Inland River Research Articles

Sustainable Development of the China Railway Express under the Belt and Road Initiative: Focusing on Infrastructure Reliability and Trade Facilitation

The China Railway Express (CR Express) is an important component of the Belt and Road Initiative (BRI). The sustainable development of CR Express provides critical support for regional economic integration and promotes a balanced development of the supply chain. Infrastructure reliability and trade facilitation greatly impact the operation of CR Express and are crucial for improving the competitiveness of transnational trade and cross-border efficiency. Inconsistent transportation infrastructure standards and low-efficient transportation service procedures affect the cross-border movement of cargo among countries. This paper integrates quantified metrics of infrastructure reliability and trade facilitation into a spatial friction model based on the electrical resistance theory, estimating the impact of these factors on the transportation flow of CR Express. Additionally, three scenarios of infrastructure reliability and trade facilitation are established for the four trade routes from Zhengzhou to Hamburg. Numerical experiments show that compared with inland river routes and traditional ocean routes, infrastructure reliability and trade facilitation significantly influence the transport flow of CR Express. These research results can provide a reference for the improvements of CR Express transportation efficiency and the simplification of customs clearance processes, potentially promoting the sustainable development of the CR Express supply chain to some extent.

Investigation of microplastics and potentially toxic elements (PTEs) in sediments of two rivers in Southwestern Nigeria.

Microplastics (MPs) are emerging and ubiquitous contaminants, known to accumulate in river sediments. In many developing nations, the absence of policies for managing plastic waste puts the inland river ecosystems at risk of excessive abundance of plastics and MPs. However, only limited studies have reported MPs in river environments in these countries. The current study therefore examined the abundance and nature of MPs and potentially toxic elements (PTEs) in the sediments of the Odo-Ona and Ogun Rivers in Southwest Nigeria. MPs were extracted from the sediments using the density separation method and categorized according to their size, colour and shapes. The range of MP abundances found in the Ogun River sediments was 66.6 ± 12.2 to 311 ± 20.8 particles/kg, while that of the Odo-Ona River ranged from 133 ± 50 to 433 ± 100 particles/kg. The MPs polymer analyses revealed the presence of polyethylene (PE), polypropylene (PP) and polyamide (PA) particles in the sediments. PE was most abundant in the two rivers, constituting 72.8% and 59.7% of MPs (with 0.5 - 5mm size), recovered from the Odo-Ona and Ogun Rivers, respectively. High concentrations of Cr and Pb with ranges of 10.3 - 48.3 and 10.1 - 211mg/kg, respectively, were detected in the sediments and were associated with anthropogenic effects. This study reveals the impact of indiscriminate waste dumping on the water bodies, and calls for strict enforcement of environmental laws in the country.

Numerical simulation of morphological evolution in a gravel-bed meandering river during floods: a case study on the Sai-Jiang river

ABSTRACT The water velocity undergoes a significant increase during the initial stage of floods. The present study focuses on investigating the scours and silting occurring in an S-shaped gravel-bed river. The primary objective is to analyze the impact of 10-year flood events on both the riverbed and bank stability. This river is located in the Sai-jiang River reach, Fujian Province, China. A numerical model of riverbed scours and silting is herein tested. The research results indicate that the morphological evolution of the whole river section is affected in the early stage of flood evolution; however, in the later stage, some key places such as the bridge and the river land are still greatly affected. The apex of the river bend is in close proximity to the downstream river island, resulting in scour at the head of the river island that deviates from conventional patterns of head scour and tail siting. Furthermore, the presence of artificial structures like bridges exacerbates the scour and silting processes in river beds during flood events. For this case, the riverbed adjacent to the Banzhong Bridge pier experienced a widening of approximately 50 m and downstream extension of around 300 m, with a maximum vertical scouring depth of 2.87 m.

Ecosystem Services’ Supply–Demand Assessment and Ecological Management Zoning in Northwest China: A Perspective of the Water–Food–Ecology Nexus

The coordinated development of the water–food–ecology (WFE) nexus is a practical issue that has to be addressed urgently for northwest China’s (WTL) sustainable development. Optimizing the linkage relationship and accomplishing the rational distribution of resources from the perspective of the supply and demand for ecosystem services (ESSD) are imperative. Thus, in this study, a numerical indicator system for ESSD from the perspective of the WFE nexus was constructed with the incorporation of the water and carbon footprint. Based on this premise, the ecological management zoning method was enhanced by integrating supply and demand risks, and optimization suggestions were proposed for various zones. The results showed that (1) carbon sequestration (CS), food production (FP), and water yield (WY) supply and demand significantly increased between 2000 and 2021. High ESSDs were concentrated in the west side of northwest China. Maize, wheat, cotton, vegetables, and garden fruits had a higher demand for ecosystem services (ESs). (2) The three ESSDs were bound in a synergistic relationship. The synergy between supply exhibited significant spatial heterogeneity, while the synergies between demand showed similar distribution patterns. (3) Regarding quantity matching, the supply for FP and CS surpassed demand, while the WY supply could not meet the demand. The three ESs’ supply and demand deficits rose. Ecological supply–demand ratio (ESDR) regional differentiation for the three ESs was apparent. Regarding spatial matching, FP and CS concentrated on low supply–low demand, while WY focused on high supply–high demand. FP risk was concentrated in Qaidam Basin, whereas WY risk was mostly in Hexi inland river basin (HX), the Yellow River Basin area (HH), and both sides of the “Qice line”. (4) The ecological management zones were formed by integrating WTL’s three dominant weak functional zones, four categorized strategy regions, and four governance models. This study can serve as a scientific benchmark for regional ecological management, which is significant in ensuring northwest China’s water, food, and ecological safety.

Scale-specific controls of monthly suspended sediment load in a typical inland river

Sediment transport is a multi-scale and non-linear process controlled by multiple variables. Given the intricate nature of sediment transport mechanisms and the overlap of different factors’ effects on it at various time scales, unraveling the relationship between sediment load and its influencing factors is challenging. This study aimed to elucidate the multi-timescale effects of factors on monthly suspended sediment load in a seasonal inland river. In this study, monthly sediment loads measured by the depth-integrating method were obtained from the Tabu River Basin in northern China from 2007 to 2021, alongside data on four controlling factors: runoff, precipitation, water surface evaporation, and the normalized difference vegetation index (NDVI). The results showed that sediment load, runoff, and precipitation showed strong variability during 2007–2021, while water surface evaporation and NDVI exhibited moderate variability. Multivariate empirical mode decomposition (MEMD) decomposed the temporal patterns of sediment load and associated variables into five intrinsic mode functions (IMF) and a residue. IMF1 (4.7 months), IMF2 (9.0 months) and IMF3 (14.2 months) collectively explained 115.88 %, 91.73 %, 91.28 %, 107.69 %, and 106.09 % of the total variability in sediment load, runoff, precipitation, water surface evaporation, and NDVI, respectively. Subsequently, the time-dependent intrinsic correlation (TDIC) was utilized to illustrate the inherent relationships between sediment load and its controlling factors across various time scales. The associations between sediment load and the controlling factors changed significantly with the scale. Runoff was the dominant factor controlling sediment load at IMF1 (4.7 months), IMF2 (9.0 months), IMF3 (14.2 months), and IMF4 (25.1 months). Water surface evaporation controlled the sediment transport process at IMF5 (63.6 months). The prediction of sediment load on the measurement scale, using scale-specific controls analyzed with MEMD (R2 = 0.993), demonstrated superior performance compared to traditional multiple linear regression prediction (R2 = 0.748). This study will provide a theoretical basis for effective prevention and control of soil erosion and watershed management in inland river basins.

Extraction of River Water Bodies Based on ICESat-2 Photon Classification

The accurate extraction of river water bodies is crucial for the utilization of water resources and understanding climate patterns. Compared with traditional methods of extracting rivers using remote sensing imagery, the launch of satellite-based photon-counting LiDAR (ICESat-2) provides a novel approach for river water body extraction. The use of ICESat-2 ATL03 photon data for inland river water body extraction is relatively underexplored and thus warrants investigation. To extract inland river water bodies accurately, this study proposes a method based on the spatial distribution of ATL03 photon data and the elevation variation characteristics of inland river water bodies. The proposed method first applies low-pass filtering to denoised photon data to mitigate the impact of high-frequency signals on data processing. Then, the elevation’s standard deviation of the low-pass-filtered data is calculated via a sliding window, and the photon data are classified on the basis of the standard deviation threshold obtained through Gaussian kernel density estimation. The results revealed that the average overall accuracy (OA) and Kappa coefficient (KC) for the extraction of inland river water bodies across the four study areas were 99.12% and 97.81%, respectively. Compared with the improved RANSAC algorithm and the combined RANSAC and DBSCAN algorithms, the average OA of the proposed method improved by 17.98% and 7.12%, respectively, and the average KC improved by 58.38% and 17.69%, respectively. This study provides a new method for extracting inland river water bodies.

Analysis of Ecological Environment Changes Associate with Driving Factors in the Inland River Basin of Northwest China Based on GeoDetector

Analysis of Ecological Environment Changes Associate with Driving Factors in the Inland River Basin of Northwest China Based on GeoDetector

Urban flooding simulation and flood risk assessment based on the InfoWorks ICM model: A case study of the urban inland rivers in Zhengzhou, China.

Urban flooding intensifies with escalating urbanization. This study focuses on Xiong'er river as the study area and couples a 1D/2D urban flooding model using InfoWorks ICM (Integrated Catchment Modeling). Ten scenarios are set respectively with a rainfall return period of 5a 10a, 20a, 50a, and 100a, alongside rainfall durations of 1 and 24 h. Subsequently, the H-V (hazard-vulnerability) method was applied to evaluate urban flooding risk. Three indicators were selected for each of hazard factors and vulnerability factors. The relative weight values of each indicator factor were calculated using the AHP method. The result shows that (1) flood depth, rate, and duration escalate with longer rainfall return periods, yet decrease as the duration of rainfall increases; (2) as the rainfall return period lengthens, the proportion of node overflow rises, whereas it diminishes with longer rainfall durations, leading to an overall overloaded state in the pipeline network; and (3) the distribution in the research area is mainly low-risk areas, with very few extremely high-risk. Medium to high-risk areas are mainly distributed on both sides of the river, in densely built and low-lying urban areas. This study demonstrates that the model can accurately simulate urban flooding and provide insights for flood analyses in comparable regions.

Examining the influence mechanisms of gateway ports on inland ports in the context of Port regionalization - A case study of the Yangtze River Port system

This study examines the influence of gateway seaports on inland ports within a river port system, focusing on the Yangtze River port system as a case study. The research initially employs a fixed-effects panel model to confirm the overall positive impact of Shanghai Port on Yangtze River inland ports. Subsequently, using Panel data model with individual-specific slopes, this study reveal that Shanghai Port positively affects each inland port, but the magnitude of this impact varies significantly. The research further employs a panel threshold regression model to dissect the mechanisms through which Shanghai Port influences inland ports in terms of geographical, operational, and economic distances. In terms of geographical distance, the influence of Shanghai Port on the throughput of Yangtze inland ports diminishes as the navigational distance increases. Notably, inland ports located downstream on the Yangtze River are the first and most impacted, marking the downstream area as an early influencer in the port regionalization process. As to operational distance, Shanghai Port exerts a stronger influence on inland ports with higher throughput levels, as opposed to those with lower throughput. With respect to economic distance, inland ports in cities with higher economic development are found to be less influenced by Shanghai Port compared to those in less economically developed regions. This nuanced understanding provides invaluable insights into the interconnectedness of major gateway ports and their inland counterparts.

Zoning and regulation of compound flooding in coastal cities coupled with tracer method

Urban inland rivers play a significant role in mitigating flooding. However, the influence of their discharge on urban flooding affected by different flood drivers remains to be fully explored. Taking a catchment area in Haikou City, Hainan Province, China as an example, in light of the urban flooding model coupled with the water tracer method, this study investigates the degree of inundation in each flood zone under different inland river flows. The flood zones are determined by the flooding simulation results of three cases, and then are verified by the zonation based on the tide tracer approach. Finally, the tracer method is used to study the impact of urban inland rivers on flooding and the connection of hydraulic and water volume between rivers and pipelines. The results indicate that the inundation area decreased by 3.71 % as the river flow increased from 15 to 25 m3/s. In the process of river flow rising from 5 to 45 m3/s, The average flooding depth in the rainfall-affected area climbs slowly from 0.53 m to 0.62 m; In the tidal-affected area, the average flooding depth drops from 0.52 m to 0.12 m when the inland river flow increases from 5 to 25 m3/s, and rises from 0.12 m to 0.54 m when the inland river flow continues from 25 to 45 m3/s; The percentage of pipelines grows from 18.5 % to 28.0 %. This study provides valuable scientific insights and support for flood prevention planning and flood control strategies in coastal cities.

Ship deployment problem with green technology adoption for an inland river carrier under non-identical streamflow and speed limits

The maritime industry is currently experiencing a shift towards green corridors. The inland waterway is the main transportation corridor with a relatively low adoption of green technologies, which produces heavy air pollution in inland cities. This paper investigates the ship deployment problem for an inland river carrier considering the adoption of green fuel and green technologies for a given ship fleet. A non-linear programming (NLP) model is proposed to jointly optimize green technology adoption, sailing speed, and routing problems while considering two unique characteristics of inland river shipping, including the non-identical streamflow and the speed limits on each shipping leg. The analytical propositions reveal the optimal operation strategy of the inland river ship fleet, and a column generation-based algorithm is further designed to solve the proposed model. By jointly investigating the ship operation strategy and sulphur emissions, we find the following management insights: Firstly, the ship would have a lower willingness to invest in shore power (scrubber) if it installed scrubber (shore power). The higher streamflow and looser speed limits would reduce the spillover effect of green technology adoption. Secondly, emissions will spillover from ports to river legs if only shore power is provided. Our findings provide valuable insights for policymakers to promote complete green technology adoption to achieve comprehensive abatement of the entire inland river.

A novel image dehazing algorithm for complex natural environments

As an essential preprocessing step in computer vision tasks, image dehazing is preparatory work in many practical applications. To ensure the navigation safety of intelligent ships in complex haze weather, this paper proposes a lightweight real-time dehazing method for the natural environment based on an all-in-one dehazing network. Specifically, a hybrid dilated convolution is used to construct a dehazing network, which effectively expands the receptive field and improves the ability to extract characteristic information without increasing the calculation amount of the model. Secondly, a hybrid attention module is developed to enhance the model's ability to remove haze while retaining more detailed features by giving weights to light haze and heavy haze areas in the image. Finally, considering the subjective perception of human eyes, a mixed loss function is designed to address image dimness and color distortion after dehazing. Through experiments on both synthetic and real-world haze datasets, the proposed method attains ideal dehazing results and has high real-time performance. It can dehaze under different haze conditions, address the critical challenge of degraded visual perception in severe weather conditions of intelligent ship navigation on inland rivers in complex environments, and promote intelligent ships' development.

Using the Potential Transformation of Dissolved Organic Matter to Understand Carbon Emissions from Inland Rivers.

Understanding the transformation of river dissolved organic matter (DOM) is important for assessing the emissions of greenhouse gases (GHGs) in inland waters. However, the relationships between the variations in DOM components and GHGs remain largely unknown. Here, parallel factor analysis (PARAFAC) was applied to investigate the DOM components in 46 inland rivers in China. We found that the GHG emissions in peri-urban rivers were 1.10-2.15 times greater than those in urban rivers. Microbial and environmental factors (e.g., living cell numbers, microbial activity and pH) explained more than 70% of the total variance in GHG emissions in rivers. DOM variations relationships between different components ware revealed based on compositional data principal component analysis (CoDA-PCA). Microbial-mediated DOM production and degradation were quantified, and the degradation levels in peri-urban rivers were 11.8-25.2% greater than those in urban rivers. Differences in carbon emission potential between urban and peri-urban rivers were related to DOM variances and transformations and were affected by water chemistry (e.g., NH4-N and As). This study clarifies the regulatory effects of DOM composition variations and transformations on GHG emissions, and enhances the understanding of the DOM biogeochemical cycle.

Optimizing Crop Spatial Structure to Improve Water Use Efficiency and Ecological Sustainability in Inland River Basin

Optimizing Crop Spatial Structure to Improve Water Use Efficiency and Ecological Sustainability in Inland River Basin

Revealing the Ground Deformation and Its Mechanism in the Heihe River Basin by Interferometric Synthetic Aperture Radar and Optical Images.

The Heihe River Basin (HRB), located on the northeast margin of the Qilian Mountains, is China's second largest inland river basin. It is a typical oasis-type agricultural area in northwest China's arid and semiarid areas. It is important to monitor and investigate the spatiotemporal distribution characteristics and mechanisms of surface deformation in HRB for the ecology of inland river basins. In recent years, research on HRB has mainly focused on hydrology, meteorology, geology, or biology. Few studies have conducted wide-area monitoring and mechanism analysis of the surface stability of HRB. In this study, an improved interferometric point target analysis InSAR (IPTA-InSAR) technique is used to process 101 Sentinel-1 SAR images from two adjacent track frames covering the HRB from 2019 to 2020. The wide-area deformation of the HRB is obtained first for this period. The results show that most of the surface around the HRB is relatively stable. There are six areas with an extensive deformation range and magnitude in the plain oasis area. The maximum deformation rate is more than 50 mm/year. The maximum seasonal subsidence and uplift along the satellites' line-of-sight (LOS) direction can be up to -70 mm and 60 mm, respectively. Moreover, we use the Google Earth Engine platform to process the multisource optical images and analyze the deformation areas. The remote sensing indicators of the deformation areas, such as the normalized difference vegetation index (NDVI), soil moisture (SMMI), and precipitation, are obtained during the InSAR monitoring period. We combine these integrated remote sensing results with soil type and precipitation to analyze the surface deformations of the HRB. The spatiotemporal relationships between soil moisture, vegetation cover, and surface deformation of the HRB are revealed. The results will provide data support and reference for the healthy and sustainable development of the inland river basin economic zone.

Response of vegetation variation to climate change and human activities in the Shiyang River Basin of China during 2001–2022

Understanding the response of vegetation variation to climate change and human activities is critical for addressing future conflicts between humans and the environment, and maintaining ecosystem stability. Here, we aimed to identify the determining factors of vegetation variation and explore the sensitivity of vegetation to temperature (SVT) and the sensitivity of vegetation to precipitation (SVP) in the Shiyang River Basin (SYRB) of China during 2001–2022. The climate data from climatic research unit (CRU), vegetation index data from Moderate Resolution Imaging Spectroradiometer (MODIS), and land use data from Landsat images were used to analyze the spatial-temporal changes in vegetation indices, climate, and land use in the SYRB and its sub-basins (i.e., upstream, midstream, and downstream basins) during 2001–2022. Linear regression analysis and correlation analysis were used to explore the SVT and SVP, revealing the driving factors of vegetation variation. Significant increasing trends (P<0.05) were detected for the enhanced vegetation index (EVI) and normalized difference vegetation index (NDVI) in the SYRB during 2001–2022, with most regions (84%) experiencing significant variation in vegetation, and land use change was determined as the dominant factor of vegetation variation. Non-significant decreasing trends were detected in the SVT and SVP of the SYRB during 2001–2022. There were spatial differences in vegetation variation, SVT, and SVP. Although NDVI and EVI exhibited increasing trends in the upstream, midstream, and downstream basins, the change slope in the downstream basin was lower than those in the upstream and midstream basins, the SVT in the upstream basin was higher than those in the midstream and downstream basins, and the SVP in the downstream basin was lower than those in the upstream and midstream basins. Temperature and precipitation changes controlled vegetation variation in the upstream and midstream basins while human activities (land use change) dominated vegetation variation in the downstream basin. We concluded that there is a spatial heterogeneity in the response of vegetation variation to climate change and human activities across different sub-basins of the SYRB. These findings can enhance our understanding of the relationship among vegetation variation, climate change, and human activities, and provide a reference for addressing future conflicts between humans and the environment in the arid inland river basins.

Multi-objective double layer water optimal allocation and scheduling framework combing the integrated surface water – groundwater model

Balancing the water consumption of agricultural and ecological is the key point of sustainable social and economic development in an inland river basin. The growth of desert riparian forests in inland river basins mainly depends on a certain phreatic water table depth (PWTD). The main object of this study was to allocate and schedule water resources to regulate the PWTD and satisfy agricultural water demand. Therefore, a multi-objective double layer optimal allocation and scheduling framework based on the computationally efficient integrated surface water-groundwater model (ISGWM), which can simulate the surface water processes, groundwater recharge and discharge processes, and PWTD changes, was constructed and applied to the mainstream of Tarim River Basin (TRB). The top layer model of the framework is an optimal ecological water allocation model, and its optimal allocation results are used as the initial solution of the bottom layer model. The results show that under 5 different inflow frequencies, the agricultural water shortage rate is 0, 17.38 %, 17.41 %, 14.06 %, and 19.94 %, respectively. The PWTD regulation has a great performance. After the optimal scheduling, the proportions of good growth of the control area behind the gate under different inflow frequencies were 98.18 %, 98.18 %, 98.18 %, 90.91 %, and 94.55 %. Agricultural water shortage is mainly due to the non-uniformity distribution of intra-annual inflow and the lack of controlling hydraulic engineering. The regulation of PWTD can guarantee the growth of desert riparian forests on both sides of the mainstream of TRB. Besides, we explored the feasibility of exploiting groundwater to supplement agricultural water consumption. The groundwater exploitation should be controlled within the scope of not causing excessive increase of PWTD (difference between PWTD and target depth <1 m), due to the groundwater exploitation to supplement agricultural water will lead to the increase of PWTD. Overall, this framework, which regulates the PWTD with the change of ecological water supply based on the ISGWM, provides a new idea for the allocation and scheduling of agricultural and ecological water resources in arid inland river basins. It also provides a new method for the coupled cooperative operation of surface water and groundwater.

Pattern of water use by Tamarix ramosissima seedlings in floodplains under varied groundwater depths in the hinterland of the Taklimakan Desert

The water use of Tamarix ramosissima Ledeb. seedlings after flooding were analyzed both to explore the maintenance mechanism and pattern of natural regeneration of riparian forest, which will provide a scientific basis for restoration of desert riparian forest and ecosystem stability in the lower reaches of inland rivers of arid regions. This study area was located in the hinterland of the Taklimakan Desert in Xinjiang, China. Tamarix ramosissima seedlings growing on different groundwater depths at the river floodplain were used as the study system. The rooting depths of T. ramosissima seedlings with different basal stem diameters were ascertained by the root excavation method. The water source for the T. ramosissima seedlings was clarified using hydrogen and oxygen stable isotope methods, and the water use efficiency of T. ramosissima seedlings was investigated by stable carbon isotope (δ13C) analysis. As the basal stem diameter classes of the T. ramosissima seedlings increased, their root depths increased. As the groundwater depth increased, the seedlings changed from primarily utilizing deep soil water to utilizing shallow soil water. In the three sample sites, the average depth of water uptake of the seedlings with basal stem diameters of 0–5 mm was 110.5, 44.1 and 39.1 cm, respectively, and that of seedlings with basal stem diameters of 5–11 mm was 83.8, 73.6 and 37.7 cm, respectively. As groundwater depth increased, the average water uptake depth of the seedlings gradually became shallower. There was no significant difference in the δ13C values of leaves under different groundwater depths, indicating that the seedlings were not subjected to water stress. Thus, surface water played a greater role than groundwater in T. ramosissima seedling water utilization. Therefore, when analyzing ecological water conveyance patterns, attention should be paid to T. ramosissima located in areas with deep groundwater. Shallow-rooted seedlings with small basal stem diameters face an increased risk of wilting if they do not receive timely recharges of surface water. Data AvailabilityAll data generated or analyzed during this study are included in this published article.

Forecasting ecological water demand of an arid oasis under a drying climate scenario based on deep learning methods

Ecological water diversion projects (EWDP) are an effective management tool for restoring oasis ecosystems in arid regions. Given the potential for drier climatic conditions in arid regions in the future, it is essential to develop water diversion strategies that can adapt to climate change and reduce the risk of oasis ecosystem degradation. Here, this study used a Bayesian optimization-based long- and short-term memory (BO-LSTM) model to determine the optimal amount of water diversion needed to maintain healthy growth of oasis vegetation under future climate change scenarios in the Qingtu Oasis, which is a typical downstream oasis of inland rivers restored by EWDP in China. The results showed that the BO-LSTM model effectively captured the response of oasis vegetation to changes in water inundation areas and drought stress with low computational cost and high accuracy. The study revealed that regional vegetation became more vulnerable than previously thought when extreme drought and a drying trend were taken into account. It was found that if the amount of water entering the oasis ranges from 10 to 15 million m3, there will be a decline in the growth of oasis vegetation as indicated by the normalized difference vegetation index (NDVI). Even if current levels of water diversion (20 million m3) are maintained, oasis vegetation may still face growth decline due to meteorological drought. The optimal amount of water diversion was determined to be 25 million m3, resulting in a 21.7% increase in NDVI regardless of drought events. This study represents an innovative approach as it couples EWDP, climate change, and oasis vegetation dynamics based on deep learning models, which unveils divergent responses of oasis vegetation to climate change and EWDP and verifies a non-linear relationship between water diversion amounts and ecological benefits generated.

The response of agricultural drought to meteorological drought modulated by air temperature

Due to climate change, there is an increasing occurrence of combined extreme events. The interaction between agricultural drought and meteorological drought may be significantly influenced by the temperature conditions. However, the specific process and the extent of air temperature’s impact on the dynamic remain unknown. To this end, the present study develops a copula-based coupling model to integrate agricultural drought, meteorological drought, and temperature state. This model is designed to investigate how temperature affects the agricultural drought response to meteorological drought, and to determine the transition threshold of temperature state on agricultural drought responding to meteorological drought from inhibition to promotion under diverse drought conditions. Furthermore, the proposed model is used to explore the spatial distribution characteristics of sensitivity and temperature thresholds in summer over mainland China. Finally, the geographical detector model is employed to investigate the primary factors influencing the spatial distribution of sensitivity and temperature thresholds. Results indicated that: (1) high temperatures have intensified the response of agricultural drought to meteorological drought in over 88% of mainland China, while in the Qinghai-Tibet Plateau region of the Inland River basin, this response is mitigated by glacier meltwater resulting from high temperatures; (2) the thresholds are lower in the Southeast River basin, the lower reaches of the Yangtze River, the Pearl River basin, the southern Songliao River basin and the Haihe River basin, but higher in the Yellow River basin, the western Yangtze River basin, the southern Inland River basin and Yunnan Province; and (3) the land-atmosphere coupling is crucial in determining both sensitivity and threshold levels.