dynamics model that simulates water security during 1980–2020 and future changes under different climate, socioeconomic development, and inter-basin water diversion scenarios during 2021–2050. The results showed that (1) by the end of 2020, the regional water security level gradually approached the water scarcity threshold indicated by the water deficit index surpassing 0; (2) under unfavorable climate and progressive socioeconomic growth conditions, up to 16 out of 30 years of simulation demonstrated water insecurity in the form of a net water quantity deficit; and (3) the water diversion project can offset such deficits in the short term, but potentially aggravates water insecurity risk by eliciting a more rapid socioeconomic growth pattern. The results indicate that curbing demand and improving water-saving technology are instructive in water resource management. For the Yanhe Watershed, the quantity and pattern of water diversion should be improved in the future to guarantee water resource security on a full temporal scale. We suggest a moderate socioeconomic growth rate to be more appropriate for this region and that efforts to solidify water use redlines and advancement in water-saving technologies are essential in the future. This study provides a scientific basis for the long-term evaluation of regional water security on a full timescale with tightly coupled hydrological components and a modeling framework for decision-makers to manage water resources sustainably.

Multiscale Analysis of Runoff Complexity in the Yanhe Watershed

Runoff complexity is an important indicator reflecting the sustainability of a watershed ecosystem. In order to explore the multiscale characteristics of runoff complexity and analyze its variation and influencing factors in the Yanhe watershed in China during the period 1991–2020, we established a new analysis method for watershed runoff complexity based on the complete ensemble empirical mode decomposition with adaptive noise (CEEMDAN) method for the decomposition of multiscale characteristics and the refined composite multiscale entropy (RCMSE) method for the quantification of the system complexity. The results show that runoff and its components all present multiscale complexity characteristics that are different from random signals, and the intermediate frequency modes contribute the most to runoff complexity. The runoff complexity of the Yanhe watershed has decreased gradually since 1991, and 2010 was a turning point of runoff complexity, when it changed from a decline to an increase, indicating that the ecological sustainability of this basin has improved since 2010, which was mainly related to the ecological restoration measures of the Grain for Green Project. This study expands the research perspective for analyzing the variation characteristics of runoff at the multiscale, and provides a reference for the study of watershed ecological sustainability and ecological management.

Evaluation of the impact of the Gully Land Consolidation Project on runoff under extreme rainfall

AbstractExtreme rainfall is an important driver of soil erosion and land damage. The Gully Land Consolidation program (GLCP) was first launched in 2011 as a major land reclamation practice to increase farmland in the Loess Plateau of China. Studying the impact of artificial projects on hydrology can help humans to respond to the various water issues, but the assessment of the effects of the GLCP on extreme rainfall‐induced water runoff at watershed scale is currently lacking. Our study used the soil and water assessment tool (SWAT) to evaluate the influence of the GLCP at different locations and areas on water runoff under extreme rainfall events in the Yanhe watershed. Results showed that: (1) the GLCP can improve the interception of surface runoff, with interception efficiency in downstream of the watershed approximately twice that at midstream and entire watershed as well as seven‐times that at the upstream; (2) when GLCP measures are evenly distributed in a watershed, as the area of GLCP increases from 76.40 km2 (1% of watershed area) to 382.01 km2 (5%), the interception of surface runoff increases by 0.77 mm; (3) and the GLCP can increase soil infiltration and groundwater recharge. This research is expected to provide insights into the optimized layout of the GLCP at watershed scale. Correspondingly, policymakers can refer to this information in developing policies on the sustainable use of land.

Evaluating the flow and sediment effects of gully land consolidation on the Loess Plateau, China

Gully land consolidation (GLC) is a slope-gully reclamation program that was implemented after “Grain for Green” project on the Loess Plateau, China. Through the GLC project, the Chinese government planned to increase the area of cropland by 337.80 km2 from 2013 to 2017. To quantify the impact of GLC on runoff and sediment transport, the coupled SWAT (Soil and Water Assessment Tool) model, which was integrated with a process-based terrace algorithm, was employed in this research. The results showed that the improved SWAT model was proven to be a powerful tool for detecting the effect of GLC on flow and sediment discharge. The effect of GLC on flow and sediment loading was concentrated in the flooding period, its runoff interception efficiency was 169,350 m3/(km2·yr), and sediment trap efficiency was 3979 t/(km2·yr), showing that it had good flow and sediment reduction benefits. However, the GLC project drastically altered the water and sediment flux equilibrium, and excessive expansion was likely to lose parts of riparian-ecosystem functions of the downstream river. In view of this, we integrated the improved SWAT (embedded in the terrace module), double-mass curve and Pettitt test to identify the recommended ratio of GLC area to the total area in the Yanhe watershed. The results demonstrated that if the reclaimed gully area accounted for 0.8% (61 km2) of the total area (7608 km2), the runoff abruptly changed. Therefore, the reclaimed gully area should remain within 0.8% of the total area in the Yanhe watershed, if so, GLC not only alleviates the contradiction between agricultural development and ecological restoration, but also gives full play to its functions of reducing flood and restricting sediment transport.

Watershed Drought and Ecosystem Services: Spatiotemporal Characteristics and Gray Relational Analysis

This study explored the spatiotemporal characteristics of drought and ecosystem services (using soil conservation services as an example) in the YanHe Watershed, which is a typical water basin in the Loess Plateau of China, experiencing soil erosion. Herein, soil conservation was simulated using the Soil and Water Assessment Tool (SWAT), and the relationship between drought, soil conservation services, and meteorological, vegetation, and other factors since the implementation of the ‘Grain for Green’ Project (GFGP) in 1999, were analyzed using the gray relational analysis (GRA) method. The results showed that: (1) The vegetation cover of the Watershed has increased significantly, and evapotranspiration (ET) increased by 14.35 mm·a−1, thereby increasing water consumption by 8.997 × 108 m3·a−1 (compared to 2000). (2) Drought affected 63.86% of the watershed area, gradually worsening from south to north; it decreased in certain middle areas but increased in the humid areas on the southern edge. (3) The watershed soil conservation services, measured by the soil conservation modulus (SCM), increased steadily from 116.87 t·ha−1·a−1 in 2000 to 412.58 t·ha−1·a−1 in 2015, at a multi-year average of 235.69 t·ha−1·a−1, and indicated great spatial variations, with a large variation in the downstream and small variations in the upstream and midstream areas. (4) Integrating normalized difference vegetation index (NDVI) data into SWAT model improved the model simulation accuracy; during the calibration period, the coefficient of determination (R2) increased from 0.63 to 0.76 and Nash–Sutcliffe efficiency (NSE) from 0.46 to 0.51; and during the validation period, the R2 increased from 0.82 to 0.93 and the NSE from 0.57 to 0.61. (5) The GRA can be applied to gray control systems, such as the ecosystem; herein, vegetation cover and drought primarily affected ET and soil conservation services. The analysis results showed that vegetation restoration enhanced the soil conservation services, but increased ET and aggravated drought to a certain extent. This study analyzed the spatiotemporal variations in vegetation coverage and the response of ET to vegetation restoration in the YanHe Watershed, to verify the significant role of vegetation restoration in restraining soil erosion and evaluate the extent of water resource consumption due to ET in the semi-arid and semi-humid Loess-area basin during the GFGP period. Thus, this approach may effectively provide a scientific basis for evaluating the ecological effects of the GFGP and formulating policies to identify the impact of human ecological restoration on ecosystem services.

Multilevel analysis of factors affecting participants' land reconversion willingness after the Grain for Green Program.

Understanding the postprogram land use plans of participants is necessary for the sustainability of the conservation achievements from payments for ecosystem services (PES) programs. Previous studies have analyzed many individual factors affecting participants' reconversion plans after PES programs. However, whether the regional ecosystem services changes caused by PES programs affect reconversion willingness remains elusive. Here, we used the multilevel linear model to determine the effects of regional ecosystem services changes and individual characteristics on participants' land reconversion willingness after the Grain for Green Program (GFGP) in the Yanhe watershed of the Loess Plateau. We found that household income, ecological awareness, and employment changes negatively affected reconversion willingness, while nonfarm employment positively affected it at the individual level. At the regional level, the grain production and water yield changes could influence the reconversion willingness of respondents with different individual characteristics. With improved understanding of the factors affecting reconversion willingness, several suggestions to improve the sustainability of the GFGP were proposed. Our study provides a template for analyzing the multilevel factors that affect the sustainability of other PES programs.

黄土高原植被恢复与生态系统土壤保持服务价值增益研究——以延河流域为例

为探究黄土高原地区退耕还林（草）工程（1999）实施后植被恢复的生态效益，选择黄土高原延河流域为研究区，利用趋势线分析法、SWAT（Soil and Water Assessment Tool）水文模型和生态系统服务价值评价方法（市场价值法、机会成本法、恢复费用法和影子工程法等），重点分析2000-2015年该区域植被恢复状况及其对土壤保持的作用，并评估生态系统服务价值的提升效应。研究结果表明：（1）退耕还林（草）工程实施后，延河流域植被覆盖均呈增加趋势，植被恢复显著；（2）植被恢复对土壤侵蚀的抑制作用明显。在没有植被覆盖的条件下，土壤极易发生侵蚀，且侵蚀模数大；从该工程实施以来，2001-2014年土壤保持量具有不同程度的增幅，表明多年来流域治理取得一定的成效；（3）流域植被覆盖以中覆盖为主，土壤保持量以低保持为主。不同植被覆盖下土壤保持量存在差异。其中，中低、中、中高覆盖能有效保持土壤；（4）生态系统土壤保持服务价值时空分布特征明显。流域年均（2000-2015）土壤保持服务价值为3.64×10⁸元，生长季月均土壤保持服务价值为6.06×10⁷元，生态系统土壤保持服务价值显著提升。时间尺度上，生态系统土壤保持服务价值受降水因素影响；空间尺度上，流域生态系统土壤保持服务价值空间差异大，具体表现为下游残塬平梁沟壑区最高，上游山地区次之，中游梁峁丘陵沟壑区最低。通过研究延河流域植被恢复状况以及定量评估土壤保持服务价值，不仅阐明了退耕还林（草）工程带来的巨大生态效益，同时也为流域乃至黄土高原的水土流失治理工作提供一定的参考作用。;In order to explore the ecological benefits of vegetation restoration after the implementation of the Grain for Green Project (GFGP) in 1999, this study selected the Yanhe Watershed in the Loess Plateau as the study area. By using the trendline analysis, SWAT (Soil and Water Assessment Tool) Model and the evaluation approach of ecosystem services (including market value, opportunity cost, restoration cost, and shadow project approaches), the paper analyzed the vegetation restoration status and its effect on soil conservation after the implementation of the GFGP, and assessed the effect of ecosystem service value enhancement. The results showed that:(1) since the GFGP was implemented, the vegetation recovery effect has been remarkable, which was specifically reflected in the increasing trend of vegetation coverage in the Yanhe Watershed from 2000 to 2015. (2) The effect of vegetation restoration on soil erosion was obvious. Without vegetation cover, the soil is prone to erosion with the large erosion modulus. Taking 2000 as the base year when the GFGP was implemented, the soil conservation from 2001 to 2014 has increased to varying degrees, indicating that the watershed management has achieved certain outcomes over the years. (3) The vegetation cover in the watershed is dominated by medium vegetation cover, and the soil conservation is dominated by low soil conservation. There are differences in soil conservation under different vegetation cover. Among them, medium-low, medium and medium-high vegetation cover can effectively maintain the amount of soil. (4) The temporal and spatial distribution characteristics of the value of the ecosystem soil conservation services are obvious. From 2000 to 2015, the annual average soil conservation service value of the watershed was 3.64×10⁸ yuan, and the monthly average soil conservation service value was 6.06×10⁷ yuan during the growing season. The value of the ecosystem soil conservation service increased significantly. On the temporal scale, the precipitation is an important factor in the value of the ecosystem soil conservation service; on the spatial scale, the spatial differences in the value of ecosystem soil conservation service in the watershed is large, which is specifically manifested as the highest in the downstream, followed by the upstream, and the lowest in the middle-stream. This study not only clarified the huge ecological benefits brought by the GFGP, but also provided a certain reference role for the soil and water loss management in the watershed and even the Loess Plateau.

A network perspective for mapping freshwater service flows at the watershed scale

Spatial mismatch often occurs between high-supply and high-demand regions of ecosystem services (ES), as human dwellings and workplaces are usually distant from natural ecosystems. In this regard, studies have increasingly focused on ecosystem service flows (ESF) from ecosystems to humans. However, current mapping methods for ESF are rarely able to visually display the flow relationships between supply and demand regions. Network models that commonly used for dealing with relational data show great potential in mapping ESF. Here, we demonstrated the effectiveness of the network model in mapping ESF by constructing a freshwater service flow network for the Yanhe watershed in China. We concluded that from 2000 to 2015 freshwater demand was approaching the limit of freshwater supply in the Yanhe watershed, with the freshwater demand continuously increasing. Due to the shortage of freshwater service, the deficit nodes and stop-flowing edges in the freshwater service flow network increased, and the network density decreased. These results can provide useful information to guide watershed freshwater resource management (e.g. optimizing the allocation of freshwater resources across the watershed and designing payment schemes for freshwater service) in the Yanhe watershed, particularly in a time of population growth, climate change, and threats of water scarcity. Finally, we pointed out that applications of the network model in ESF deserves more attention and further study and analyzed the wide applicability of the network model in mapping ESF and the possible future efforts in this field.

延河流域水供给服务供需平衡与服务流研究

PDF HTML阅读 XML下载 导出引用 引用提醒 延河流域水供给服务供需平衡与服务流研究 DOI: 10.5846/stxb201811132456 作者: 作者单位: 作者简介: 通讯作者: 中图分类号: 基金项目: 国家自然科学基金项目（41771198，41771576）；陕西省自然科学基础研究计划项目（2018JM4010） Quantification and simulation of supply, demand and flow of water provision service in the Yanhe watershed, China Author: Affiliation: Fund Project: 摘要 | 图/表 | 访问统计 | 参考文献 | 相似文献 | 引证文献 | 资源附件 | 文章评论 摘要:水供给服务的供需定量评估与空间制图是当前研究的核心与前沿议题，然而耦合人类需求与自然过程进行供需时空关联分析和服务流模拟仍需进一步加强。以延河流域为研究区，基于GIS手段和SWAT模型，融合多源数据构建了水供给服务供需平衡与空间流动模型，从子流域尺度探究了延河流域水供给服务的供需空间匹配特征与流动规律，明确流域供给区和受益区的空间范围与流量。研究结果表明：1）2005-2015年延河流域水供给量先增多后减少，水需求量则逐年增多，供需平衡状况在逐年恶化。到2015年，流域的水资源安全指数（Freshwater Security Index，FSI）仅为0.095。2）延河流域水供给服务的供给与需求在空间分布上呈现显著的不匹配特征，尤其是位于延河中游的延安市区及周边地区，水资源供需矛盾突出。3）在水供给服务流研究的框架下，本文明确了流域内4个主要受益区的空间范围及其接受的相应上游子流域（供给区）提供的服务流量，分别为安塞城区、延安市区、青化砭镇、延长县城区及其附近城镇。本评估模型与研究结果不仅可以为实现延河流域水资源的合理配置和保障流域用水安全提供科学依据，也可以为其他流域的水资源管理提供参考。 Abstract:Quantitative assessment and spatial mapping of supply and demand of water provision service are frontier issues of current research. However, the spatial-temporal connections of supply and demand and the space flow of water provision service still need to be further strengthened. In this study, the Yanhe watershed was selected as the study area. Based on GIS technology and SWAT model, the supply-demand balance and spatial flow models of the water provision service were proposed by integrating multi-source data. According to the proposed methods, the spatial matching characteristics and flow laws of the water provision service in Yanhe watershed were explored at the sub-basin scale. Moreover, the spatial scope of the provisioning and benefitting areas of the basin were determined. The results showed that, from 2005 to 2015, the water supply first increased and then decreased, while the water demand increased year by year. The supply-demand balance of the water provision service deteriorated year by year, and the freshwater security index (FSI) was reported to be 0.095 in 2015. Significant mismatch in the spatial distribution was observed in terms of the supply and demand of the water provision service in Yanhe watershed. This was particularly evident in urban area and surrounding areas of Yan'an city, which is located in the middle reaches of Yanhe watershed, where the contradiction between supply and demand of the water resources was prominent. Under the framework of the water provision service flow, the study defined the spatial scope of the four main benefiting areas within the water basin and the service flow provided by the corresponding upstream sub-basins (provisioning areas), which included the urban areas of Ansai county and Yan'an city, Qinghuabian town, and Yanchang county. The framework and results presented in the study not only provide a scientific basis for realizing the rational allocation of water resources and ensuring water security in the Yanhe River basin, but also provide a reference for the management of water resources in other basins. 参考文献 相似文献 引证文献

Quantitative Analysis of Hydrological Responses to Climate Variability and Land-Use Change in the Hilly-Gully Region of the Loess Plateau, China

Climate and land-use change are the two main driving forces that affect watershed hydrological processes. Separately assessing their impacts on hydrology is important for land-use planning and water resource management. In this research, the SWAT (Soil and Water Assessment Tool) and statistical methods were applied to evaluate the effects of climate and land-use change on surface hydrology in the hilly-gully region of the Loess Plateau. The results showed that surface runoff and soil water presented a downward tendency, while evapotranspiration (ET) presented an upward tendency in the Yanhe watershed from 1982 to 2012. Climate is one the dominant factors that influence surface runoff, especially in flooding periods. The average contribution rate of surface runoff on stream flow accounted for 55%, of which the flooding period accounted for 40%. The runoff coefficient declined by 0.21 after 2002 with the land-use change of cropland transformed to grassland and forestland. The soil water exhibited great fluctuation along the Yanhe watershed. In the upstream region, the land-use was the driving force to decline soil water, which reduced the soil water by 51%. Along the spatial distribution, it converted from land-use change to climate variability from northwest to southeast. The ET was more sensitive to land-use change than climate variability in all sub-basins, and increased by 209% with vegetation restoration. To prevent the ecosystem degradation and maintain the inherent ecological functions of rivers, quantitative assessment the influence of climate variability and land-use change on hydrology is of great importance. Such evaluations can provide insight into the extent of land use/cover change on regional water balance and develop appropriate watershed management strategies on the Loess Plateau.

Socio-cultural valuation of rural and urban perception on ecosystem services and human well-being in Yanhe watershed of China

Rapid environment change and urbanization process have profoundly altered the socio-ecological relationships and influenced on how local residents perceive ecosystem services (ES) and human well-being (HW). However, the quantified socio-cultural valuation of rural-urban comparison is still insufficient. In this study, we investigated the perception on provisioning, regulating, and cultural ES importance and HW satisfaction degree of basic materials, health, security, and social relations. Subsequently, we explored the linkages between and within ES and HW by face-to-face interviews with urban and rural residents. The results showed that rural residents valued more genetic resources, flood regulation, erosion regulation, and aesthetics ES, while urban residents gave high importance to wood & fiber ES. Overall, urban residents valued provisioning ES, while rural residents valued regulating ES. No difference was observed in cultural ES. For HW, rural residents felt more satisfied with security and health, while urban residents were more satisfied with basic materials. We observed strong relationships among provisioning and regulating ES in rural and urban communities, and the same was observed as in health and security HW. Principal component analysis (PCA) results showed the different variable associations in rural ES and urban HW as well as different groups in urban ES and rural HW. Through confirmation factor analysis (CFA), we screened out freshwater, water purification, air purification, and cultural value as dominant ES indicators for rural and urban population according to the framework of Millennium Ecosystem Assessment in Yanhe watershed. The assessment of people's perception can contribute to the integration of socio-cultural values into the policymaking process.

Scale effects of vegetation restoration on soil and water conservation in a semi-arid region in China: Resources conservation and sustainable management

The scale effect of vegetation restoration on soil and water conservation has received little attention, despite numerous studies on the assessments of vegetation restoration at different spatial scales. This study investigated the scale effect of vegetation restoration on soil erosion and water yield at Yanhe watershed, Chinese Loess Plateau. It provides the site-based temporal and spatial varying relationships among vegetation restoration, soil erosion, and water yield. Spatial modeling and mapping methods were used to analyze the scale effect at regional and sub-watershed scales. Our results indicated vegetation restoration has generated positive impacts on soil erosion reduction and negative impacts on water provision in the whole watershed. Croplands, sparse grasslands, and moderate grasslands were the land types which contributed the most to soil erosion. The decrease of cropland was the major contribution to soil erosion reduction. Moreover, the trade-off relationship between soil erosion and water yield existed in the whole watershed, but the degree of trade-off varied from one sub-watershed to another. High-risk soil erosion regions were concentrated in the central watershed. But in this region, the impacts of vegetation restoration on soil erosion control varied with different sub-watersheds. A simple increase of vegetation might not help reduce soil erosion in sub-watersheds where are characterized by low vegetation coverage and scattered vegetation restoration. Vegetation restoration should be based on past spatial LULC patterns. Soil erosion control should focus on the current level of cropland management and areas of vegetation maintenance than new afforestation in the high-risk soil erosion regions.

Pathways from payments for ecosystem services program to socioeconomic outcomes

Payment for ecosystem services (PES) is a widely accepted policy tool for achieving environmental conservation and socioeconomic development goals. However, the mechanisms through which PES programs affect socioeconomic outcomes remain elusive. Here, we use a framework which integrates links between PES programs, livelihood activities, and socioeconomic outcomes, to determine how China’s Grain-to-Green Program (GTGP) has affected the incomes of participating households in the Yanhe watershed of the Loess Plateau. The results show that although the total effect of the GTGP on household income is not statistically significant, there are still two significant pathways. Through the analysis we found that implementation of the GTGP significantly increased the participations in local non-farm jobs, which leads to increased household incomes. Based on our findings, we suggest several ways of improving the socioeconomic outcomes of the GTGP through increasing non-farm work benefit of participating households, maximizing the positive effect of economic forest, and reducing the reliance of households on income from crop production. Our study provides a template for revealing the underlying pathways to socioeconomic outcomes of PES programs – crucial knowledge if we are to design and implement better PES programs and achieve the desired environmental conservation and poverty reduction goals.

Soil aggregate stability under different rain conditions for three vegetation types on the Loess Plateau (China)

Soil aggregate stability is essential for moderating the soil quality and preventing soil erosion. Vegetation restoration may effectively increase the stability of soil aggregates via soil organic matter. This study was designed to investigate the effects of vegetation types with long-term revegetation on the soil aggregate characteristics. Three vegetation type zones (grass land, forest-grass land and forest land) were selected in the Yanhe Watershed (northwest China) as the subjects. Soil aggregate stability was determined by the method of Le Bissonnais, including three disruptive tests: fast wetting (FW), slow wetting (SW) and mechanical breakdown (WS). The results showed that the mean weighted diameter (MWD) significantly differed from the tests and vegetation types. In the 0–10 cm soil layer, MWD ranged from 2.65 to 3.26 mm for the SW test, which corresponded to very stable soil aggregate; they ranged from 0.53 to 1.08 mm for the WS test, and from 0.57 to 1.96 mm for the FW test, both of which corresponded to very unstable soil aggregates. In the 10–20 cm soil layer, MWD ranged from 2.75 to 3.33 mm for the SW test, 0.39 to 0.83 mm for the WS test, and 0.44 to 1.37 mm for the FW test. The MWDs under the three tests were the lowest for the grass land at both soil layers, and the MWDs for the WS and FW tests were significantly lower than the MWD for the SW test. In all three tests, MWDs showed the same order: forest land > forest-grass land > grass land. MWD indicated that forest land had much stronger ability to resist soil erosion no matter the rain conditions. The correlations between soil organic matter content and MWD for the FW and WS tests were significant (P < 0.05). These results demonstrated that vegetation types had significant effects on the soil aggregates under the different rain conditions, and the soil organic matter and clay contents were significantly related to the soil aggregate stability. These results will guide the practice of reducing soil erosion for the different conditions and different vegetation types.

A NEW MULTI-SPECTRAL THRESHOLD NORMALIZED DIFFERENCE WATER INDEX (MST-NDWI) WATER EXTRACTION METHOD – A CASE STUDY IN YANHE WATERSHED

Abstract. Accurate remote sensing water extraction is one of the primary tasks of watershed ecological environment study. Since the Yanhe water system has typical characteristics of a small water volume and narrow river channel, which leads to the difficulty for conventional water extraction methods such as Normalized Difference Water Index (NDWI). A new Multi-Spectral Threshold segmentation of the NDWI (MST-NDWI) water extraction method is proposed to achieve the accurate water extraction in Yanhe watershed. In the MST-NDWI method, the spectral characteristics of water bodies and typical backgrounds on the Landsat/TM images have been evaluated in Yanhe watershed. The multi-spectral thresholds (TM1, TM4, TM5) based on maximum-likelihood have been utilized before NDWI water extraction to realize segmentation for a division of built-up lands and small linear rivers. With the proposed method, a water map is extracted from the Landsat/TM images in 2010 in China. An accuracy assessment is conducted to compare the proposed method with the conventional water indexes such as NDWI, Modified NDWI (MNDWI), Enhanced Water Index (EWI), and Automated Water Extraction Index (AWEI). The result shows that the MST-NDWI method generates better water extraction accuracy in Yanhe watershed and can effectively diminish the confusing background objects compared to the conventional water indexes. The MST-NDWI method integrates NDWI and Multi-Spectral Threshold segmentation algorithms, with richer valuable information and remarkable results in accurate water extraction in Yanhe watershed.