Groundwater Depth Research Articles

Groundwater Depth and Harvest Frequency Affect Alfalfa Nitrogen Uptake, Water Use and Forage Quality in Coastal Saline Soil of North China

Groundwater Depth and Harvest Frequency Affect Alfalfa Nitrogen Uptake, Water Use and Forage Quality in Coastal Saline Soil of North China

Geodetic/gravimetric evidence for mass loss in the subsidence area of Bandung, Indonesia

Land subsidence monitoring in Bandung, Indonesia, was initiated in the 2000 s. However, the monitoring has been limited to geometric observations only, which may restrict the further physical interpretation of the cause of the subsidence. In this study, we combine geometric and gravity observation methods to monitor surface subsidence in Bandung. 63 Synthetic Aperture Radar (SAR) images from Sentinel-1A covering the period of 2014–2020 were used to estimate the mean surface geometric changes. For the gravity observations, a hybrid gravity configuration that incorporates absolute (2008–2014) and relative (2011–2016) gravity observations were used to estimate the gravity changes. We estimated geometric changes of up to − 160 mm/yr, indicating rapid subsidence in the greater Bandung area. We obtained gravity changes ranging between − 56.7 and 40.1 μGal/yr. Upon subtracting the deformation-induced gravity field from the observed field, we produced a residual gravity field that was presumed to be dominated by the groundwater signal, which was then investigated further. We found that the gravity-derived groundwater signal was mainly negative, indicating subsurface mass loss. We further compared the signal with the modeled gravity effect from deep groundwater observations (1996–2008). The median difference between the observed and modeled groundwater gravity signal was estimated to be 2.8 ± 18.0 μGal/yr or equivalent to 0.08 ± 0.55 m/yr in terms of water height if we set the integration cap and groundwater depth to 1.4 km and 150 m, respectively. The discrepancy can be attributed to modeling (simple geohydrological assumption) and measurement (different observation periods and noise) factors. Nevertheless, both measurements indicate that the mass is decreasing due to groundwater depletion, demonstrating the potential of geometric-gravimetric observations to infer sub-surface mass loss.

Pond basin colonization by terrestrial vegetation indicates wetland deterioration

Abstract Efforts to conserve the pond network in the Doñana National Park are being threatened by groundwater overexploitation. The dramatic expansion of farming and tourism in nearby areas has caused a severe lowering of the water table, reducing pond hydroperiod length or even instigating pond desiccation. It is important to document the link between groundwater abstraction and pond deterioration with a view to decreasing human pressures on the park and preserving the pond network's singular biodiversity. Here, the gradual deterioration of one of the network's main ponds is described in detail by characterizing vegetation patterns within the pond's basin using orthophotos taken between 1956 and 2019. In the earliest images, the pond contained a wide central area of bare soil during its dry phase. This area was surrounded by reeds and had a line of Tamarix canariensis trees along its southern edge. Starting in 2000, the orthophotos showed the pond's gradual colonization by terrestrial vegetation. In tandem, pond hydroperiod decreased, as did the length of time the pond retained certain depths of water. In recent years, Tamarix trees finally fully invaded the pond's central area, which is surrounded by reeds and has scattered terrestrial bushes and pines. This invasion resulted from the pond's sparse inundation over recent decades, being the cover of trees related to the depth of groundwater, and is a clear sign of pond deterioration. More broadly, colonization by terrestrial vegetation has been observed in approximately 60% of the network's ponds. Colonization of temporary pond basins by terrestrial vegetation can be used as an indicator of deterioration and highlights the need for active restoration and management.

Agricultural Land Quality Evaluation and Utilization Zoning Based on the Production–Ecology–Health Dimension: A Case Study of Huanghua City

Clarifying the constituent elements of agricultural land quality, carrying out multi-dimensional quality evaluation of agricultural land, and implementing precise land consolidation and utilization zoning all have important guiding significance for achieving efficient utilization of agricultural land in China. This work analyzed the multi-dimensional evaluation framework of agricultural land based on its comprehensive quality elements and the production, ecological, and health functions. This paper constructed a multi-dimensional agricultural land “production–ecology–health” quality evaluation index system and evaluation criteria, and carried out a multi-dimensional quality evaluation of agricultural land in Huanghua City, Hebei Province, China. The spatial superposition of each dimension′s evaluation results, combined with the logical relationship between agricultural land use and each dimension′s quality, realized the renovation and utilization zoning of agricultural land. The results are as follows: (1) The production, ecological, and health qualities of agricultural land in Huanghua City were below the average and there is spatial variability, whose proportions of grade III and below were 63.12, 66.23, and 69.32%, respectively. In addition, low score areas are mainly located in the south and northwest of the study area. (2) The obstacle factors to quality in different dimensions were different: The obstacle factors to production quality were matter content, soil pH, irrigation guarantee rate, and alkaline hydrolysis nitrogen; groundwater salinity and depth, soil pH, and chemical fertilizers consumption for ecological quality; and groundwater salinity and depth and soil pH for health quality. (3) Agricultural land in Huanghua city is divided into five types of remediation, including 30,277.34 hm2 for high efficiency utilization area, 10,576.54 hm2 for production quality cultivation area, 34,387.86 hm2 for health quality cultivation area, and 56,311.22 hm2 for comprehensive consolidation and restoration area; special remediation measures are proposed for different types of zones. The work improves the multi-objective quality evaluation index system for agricultural land and implements differentiated land remediation strategies by identifying obstacle factors through zoning. It provides methodological ideas to improve the efficiency of land remediation and utilization.

Effects of groundwater depth on groundwater recharge and soybean growth dynamics in Northeast China Plain.

To explore the groundwater recharge rate and soybean growth dynamics under different groundwater depths, we conducted a field experiment with four groundwater depth treatments (1 m, D1; 2 m, D2; 3 m, D3; 4 m, D4) through the groundwater simulation system in 2021 and 2022 and explored the relationships between groundwater depth and groundwater recharge, irrigation, growth dynamics of soybean plants, and yield. We used the Logistic regression model to simulate the dynamics of soybean growth indices, including plant height, leaf area index, and dry matter accumulation. The results showed that compared with D1 treatment, the amount of groundwater recharge under D2, D3, and D4 treatments decreased by 81.1%, 96.8%, 97.5% and 80.7%, 96.7%, 97.3% in the two years, respectively. The groundwater in D1 treatment could meet water needs of soybean throughout the whole growth period, except that irrigation was needed in the sowing stage. The amount of irrigation under D1 treatment was decreased by 91.7%, 93.0%, 94.2%, and 90.9%, 92.9%, 94.0% in the two years, respectively, compared with D2, D3, D4 treatments. Among the four treatments, D1 treatment took the shortest time for entering the rapid growth stage and reach the maximum growth rate, which had the highest maximum growth rate. At the mature stage of soybean, the dry matter distribution ratio of stem in D1 treatment was the highest. D1 treatment promoted the translocation of post-flowering assimilates in soybean, and its post-flowering assimilate contribution to seeds increased by 15.5%, 16.2%, 32.6% and 45.5%, 48.7%, 63.3% in the two years, respectively, compared with D2, D3, D4 treatments. D1 treatment had the highest plant height, leaf area index, and dry matter accumulation, follo-wed by D4 treatment, while D3 treatment had the lowest. Soybean yield, number of pods per plant, number of grains per plant, and 100-grain weight all decreased and then increased with increasing groundwater depth, following an order of D1>D4>D2>D3. Soybean yield was significantly positively correlated with groundwater recharge, which was positively correlated with plant height, leaf area index, and dry matter accumulation. Our results indicated that the D1 treatment with adequate groundwater recharge increased plant height, leaf area index, and dry matter accumulation, coordinated the distribution and translocation of dry matter among all plant parts in the late soybean growth period, and ultimately achieved the highest yield. When groundwater depth was deep (D4), groundwater recharge was small. In such case, the growth and development status and yield of soybean could also reach a high level if there was sufficient water supply.

Delineation of the Groundwater Potential Zone in Kantli River Basin, Jhunjhunu District, Rajasthan: A Geospatial Approach

Remote sensing and GIS are advanced techniques and tools that have been used for various researches including groundwater geology. The Landsat and the IRS satellite datasets have been utilized to extract information on the hydrogeomorphic and groundwater related features of a semi-arid Precambrian hard rock terrain in the Kantli River Basin of Jhunjhunu District, Rajasthan, India. It is the upper part of the Shekhawati River. The study area is covering about 2313.2013 km2 in the Jhunjhunu District, Rajasthan. In the present study, the groundwater potential zone is identified by the GIS overlay techniques using the spatial analyst tool in ArcGIS 10.2. The developed methodology is demonstrated in the Kantli River Basin of Rajasthan, western India. Originally, nine thematic layers, viz. topographic elevation, land slope, geomorphology, geology, soil, pre and post-monsoon groundwater depths, annual net recharge, annual rainfall and proximity to surface water bodies were considered in this study. Therefore, five groundwater potential zones were identified and distinguished in the study area, viz. 'very good', 'good', 'moderate', 'poor' and 'very poor' based on groundwater potential index values, which will enable the local bodies for the future planning and management of the groundwater resource. Severe groundwater contamination has been found occasionally in the study area. Every year during the summer, the region is facing a lot of problems with portable groundwater. As the study area is semi-desert, the influences of salinity have been increasing day by day in the groundwater. Keywords: Groundwater, Remote Sensing, Kantli River, Satellite Images, GIS, Potential zone

Delineation of the Groundwater Potential Zone in Kantli River Basin, Jhunjhunu District, Rajasthan: A Geospatial Approach

Remote sensing and GIS are advanced techniques and tools that have been used for various researches including groundwater geology. The Landsat and the IRS satellite datasets have been utilized to extract information on the hydrogeomorphic and groundwater related features of a semi-arid Precambrian hard rock terrain in the Kantli River Basin of Jhunjhunu District, Rajasthan, India. It is the upper part of the Shekhawati River. The study area is covering about 2313.2013 km2 in the Jhunjhunu District, Rajasthan. In the present study, the groundwater potential zone is identified by the GIS overlay techniques using the spatial analyst tool in ArcGIS 10.2. The developed methodology is demonstrated in the Kantli River Basin of Rajasthan, western India. Originally, nine thematic layers, viz. topographic elevation, land slope, geomorphology, geology, soil, pre and post-monsoon groundwater depths, annual net recharge, annual rainfall and proximity to surface water bodies were considered in this study. Therefore, five groundwater potential zones were identified and distinguished in the study area, viz. 'very good', 'good', 'moderate', 'poor' and 'very poor' based on groundwater potential index values, which will enable the local bodies for the future planning and management of the groundwater resource. Severe groundwater contamination has been found occasionally in the study area. Every year during the summer, the region is facing a lot of problems with portable groundwater. As the study area is semi-desert, the influences of salinity have been increasing day by day in the groundwater. Keywords: Groundwater, Remote Sensing, Kantli River, Satellite Images, GIS, Potential zone

Impact of deeper groundwater depth on vegetation and soil in semi-arid region of eastern China.

Understanding the impact of deep groundwater depth on vegetation communities and soil in sand dunes with different underground water tables is essential for ecological restoration and the conservation of groundwater. Furthermore, this understanding is critical for determining the threshold value of groundwater depth that ensures the survival of vegetation. This paper was conducted in a semi-arid region in eastern China, and the effects of deep groundwater depth (6.25m, 10.61m, and 15.26m) on vegetation communities and soil properties (0-200 cm) across three dune types (mobile, semi-fixed, and fixed dunes) were evaluated in a sand ecosystem in the Horqin Sandy Land. For vegetation community, variations in the same species are more significant at different groundwater depths. For soil properties, groundwater depth negatively influences soil moisture, total carbon, total nitrogen, available nitrogen, available phosphorus concentrations, and soil pH. Besides, groundwater depth also significantly affected organic carbon and available potassium concentrations. In addition, herb species were mainly distributed in areas with lower groundwater depth, yet arbor and shrub species were sparsely distributed in places with deeper groundwater depth. As arbor and shrub species are key drivers of ecosystem sustainability, the adaptation of these dominant species to increasing groundwater depth may alleviate the negative effects of increasing groundwater depth; however, restrictions on this adaptation were exceeded at deeper groundwater depth.

Влияние почвенно-мелиоративных факторов на выбор способов орошения в Азербайджанской Республике

The factors affecting the choice of irrigation equipment are enumerated in the article. A brief description of the water permeability of the soil was obtained, the depth of groundwater, the degree of soil salinization is given, and their variability in the republic's zones was shown. Also, choice of irrigation methods was carried out in the republic zones according according into account the given factors.

Effect of Autumn Irrigation on Salt Leaching under Subsurface Drainage in an Arid Irrigation District

Non-growing season irrigation and farmland subsurface drainage play a crucial role in salt leaching and salinization control in arid irrigation areas. This study aimed to investigate the reduction of autumn irrigation quotas and drainage discharge while maintaining soil moisture retention and reducing soil salinization. Field experiments were conducted with different autumn irrigation quotas (160 mm for SD1, 180 mm for SD2, and 200 mm for SD3) combined with subsurface drainage (1.5 m drain depth and 45 m spacing). A control treatment (referred to as CK) without subsurface drainage received 200 mm of irrigation. The results showed that, after 31 days of autumn irrigation, the groundwater depth in all three subsurface drainage plots stabilized to 1.5 m, with the CK being 0.2–0.3 m shallower compared to the SD plots. The mean soil water content in the 0–150 cm soil layer of the SD1, SD2, SD3, and CK after autumn irrigation was 0.36, 0.39, 0.41, and 0.42 cm3cm−3, respectively. The combination of autumn irrigation and subsurface drainage significantly reduced the soil salt content. The mean desalination rates in the root zone (0–60 cm) soil layer were 57.5%, 53.7%, 51.9%, and 45.1% for the SD3, SD2, CK, and SD1, respectively. The mean desalination rate of 60–150 cm was not significantly different between the SD2 and SD3 (p > 0.05), and both were significantly higher than that of the SD1 and CK (p < 0.05). The drainage discharge was 31, 36, and 40 mm in the SD1, SD2 and SD3, respectively. The amount of salt discharge through the drain pipe increased with increasing irrigation quota, which was 1.22 t/ha, 1.41 t/ha, and 1.50 t/ha for the SD1, SD2, and SD3, respectively. Subsurface drainage is an effective way to prevent salt accumulation in the soil, and an autumn irrigation quota of 180 mm is recommended for leaching of salinity in the Hetao Irrigation District. These findings provide valuable insights into optimizing irrigation practices and managing soil salinization in arid regions.

UNRAVELING THE SUBTERRANEAN: A COMPREHENSIVE EXPLORATION OF AQUIFER PROPERTIES AND HYDROGEOLOGICAL DYNAMICS IN WARRI SOUTH, DELTA STATE, NIGERIA

This paper investigates the complex relationship between apparent resistivity and electrode separation, revealing key underlying features. The research uses a range of field curve types to quantitatively and qualitatively analyse data from Vertical Electrical Sounding (VES). The study is divided into two sections: a qualitative interpretation section and a quantitative interpretation section, the latter of which focuses on the dynamics of aquifer potential in the Warri South region. Understanding the link between apparent resistivity and electrode separation is essential for hydro-geoelectric research. To increase the reliability of the results, curve matching, sophisticated modelling, and geological knowledge are used. Particularly, the predominance of HH curve types, followed by AH, HQ, KH, and KK configurations, provides a complete description of the hydrogeological terrain and a thorough description of subsurface features. To comprehend groundwater flow, distribution, and management, aquifer resistivity, thickness, depth, transverse resistance, longitudinal conductance, hydraulic conductance, and transmissivity are all researched. The complex interaction between resistivity levels and different rock types emphasises the dynamic nature of aquifer resistivity and disproves the idea that it has a set range. The patterns in the regional distribution of aquifer resistivity reflect the complexity of subsurface water supply. Aquifer thickness, depth, and transverse resistance, which highlight the complex interaction of geology and aquifer characteristics, are additional factors that aid in understanding hydrogeological processes. The hydrological potential of aquifers is discovered through variables like transmissivity and hydraulic conductivity, indicating the balance between geological characteristics and hydraulic gradients. These discoveries open the door to responsible water resource management and sustainable use by providing insights into the dynamics of hidden aquifers under the Earth’s surface.

Dependence of evapotranspiration validity on shallow groundwater in arid area-a three years field observation experiment

Groundwater resources strongly support crop water requirement and economic yield improvement in semi-arid and arid areas. Water resources management require more investigation in the response of evapotranspiration (ET) partitioning and water use efficiency to groundwater change. Observational data collected over a three-year period, including water and carbon flux, vegetable sap flow, meteorological factors, soil water content, and groundwater depth, were employed in this study. Additionally, an improved Shuttleworth-Wallace model was used for partitioning plant transpiration and bare soil evaporation (E) in a sunflower cropland with shallow groundwater. The ET of the sunflower was founded to be 353.5 ± 15.0 mm, and approximately 48.3 ± 7.4% derived from the groundwater evaporation. E amounted approximately 145.6 ± 6.1 mm over the growth season, and around 47.2% of which was lost during the seeding stage. Furthermore, its dynamics depended on crop growth and groundwater table depth (WTD). These large amounts of non-productive soil E had a negative impact on the water-carbon coupling. The presence of E had resulted in a lower ecosystem water use efficiency (WUEe), measured at 1.02 ± 0.33 g C kg−1 H2O, compared to canopy water use efficiency (WUEc) of 1.68 ± 0.41 g C kg−1 H2O. These results demonstrated that regulating WTD could improve WUEe by increasing WUEc and reducing soil E. To achieve the higher WUEe, an optimum WTD was range of 1.5–2.0 m for border-irrigated sunflower field grown on sandy loam, identified by an analysis of normalized evaporation difference at the varying WTD. This finding highlights the significance of maintaining specified WTD, providing valuable insights into the complex interplay between crop evapotranspiration components and shallow groundwater. Moreover, it offers guidance for precision agriculture irrigation practices.

Groundwater Pollution Risk Assessment in Plain Area of the Yarkant River Basin

Groundwater pollution risk assessment is an effective method to manage groundwater resources and prevent groundwater pollution. The DRSTIW model was used to evaluate the groundwater vulnerability in a plain area of the Yarkant River Basin, and factor analysis was used to identify pollution sources for pollution loading evaluation. The functional value of groundwater was estimated by considering both the mining value and the in-situ value. The entropy weight method and the analytic hierarchy process (AHP) were used to determine the comprehensive weight, and a groundwater pollution risk map was generated based on the overlay function of ArcGIS software. The results showed that the natural geological factors such as large groundwater recharge modulus, wide recharge sources, strong permeability of soil surface and unsaturated zone, and shallow groundwater depth facilitated pollutant migration and enrichment, resulting in a higher overall groundwater vulnerability. Very high vulnerability and high vulnerability areas were mainly distributed in Zepu County, Shache County, Maigaiti County, Tumushuke City, and the eastern part of Bachu County. The pollution loading of groundwater was generally low, the main pollution sources were point source pollution caused by water-rock interaction, non-point source pollution caused by pesticides and fertilizers, and point source pollution caused by industry and life. The overall functional value of groundwater was low because of human economic activities, fine water quality, and good habitat quality. Groundwater pollution risk was generally low, and very high and high pollution risk areas accounted for 20.7% of the study area, mainly distributed in Shache County, Zepu County, Maigaiti County, Tumushuke City, and the western part of Bachu County. Natural conditions such as strong aquifer permeability, weak groundwater runoff conditions, large groundwater recharge modulus, low vegetation coverage, and strong water-rock interaction, coupled with frequent human activities such as application of agricultural fertilizers and discharge of industrial and domestic sewage, made the groundwater pollution risk higher in these areas. Groundwater pollution risk assessment provided strong data support for the optimization of the groundwater monitoring network and the prevention of groundwater pollution.

Dwindling Ground Water Table: An Ecological Study of Southern Haryana

The dwindling ground water level is one of the critical issues that plague India in the present times. This research study primarily has its basis in the secondary data, gathered from the Ministry of Water Resources. The main aim of the present research study is to highlight the issues related to ground water in various parts of India with the main focus on southern part of Haryana state. The spatial pattern of the ground water depth is studied using the secondary data from various sources. The water table depth and fluctuation maps in Arch GIS 9.3 are analysed by making use of geological analysis extension. The water elevation is examined by employing the Kriging estimator. Also, the different ways of prevention that can help in checking the quick dwindling of ground water table are discussed so that the sustainable use of ground water can be encouraged and achieved. It is observed that the menace of ground water depletion has posed alarming threat to the states of Punjab, Haryana, Uttar Pradesh and some south Indian states. This is attributed mainly to the agricultural, industrial and human needs amidst the ever-rising rate of population in India. In the southern Haryana, the Mahendergarh district and Firozpur block of Mewat area have been identified as most critical zones in relation to water depletion. The study suggests judicious and sustainable use of water resources so as to check the alarming dwindling of the ground water table.

Proxy modeling approach to evaluate groundwater recharge potentiality zones in the data scarce area of upper Blue Nile Basin, Ethiopia.

Prioritization of groundwater recharge potentiality evaluation is critical for sustainable water resources management. Since recharge is a main source for enhancing groundwater availability. Water scarcity is extremely severe in the upper Blue Nile Basin (i.e., Gunabay watershed). Therefore, this study emphasizes groundwater recharge delineating and mapping 3920.25 km2 in the data-limited area of the upper Blue Basin using proxy modeling (i.e., WetSpass-M model and geodetector model) and tools. The driving/influencing factors are rainfall, temperature, wind speed, evapotranspiration, elevation, slope, land cover, soil, groundwater depth, drainage density, geomorphology, and geology that control the movement of groundwater recharge. However, the first nine factors were used as inputs in the WetSpass-M model to evaluate groundwater recharge. To validate the groundwater recharge availability, water table fluctuation was established based on recorded groundwater levels. Furthermore, the major influencing factors and their interaction have been quantified using geodetector model. Spatiotemporal recharge distribution (in mm) is classified as very low (0-6), low (6-30), moderate (30-51), high (51-83), and very high (83-508) comprising 21%, 20%, 20%, 20%, and 19% of the total area, respectively. Very high groundwater recharge zone has been found in the northwest part of the area. The geodetector results showed that soil (0.841) and temperature (0.287) had larger individual contributions, but the interaction between soil and temperature (0.962) was more significant. It indicates that the interaction between climate and soil has the largest influence on groundwater recharge variability. Generally, the overall approach of this study can be applied to water sectors, policymakers, and decision-makers to overcome future water scarcity.

Free power, irrigation, and groundwater depletion: Impact of farm electricity policy of Punjab, India

AbstractThis paper examines the impact of a change in the policy regime from flat rate to free farm electricity pricing, introduced in Punjab, India in February 1997 using a difference‐in‐differences framework. Based on village‐level data from the second and the third rounds of the Minor Irrigation Census, the study finds a differential increase in the number of electric‐operated tubewells and horsepower load of pumps in Punjab as compared to an agriculturally‐similar and neighboring state, Haryana, which is taken as the control group. Through these channels, the study finds that the average groundwater depth increased by 1.9 meters more in Punjab as compared to Haryana, which is 22 percent of the baseline average groundwater depth in Punjab. Nationally‐representative well‐level data on groundwater depths from the Central Ground Water Board shows impact heterogeneity with sharper effect on groundwater depth for wells that are lying closer to the cut‐off of about 10 meters where a technological shift from centrifugal to submersible pumps is required to maintain access to groundwater pumping.

Identification of priority pollutants and key factors affecting environmental risks of lead‑zinc mine tailing sites

Lead‑zinc mine tailing sites are widely distributed in China. Tailing sites with different hydrological settings tend to have different susceptibilities toward pollution and hence different priority pollutants and environmental risks. This paper aims to identify priority pollutants and key factors influencing environmental risks of lead‑zinc mine tailing sites with different types of hydrological settings. A database with detailed information on hydrological settings, pollution, etc. of 24 typical lead‑zinc mine tailing sites in China was built. A rapid classification method of hydrological settings was proposed considering the groundwater recharge and migration of pollutants in the aquifer. Priority pollutants in leach liquor of tailings, soil, and groundwater of sites were identified using the osculating value method. The key factors affecting environmental risks of lead‑zinc mine tailing sites were identified using the random forest algorithm. Four types of hydrological settings were classified. Pb/Zn/As/Cd/Sb, Fe/Pb/As/Co/Cd, and nitrate/iodide/As/Pb/Cd are identified as priority pollutants of leach liquor, soil, and groundwater, respectively. The lithology of the surface soil media, slope, and groundwater depth were identified as the top 3 key factors that affect the environmental risks of sites. Priority pollutants and key factors identified in this study can provide benchmarks for the risk management of lead‑zinc mine tailing sites.

Abiotic stress and human activities reduce plant diversity in desert riparian forests

Plant diversity is very important for maintaining the structure and function of ecosystems. Affected by climate change, it is increasingly sensitive to abiotic stresses, especially in ecologically fragile arid areas. Moreover, human activities have accelerated this process, resulting in a reduction in plant diversity. Revealing the spatial pattern and effecting mechanisms of plant diversity at the watershed level is beneficial to biodiversity conservation. Here, we analyze changes in plant diversity and its influencing factors in the desert riparian forest in the lower reaches of the Kashgar River using niche theory, interspecific association analysis, geographic information system (GIS) mapping, redundancy analysis (RDA), and structural equation modelling (SEM). We show that the niche breadth of plants varies from 0.174 to 0.451, and niche overlap ranges from 0.059 to 0.995, and Populus euphratica and Tamarix chinensis are the dominant species for improving the desert environment and maintaining the stable and ecological balance of communities. Plant diversity has spatial heterogeneity that woody plants are higher than herbaceous plants, which decreases with increasing groundwater depth and salt content. Groundwater depth was the key factor to stress plant diversity. In fact, it works by influencing soil moisture and salt content. LULC change significantly reduced plant diversity (P < 0.05) and destroyed ecosystem balance. Plant diversity and NDVI were significantly positively correlated (P < 0.01). It is useful for understanding and predicting changes in plant diversity. Therefore, the effective implementation of ecological water conveyance can promote groundwater rise, alleviate soil water shortage, reduce salt content, and promote the increase in plant diversity. In addition, reasonable control of LULC changes and improvement of vegetation cover will help maintain higher plant diversity.

Influences of paleoclimatic environment and hydrogeochemical evolution on groundwater salinity in an arid inland plain in northwestern China

Highly saline groundwater limits the availability of freshwater resources, especially in arid/semi-arid inland areas with a growing demand but a scarcity of water resources. Understanding the spatial distribution of groundwater salinity and the factors that control their variability is vital for the scientific management of water resources in these areas. Integrated hydrogeochemistry and environmental isotopes (δD, δ18O, 3H, 14C) were used to study the distribution and evolution of fresh and saline groundwater in the Aksu Plain and its links to the paleo-climatic environment since the Late Pleistocene. The results indicated that the sources of groundwater was meteoric water from the Tianshan Mountains. Modern groundwater was found in the piedmont plain and shallow groundwater adjacent to the surface water. The paleo-atmospheric precipitation replenished the deep confined groundwater during the Last Glacial Period. There was no correlation between groundwater salinity and depth. Along the flow path, groundwater salinity has no increasing trend. We found that the paleoclimatic environment and water-rock interaction jointly determine the distribution of groundwater salinity, while evaporation had a slight effect based on the isotopic composition. The long residence time (8–19 ka) and evaporites in sediments (such as halite and gypsum) could provide the conditions for sufficient water-rock interactions, leading to the formation of brackish/saline groundwater. Conversely, the fresh, deep, confined groundwater corresponds to paleo-recharge conditions during the humid Last Glacial Period (21–24.5 ka). Surface water infiltration reduces the salinity of shallow groundwater, but the influence is limited. This study presents a mode that combines hydrogeochemical evolution and paleoclimatic environments to better assess groundwater salinity in the arid inland region.

Temporal and spatial characteristics of vegetation coverage and their influencing factors in the Sugan Lake wetland on the northern margin of the Qinghai–Tibet Plateau

Fractional vegetation cover (FVC) is an important indicator of the development or reversal of salt marsh due to its absence in arid desert areas. Many studies have emphasized the differences in factors that affect fractional vegetation cover (FVC) in different temporal and spatial scales. However, few studies have reported on the temporal and spatial variations in vegetation coverage and their response to climate and also on the hydrological environment in inland salt marsh wetlands. Accordingly, based on a wetland community survey, different types of data, such as meteorological data, hydrological data, and Landsat remote sensing image data, recorded during the period from 1990 to 2020 were collected. The characteristics of the spatial and temporal distribution of vegetation coverage in the Sugan Lake wetland over the past 30 years were analyzed using a binary pixel model. Furthermore, a quantitative analysis on the response of vegetation coverage to hydrological and meteorological factors was undertaken. The results of the present study showed that the dimidiate pixel model had a high simulation accuracy in retrieving the vegetation coverage in inland salt marsh wetlands. The vegetation coverage of the Sugan Lake wetland increased with each year from 1990 to 2020, and its annual average was 19.34%. The spatial distribution of vegetation coverage was patchy and decreased from the center to the edge of the wetland. Within the same period, the vegetation coverage showed an increasing trend in Quan-shui and He-hong areas and a decreasing trend in the Shan-hong area. Vegetation coverage was mainly affected by various factors, such as precipitation, lake area, surface runoff, groundwater depth, and residential density, respectively. It was significantly positively correlated with precipitation (R2 = 0.56, P &amp;lt; 0.01), lake area (R2 = 0.50, P &amp;lt; 0.01), air temperature (R2 = 0.46, P &amp;lt; 0.01), and river system density (R2 = 0.52, P &amp;lt; 0.01) and negatively correlated with groundwater depth (R2 =-0.57, P &amp;lt; 0.01) and residential density (R2 = −0.38, P &amp;lt; 0.05). Implicit in these findings are complex mechanisms of change in vegetation coverage that help prevent the degradation of vegetation in fragile ecosystems.