Downstream Cities Research Articles

Spatiotemporal Changes and Influencing Factors of the Coupled Production–Living–Ecological Functions in the Yellow River Basin, China

The imbalance in the “production–living–ecology” function (PLEF) has become a major issue for global cities due to the rapid advancement of urbanization and industrialization worldwide. The realization of PLEF coupling and coordination is crucial for a region’s sustainable development. Existing research has defined the concept of PLEF from the perspective of land function and measured its coupling coordination level using relevant models. However, there is still room for improvement in the indicator system, research methods, and other aspects. This work builds a PLEF coupling coordination evaluation-index system based on the perspective of human habitat using multi-source data in order to examine the spatial differences in PLEF coupling coordination level and the influencing factors in the Yellow River Basin (YRB). Using the modified coupling coordination model, the Moran index, spatial Markov chain model, and geographically weighted random forest model were introduced to analyze its spatial and temporal differentiation and influencing factors. The results found that (a) the level of PLEF coupling coordination in the YRB from 2010 to 2022 has been improving, and the number of severely imbalanced cities has been reduced from 23 to 15, but the level of downstream cities’ coupling coordination is significantly higher than that of upstream cities. The probability of cities maintaining their own level is greater than 50%, and there is basically no cross-level transfer. (b) The Moran index of the PLEF coupling coordination level has risen from 0.137 to 0.229, which shows a significant positive clustering phenomenon and is continually strengthening. The intercity polarization effect is being continually enhanced as seen in the LISA clustering diagram. (c) There is significant heterogeneity between the influencing factors in time and space. In terms of importance level, the series is per capita disposable income (0.416) > nighttime lighting index (0.370) > local general public budget expenditure (0.332) > number of beds per 1000 people (0.191) > NO2 content in the air (0.110). This study systematically investigates the dynamic evolution of the coupled coordination level of PLEF in the YRB and its influencing mechanism, which is of great practical use.

Mechanism and spatial spillover effect of digital economy on common prosperity in the Yellow River Basin of China

The digital economy has emerged as a new trend in economic development and has profoundly influenced the process of achieving common prosperity. However, current research on the correlation between the digital economy and common prosperity from the perspective of a river basin still needs to be strengthened. Based on this, the present study first theoretically elaborates the conceptual meanings of “digital economy” and “common prosperity”, as well as the mechanism by which the digital economy empowers common prosperity. Subsequently, a scientifically-constructed performance evaluation index system for the digital economy and common prosperity is established. Considering the Yellow River Basin as an empirical case study area, this study investigates the mechanism and spatial spillover effects of the digital economy in empowering common prosperity from 2005 to 2020. The research findings reveal that: (1) The Yellow River Basin exhibits a basin characteristic with downstream > midstream > upstream areas regarding the level of common prosperity and digital economy. It indicates that a distinct spatial correlation exists between the two factors. However, the ongoing decrease in both high-level and very high-level areas reflects the lengthy and challenging journey of enhancing the quality and efficiency of the digital economy in empowering common prosperity. (2) The digital economy not only directly impacts common prosperity, but also fosters its development through spatial spillover effects. Among the control factors, informatization and housing levels have a major stimulating effect. (3) There exists a clear regional heterogeneity in how the digital economy affects common prosperity in the Yellow River Basin. Specifically, common prosperity of downstream cities is significantly impacted by the digital economy. The spatial spillover effects of the digital economy on common prosperity exhibit a pronounced “neighborhood as a moat” characteristic. (4) The digital economy facilitates the achievement of shared prosperity through the implementation of mechanisms centered on sharing, affluence, and sustainability. These research findings illuminate the empowering mechanisms and spatial spillover pathways of the digital economy in promoting shared prosperity, aligning with national strategies for ecological conservation and high-quality development in the Yellow River Basin.

Differential Evaluation of Ecological Resilience in 45 Cities along the Yangtze River in China: A New Multidimensional Analysis Framework

The rapid pace of urbanization and global climate change necessitates a thorough assessment of urban ecological resilience to cultivate sustainable regional ecosystem development. Cities along the Yangtze River face an intensifying conflict between ecological preservation and socio-economic growth. Analyzing the ecological resilience of these urban centers is essential for achieving equilibrium in regional urban ecosystems. This study proposes a “system process space” attribute analysis framework, taking into account urban development processes, ecosystem structure, and resilience evolution stages. Utilizing data from 45 Yangtze River cities, we establish a “Driver, Pressure, State, Impact, and Response” (DPSIR) evaluation index system to evaluate changes in ecological resilience levels and evolution trends from 2011 to 2022. Our findings indicate that: (1) The ecological resilience index of Yangtze River cities increased from 0.177 to 0.307 between 2011 and 2022, progressing through three phases: ecological resilience construction, rapid development, and stable development. (2) At the city level, ecological resilience along the Yangtze River exhibits uneven development characteristics. Upstream cities display a significant “stepped” pattern, midstream cities exhibit a significant “Matthew effect”, and downstream cities present a pyramid-shaped pattern. While regional differences in ecological resilience persist, overall polarization is gradually decreasing, intercity connections are strengthening, and there is a growing focus on coordinated regional development. (3) The spatial distribution of ecological resilience in Yangtze River cities demonstrates both continuity and evolution, generally forming a “core-edge” clustered pattern. Based on these findings, we recommend enhancing inter-city cooperation and connectivity, addressing imbalances in urban ecological resilience, and promoting high-quality ecological resilience development along the Yangtze River through tailored development strategies for each city.

Comparison of the polluted dust plume and natural dust air mass in a spring dust event in Beijing 2023

The occurrence of extreme weather events is becoming more frequent due to global climate change. A long-lasting dust outbreak in the spring of 2023 was triggered by Mongolia cyclones and cold fronts in the dust source areas. In this study, we illustrate the spatial distribution, the transport path of the dust and its influence on the air quality of downstream cities utilizing ground-based and space-borne measurements. Results indicate a more complicated pollution, coexisting of polluted dust stage S1 and pure dust stage S2. In S1, the aerosol was characterized by a dual-layer vertical structure—high extinction coefficient of nearly 1.0 km−1 with a low particle depolarized ratio (PDR) of < 0.1 under 500 m, and a small extinction coefficient of 0.3 km−1 with a high PDR of 0.15 above 500 m. Then the intrusion of the Mongolian cyclone carried new dust plumes on 10 March, suggesting the onset of pure dust period S2. The source transition was also confirmed by the MODIS, CALIPSO and Hysplit observations. The pure Asian dust evolved rapidly with one thickening layer and distributed homogeneously in the boundary layer. The PDR increased significantly to the peak of 0.35 and resulted in the peak PM10 value of > 1300 µg/m3. PM10 positively correlated with trace gases in S1 while varying inversely with the pollution gases in S2. The results help to shed light on the classification of different types of dust and also be useful in developing an effective strategy to forecast air pollution in downstream areas.

Downstream and upstream effects of urban chains on precipitation in Beijing

A summer convective rainfall event in Beijing on June 26, 2018 was investigated though a series of numerical simulations. The system moved from northwest to southeast, passing through Yanqing (YQ), Changping (CP), and the central urban area (CUA) of Beijing. The combined influences of the multiple urban areas and the mechanisms of the mutual impacts of upstream and downstream cities on precipitation were investigated. Results showed that the urban surfaces led to an increase in near-surface temperature, a decrease in lower-level wind speed, and airflow triggered convergence and updrafts. The resulting upward moisture transport and latent heat release in the cloud were promoted during the subsequent precipitation. The thermal and dynamic impacts of CUA and CP urban areas propagated downstream along the low-level southeasterly flow, resulting in increased temperatures, strengthened updrafts, and latent heat release in the cloud along YQ-CP-CUA region. The urban effects propagated downstream under the southeasterly wind, leading to enhanced precipitation over YQ and CP. The YQ also, however, contributed to the increased precipitation in CUA. The “city chain” comprised of YQ, CP, and CUA thus promoted the progression and advancement of the precipitation system. This study highlights the importance of the correct identification of the “upwind” and “downwind” directions when studying urban impacts on precipitation.

Impacts of Urban Form on Carbon Emissions Under the Goal of Carbon Emission Peak and Carbon Neutrality: A Case Study of the Yangtze River Economic Belt

Clarifying the mechanism of influence of urban form on carbon emissions is an important prerequisite for achieving urban carbon emission reduction. Taking the Yangtze River Economic Belt as an example, this study elaborated on the general mechanism of urban form on carbon emissions, used multi-source data to quantitatively evaluate the urban form, and explored the impacts of urban form indicators on carbon emissions from 2005 to 2020 at global and sub-regional scales with the help of spatial econometric models and geodetector, respectively. The results showed that:① The carbon emissions of the Yangtze River Economic Belt increased from 2 365.31 Mt to 4 230.67 Mt, but the growth rate gradually decreased. Its spatial distribution pattern was bipolar, with high-value areas mainly distributed in core cities such as Shanghai and Chongqing and low-value areas concentrated in the western regions of Sichuan and Yunnan. ② The area of construction land in the study area expanded over the past 15 years, but the population density of construction land had been decreasing. The degree of urban fragmentation was decreasing, and the difference between cities was also progressively narrowing. The average regularity of urban shape improved, and the compactness increased significantly. ③ All indicators of urban scale had significant positive effects on carbon emissions at the global scale, urban fragmentation had a significant negative effect in 2005, and the effective mesh size (MESH) indicator of urban compactness showed a significant negative correlation with carbon emissions in the study period. ④ Total class area, patch density, and effective mesh size had the most significant impacts on carbon emissions in upstream cities. Effective mesh size, mean perimeter-area ratio, and total class area had higher influences in midstream cities. Effective mesh size, percentage of like adjacencies, and largest patch index were the key factors to promote carbon reduction in downstream cities. Cities in different regions should comprehensively consider the impacts of various urban form indicators on carbon emissions and then optimize their urban form to promote sustainable development.

Disinfectant-induced ammonia oxidation disruption in microbial N-cycling process in aquatic ecosystem after the COVID-19 outbreak

Anthropogenic activities significantly impact the elemental cycles in aquatic ecosystems, with the N-cycling playing a critical role in potential nutrient turnover and substance cycling. We hypothesized that measures to prevent COVID-19 transmission profoundly altered the nitrogen cycle in riverine ecosystems. To investigate this, we re-analyzed metagenomic data and identified 60 N-cycling genes and 21 host metagenomes from four urban reaches (one upstream city, Wuhan, and two downstream cities) along the Yangtze River. Our analyses revealed a marked decrease in the abundance of bacterial ammonia monooxygenase genes, as well as in the host, ammonia-oxidizing autotrophic Nitrosomonas, followed by a substantial recovery post-pandemic. We posited that discharge of sodium hypochlorite (NaOCl) disinfectant may be a primary factor in the reduction of N-cycling process. To test this hypothesis, we exposed pure cultures of Nitrosomonas europaea to NaOCl to explore the microbial stress response. Results indicated that NaOCl exposure rapidly compromised the cell structure and inhibited ammonia oxidation of N. europaea, likely due to oxidative stress damage and reduced expression of nitrogen metabolism-related ammonia monooxygenase. Using the functional tagging technique, we determined that NaOCl directly destroyed the ammonia monooxygenase protein and DNA structure. This study highlights the negative impacts of chlorine disinfectants on the function of aquatic ecosystems and elucidates potential mechanisms of action.

Synergy level of urban resilience and urban land use efficiency in the Yellow River Basin: Spatial-temporal evolution characteristics and driving factors

The complex global context, including globalization, rapid urbanization, and climate change, poses significant challenges to urban stability and development. Balancing urban land use efficiency and resilience is crucial for sustainable progress. Focusing on the vulnerable Yellow River Basin (YRB), this study examines the interplay between urban resilience and land use efficiency. Panel data from 2013 to 2020 for 54 cities in the YRB were used, it quantifies the Coupling Coordination Degree of Urban Resilience and Urban Land Use Efficiency (CCDUU), explores its spatiotemporal evolution and influencing factors. Key findings include: The CCDUU exhibits a sustained and discernible growth trend. Notably, CCDUU is higher in downstream areas in comparison to the middle reaches, reaching its lowest point in the upstream areas; however, the increase in CCDUU in the upstream areas surpasses that observed in other regions. Concurrently, regional disparities in CCDUU are diminishing. Despite the presence of a notable positive spatial correlation in CCDUU within the YRB, the strength of this spatial association is not sufficiently robust. Of paramount importance factor is the role of regional innovation, which significantly influences the enhancement of CCDUU. Following closely is the degree of openness, whereas the positive effects of government support and population density are concentrated predominantly in the upper YRB region. In contrast, urban-rural disparity exerts an adverse impact on CCDUU in most regions. Policy recommendations for enhancing CCDUU in YRB cities include strengthening government support and planning control, particularly in upstream regions, to achieve efficient resource utilization and environmental protection. Implementing population density management policies, encouraging rational movement, and promoting population migration to upstream areas can alleviate pressure in downstream cities. Enhancing openness, attracting foreign investment, and promoting innovation and industrial upgrading will drive economic structural upgrades and improve CCDUU.

Atmospheric environment characteristic of severe dust storms and its impact on sulfate formation in downstream city

This study comprehensively investigated the impact of dust storms (DSs) on downstream cities, by selecting representative DS events. In this paper, we discussed the characteristics of meteorological conditions, air pollutants, PM2.5 components, and their influence on sulfate formation mechanisms. During DSs, strong winds, reaching speeds of up to 10 m/s, led to significant increases in PM10 and PM2.5, with maximum concentrations of 2684.5 and 429 μg/m3, respectively. Primary gaseous pollutants experienced substantial reductions, with decline rates of 48.1, 34.9, 36.8, and 9.0 % for SO2, NO2, NH3, and CO, respectively. Despite a notable increase in PM2.5 concentrations, only 7.6 % of the total mass of PM2.5 was attributed to ionic and carbonaceous components, a much lower value than observed before the DSs (77.3 %). Concentrations of Fe, Ti, and Mn exhibited increases by factors of 6.5–14.1, 10.4–17.0, and 1.6–4.7, respectively. In contrast to the significant decrease of >76.2 % in nitrogen oxidation ratio (NOR), sulfur oxidation ratio (SOR) remained at a relatively high level, displaying a strong positive correlation with high concentrations of Fe, Mn, and Ti. Quantitative analysis revealed an average increase of 0.187 and 0.045 μg/m3 in sulfate from natural sources and heterogeneous generation, respectively. The heterogeneous reaction on mineral dust was closely linked to atmospheric humidity, radiation intensity, the form of metal existence, and concentrations of it. High concentrations of titanium dioxide and iron‑manganese oxides in mineral dust promoted heterogeneous oxidation of SO2 through photocatalysis during the daytime and metal ion catalysis during the nighttime. This study establishes that the metal components in mineral dust promote heterogeneous sulfate formation, quantifies the yield of sulfate generated as a result, and provides possible mechanisms for heterogeneous sulfate formation.

Quantitative analysis of spatiotemporal disparity of urban water use efficiency and its driving factors in the Yangtze River Economic Belt, China

Study regionYangtze River Economic Belt, China Study focusAs the major national strategic development area of China, there have always been vital problems about imbalance of the water resources distribution and the disparity of economic levels in YREB. Quantitative analysis of water use efficiency (WUE) is essential to the rational use of water resources, as well as the sustainable development. In this study, a WUE evaluation index system for prefecture-level cities in the YREB was constructed, and Super-Efficiency Data envelopment analysis Slacks-Based Measure (DEA-SBM) model, Global Malmquist-Luenberger productivity index, combined with geographically weighted regression model were utilized to measure and identify the spatiotemporal evolution characteristics of WUE and its influencing factors. New hydrological insights for the regionFrom the temporal perspective, the WUE manifests a significant upward trend from 2005 to 2020, and the growth presents lower reach > middle reach > upper reach; in the spatial pattern, the WUE has significant spatial divergence characteristics, high WUE mainly occurred in developed leading cities, while developing cities in the midstream and upstream tended to be inefficient; various effects on WUE were also analyzed, highlighting that technical advancement was the key driver of WUE evolution. Then the negative effects of industrial structure and urban environment was becoming more and more significant. Finally, effective measures for upstream, middle and downstream cities in the YREB were discussed.

Industrial agglomeration and PM2.5 pollution in Yangtze River Economic Belt in China: non-linear estimation and mechanism analysis

Introduction: The uncertainty associated with PM2.5 pollution hinders the economic high-quality development and threatens public health. Industrial agglomeration stands as a critical factor in regional economic and environmental governance, and the current studies about its impact on PM2.5 pollution are mostly limited to a specific industry or unidirectional influence.Methods: Our study constructed spatial econometric models to analyze the effect of three major industrial agglomerations on PM2.5 pollution, based on evidence from 110 prefecture-level cities of the Yangtze River Economic Belt in 2005–2019.Results: The results show that: 1) The three major industrial agglomerations and PM2.5 pollution present different spatiotemporal characteristics and show prominent positive spatial autocorrelation and agglomeration effect. 2) The primary industrial agglomeration contributes to a decrease in PM2.5 pollution and exhibits negative spatial spillover effects. A nonlinear relationship is observed between the secondary industrial agglomeration and PM2.5 pollution. The tertiary industrial agglomeration results in an increase in PM2.5 pollution. 3) The effects of secondary industrial agglomeration on PM2.5 pollution exhibit varying degrees of ‘inverted U-shape’ curves in the upstream, midstream, and downstream cities. The midstream cities are the first to reach the inflection point of agglomeration. 4) Industrial agglomeration affects PM2.5 pollution through three mechanisms, including scale expansion effect, technological spillover effect, and population scale effect.Discussion: Based on the empirical findings, this study provides scientific support and decision-making reference to improve the positive impacts of industrial agglomerations on PM2.5 pollution.

Variability in evapotranspiration in the Andean páramo as influenced by fog and rainfall

AbstractTropical mountains such as the páramos of the Andes, which serve as ‘water towers’ for local communities and downstream cities, are important areas for early detection of climate change. Here, fog and low‐intensity rainfall are very common and play a key role in ecohydrological processes. Although evapotranspiration (ET) represents an important part of the water cycle, how ET and fog processes interact and how they affect páramo vegetation and water resources availability are poorly understood. This study investigated the effects of foggy (fog only) and mixed (fog and rainfall) conditions on ET. To determine whether fog significantly reduces ET, we compared ET and meteorological data under these two conditions with those during dry days. We found that on foggy days, when fog was most prevalent in the early morning, ET declined on average by 4% and net radiation (Rn) by 9.2%. Under mixed conditions, daily ET declined by 42% and Rn by 33%. In the páramo, where mean annual precipitation and ET are 1210 and 635 mm, respectively, the estimated annual reduction in ET due to fog and rainfall combined is between 77 and 174 mm. We found that during fog and rainfall mixed conditions, solar radiation was reduced, consequently constraining the energy available for ET while sustaining high relative humidity, ultimately reducing water loss. Our findings, which suggest that the presence of fog and low‐intensity rainfall restricts water losses by evaporative demand, contribute to a better understanding of the ecohydrological importance of these water inputs in the Andes.

Does Regional Integration Improve Carbon Emission Performance?—A Quasi-Natural Experiment on Regional Integration in the Yangtze River Economic Belt

Carbon emission performance (CEP) comprehensively considers the four-dimensional factors of “carbon reduction, pollution reduction, green expansion, and growth” and constitutes a key indicator for low-carbon and high-quality development. Although some studies have previously explored the relationship between regional integration and carbon emissions from different perspectives, it remains unclear how regional integration affects carbon emission performance. This article regards the regional integration construction of the Yangtze River Economic Belt as a quasi-natural experiment and uses the difference-in-difference (DID) model to empirically examine the mechanisms behind regional integration and their impact on carbon emission performance. The results show that regional integration significantly promotes improvements in carbon emission performance, primarily through three transmission mechanisms: resource factor allocation, economies of scale, and green innovation. It can also promote improvements in carbon emission performance in high-level carbon emission performance cities, middle- and downstream cities, non-natural-resource-oriented cities, and non-riverside cities. This article provides theoretical and empirical evidence that can be utilized to promote China’s high-quality, low-carbon transformation through regional integration construction in the Yangtze River Economic Belt.

New evidence of high-speed rail promoting green economic growth in the Yangtze River Economic Belt: empirical analysis based on difference-in-differences.

The Yangtze River Economic Belt (YREB) is an important ecological barrier in China. From new perspectives, this paper explores the mechanism of high-speed rail (HSR) for green economic growth (GEG) in the YREB. This paper constructs 108 city panel data at the prefecture level and above in the YREB from 2003 to 2020. Difference-in-differences (DID) is adopted to research the impact of high-speed rail on GEG in the YREB. (1) HSR has significantly improved the GEG of the YREB. The effect value is 4.88%. The parallel trend test suggests that DID is valid. A time-varying instrumental variable combining average altitude and historical railway network is constructed for the endogeneity test. (2) Propensity score matching (PSM) and DID (PSM-DID) were employed to test the sample selection bias. (3) A battery of robustness tests, including the placebo test, variable replacement, and policy interference exclusion, is carried out. The conclusions are still valid. (4) HSR can promote the GEG of the YREB by encouraging technological innovation, industrial upgrading, and increasing ecological efficiency. The contribution rate from the largest to the smallest is ecological efficiency, industrial upgrading, and technological innovation. (5) Heterogeneity analysis shows that HSR has played an important role in encouraging GEG in the eastern, peripheral cities, and the downstream cities of the YREB. Finally, this paper puts forward policy suggestions for promoting GEG in the YREB.

Water scarcity risk through trade of the Yellow River Basin in China

Water scarcity poses economic risks and affects the quality of national and regional development. The risk of local water scarcity can be conveyed to downstream economies through interregional trade for potential economic losses. However, most previous water scarcity studies focused on the availability of adequate freshwater supplies, ignoring the economic losses associated with inadequate water quality. With the aggravation of water pollution, water scarcity caused by inadequate water quality is exacerbated. This study incorporates water quality and quantity into local water scarcity risk assessments, revealing the virtual water scarcity risks and transmission pathways of the cities and sectors in the Yellow River Basin (YRB) in China. The results show that the number of cities with severe water stress increases from 13 to 53 when water quality is considered. Virtual water scarcity risks transfer from upstream cities to downstream cities in Henan and Shandong Provinces, and high-risk cities in Henan can be identified by considering water quality. Key transmission pathways for intersectoral transfer are identified. This study validates the significance of considering water quality factors in water scarcity risk assessments and provides a perspective for policy decisions to mitigate water scarcity and thus ensure water security in the YRB.

Research on the impact and mechanism of financial development on new urbanization: A case study of the Yangtze River Economic Belt.

Based on panel data of 108 cities in China's Yangtze River Economic Belt from 2003 to 2019, a multiple mediation model is used in this study to assess the impact and mechanism of financial development on new urbanization. The main conclusions are that financial development can directly promote the improvement of new urbanization and indirectly improve the level of new urbanization by increasing infrastructure investment, optimizing industrial structure, and enhancing human capital. Further, the financial development of middle-upstream cities has a stronger promoting effect on new urbanization. Whereas the financial development of downstream cities mainly promotes the construction of new urbanization through both infrastructure investment and industrial structure optimization, middle-upstream cities rely more solely on infrastructure investment.

Mandatory pollution abatement and firm export product quality

This study investigates the effect of mandatory pollution abatement on the export product quality of firms. Using the chemical oxygen demand reduction targets specified in the 11th Five-year Plan of China as an exogenous shock, we document that firms under stringent environmental regulation experience an upgrading in their export product quality, and our findings remain robust under a battery of tests. Plausible mechanisms are reduced wastewater emissions, the adoption of sewage treatment facilities, and promoted innovation. We show that the effect is highly pronounced in non-state-owned enterprises and firms located in downstream cities. Our findings provide policy implications on unintended consequences of environmental regulation on local firms’ product quality.

Heterogeneous human capital, spatial spillovers and regional innovation: evidence from the Yangtze River Economic Belt, China

Investing in human capital can assist in achieving technological innovations, while the spatial spillover effects of human capital on urban innovation in urban agglomeration are largely ignored. Using the panel data of 108 cities in China’s Yangtze River Economic Belt (YREB) during 2011–2020, this paper explores the interactions between human capital and urban innovation with a two-way fixed effects Spatial Durbin Model framework, which incorporates the interpretation of spatial spillover effects. The results show that urban innovation in the YREB has spatial heterogeneity in the structure, which is reflected in its diffusion from the downstream cities on the eastern coast to the upstream cities in the western region. Then, the low-level human capital inhibits the development of local innovation, while intermediate and high-level human capital improves local innovation. Furthermore, the spatial spillover effect shows an opposite trend. The impact of human capital on urban innovation is not significant in the downstream cities, such as Shanghai and Nanjing. Finally, three policy directions are proposed to optimize the human capital structure of the YREB, which are, strengthening investment in human capital and technological innovation, enhancing the talent spillover effect, and improving basic education.

Monitoring and Modelling Morphological Changes in Rivers Using RS and GIS Techniques

River geomorphological investigation issues have received little attention in most countries of the world. Such processes become a pressing necessity due to climate change and anticipated events of extraordinary surges and dry seasons, which may debilitate the security of adjacent and downstream cities, particularly in locales that are exceedingly delicate and influenced by climatic changes. Al-Abbasia reach is a river that runs through the middle of the Euphrates River and is known for its numerous bends and meanders. The study of hydraulic structures such as barrages can provide important information about their influences on morphological processes in river reaches near the barrage upstream and downstream. Hydraulic analysis is made of the river behavior in u/s and d/s of hydraulic structures like barrages as a result of sediment deposition and erosion in u/s and d/s. A study, i.e., research on the impacts of the Abbassia barrage on the river system, has been conducted to address this issue using multi-temporal Landsat satellite data from 1976 to 2022 provided by the USGS. The study reach is located 5 kilometres upstream and 5 kilometres downstream of the Abbassia reach. Following the construction of the barrage, which had an impact on the sedimentation and geometry of the river, morphological variations took place in this part of the Al Abbassia reach. In this study, morphological changes throughout 49 years between 1976 and 2022 were investigated utilising remote sensing (RS) and geographic information system (GIS) approaches. Additionally, four image groups from three separate decades were used to perform change detection (1990–2000, 2000–2010, and 2010–2022). In this study, a monitoring system using Landsat-3 MSS: 1985, Landsat-5 TM: 1990, 1995, 2000, 2005, and Landsat-8 OLI: 2010, 2011, 2015, 2021, 2022 were employed to map river planform changes. The long-term comparison of this series of satellite images and historical maps for the period 1976–2022 indicates a continuation of change in the reach study with a rate of approximately 56, 33, 97, and 55% for upstream and 19%, 26%, 3%, and 45% for downstream for the width, area, deposition, and erosion, respectively. Furthermore, it is observed that there is a shift in river course within 200 m downstream of the barrage for the period of 1985–1990. The findings of this study, which monitor river morphological change at finer temporal and spatial resolutions, are crucial for promoting sustainable river management. They also aid in the investigation of river behaviour, which is necessary for providing the best management possible and overcoming the difficulties posed by this important research issue. Doi: 10.28991/CEJ-2023-09-03-03 Full Text: PDF

Distribution, Transport, and Impact on Air Quality of Two Typical Dust Events in China in 2021

The dust event from 12 January to 17 January 2021 (“1.12 event”) is the first dust process in 2021 and the earliest dust event in the last two decades. The dust event from 14 to 18 March 2021 (“3.15 event”) was the strongest dust storm in the past decade. Distribution, transport, and impact on urban air quality of these two typical dust events were studied using multi-source satellite data, a HYSPLIT trajectory model, and a 3D concentration-weighted trajectory model. Results show that both dust events affected a wide range of areas, covering Northwest, North, Northeast, East, and Central-South China. A strong dust belt spanning Northwest, North, and Northeast China was formed in northern China on 15 March 2021. The distribution heights of the 1.12 and 3.15 events were 0–5 km and 0–10 km, respectively. Dust from western Inner Mongolia and southern Mongolia dominated the 1.12 event, while dust from southern Mongolia dominated the 3.15 event. Both of these dust sources had eastward and southeastward transport paths. The majority of the dust was near-ground in downstream cities from an altitude of 0–3 km. Most cities were affected by the dust backflow. The 1.12 event generated more severe particulate pollution in southern China than the 3.15 event. During high-value dust days, ozone pollution levels decreased at the majority of stations. Dust weather with low dust rising heights and dust backflow phenomena should be taken seriously in urban dust pollution forecasting and warning work. International collaboration is needed to improve China’s desertification control.