Physical geography is a basic research subject of natural sciences. Its research object is the natural environment which is closely related to human living and development, and China’s natural environment is complex and diverse. According to national needs and regional development, physical geographers have achieved remarkable achievements in applied basis and applied research, which also has substantially contributed to the planning of national economic growth and social development, the protection of macro ecosystems and resources, and sustainable regional development. This study summarized the practice and application of physical geography in China over the past 70 years in the following fields: regional differences in natural environments and physical regionalization; land use and land cover changes; natural hazards and risk reduction; process and prevention of desertification; upgrading of medium- and low-yield fields in the Huang-Huai-Hai region; engineering construction in permafrost areas; geochemical element anomalies and the prevention and control of endemic diseases; positioning and observation of physical geographical elements; and identification of geospatial differentiation and geographical detectors. Furthermore, we have proposed the future direction of applied research in the field of physical geography.

Sensitivity assessment is useful for monitoring land desertification. Research into how to prevent and control desertification is also important. In the arid region of northwest China, desertification is becoming worse and is a serious problem that affects local sustainable development. Based on remote-sensing and geographic information system technology, this study establishes a “soil-terrain-hydrology-climate-vegetation” desertification sensitivity comprehensive evaluation system to reflect the spatiotemporal changes of land desertification, and proposes a spatial distance model to calculate a desertification sensitivity index. The spatiotemporal change characteristics of land desertification sensitivity in northwest China are quantitatively assessed from 2000 to 2017. Moreover, the main driving factors are analyzed using the geographical detector method. The results show the following. (1) Terrain, soil, climate, vegetation and hydrology affect and restrict each other, and constitute the background conditions of the distributions and changes of sensitivity to desertification in northwest China. (2) Desertification sensitivity generally displays a low distribution characteristic on the periphery of the area and a high one in the interior. The low-sensitivity regions are mainly in the five major mountain ranges (Altai Mountains, Tianshan Mountains, Kunlun Mountains, Altun Mountains and Qilian Mountains), while the high-sensitivity regions are mainly in regions such as the Junggar Basin, the Tarim Basin and the Inner Mongolia Plateau, as well as the Taklimakan Desert, Badain Jaran Desert and Tengger Desert. The spatial distribution of desertification sensitivity is obviously regional, and the high- and low-sensitivity regions have clear boundaries and a concentrated distribution. (3) With regard to spatiotemporal evolution, changes in desertification sensitivity since 2000 have been predominantly stable, and the overall sensitivity has displayed a slowly decreasing trend, indicating that potential desertification regions are decreasing annually and that some achievements have been made in the control of regional desertification. (4) Soil and climate play a direct role in the driving factors of desertification in northwest China, and these have been found to be the most important influential factors. Vegetation is the most active and basic factor in changing the sensitivity. In addition, topography and hydrology play a role in restricting desertification changes. Socio-economic factors are the most rapid factors affecting regional desertification sensitivity, and their impacts tend to be gradually increasing. In general, desertification has been effectively controlled in northwest China, and positive results have been achieved in such control. However, against the backdrop of intensified global climate change, increasingly prominent human activities and new normals of socio-economic development, the monitoring, assessment and control of desertification in China still have a long way to go.

Water retention is important in forest ecosystem services. The heterogeneity analysis of water-retention capacity and its influencing factors is of great significance for the construction of water-retention functional areas, restoration of vegetation, and the protection of forest ecosystems in the Beijing-Tianjin-Hebei region. A total of 1366 records concerning water-retention capacity in the canopy layer, litter layer, and soil layer of forest ecosystem in this region were obtained from 193 literature published from 1980 to 2017. The influencing factors of water-retention capacity in each layer were analyzed, and path analysis was used to investigate the contribution of the factors to the water-retention capacity of the three layers. The results showed that mixed forests had the highest water-retention capacity, followed by broad-leaved forests, coniferous forests, and shrub forests. In addition, no matter the forest type, the ranking of the water-retention capacity was soil layer, canopy layer, and litter layer from high to low. The main influencing factors of water-retention capacity in forest canopy were leaf area index and maximum daily precipitation (R ²=0.49), and the influencing coefficients were 0.34 and 0.30, respectively. The main influencing factors of water-retention capacity in the litter layer were semi-decomposed litter (R ²=0.51), and the influencing coefficient was 0.51. The main influencing factors of water-retention capacity in the soil layer were non-capillary porosity and soil depth (R ²=0.61), the influencing coefficients were 0.60 and 0.38, respectively. This study verifies the simulation of the water balance model or inversion of remote sensing of the water-retention capacity at the site scale, and provides scientific basis for further study of the impact of global change on water retention.

Environmental stress is used as an indicator of the overall pressure on regional environmental systems caused by the output of various pollutants as a result of human activities. Based on the pollutant emissions and socioeconomic databases of the counties in Beijing-Tianjin-Hebei region, this paper comprehensively calculates the environmental stress index (ESI) for the urban agglomeration using the entropy weight method (EWM) at the county scale and analyzes the spatiotemporal patterns and the differences among the four types of major functional zones (MFZ) for the period 2012-2016. In addition, the socioeconomic driving forces of environmental stress are quantitatively estimated using the geographically weighted regression (GWR) method based on the STIRPAT model framework. The results show that: (1) The level of environmental stress in the Beijing-Tianjin-Hebei region was significantly alleviated during that time period, with a decrease in ESI of 54.68% by 2016. This decrease was most significant in Beijing, Tangshan, Tianjin, Shijiazhuang, and other central urban areas, as well as the Binhai New Area. The level of environmental stress in counties decreased gradually from the central urban areas to the suburban areas, and the high-level stress counties were eliminated by 2016. (2) The spatial spillover effect of environmental stress increased further at the county scale from 2012 to 2016, and spatial locking and path dependence emerged in the cities of Tangshan and Tianjin. (3) Urbanized zones (development-optimized and development-prioritized zones) were the major areas bearing environmental pollution in the Beijing-Tianjin-Hebei region in that time period. The ESI accounted for 65.98% of the whole region, where there was a need to focus on the prevention and control of environmental pollution. (4) The driving factors of environmental stress at the county scale included population size and the level of economic development. In addition, the technical capacity of environmental waste disposal, the intensity of agricultural production input, the intensity of territorial development, and the level of urbanization also had a certain degree of influence. (5) There was spatial heterogeneity in the effects of the various driving factors on the level of environmental stress. Thus, it was necessary to adopt differentiated environmental governance and reduction countermeasures in respect of emission sources, according to the intensity and spatiotemporal differences in the driving forces in order to improve the accuracy and adaptability of environmental collaborative control in the Beijing-Tianjin-Hebei region.

A clear understanding of the relationships among multiple ecosystem services (ESs) is the foundation for sustainable urban ecosystem management. Quantitatively identifying the factors that influence ES trade-offs and synergies can contribute to deepening ES research, from knowledge building to decision making. This study simulated soil conservation, water yield and carbon sequestration in Beijing, China, from 2015-2018. The spatial trade-offs and synergies of these three ESs within the five major river basins in Beijing were explored using geographically weighted regression. Furthermore, geographical detector was applied to quantitatively identify the driving mechanism of the environmental factors for the ES trade-offs and synergies. The results show the following: (1) the spatial relationships between soil conservation and water yield, as well as between water yield and carbon sequestration, were mainly trade-offs. There was a spatial synergy between soil conservation and carbon sequestration. (2) Regarding the spatial trade-off/synergy between soil conservation and water yield in Beijing, the dominant influencing factor was temperature/elevation, and the dominant interactions of the spatial trade-off and synergy between these two ESs in Beijing and the Chaobai River Basin are all manifested in the superposition of precipitation and potential evapotranspiration, temperature, and elevation. (3) Topographic factors were the dominant factors influencing the spatial relationship between soil conservation and carbon sequestration in Beijing and its five major river basins. As a result of the distribution of water systems and hydrological characteristics of the basins, differences were observed in the effects of different combinations of interaction factors on the spatial relationship between these two ESs in different basins. (4) Temperature had the strongest explanatory power in terms of the spatial trade-offs and synergies between water yield and carbon sequestration. The interactions between precipitation and temperature and between precipitation and elevation were the dominant interactions affecting the spatial relationship between water yield and carbon sequestration in Beijing. Overall, the explanatory power of influencing factors on the trade-offs and synergies and the degree of interaction between factors coexist in different basins with consistency and differences. Therefore, understanding the quantitative characteristics of basin-scale spatial trade-offs and synergies between ESs is important for ecosystem management and the promotion of synergy in different basins.

Exploring the spatio-temporal dynamics of poverty is important for research on sustainable poverty reduction in China. Based on the perspective of development geography, this paper proposes a panel vector autoregressive (PVAR) model that combines the human development approach with the global indicator framework for Sustainable Development Goals (SDGs) to identify the poverty-causing and the poverty-reducing factors in China. The aim is to measure the multidimensional poverty index (MPI) of China’s provinces from 2007 to 2017, and use the exploratory spatio-temporal data analysis (ESTDA) method to reveal the characteristics of the spatio-temporal dynamics of multidimensional poverty. The results show the following: (1) The poverty-causing factors in China include the high social gross dependency ratio and crop-to-disaster ratio, and the poverty-reducing factors include the high per capita GDP, per capita social security expenditure, per capita public health expenditure, number of hospitals per 10,000 people, rate of participation in the new rural cooperative medical scheme, vegetation coverage, per capita education expenditure, number of universities, per capita research and development (R&D) expenditure, and funding per capita for cultural undertakings. (2) From 2007 to 2017, provincial income poverty (IP), health poverty (HP), cultural poverty (CP), and multidimensional poverty have been significantly reduced in China, and the overall national poverty has dropped by 5.67% annually. there is a differentiation in poverty along different dimensions in certain provinces. (3) During the study period, the local spatial pattern of multidimensional poverty between provinces showed strong spatial dynamics, and a trend of increase from the eastern to the central and western regions was noted. The MPI among provinces exhibited a strong spatial dependence over time to form a pattern of decrease from northwestern and northeastern China to the surrounding areas. (4) The spatio-temporal networks of multidimensional poverty in adjacent provinces were mainly negatively correlated, with only Shaanxi and Henan, Shaanxi and Ningxia, Qinghai and Gansu, Hubei and Anhui, Sichuan and Guizhou, and Hainan and Guangdong forming spatially strong cooperative poverty reduction relationships. These results have important reference value for the implementation of China’s poverty alleviation strategy.

Location advantages of ports refer to the current developments of ports based on their conditions, such as geographic location, traffic accessibility and hinterland economy, etc., and the spatial pattern of ports’ location advantages reflects the spatial distributions, the regularities and the correlations among their conditions for development. A good understanding of the spatial patterns of ports’ location advantages can help to better identify the relative advantages of ports, position ports’ functions and make strategic plans for development. This paper selected 1259 ports from 63 countries along the Maritime Silk Road as research objects and builds an accessing model to analyze their location advantages on the bases of six factors: the influence of strategic shipping pivot, the competitiveness of port location potential, port network status, the influence of city, the influence of traffic trunk, and road network density in hinterland. The study has the following three findings. Firstly, the location advantages of ports show a “high-low-high” distribution pattern from the west to the east, displaying an obvious “core-periphery” regionalized distribution. Secondly, most ports have high location advantages, mainly located in Strait of Malacca, the United Arab Emirates, northern Mediterranean coastal region and China-Japan region, the top 10 ports are mainly located in Singapore, China, Malaysia and Japan, indicating that the shipping industry in Asia-Pacific region has stepped to the far front of the global competition; slow economic growths, wars, far away from the Belt and Road countries or bad climate have low location advantages, mainly located in African coastal areas, Oceania, Northeast Europe and Russia. Thirdly, compared with the landward location advantages, the seaward location advantages have a higher influence, and different indicators of location advantages have different influences on the evaluation results, the competitiveness of port location potential being the core indicator.

Mobile internet and wireless communication technologies have produced unprecedented location-aware data. Such big geospatial data can be used as a proxy measure of the ‘digital footprints’ left by us on the planet and provide a valuable opportunity to understand the dynamic and short-term human disturbance on the nature at fine scales. This study investigated the spatiotemporal variations of human’s digital footprints on the Qinghai-Tibet Plateau using smartphone-users-generated Tencent’s location request data. The results showed that human’s digital footprints cover less than 5% of Qinghai and Tibet, exhibiting either a U-shaped or an N-shaped temporal change pattern during the major festivals. Spatial changes of the digital footprints manifested a transition process from dispersion to concentration in Xining and Lhasa. Human disturbance assessment of seven large nature reserves on the plateau showed that the Qinghai Lake is the most disturbed one as shown by 14.6% of its area is stained with human digital footprints and the areal average of footprint intensity is 1.59, and the disturbance was significantly escalated during the National Day holiday. By contrast, the Qangtang and Hoh Xil are the least affected nature reserves with the two indices less than 1% and 0.1, respectively.

Developing a comprehensive understanding of inter-city interactions is crucial for regional planning. We therefore examined spatiotemporal patterns of population migration across the Qinghai-Tibet Plateau (QTP) using migration big data from Tencent for the period between 2015 and 2019. We initially used decomposition and breakpoint detection methods to examine time-series migration data and to identify the two seasons with the strongest and weakest population migration levels, between June 18th and August 18th and between October 8th and February 15th, respectively. Population migration within the former period was 2.03 times that seen in the latter. We then used a variety of network analysis methods to examine population flow directions as well as the importance of each individual city in migration. The two capital cities on the QTP, Lhasa and Xining, form centers for population migration and are also transfer hubs through which migrants from other cities off the plateau enter and leave this region. Data show that these two cities contribute more than 35% of total population migration. The majority of migrants tend to move within the province, particularly during the weakest migration season. We also utilized interactive relationship force and radiation models to examine the interaction strength and the radiating energy of each individual city. Results show that Lhasa and Xining exhibit the strongest interactions with other cities and have the largest radiating energies. Indeed, the radiating energy of the QTP cities correlates with their gross domestic product (GDP) (Pearson correlation coefficient: 0.754 in the weakest migration season, WMS versus 0.737 in the strongest migration season, SMS), while changes in radiating energy correlate with the tourism-related revenue (Pearson correlation coefficient: 0.685). These outcomes suggest that level of economic development and level of tourism are the two most important factors driving the QTP population migration. The results of this analysis provide critical clarification guidance regarding huge QTP development differences.

As one of the most ecologically sensitive issues in the world, migration now plays an important role in population growth on the Qinghai-Tibet Plateau. To promote sustainable development in the world’s third pole, it is necessary to investigate population migration on the Plateau. Using 2010 census data, a spatial database of county-level migrants on the Plateau was constructed, and migrants were divided into short-distance and long-distance migrants according to the hukou-registered origins. Measuring migration intensity allowed the spatial pattern of population migration on the Plateau to be ascertained. The driving factors were identified using spatial regression models, and the main conclusions are as follows: (1) In 2010, there were 1.23 million inter-county migrants on the Qinghai-Tibet Plateau, and the overall migration intensity reached 10.50%. There existed significant spatial differences in population migration intensity on the Plateau at that time, and the provincial or prefectural capitals were attractive destinations for migrants. Northwestern Qinghai, which boasted mining industries, constituted a significant spatial cluster with a relatively high migration intensity. However, most areas on the Plateau attracted relatively few migrants, especially in western and northern parts of Tibet, which were sparsely populated and uninhabitable. (2) There were 0.95 million short-distance migrants and 0.28 million long-distance migrants. The short-distance migration intensity was 8.14%, while the long-distance migration intensity was only 2.36%. Short-distance migration was the main form of population migration, with a pattern similar to the layout of overall population migration intensity. Only a few county-level units strongly attracted long-distance migrants, which were mostly distributed in northwestern Qinghai. (3) Economic factors were considered fundamental drivers for migrants to live on the Plateau. Destinations with high levels of economic development and more opportunities in non-agricultural jobs proved more attractive for migrants. For short-distance migrants, urbanization level also proved a considerable driving factor for in-migration. However, long-distance migrants were mainly affected by the job chances of the secondary industry on the Qinghai-Tibet Plateau.

Human migration between cities is one important aspect of spatial interaction that not only reflects urban attractiveness but also denotes interactions amongst agglomerations. We therefore implemented a web-based visualization system to analyze and interactively explore local and distant population flow patterns between cities on the Qinghai-Tibet Plateau (QTP). We utilized 2017 Tencent population flow data from which we initially constructed inbound and outbound vectors for cities on the QTP. We then used multidimensional scaling to examine and visualize migration patterns and similarities between cities. Results reveal the presence of six local and three distant human mobility patterns on the QTP as well as average summer monthly migrations more than twice the level of those in the winter.

The cultivation and development of modern metropolitan areas with the aim of establishing new regional centers with competitive edge is a key objective for the new-type urbanization directions in China. The construction of the Lhasa Metropolitan Area is of great significance for the promotion of the South Asia Channel, the ‘Belt and Road’ initiative, the Bangladesh-China-India-Myanmar Economic Corridor, the Himalaya Economic Cooperation Zone, and for rapid development and long-term stability of the Qinghai-Tibet Plateau. This paper examines the scope of the Lhasa Metropolitan Area including Chengguanqu (Chengguan District), Doilungdeqen, Dagze, Lhunzhub, Damxung, Nyemo, Quxu, Maizhokunggar, Samzhubze Qu (Samzhubze District), Gyangze, Rinbung, Bainang, Nedong, Gonggar, and Zhanang using a spatial field energy model that combines nodality and accessibility indices and considers multiple indicators including traffic flow between cities. By combining factors such as the natural background, population agglomeration, the social economy, infrastructure construction, and the urban spatial structure of the Lhasa Metropolitan Area, it is proposed to build a bow-and-arrow-shaped urban system with ‘one core, two centers, one axis, and two wings’ along the valleys and the transportation trunk lines of the area. The study advocates the construction of a pure land industrial system comprising a green cultural and tourism-oriented plateau.

Based on a total of 519 images, the composite images with the lowest possible cloud cover were generated at pixel level with image synthesis method on Google Earth Engine (GEE) platform. The Remote Sensing Ecological Index (RSEI) was adopted, and calculated in an efficient way with the assistance of parallel cloud computing of the GEE platform. The RSEI was used in this paper to evaluate and monitor the eco-environmental quality of the Lhasa Metropolitan Area. Results show that: (1) The ecological quality is better in the west than in the east of Lhasa Metropolitan Area, with Lhasa as an approximate dividing point. The ecological quality improved and then deteriorated dramatically before 2000, with the mean RSEI value dropping from 0.51 to 0.46; the trend was followed by a gradual increase up until 2017, with the mean RSEI value increased from 0.46 to 0.55. (2) The RSEI is weakly and positively correlated with socioeconomic indicators. This indicates that the population growth and economic development did not negatively influence the ecological quality, but actually boosted it. (3) The GEE can serve as an efficient computing platform for the assessment and monitoring of eco-environmental quality in vast regions.

The Yarlung Zangbo River Basin (YZRB) is a key ecological protection area on the Qinghai-Tibet Plateau (QTP). Determination of the ecosystem service values (ESVs) can help recognize the benefits of sustainable management. It is gradually becoming the main path that constructs plateau spatial planning of integrating ecological protection, and achieves global sustainable development goals (SDGs) in China. In this paper, the spatio-temporal dynamic evolutions of the ESVs were estimated on the multiple scales of “basin, subbasin and watershed” from 1980 to 2015. The main factors influencing ESVs were explored in terms of physical geography, human activities, and climate change. It had been proposed that sustainable spatial planning including ecological protection, basin management, and regional development was urgent to set up. Our results show that the increase in wetland and forest and results in an increase of 9.4% in the ESVs. Attention should be paid to the reduction of water and grassland. Water conservation (WC), waste treatment (WT), and soil formation and conservation (SFC) are the most important ecosystem services in the YZRB. At present, the primary problem is to solve the ESVs decreasing caused by glacier melting, grassland degradation, and desertification in the upper reaches region. The middle reaches should raise the level of supply services. Regulation services should be increased in the lower reaches region on the premise of protecting vegetation. The ESVs in adjacent watersheds are interrelated and the phenomenon of “high agglomeration and low agglomeration” is obvious, existing hot-spots and cold-spots of ESVs. Additionally, when the altitude is 4500-5500 m, the temperature is 3-8°C, and the annual precipitation is 350-650 mm, ESVs could reach its maximum. A framework of sustainable plateau spatial planning could provide references to delimit the ecological protection red line, key ecological function zone, and natural resource asset accounting on the QTP.

Land cover change has presented clear spatial differences in the New Eurasian Continental Bridge Economic Corridor (NECBEC) region in the 21st century. A spatiotemporal dynamic probability model and a driving force analysis model of land cover change were developed to analyze explicitly the dynamics and driving forces of land cover change in the NECBEC region. The results show that the areas of grassland, cropland and built-up land increased by 114.57 million ha, 8.41 million ha and 3.96 million ha, and the areas of woodland, other land, and water bodies and wetlands decreased by 74.09 million ha, 6.26 million ha, and 46.59 million ha in the NECBEC region between 2001 and 2017, respectively. Woodland and other land were mainly transformed to grassland, and grassland was mainly transformed to woodland and cropland. Built-up land had the largest annual rate of increase and 50% of this originated from cropland. Moreover, since the Belt and Road Initiative (BRI) commenced in 2013, there has been a greater change in the dynamics of land cover change, and the gaps in the socio-economic development level have gradually decreased. The index of socio-economic development was the highest in western Europe, and the lowest in northern Central Asia. The impacts of socio-economic development on cropland and built-up land were greater than those for other land cover types. In general, in the context of rapid socio-economic development, the rate of land cover change in the NECBEC has clearly shown an accelerating trend since 2001, especially after the launch of the BRI in 2013.

The study of mountain vertical natural belts is an important component in the study of regional differentiation. These areas are especially sensitive to climate change and have indicative function, which is the core of three-dimensional zonality research. Thus, based on high precision land cover and digital elevation model (DEM) data, and supported by MATLAB and ArcGIS analyses, this paper aimed to study the present situation and changes of the land cover vertical belts between 1990 and 2015 on the northern and southern slopes of the Koshi River Basin (KRB). Results showed that the vertical belts on both slopes were markedly different from one another. The vertical belts on the southern slope were mainly dominated by cropland, forest, bare land, and glacier and snow cover. In contrast, grassland, bare land, sparse vegetation, glacier and snow cover dominated the northern slope. Study found that the main vertical belts across the KRB within this region have not changed substantially over the past 25 years. In contrast, on the southern slope, the upper limits of cropland and bare land have moved to higher elevation, while the lower limits of forest and glacier and snow cover have moved to higher elevation. The upper limit of alpine grassland on the northern slope retreated and moved to higher elevation, while the lower limits of glacier and snow cover and vegetation moved northward to higher elevations. Changes in the vertical belt were influenced by climate change and human activities over time. Cropland was mainly controlled by human activities and climate warming, and the reduced precipitation also led to the abandonment of cropland, at least to a certain extent. Changes in grassland and forest ecosystems were predominantly influenced by both human activities and climate change. At the same time, glacier and snow cover far away from human activities was also mainly influenced by climate warming.

In Lhasa River Basin (LRB), land suitable for settlement or living is experiencing a shortage of resources. Alluvial fans have the potential to alleviate this problem. However, basic information, such as the distribution and land use types of alluvial fans, is rarely studied. In this study, Google Earth, ArcGIS and visual interpretation were used to obtain the outlines, areas, quantities and distribution of alluvial fans. Meanwhile, to show the utilisation potential of alluvial fans, we analysed the land use, their distance from the roads, places (town and village) and rivers. The results showed 826 alluvial fans exist in LRB, with a total area of 1166.03 km². The number of alluvial fans with areas between 0.1 and 1 km² is 517, accounting for 62.59% of the total number of alluvial fans. Grassland is the dominant land use type, accounting for 68.70% of the total area of alluvial fans. The cropland area accounted for 2.16% of alluvial fans and accounted for 18.98% of the total cropland area in LRB. Exactly 93.70%, 53.63% and 61.86% of the total number of alluvial fans were located within 5 km from the tertiary road, village, and river, respectively. To sum up, our survey results showed that alluvial fans are important land resources in LRB and may have huge utilisation potential.

Soil organic carbon density (SOCD) and soil organic carbon sequestration potential (SOCP) play an important role in carbon cycle and mitigation of greenhouse gas emissions. However, the majority of studies focused on a two-dimensional scale, especially lacking of field measured data. We employed the interpolation method with gradient plane nodal function (GPNF) and Shepard (SPD) across a range of parameters to simulate SOCD with a 40 cm soil layer depth in a dryland farming region (DFR) of China. The SOCP was estimated using a carbon saturation model. Results demonstrated the GPNF method was proved to be more effective in simulating the spatial distribution of SOCD at the vertical magnification multiple and search point values of 3.0×10⁶ and 25, respectively. The soil organic carbon storage (SOCS) of 40 cm and 20 cm soil layers were estimated as 22.28×10¹¹ kg and 13.12×10¹¹ kg simulated by GPNF method in DFR. The SOCP was estimated as 0.95×10¹¹ kg considered as a carbon sink at the 20-40 cm soil layer. Furthermore, the SOCP was estimated as -2.49×10¹¹ kg considered as a carbon source at the 0-20 cm soil layer. This research has important values for the scientific use of soil resources and the mitigation of greenhouse gas emissions.

The glacier is a crucial freshwater resource in arid and semiarid regions, and the vulnerability of the glacier change is intimately linked to regional ecological services and socio-economic sustainability. Taking the Tianshan Mountains region in China as an example, a basic framework for studying the vulnerability of glacier change was constructed so as to address factors such as physical geography, population status, socio-economic level, agricultural development, and social services. The framework was based on key dimensions, that is, exposure, sensitivity, and adaptability, and this constituted a targeted evaluation index system. We examined the spatial structure and spatial autocorrelation of the glacier change vulnerability using ArcGIS and GeoDa software. The influence and interaction of natural, social, economic, population and other factors on glacier change adaptability was examined using the GeoDetector model. The results suggested the following: (1) The vulnerability level decreased from the western region to the eastern region with significant differences between the two regions. The eastern region had the lowest vulnerability, followed by the central region, and then western region which had the highest vulnerability. (2) Significant positive and negative correlations were found between exposure, sensitivity, and adaptability, indicating that the areas with high exposure and high sensitivity to glacier change tended to have a low adaptive capacity, which led to high vulnerability, and vice versa. (3) The spatial heterogeneity regarding the ability to cope with glacier change reflected the combined effects of the natural, social, economic, and demographic factors. Among them, factors such as the production value of secondary and tertiary industries, the urban population, urban fixed-asset investment, and the number of employees played major roles regarding the spatial heterogeneity of glacier change.

Following climate change, changes in precipitation patterns and food security are major challenges faced by humans. However, research on how these changes in precipitation pattern impacts food supply is limited. This study aims to elucidate this impact and response mechanisms using precipitation data of a climate change-sensitive confluence zone of the southwest and southeast monsoons in Yunnan Province from 1988 to 2018. The results revealed that the precipitation pattern could be divided into three periods: abundant precipitation (Stage I, from 1988 to 2004), decreased precipitation (Stage II, from 2005 to 2015), and drought recovery (Stage III, from 2016 to 2018). Following the transition from Stage I to Stage II and from Stage II to Stage III, the area of precipitation changed significantly, accounting for 15.07%, 13.87%, and 16.53% of Yunnan’s total area, for Stages I, II, and III, respectively. At the provincial level, a significant positive correlation was observed between precipitation and food production (r = 0.535, P < 0.01), and the correlation coefficient between precipitation and grain yield was higher than that between precipitation and meat and milk production. Based on a precipitation-grain yield transect and breakpoint detection method, key precipitation thresholds affecting grain yield were estimated as 700 and 1500 mm, respectively; when precipitation was < 700, 700-1500, and ≥1500 mm, the correlation coefficients between precipitation and grain yield were 0.448 (P < 0.01), 0.370 (P < 0.01), and -0.229 (P > 0.05), respectively. Based on the precipitation thresholds, Yunnan Province can be divided into precipitation surplus, precipitation equilibrium, and precipitation deficit regions, corresponding countermeasures to stabilize grain yield were proposed for each of these regions. The threshold effect of precipitation on grain yield is controlled by molecular-level water-crop mechanisms, in which reactive oxygen species, a by-product of plant aerobic metabolism, plays a key regulatory role.

An indicator system is constructed and applied for comprehensive measurement of rural vulnerability in China’s counties. Through the selection of five representative transects we explore regional differences in, and driving forces of, China’s rural vulnerability. The results show that (1) The rural vulnerability of counties in China is generally within the threshold range of low to medium, and exhibits obvious spatial differences. Along the “Bole-Taipei Line”, there is a spatial pattern of north-south differentiation. Villages in the northeast part of the counties have low vulnerability, while those in the southwest are relatively vulnerable (2) External environmental phenomena are the leading factors that induce rural vulnerability. Specifically, the rural ecological subsystem composed of ecological exposure, ecological sensitivity, and ecological adaptation is the principal determinant of rural vulnerability. The rural economic subsystem composed of economic exposure, economic sensitivity, and economic adaptation is also a core determinant of rural vulnerability. The social subsystem composed of social exposure, social sensitivity, and social adaptation is also an important determinant of rural vulnerability. (3) According to the principle of adapting measures to local conditions, different regions should seek to reduce regional embeddedness and path dependence. We should strengthen the prediction and monitoring of sources of disturbance in rural areas, and scientifically control the sensitivity of the system itself. Then the adaptive capacity of the rural system can be improved pursuant of promoting sustainable development.

Urban forests play an important role in the thermal comfort and overall life of local populations in large- and medium-sized cities. This study analyzes urban forest loss and maps land use and land cover (LULC) changes between 1991 and 2018 by evaluating the use of urban planning instruments for the mitigation of urban forest loss in João Pessoa, Brazil. For this purpose, satellite-derived LULC images from 1991, 2006, 2010 and 2018 and data on urban forest loss areas obtained using the Google Earth Engine were used. In addition, this paper also discusses the instruments used for integrated urban planning, which are (a) the legal sector, responsibility and nature; (b) the urban expansion process; and (c) the elements of urban infrastructure. The results show a clear shift in land use in the study area. The major changes in LULC classes occurred in urban areas and herbaceous vegetation, while the greatest loss was in arboreal/shrub vegetation. Thus, an increase in the pressure to occupy zones intended for environmental preservation could be estimated. Our results showed similar accuracies with other studies and more spatial details. The characteristics of the patterns, traces, and hotspots of urban expansion and forest cover loss were explored. We highlighted the potential use of this proposed framework to be applied and validated in other parts of the world to help better understand and quantify various aspects of urban-related problems such as urban forest loss mapping using instruments for integrated urban planning and low-cost approaches.

Stream morphology is an important indicator for revealing the geomorphological features and evolution of the Yangtze River. Existing studies on the morphology of the Yangtze River focus on planar features. However, the vertical features are also important. Vertical features mainly control the flow ability and erosion intensity. Furthermore, traditional studies often focus on a few stream profiles in the Yangtze River. However, stream profiles are linked together by runoff nodes, thus affecting the geomorphological evolution of the Yangtze River naturally. In this study, a clustering method of stream profiles in the Yangtze River is proposed by plotting all profiles together. Then, a stream evolution index is used to investigate the geomorphological features of the stream profile clusters to reveal the evolution of the Yangtze River. Based on the stream profile clusters, the erosion base of the Yangtze River generally changes from steep to gentle from the upper reaches to the lower reaches, and the evolution degree of the stream changes from low to high. The asymmetric distribution of knickpoints in the Hanshui River Basin supports the view that the boundary of the eastward growth of the Tibetan Plateau has reached the vicinity of the Daba Mountains.

In China's Loess Plateau severe gully erosion (LPGE) region, the shoulder-line is the most intuitive and unique manifestation of the loess landform, which divides a landform into positive and negative terrains (PNTs*The spatial combination model of PNTs is of great significance for revealing the evolution of the loess landform. This study modeled and proposed the Surface Nibble Degree (SND), which is a new index that reflects the comparison of the areas of PNTs. Based on 5 m DEMs and matched high-resolution remote sensing images, the PNTs of 172 complete watersheds in the LPGE were extracted accurately, and the SND index was calculated. The spatial distribution trend of SND was discussed, and the relationship between SND and the factors that affect the evolution mechanism of regional landform was explored further. Results show that: (1) The SND can be calculated formally. It can quantify the development of the loess landform well*2) The SND of the LPGE has evident spatial differentiation that increases from southwest to northeast. High values appear in Shenmu of Shaanxi, Shilou of Shanxi, and northern Yanhe River, whereas the low values are mainly distributed in the southern loess tableland and the inclined elongated ridge area of Pingliang in Gansu and Guyuan in Ningxia*3) In the Wuding River and Yanhe River, the SND decreases with the increase in flow length (FL*In the North-Luohe River and Jinghe River, the SND increases with FL*4) SND is significantly correlated with gully density and sediment modulus and moderately correlated with hypsometric integral. As for the mechanism factors analysis, the relationship between loess thickness and SND is not obvious, but SND increased first and then decreased with the increase of precipitation and vegetation in each geographical division, and we found that the land use type of low coverage grassland has greater erosion potential.

Lake water level is an essential indicator of environmental changes caused by natural and human factors. The water level of Poyang Lake, the largest freshwater lake in China, has exhibited a dramatic variation for the past few years, especially after the completion of the Three Gorges Dam (TGD*However, there is a lack of more accurate assessment of the effect of the TGD on the Poyang Lake water level (PLWL) at finer temporal scales (e.g., the daily scale*Here, we used three machine learning models, namely, an Artificial Neural Network (ANN), a Nonlinear Autoregressive model with eXogenous input (NARX), and a Gated Recurrent Unit (GRU), to simulate the daily lake level during 2003-2016. We found that machine learning models with historical memory (i.e., the GRU model) are more suitable for simulating the PLWL under the influence of the TGD. The GRU-based results show that the lake level is significantly affected by the TGD regulation in the different operation stages and in different periods. Although the TGD has had a slight but not very significant impact on the yearly decline of the PLWL, the blocking or releasing of water at the TGD at certain moments has caused large changes in the lake level. This machine-learning-based study sheds light on the interactions between Poyang Lake and the Yangtze River regulated by the TGD.

It is of necessity to investigate the adjustment of flood discharge capacity in the Lower Yellow River (LYR) because of its profound importance in sediment transport and flood control decision-making, and additionally its magnitude is influenced by the channel and upstream boundary conditions, which have significantly varied with the ongoing implementation of soil and water conservation measures in the Loess Plateau and the operation of the Xiaolangdi Reservoir. The braided reach between two hydrometric stations of Huayuankou and Gaocun in the LYR was selected as the study area. Different parameters in the study reach during the period 1986-2015 were calculated, covering bankfull discharge (the indicator of flood discharge capacity), the pre-flood geomorphic coefficient (the indicator of channel boundary condition), and the previous five-year average fluvial erosion intensity during flood seasons (the indicator of incoming flow and sediment regime*Functional linkages at scales of section and reach were then developed respectively to quantitatively demonstrate the integrated effects of channel and upstream boundary conditions on the flood discharge capacity. Results show that: (1) the reach-scale bankfull discharge in the pre-dam stage (1986-1999) decreased rapidly by 50%, accompanied with severe channel aggradation and main-channel shrinkage. It recovered gradually as the geometry of main channel became narrower and deeper in the post-dam stage, with the geomorphic coefficient continuously reducing to less than 15 m^-1/2*2) The response of bankfull discharge to the channel and upstream boundary conditions varied at scales of section and reach, and consequently the determination coefficients differed for the comprehensive equations, with a smallest value at the Jiahetan station and a highest value (0.91) at reach scale. Generally, the verified results calculated using the comprehensive equations agreed well with the corresponding measured values in 2014-2015*3) The effect of channel boundary condition was more prominent than that of upstream boundary condition on the adjustment of bankfull discharge at the Jiahetan station and the braided reach, which was proved by a larger improvement in determination coefficients for the comprehensive equations and a better performance of geomorphic coefficient on the increase of bankfull discharge.

Tidal creeks are the main channels of land-sea ecosystem interactions, and their high dynamics are an important factor affecting the hydrological connectivity of tidal flats. Taking the Yellow River Delta as the research area, we selected remote sensing images obtained during five periods from 1998 to 2018 as the data sources. Based on the spatial analysis function in GIS, the typical morphological characteristics of tidal creeks, such as the level, length, density, curvature, bifurcation ratio, and overmarsh path length (OPL), were extracted to characterize the degree of development of the tidal creeks in the Yellow River Delta wetlands. The spatio-temporal evolution of the tidal creeks was studied, and the development process and the characteristics of the tidal creeks during the different stages of development were investigated. The results revealed that (1) The number, density, and bifurcation ratio of tidal creeks exhibit an increasing trend, but the growth of the trend is slowing. The number of tidal creeks increased by 44.9% from the initial stage of the Yellow River diversion to the late stage of the wetland restoration, but it only increased by 26.2% from the late stage of the wetland restoration to the slow expansion of the Spartina alterniflora*2) The curvature of the tidal creeks on the landward side is greater than that on the seaward side*3) The development degree of tidal creek has spatial heterogenetiy, which is Area III > Area II > Area I*4) The drainage efficiency is significantly correlated with the tidal creak density and bifurcation ratio. Based on the analysis of the various morphological parameters and the drainage efficiency, it was found that after the rapid change in the tidal creek system in the early stage, the tidal creeks entered a state of slow change, and the development state of the tidal creeks tends to be in dynamic balance. The results of this study are expected to provide scientific support for the sustainable development and utilization of coastal tidal flats.

Giant clam shell mining (GCSM), a unique phenomenon occurring at remote coral reefs in the southern South China Sea (SCS), forms striking scars on the reef flats and damages the reef flat substrate. Through image analyses at three times (2004.02.02, 2014.02.26, and 2019.04.10) and in situ surveys at Ximen Reef, a representative site that has experienced GCSM, we quantified the GCSM-generated substrate damage and the corresponding recovery. GCSM was estimated to have occurred sometime between 2012 and 2014, causing reduction in live coral subarea and formation of micro-relief as trenches and mounds. GCSM-generated damage was restricted to the reef flat. After GCSM, coral and algae subarea increased, and the trenches and mounds tended to be filled and eroded, representing a natural recovery of the substrate. The legal prohibition on human disturbances at the coral reefs contributed to substrate recovery at Ximen Reef. This case also implied that recovery of the other coral reefs that suffered from GCSM is possible.

Heavy metal pollution is hazardous for the environment and human health. However, there are few studies of heavy metal pollution caused by historic metallurgical activity. The Laoniupo site in the Bahe River valley, Guanzhong Basin, China, was an important settlement of the Shang Culture (1600-1046 BCE*We studied two stratigraphic profiles at the Laoniupo site, which were used for measurements of magnetic susceptibility, heavy metal concentrations, and AMS ¹⁴C ages to provide evidence of copper smelting activity at the site during the Shang Dynasty. The Nemerow Pollution Index and Geoaccumulation Index were calculated to assess the heavy metals record (Cu, Zn, Ni, Pb, Cr, and As) in the topsoil on the loess tableland. According to the Single Pollution Index, the topsoil was slightly polluted by As and unpolluted by Cu, Zn, Ni, Pb and Cr; according to the Nemerow Composite Pollution Index the topsoil was mildly polluted; and according to the Geoaccumulation Index, the topsoil was moderately polluted by As, slightly polluted by Cu, and unpolluted by Zn, Ni, Pb and Cr. The main cause of the heavy metal pollution in the topsoil is the presence of copper slag in the cultural layers that was disturbed by modern farming activity.

Background vales (mg/kg)

On 10th Oct. and 3rd Nov. 2018, two successive landslides occurred in the Jinsha River catchment at Baige Village, Tibet Autonomous Region, China. The landslides blocked the major river and formed the barrier lake, which finally caused the huge flood disaster loss. The hillslope at Baige landslide site has been still deforming after the 2018 slidings, which is likely to fail and block the Jinsha River again in the future. Therefore the investigation of 2018 flood disaster at the Baige landslide is of a great significance to provide a classic case for flood assessment and early warning for the future disaster. The detailed survey revealed that the outstanding inundations induced bank collapse disasters upstream the Baige landslide dams, and the field investigations and hydrological simulation suggested that the downstream of the Baige landslide were seriously flooded due to the two periods of the outburst floods. On these bases, the early warning process of potential outburst floods at the Baige landslide was advised, which contains four stages: Outburst Flood Simulating Stage, Outburst Flood Forecasting Stage, Emergency Plan and Emergency Evacuation Stage. The study offers a conceptual model for the mitigation of landslides and flood disasters in the high-relief mountainous region in Tibet.

To realize efficient and sustainable poverty alleviation, this study firstly investigated the identification of multidimensional poverty and relative poverty, and then explored relevant poverty alleviation pathways. Poverty levels in 31 provinces including the autonomous regions and municipalities of China were identified at the county level using the average nighttime light index (ANLI), county multidimensional development index (CMDI), and a method combining multidimensional poverty index and relative poverty standards. Poverty alleviation pathways for poverty-stricken counties were explored from the aspects of industry, education, tourism and agriculture. The results revealed that nearly 60% of counties in China were primarily under relative poverty, most of which were corresponded to light relative poverty. In terms of ANLI and CMDI, 63% and 79% of the national poverty-stricken counties, as of 2018, could be identified, suggesting that CMDI had a higher performance for identifying poverty at the county level. In terms of poverty alleviation pathways, 414, 172, 442, and 298 poverty-stricken counties were receptive to industry poverty alleviation, education poverty alleviation, tourism poverty alleviation, and agriculture poverty alleviation, and 61% of counties had more poverty-causing factors, implying that multidimensional poverty alleviation is suitable in most of the counties.

This article explored China’s urban employment dynamics with particular focus on the city size effect. Big data derived from the largest recruitment website were used to examine the direct and indirect impacts of city size on employment demand by using mediating and moderating models. We also investigated the roles of the government and location factors which have seldom been considered in literature. Results showed that the concentration degree of new jobs is higher than that of stock employment and population across cities, implying a path dependency mechanism of job creation and employment expansion. Meanwhile, numerous job posts in inland central cities are probably a symptom of more even distribution of employment in future China. Econometric models further verified the significant correlation between city size and job creation. Moreover, industrial diversity, fixed asset investment, and spatial location have heterogeneous effects on employment demand in cities of different sizes and different levels of administration. These results can not only deepen our understanding of the crucial role of city size in urban employment growth but also demonstrate the future trend of labor and population geography of China. Policy implications are then proposed for job creation in cities of China and other developing countries.

Residential segregation is a dual process of socio-spatial differentiation in residents and spatio-temporal heterogeneity in dwelling. However, most of the existing studies are established from the single perspective of urban residents based on demographic data, which is difficult to reveal the dynamics and complex spatial reconstruction within and between cities. With the characteristics of both stability and timeliness, the rapidly changing housing market is one of the processes and results of socio-spatial reconfiguration, and it is undoubtedly a better lens to observe residential segregation. This paper adopts methods such as multi-group segregation index, multi-scalar segregation profiles, and decomposition of segregation index, with Nanjing and Hangzhou as case cities, and establishes multi-scalar segregation profiles and comparative models based on three geographical scales of census tract, block and grid, and different residential types. A quantitative study was conducted on the degree and pattern of multi-scalar residential segregation in Nanjing and Hangzhou from 2009 to 2018. The paper found that the spatial segregation index is an improvement of the non-spatial segregation index. There are differences between Nanjing and Hangzhou in the evolution process of residential segregation. Nanjing has a higher degree of spatial differentiation as a whole, among which spatial components have a more significant impact.

Administrative divisions are the important foundation of national governance and social development, and the adjustment of administrative divisions is a critical way to promote regional coordinated development. Under the background of globalization and regionalization, timely adjustment of administrative divisions is a major step to reconstruct the regional development pattern. In the perspective of regional coordinated development, this paper constructs an Administrative Rank Potential Energy (ARPE) model to explore the mechanisms of administrative division adjustment (ADA) under coordinated regional development based on the theory of regional interaction, spatial field energy model and power exponential function. The results show that: (1) The development potential and influence of an administrative region are closely related to the administrative jurisdiction, administrative resources, and the potential of regional coordinated development. (2) The growth rate of ARPE in the study area from 2010 to 2015 was 20.7% compared to the period 2005 to 2010, and the potential for coordinated development increased to 3.05% from 0.21% before the “cancelling” the prefecture-level city of Chaohu. (3) The measurement results of the usefulness of ADA can not only distinguish the complex impacts brought about by social development, but also accord with real social and economic development conditions. The ARPE focuses on the both regional integrated development and individual development, thereby serving as a reference for explaining and evaluating adjustments to administrative divisions at the macro- and micro-scales.

With so many sports becoming increasingly popular, sports have come to play an important role in promoting the process of globalization and formatting the world city network (WCN). Previous studies have constructed the WCN based on the distribution of international sport federations (ISFs) and the sites of international sport events (ISEs), but there is still a lack of systematic research on the intercity connections caused by ISEs. Taking three most recent Olympic Games as cases, this paper explores intercity connections and WCN based on ISEs. The results show that (1) the Olympic WCN has city nodes around the world except in Antarctica, and the number and activity values of the cities in host countries may increase intensively during the Olympic Games. (2) A hierarchical city system with four tiers (global central cities, specialized central cities, national central cities and specialized cities) is formed by the intercity connections caused by the Olympic Games. (3) The WCN based on the Olympic Games, is made up of many subnetworks, while many differences occur due to the diverse decisions made by the Organizing Committee for the Olympic Games (OCOG), host cities or even host countries in the events associated with sponsorship activity and publicity activity. This study not only broadens the relevant fields of sports culture-oriented WCN research but also explores the instability of the WCN, which makes it an effective reference for WCN research based on ISEs.

The continuous degradation of ecosystem services is an important challenge faced by the world. Improvements in transportation infrastructure have had substantial impacts on economic development and ecosystem services. Exploring the influence of traffic accessibility on ecosystem services can delay or stop their deterioration; however, studies on its impact are lacking. This study addresses this gap by analysing the impact of traffic accessibility on ecosystem services using an integrated spatial regression approach based on an evaluation of the ecosystem services value (ESV) and traffic accessibility in the Middle Reaches of the Yangtze River Urban Agglomeration (MRYRUA) in China. The results indicated that the ESV in the MRYRUA continuously decreased during the study period, and the average ESV in plain areas, areas surrounding the core cities, and areas along the main traffic routes was significantly lower than that in areas along the Yangtze River and the surrounding mountainous areas. Traffic accessibility continued to increase during the study period, and the high-value areas centred on Wuhan, Changsha, Nanchang, and Yichang were radially distributed. The global bivariate spatial autocorrelation coefficient between the average ESV and traffic accessibility was negative. The average ESV and traffic accessibility exhibited significant spatial dependence and spatial heterogeneity. Spatial regression also proved that there was a negative association between the average ESV and traffic accessibility, and scale effects were evident. The findings of this study have important policy implications for future ecological protection and transportation planning.

Deep-water navigation channels in the tidal reaches of the lower Yangtze River are affected by water and sediment fluxes that produce complex shoals and unstable channel conditions. The Fujiangsha reach is particularly difficult to manage, as it has many braided channels within the tidal fluctuation zone. In this study, hydrologic and topographic data from the Fujiangsha reach from 2012 to 2017 were used to examine the variations in deposition and erosion, flow diversion, shoals, and channel conditions. Since the Three Gorges Dam became operational and water storage was initiated, the Fujiangsha reach has shown an overall tendency toward erosion. Channels deeper than 10 m accounted for 83.7% of the total erosion of the Fujiangsha reach during 2012-2017. Moreover, the dominant channel-forming sediments have gradually changed from suspended sediments to a mixed load of suspended and bed-load sediments. Deposition volumes of these sediments has varied significantly among different channels, but has mainly occurred in the Fubei channel. Furthermore, periodic variations in the Jingjiang point bar have followed a deposition-erosion-deposition pattern, and the downstream Shuangjian shoal mid-channel bar has been scoured and shortened. Approximately 44.0% of the bed load from the upstream Fujiangsha reach is deposited within the 12.5-m deep Fubei channel. The increased erosion and river flow from the Jingjiang point bar and the Shuangjian shoal during the flood season constituted 59.3% and 40.7%, respectively, of the total amount of siltation in the Fubei channel.

It is common to obtain the topography of tidal flats by the Unmanned Aerial Vehicle (UAV) photogrammetry, but this method is not applicable in tidal creeks. The residual water will lead to inaccurate depth inversion results, and the topography of tidal creeks mainly depends on manual survey. The present study took the tidal creek of Chuandong port in Jiangsu Province, China, as the research area and used UAV oblique photogrammetry to reconstruct the topography of the exposed part above the water after the ebb tide. It also proposed a Trend Prediction Fitting (TPF) method for the topography of the unexposed part below the water to obtain a complete 3D topography. The topography above the water measured by UAV has the vertical precision of 12 cm. When the TPF method is used, the cross-section should be perpendicular the central axis of the tidal creek. A polynomial function can be adapted to most shape of sections, while a Fourier function obtains better results in asymmetrical sections. Compared with the two-order function, the three-order function lends itself to more complex sections. Generally, the TPF method is more suitable for small, straight tidal creeks with clear texture and no vegetation cover.

Baseflow is an important component of river or streamflow. It plays a vital role in water utilization and management. An improved Eckhardt recursive digital filter (IERDF) is proposed in this study. The key filter parameter and maximum baseflow index (BFI_max) were estimated using the minimum smoothing method to improve baseflow estimation accuracy. The generally considered BFI_max of 0.80, 0.50 and 0.25 according to the drainage basin’s predominant geological characteristics often leads to significant errors in the regions that have complex subsurface and hydrologic conditions. The IERDF improved baseflow estimation accuracy by avoiding arbitrary parameter values. The proposed method was applied for baseflow separation in the upstream of Yitong River, a tributary of the Second Songhua River, and its performance was evaluated by comparing the results obtained using isotope-tracer data. The performance of IERDF was also compared with nine baseflow separation techniques belonging to filter, BFI and HYSEP methods. The IERDF was also applied for baseflow separation and calculation of rainfall infiltration recharge coefficient at different locations along the Second Songhua River’s mainstream for the period 2000-2016. The results showed that the minimum smoothing method significantly improved BFI_max estimation accuracy. The baseflow process line obtained using IEDRF method was consistent with that obtained using isotope ¹⁸O. The IERDF estimated baseflow also showed stability and reliability when applied in the mainstream of the Second Songhua River. The BFI alone in the river showed an increase from the upstream to the downstream. The proportion of baseflow to total flow showed a decrease with time. The intra-annual variability of BFI was different at different locations of the river due to varying climatic conditions and subsurface characteristics. The highest BFI was observed at the middle reaches of the river in summer due to a water surplus from power generation. The research provided valuable information on baseflow characteristics and runoff mode determination, which can be used for water resources assessment and optimization of economic activity distribution in the region.

The article considers the long-term (1941-2018) transformation of the Krasnodar valley reservoir, the largest in the North Caucasus. The main functions of the Krasnodar reservoir are irrigation of rice systems and flood protection of land in the Krasnodar reservoir region and the Republic of Adygea. According to topographic maps, Landsat satellite images (1974-2018) and field observations (2016-2018), four stages of transformation of the floodplain reservoir are identified. The selected stages are characterized by both natural causes (the transformation of the filling deltas into the extended deltas, etc.) and man-made causes (runoff diversions in the delta areas, etc.). The key factor of transformation is the formation of deltas of rivers flowing into the reservoir. Each of the selected stages, against the background of a gradual reduction in the area and volume of the reservoir, is characterized by the peculiarities of the formation of river deltas with the formation of genetically homogeneous sections of delta regions. During the period of operation of the reservoir, the delta of the main Kuban River moved up to 32.4 km and took away an area of 35.4 km² of the reservoir. During the formation of the deltas of the Kuban and Belaya rivers, a bridge was formed on the Krasnodar reservoir. The evolution of the delta regions led to the division of the reservoir into two autonomous reservoirs. The total area of the delta regions was 85.9 km² by 2018, i.e., 21% of the initial area of the reservoir. The transformation of the Krasnodar reservoir leads to a decrease in its regulated volume and gradual degradation.