Arid Inland River Basin Research Articles

Identification of dominant drivers of streamflow spatiotemporal variations in typical mountainous areas in the Hexi Corridor, China

Study regionTypical mountain areas in the Hexi Corridor, China. Study focusWater security and ecosystem sustainability of arid inland river basins are highly dependent on upstream streamflow. However, due to the complex geographical environment and limited observation data in the study region, the attribution of spatiotemporal variations in streamflow influenced by climate change and/or human activities remains unclear. Here, we used partial least squares regression (PLSR) and the Budyko framework to unravel the dominant drivers of spatiotemporal variation in streamflow over the past 30 yr. New hydrological insight for the regionPrecipitation, topographic wetness index, slope, forest land, gross primary productivity, hydrological connectivity, soil organic carbon content, silt content, relative relief, NDVI and gravel content dominated spatial variation in streamflow. Temporal variation of streamflow was sensitive to precipitation and land surface. Specifically, increased precipitation and land surface alteration dominated the increase in streamflow in 50 % of the watersheds and the decrease in streamflow in 33 % of them, respectively. Further, land surface alteration was dominated by expansion of agricultural and built-up areas, weakened hydrological connectivity, increased landscape aggregation and forest cover. Controlling agricultural and built-up areas and the scale of afforestation, and focusing on the dynamics of hydrological connectivity and landscape patterns in the upstream reaches are imperative to maintain the security and sustainability of water resources in the arid inland river basins.

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.

Dynamics of carbon and water vapor fluxes in three typical ecosystems of Heihe River Basin, Northwestern China

Understanding the dynamics of carbon and water vapor fluxes in arid inland river basin ecosystems is essential for predicting and assessing the regional carbon-water budget amid climate change. However, studies aiming to unravel the mechanisms driving the variations and coupling process of regional carbon-water budget in a changing environment in arid regions are limited. Here, we used the eddy covariance technique to analyze the relationship between CO2 and H2O fluxes in three typical ecosystems across the upper, middle, and lower reaches of an arid inland river basin in Northwestern China. Our results showed that all ecosystems acted as carbon sinks, with the alpine swamp meadow, cropland, and desert shrubland sequestrating −300.2 ± 0.01, −644.8 ± 2.9, and − 203.7 ± 22.5 g C m−2 yr−1, respectively. Air temperature (Ta) primarily controlled daily gross primary productivity (GPP) and net ecosystem CO2 exchange (NEE) in the irrigated cropland during the growing season, while soil temperature (Ts) and vapor pressure deficit (VPD) regulated these parameters in the alpine swamp meadow and desert shrubland. Additionally, Ta and net radiation (Rn) controlled daily evapotranspiration (ET) in cropland, while Ts and Rn regulated ET at other sites. Consequently, carbon and water vapor fluxes of all three ecosystems tended to be energy-limited during the growing season. The differential responses of carbon and water vapor fluxes in the upper, middle, and lower reaches of these ecosystems to biophysical factors determined their distinct coupling and variations in water use efficiency. Notably, the desert shrub ecosystem in the lower reach of the basin maintained a stable balance between carbon gain and water loss, indicating adaptation to aridity. This study provides valuable insights into the underlying mechanisms behind the changes in carbon and water vapor fluxes and water-use efficiency in arid river basin ecosystems.

The ternary water cycle of ‘nature–society–trade’ in the inland arid areas

AbstractWater cycle is important for maintaining the dynamic balance of regional water resources. Here, based on the input–output water circulation flux accounting model, we take Xinjiang as a case area to empirically explore the mechanism of the ‘nature‐society‐trade’ ternary water cycle. The results show that the water transferred out was much larger than the transferred in in Xinjiang. The scale of water resources development and utilization and the social water cycle fluxes have been constantly expanding, but there was a mismatch between the hydrological system and the socio‐economic system in terms of water resource utilization. From 2007 to 2017, agriculture had always been the department with the largest amount of direct water consumption and virtual water transfer in Xinjiang, which mainly transferred virtual water to the light industry and service sector where the production of final products requires large amounts of agricultural products as raw materials or intermediate products. In Xinjiang, the virtual water transferred outside through trade in products and services was much larger than the virtual water transferred in from other regions, and it was thus always in a state of net virtual water outflow as a whole. In inter‐provincial trade of China, Xinjiang mainly transferred virtual water to areas with abundant water resources, developed economies and dense populations in eastern China. Lastly, we put forward targeted suggestions on the optimal allocation of water resources to promote the sustainable development of Xinjiang and we hope that our study will be instructive for water resources management in other arid inland river basins.

The potential risk of soil salinization on vegetation restoration by ecological water conveyance project in Qingtu Lake Wetland, northwestern China

AbstractThe Ecological Water Conveyance Project (EWCP) is an important measure to restore the degraded vegetation ecosystem in Qingtu Lake Wetland (QLW), a terminal lake wetland of an arid inland river basin in northwestern China. Although many previous studies have demonstrated the positive effect of EWCP for vegetation restoration, they have ignored the possible soil salinization by EWCP which could lead to re‐degradation of restored vegetation in QLW. Therefore, the purpose of this study is to reveal the potential risk of soil salinization on sustainable vegetation restoration in QLW. Three satellite remote sensing‐based indices (i.e., Normalized Difference Vegetation Index (NDVI), Salinity Index, and Normalized Difference Water Index) are used to indicate the spatio‐temporal evolutions of vegetation growth status, surface soil salinity, and water surface. Additionally, ground data of groundwater, soil, and ecological water volume are collected. The development of soil salinization and its risk on vegetation restoration as well as its controlling factors are subsequently studied by combining remote sensing and ground‐based data. The results indicate that the vegetation restored during the first few years of EWCP in the southwest, west, and north of QLW has degraded again due to the aggravation of soil salinization in these regions since 2019. Soil salinization was accelerated by the low groundwater depth with high mineralization and high evaporation capacity of climate without adequate inundation of ecological water. Under current ecological water management in QLW, soil salinization will intensify and vegetation will further degrade. The artificial management of ecological water in QLW has created a complex relationship among vegetation growth, soil salinization, and groundwater. This indicates the irrationality of using a fixed relationship between groundwater depth and NDVI for the computation of optimal ecological water volume in previous studies. More field monitoring of groundwater‐soil‐surface water‐plant‐atmosphere continuum and process‐based modeling of water‐salt transport and vegetation growth should be conducted in the future.

Simulation of the Spatial Flow of Wind Erosion Prevention Services in Arid Inland River Basins: A Case Study of Shiyang River Basin, NW China

Wind erosion is a key global environmental problem. As an important protective measure to provide services to the ecosystems in wind-eroded areas, the wind erosion prevention service is of great significance to the management of wind and sand hazards and ecological environment restoration in the wind-eroded areas and the neighboring areas. Taking the Shiyang River basin as the study area, the quality of supplies for wind erosion prevention services was estimated using the RWEQ model for the years 2005, 2010, 2015, and 2020; the trajectories of air masses at wind speeds higher than the sand-causing wind speeds were simulated based on the forward trajectory module of the HYSPLIT model for a 24 h period; the spatial simulation of the flow of wind erosion prevention services on a daily scale with Minqin Station as the sand source was carried out; and the beneficiary areas of wind erosion prevention services were identified. Based on the RWEQ model, the spatial patterns of potential wind erosion, actual wind erosion, and wind and sand stabilization services were obtained, and the supply areas were divided. From 2005 to 2020, the wind erosion prevention service flow in the Shiyang River basin was distributed along a northwest–southeast direction, with a radial decrease from the center to the periphery, and with an extremely strong extraterritorial effect. The amount of wind erosion in the basin has a variable downward tendency over time and a spatial distribution pattern of high in the north and low in the south. The area of higher sand fixation is distributed in the eastern oasis area and desert junction zone. The HYSPLIT model was used to simulate the transport paths of wind and sand within 24 h during 2005–2020, the transmission paths of the wind erosion prevention service flow were obtained to be 59–134, and the flows were 2.55 × 104–3.85 × 106 t, displaying a changing trend of first decreasing, then increasing, and then decreasing. Gansu Province, Ningxia Hui Autonomous Region, and Inner Mongolia Autonomous Region are the most important areas benefiting from the wind erosion prevention service flow in the Shiyang River basin. The wind erosion prevention service flows in the basin benefit 47 cities in 9 provinces.

Optimal Scale and Scenario Simulation Analysis of Landscape Ecological Risk Assessment in the Shiyang River Basin

The evaluation of landscape ecological risk (LER) in a river basin holds significant importance for the overall ecological environmental protection of the basin and subsequent sustainable development. The Shiyang River basin, a typical arid inland river basin, was selected as the research object, and the optimal scale of LER research was explored. Multi-period land use data was used to build an LER assessment model and reveal the temporal and spatial changes of LER in the Shiyang River basin. The PLUS model was used to simulate the spatial distribution characteristics and change trends of LER under different scenarios in 2030. The results show that the LER in the Shiyang River Basin has obvious scale dependence, with optimal granularity and magnitude of 60 m and 4.5 km, respectively. LER is dominated by higher risk and high risk categories, with significant spatial differences, showing a trend of low in the southwest and high in the northeast. The LER of the Shiyang River Basin decreased from 2000 to 2020. It is expected that the LER value under different scenarios in 2030 will show a downward trend, and the LER value under the ecological conservation priority scenario will be the lowest. This study can provide a reference for LER assessment in arid inland river basins.

Spatial and Temporal Variation Characteristics of Stable Isotopes in Precipitation and Their Relationships with Meteorological Factors in the Shiyang River Basin in China

Stable isotopes of precipitation play an important role in understanding hydrological and climatic processes of arid inland river basins. In order to better understand the difference of regional water cycle and precipitation patterns, precipitation samples were collected in Shiyang River Basin from June 2018 to May 2020, and spatial and temporal variation characteristics of stable isotopes in precipitation and their relationships with meteorological factors were discussed. The results showed that stable isotopes in precipitation showed seasonal variation characteristics, that δ2H and δ18O values were higher in summer and autumn and lower in winter and spring, and d-excess values were higher in spring and autumn and lower in winter and summer. Slopes and intercepts of the local meteoric water lines gradually increased with elevation increasing. δ18O significantly showed a positive correlation with temperature but a negative correlation with precipitation in summer. Contrary to below 15 hPa, δ18O significantly showed a negative correlation with water vapor pressure above 15 hPa. Due to the influence of meteorological factors, there are significant differences in stable isotopes of precipitation in arid inland river basins, which were more influenced by local moisture recycling in upstream area but by below-cloud secondary evaporation in mid-downstream area.

Interkingdom ecological networks between plants and fungi drive soil multifunctionality across arid inland river basin.

Despite the known collective contribution of above- (plants) and below-ground (soil fungi) biodiversity on multiple soil functions, how the associations among plant and fungal communities regulate soil multifunctionality (SMF) differentially remains unknown. Here, plant communities were investigated at 81 plots across a typical arid inland river basin, within which associated soil fungal communities and seven soil functions (nutrients storage and biological activity) were measured in surface (0-15 cm) and subsurface soil (15-30 cm). We evaluated the relative importance of species richness and biotic associations (reflected by network complexity) on SMF. Our results demonstrated that plant species richness and plant-fungus network complexity promoted SMF in surface and subsurface soil. SMF in two soil layers was mainly determined by plant-fungus network complexity, mean groundwater depth and soil variables, among which plant-fungus network complexity played a crucial role. Plant-fungus network complexity had stronger effects on SMF in surface soil than in subsurface soil. We present evidence that plant-fungus network complexity surpassed plant-fungal species richness in determining SMF in surface and subsurface soil. Moreover, plant-fungal species richness could not directly affect SMF. Greater plant-fungal species richness indirectly promoted SMF since they ensured greater plant-fungal associations. Collectively, we concluded that interkingdom networks between plants and fungi drive SMF even in different soil layers. Our findings enhanced our knowledge of the underlying mechanisms that above- and below-ground associations promote SMF in arid inland river basins. Future study should place more emphasis on the associations among plant and microbial communities in protecting soil functions under global changes.

Developing a multi-objective simulation-optimization model for ecological water conveyance in arid inland river basins

Study regionMiddle and lower reaches of Tarim River, southwestern of Xinjiang Province, China. Study focusEcological water conveyance is an important measure to protect the fragile ecosystem of inland rivers in arid areas. This paper attempted to present a integrated model for optimal ecological water conveyance scheme (EWCS). In this model, the impact of the duration of water conveyance and the water allocation of each channel on the groundwater level was considered. The optimized ecological water conveyance scheme can simultaneously maximize groundwater level rise value (GLRV) and minimize ecological water conveyance volume (EWCV). New hydrological insights for the regionAn simulation-optimization model was proposed based on MODFLOW model, Kriging surrogate model and NSGA-II. The study obtained the Pareto frontiers of EWCS in three typical years (dry, normal and wet), and made decisions using the TOPISIS-Entropy method. The scenario comparison results indicated that the optimized EWCS requires less EWCV than the existing one when achieving the same GLRV, proving that the optimized EWCS has higher water resource utilization efficiency. This simulation-optimization model fills the research gap of EWCS in arid inland river basins and provides scientific guidance for government management.

Assessing the evolution and attribution of watershed resilience in arid inland river basins, Northwest China

Water scarcity significantly limits the sustainable development of oasis economies in arid inland river basins. Quantifying watershed resilience and its drivers is a major focus in the fields of hydrology and water resources. In this study, the resilience indicator pi represents watershed resilience, while meteorological, hydrological, socioeconomic, and ecological factors are used to investigate the spatial and temporal patterns of resilience and important driving factors in the Hotan River Basin from 1958 to 2020 by combining principal component analysis and random forest model. Results show that the overall resilience of the Hotan River Basin is low, decreasing from the upper (upstream) to the middle and lower (downstream) reaches, and that the intensity of human activities has a negative impact on resilience. Rivers are more likely to reach maximum resilience after experiencing periods of wet and dry conditions, although there is a lag in this progress. The random forest machine learning algorithm was used to accurately predict the resilience levels of the two upstream tributaries Yurungkash and Karakash Rivers, and the downstream Hotan River, with classification accuracies of 84.2 %, 71.4 %, and 87 %, respectively. The factors affecting the resilience of the Yurungkash River are the 30-day maximum, base flow index, low pulse duration, median streamflow in May, median streamflow in August, median streamflow in October, and 7-day maximum. The set of factors used to classify the resilience of the Karakash River include the 7-day maximum, 1-day maximum, median streamflow in June, 30-day maximum, 3-day maximum, median streamflow in February, and autumn temperature. The factors affecting the resilience of the Hotan River are the watershed inflow, Xiaota station runoff, population growth rate, and effective irrigated area. The findings of this study provide a theoretical basis for integrated water resource management and the sustainable development of the oasis economy in the Hotan River Basin.

Impact of Ecological Restoration Project on Water Conservation Function of Qilian Mountains Based on InVEST Model—A Case Study of the Upper Reaches of Shiyang River Basin

Scientifically evaluating the influence of ecological restoration projects on the water conservation function (WCF) of regional ecosystems is the foundation for formulating regional ecological restoration policies and optimizing and adjusting ecological restoration projects. In this paper, we considered fully the runoff generation and confluence process in the Qilian Mountains with the actual situation of the basin and re-rated the parameter Z to improve the simulation accuracy of InVEST model. On this basis, the impact of ecological restoration project on the WCF in the upper reaches of Shiyang River Basin (SRB) in the eastern part of Qilian Mountains was quantified. The results showed that, on the whole, the water conservation depth (WCD) of forest land was the largest (138.5 mm) and that of cultivated land was the smallest (24.78 mm), while the water conservation coefficient of forest land was also the largest (93.36%) and that of unused land was the smallest (16.67%). From 1986 to 2018, the WCD showed an increasing trend in the upper reaches of SRB, among them, the WCD in the western tributaries increased faster than that in the eastern tributaries from 1986 to 2000. The significantly increased areas were mainly distributed in the middle reaches of the western tributaries and the river source areas of the eastern tributaries, while the significantly decreased areas were mainly distributed in the river source areas of the western tributaries and the cultivated land expansion area in the middle reaches of the eastern tributaries. From 2000 to 2018, the WCD of the eastern tributaries increased more than that of the western tributaries. The significantly increased areas were mainly distributed in the four eastern tributaries, and the significantly decreased areas were scattered in the middle and lower reaches of each tributary. From 1986 to 2000, the overall influence of land use change on the increase in WCD was negative, while the influence of climate and land use change on the increase in water conservation were both positive from 2000 to 2018. The influence of land use change on WCD was different in different tributaries. Among them, that of the western tributaries (except the Dongda River) was positive in two different periods, while that of the eastern tributaries (except the Xiying River) was changed from negative to positive. The implementation of ecological restoration project was one of the main reasons for the improvement of WCF in Qilian Mountains from 2000 to 2018, with a contribution of 9.04%. In the future, the protection and restoration of decreased areas of WCF should be strengthened, and the Z value determined in this paper is expected to be applied in the arid inland river basins of northwest China.

Coupling Simulation and Prediction of Sustainable Utilization of Water Resources in an Arid Inland River Basin under Climate Change

The arid endorheic basin of northwest China is characterized by rich land resources, water shortage, and a fragile ecological environment. The establishment of a credible coupling model of groundwater and surface water based on multi-source observation data is an effective means to study the change in basin water cycles and the sustainable utilization of water resources in the past and future. Based on the latest understanding of hydrogeological conditions, hydrology and water resource utilization data in the middle reaches of the Heihe River Basin (HRB), this paper constructs an up-to-date coupling model of surface water and groundwater to study the water balance change of the basin. The water resources data series under historical replay and CMIP5 climate model prediction are constructed to predict future changes in water resources. The study shows that, under the joint influence of natural conditions and human activities, the average annual recharge of groundwater in the study area from 1990 to 2020 is 17.98 × 108 m3/a, the average annual discharge is 18.62 × 108 m3/a, and the difference between recharge and discharge is −0.64 × 108 m3/a. The total groundwater storage is −19.99 × 108 m3, of which the groundwater storage from 1990 to 2001 was −17.52 × 108 m3 and from 2002 to 2020 was −2.47 × 108 m3. Abundant water from 2002 to 2020 in the basin significantly improved the loss of groundwater storage. Under the prediction of historical reappearance and the CMIP5 CNRM-CM5 model RCP4.5 and RCP8.5 pathways, the groundwater level of the Heihe River–Liyuanhe River inclined plain falls first because the HRB has just experienced a wet season and then rises according to future climate change. The groundwater level of the inclined plain east of the Heihe River and Yanchi basin decreases continuously because of the change in water cycle caused by human activities. The erosion accumulation plain is located in the groundwater discharge zone, and the water level is basically stable. Under the conditions of water resource development and utilization, the runoff of Zhengyixia hydrological station cannot meet the requirements of the “97 Water Dividing Plan” of the State Council in most years in the future, and the ecological and production water in the lower reaches of HRB cannot be effectively guaranteed. With the implementation of water-saving irrigation under the RCP4.5 and RCP8.5 scenarios, the runoff of Zhengyixia can meet the “97 Water Diversion Plan”. It is suggested to further improve the level of agricultural water savings in the middle reaches of the HRB and control the reasonable scale of cultivated land in order to reduce water consumption in the middle reaches of the HRB and implement sustainable utilization of water resources in the HRB.

Vegetation responses to ecological water delivery and prolonged droughts in an artificial desert oasis, Northwestern China

Irrational water usage in the middle reaches of inland rivers is detrimental to downstream oases, and the Qingtu Oasis is a typical downstream oasis that is degraded by water resource scarcity. The Qingtu Lake ecological water diversion project (EWDP) has restored the oasis, but the response pattern of different vegetation communities to environmental water and the dominant drivers of vegetation dynamics are not clear. Here, based on ground and satellite observations, this study investigated the spatial and temporal patterns of vegetation distribution and growth in the Qingtu Oasis from 2010 to 2022, and the reasons for the interannual variability in vegetation growth were also explained. The results showed that temporal variations in the distribution area of Phragmites australis (PA) followed a logistic curve after the EWDP, which increased rapidly from 2010 to 2019 and stabilized afterward. Meanwhile, the distribution area of Nitraria tangutorum (NT) presented a linear increase during the study period, with a 121.2% increase. Due to water inundation, the central region was occupied by PA communities, while NT communities moved to the edge. The spatial connectivity of PA patches increased significantly in contrast to the overall fragmentation tendency of NT patches in 2010–2022. The oasis tended to be homogenized and aggregated according to the morphological spatial pattern analysis, along with the landscape diversity and contagion indices. Enhanced vegetation growth, as indicated by the normalized difference vegetation index (NDVI), was observed in 76.1% of the vegetated lands, and the NDVI increasing rate was high near the canal. Using the random forest model, this study found that changes in groundwater depth were the most important driver of NDVI variability. The following influencing factors were atmospheric CO2 concentration, water inundation area and water delivery amount. In the absence of large increases in water delivery amount, oasis vegetation growth was susceptible to prolonged droughts. This study uncovers a nonlinear response of different vegetation communities to climate change and the EWDP in the downstream region of arid endorheic basins and identifies meteorological droughts as a key factor that should be fully considered in water delivery strategies. These findings lay a solid foundation for managing oasis restoration and water resource allocation in arid inland river basins.

Optimal allocation for land in an arid inland basin in northwest China: framework and application based on CLUE-S and MCR models.

Reasonable planning of the limited land resources can promote the coordinated development of social economic and ecological protection. It is very important to optimize the rational distribution of land resources in the arid inland river basin because of the scarce land. In this paper, the GIS technologies of spatial analysis, conversion of land use, and its effects at small regional extent (CLUE-S) and minimum cumulative resistance (MCR) model were used to optimize the land allocation. The ecological security pattern (ESP) was constructed through using MCR model, which included ecological source and resistance surface. The dynamics of land use and spatial optimizing allocation of Shiyang River Basin in 2025 and 2030 was simulated under three different optimization scenarios including farmland protection scenario (FPS), free development scenario (FDS), and ecological security pattern scenario (ESPS). It was found that under ESPS, farmland was reduced, but woodland, grassland, and water body were increased significantly. Under FPS, land for construction was controlled effectively, a large part of homestead was converted into farmland, and the potential of unused land was developed vigorously. Furthermore, the current FDS and macro policy guidance should be comprehensively considered. The ESPS was more suitable for the scientific development of Shiyang River Basin on a long view. The combination of CLUE-S and MCR can effectively improve the optimization methods under ecological process and ecological resistance of landscape elements.

Spatial Distribution and Driving Mechanisms of Rural Settlements in the Shiyang River Basin, Western China

In the context of the rural revitalization strategy, an accurate grasp of the spatial differentiation characteristics and influencing factors of rural settlements in underdeveloped arid inland river basins is urgently required. Taking the Shiyang River Basin as an example, rural settlements from 2000 to 2019 were examined via visual interpretation using satellite remote sensing data and official statistical data. Following the logic of “state characteristics—evolutionary patterns—influence factors—layout optimization”, the average nearest index, the gravity-center migration model, spatial statistical analysis, and other methods were used in combination with GIS. The spatiotemporal pattern evolution characteristics of rural settlements in the past 20 years were analyzed. The results revealed the following: (1) The distribution pattern of rural settlements in the study area is sheet-like and strip-shaped. The projects in the southeast are mostly distributed in a patchy pattern with high density, while the characteristics in the west and north are exactly opposite. The objects in the south are distributed in an alluvial area of rivers, while settlements in the north are located in an oasis area. (2) From 2000 to 2019, the scale of rural settlements in the Shiyang River Basin, where there is a simultaneous occurrence of newly-built and disappearing phenomena, shows an expansion trend that first increased quickly and then slowed down. Spatially, rural settlements in the basin show a clustering trend toward the southwest. (3) The distribution characteristics of rural settlements are close to water and roads, and they are greatly influenced by urban–rural integration and ecological migration. The results will provide a scientific basis for accelerating the modernization of rural areas and the construction of new rural areas according to local conditions.

Water use strategy of nitraria tangutorum shrubs in ecological water delivery area of the lower inland river: Based on stable isotope data

Excessive water use in the upper and middle reaches of arid inland river basins will inevitably lead to the drying up of the lower reaches. Water allocation and ecological water delivery have been widely used as water resources management strategies in global arid regions, and the implementation of such strategies has a great impact on the downstream ecosystem. We established an ecohydrological observation system at the lower reaches of the Shiyang River, an inland river in the arid region of China. The stable hydrogen and oxygen isotope technique was used to study the influence mechanism of artificial water delivery on the water use strategy of nitraria tangutorum shrubs, the typical dominant species around Qingtu Lake. The results showed that: (1)12.33% of the water used by the dominant species in the terminal lake area came directly from ecological water delivery, 77.88% from soil water formed by water delivery, and only 9.79% from precipitation. (2)With the increase of distance, nitraria tangutorum shrubs absorbed less surface soil water and lake water, and gradually turned to using deeper soil water and precipitation. (3) Ecological water delivery cycles affected the water use strategies of nitraria tangutorum shrubs. The proportion of deep soil water used by plants increased in the non-water delivery period, and the proportion of precipitation absorbed by plants also increased. Thus, Vegetation in the terminal lake region mainly depended on ecological water use, and the amount and time of water delivery directly determined the water use of dominant species. The results help us to understand the adaptation mechanism of plants under the background of artificial water delivery in the low reaches of arid inland river basins and provide a reference for the rational use of water resources and ecological construction.

Untangling the coupling relationships between socio-economy and eco-environment in arid inland river basin

Untangling the coupling relationships between socio-economy and eco-environment in arid inland river basin

Assessment and Factor Diagnosis of Water Resource Vulnerability in Arid Inland River Basin: A Case Study of Shule River Basin, China

Water resources in arid and semi-arid inland regions are highly vulnerable, facing threats from global climate change and human activities. Ensuring water resource sustainability requires scientifically evaluating the vulnerability of water resources and its driving factors. Taking the Shule River Basin, an inland river in northwest China, as an example, this study established an assessment system considering 16 influencing factors based on three aspects, including natural vulnerability, anthropogenic vulnerability, and carrying capacity vulnerability. The mature-element fuzzy model based on comprehensive weight and the Delphi method were used to evaluate the water resource vulnerability of the basin from 2005 to 2021. The results were as follows: (1) The water resource vulnerability in the Shule River Basin was between severe and moderate from 2005 to 2021, with a trend towards severe vulnerability. (2) The barrier analysis at the index level shows that factors of natural vulnerability had a low impact on water resource vulnerability in the basin from 2005 to 2019 but exerted a greater impact in 2020–2021, an impact that was far higher than that caused by factors of man-made vulnerability and water resource vulnerability. The impact of factors of anthropogenic vulnerability on water resource vulnerability was relatively low in the entire study period, except in 2016, 2017, 2020, and 2021. In 2005–2010, the factors of bearing capacity vulnerability had a great impact on water resource vulnerability, but in 2011–2021, the impact was alleviated and was gradually reduced. (3) Among the 16 factors affecting water resource vulnerability, the obstacle degree was higher than 6.5% for the following factors: the ratio of irrigation water use on farmland, the annual precipitation, total water resources, the annual quantity of wastewater effluent, the urbanization rate, the surface water control rate, and the degree of groundwater resource amount, exploration, and utilization obstacle values.