Groundwater Security Research Articles

Evaluation of Groundwater Security under Engineering Environment in Geda Township Area,Tibe

Water body is one of the important factors of engineering spatial structure, and also the carrier of spatial activities. The Tibetan Plateau is known as the “third pole in the world”. It has a special geographical location and a large number of projects for engineering infrastructure. Therefore, how to build various major and large-scale projects under the plateau environment needs to be further strengthened to the importance of water bodies. In this paper, through the geological conditions in Geda Township, Tibet, Analysis and performance of water mechanism in the area, through the field discovery, The water direction in the survey area is controlled by the structure and terrain; at the same time, the project water supply guarantee is mainly for the qualitative and quantitative evaluation of water quality and quantity information, the water supply guarantee of the investigation area is mainly divided into surface water supply water guarantee and groundwater water supply guarantee. This paper describes the relevant content of groundwater protection, through the field investigation and field water quality collection, the basic situation in the investigation area is that: the groundwater quality is generally superior to that of the surface water, especially more than Jilin spring water, better water quality and larger amount of water; It is of guiding significance to water quality investigation and geological engineering construction in other areas.

Groundwater Marketing Dynamics in Northern Dry Zone Farms of Karnataka: A Comparative Study (2006 to 2021)

Groundwater is an essential resource, but it is becoming increasingly scarce and depleting rapidly, particularly in Karnataka. As a result, groundwater markets have emerged as an alternative strategy to manage this limited resource more efficiently and equitably. These markets enable farmers who cannot afford water extraction machinery to access irrigation. This article, aims to study present status of groundwater markets, temporal depletion of water table, groundwater security, economics and factors affecting water trade in Northern Dry Zone of Karnataka, mainly to compare with the results obtained in the past study [1] to analyze changes in scenario and have historical lessons. Multi-stage random sampling technique was used to select farmers, who were then categorized into water sellers, self-users, and buyers. Primary data was collected through a structured, pre-tested schedule and analysed using descriptive and logit regression analysis. Results show that unlike earlier study, buyers in present study owned wells. Depth of borewells has increased (overall 44%), resulting in increased drilling, deepening, and pumping costs. Very few farmers (8%) acknowledged over-extraction from their farms could also contribute to groundwater insecurity. While studying economics it was found that perennial crops had the highest economic rents (260, 610Rs/hr for sellers and buyers).Reason for participation in water market has shifted from no investment capacity to water scarcity compared to earlier study. So farmers could be motivated to participate in water markets instead of relying on new wells during water shortages to encourage optimal water use and reduce negative externalities like increasing wells.

Unveiling subsurface heterogeneity in porous aquifers: Insights from hydrogeophysics and derivative analysis

Groundwater is a crucial resource, particularly in urban areas where the need for alternative water sources is rising. Securing groundwater resources is paramount, requiring a concentrated effort to assess these resources and mitigate the increasing water shortages in urban regions. Despite its significance, the application of hydrogeophysics and derivative analysis in understanding aquifer dynamics is often overlooked and underused. Consequently, this study argues that neglecting the integration of hydrogeophysics dataset and derivative analysis in aquifer characterization leads to developing models that lack solution-oriented approaches, hindering effective groundwater management. This study aimed to enhance understanding of aquifer dynamics for solution-based modeling while emphasizing the importance of integrating hydrogeophysics dataset and derivative analysis to highlight aquifer system heterogeneities. The electrical resistivity tomography and derivative analysis of pumping test were used in this study to image the subsurface and amplify aquifer flow regimes respectively. The results of the electrical resistivity survey revealed a distinct layer of fine to medium-grain sand at depths of approximately 60 m in certain areas intercalated with medium-to-coarse-grain sand and thin layers of peat. Derivative analysis plots indicated that the predominant flow regime is linear and bilinear, with evidence of fracture dewatering during pumping cycles suggesting an unconfined aquifer. Additionally, aquifer heterogeneity and a no-flow boundary were evident during the pumping cycle. This study underscores the efficacy of combining hydrogeophysics and derivative analysis of pumping tests as a robust approach for imaging and validating subsurface conditions. The implications of these findings extend beyond the specific case study, offering valuable insights for groundwater utilization, monitoring, and management on a broader scale. By elucidating effective methodologies, this research enhances groundwater security and meets the escalating demand for sustainable water sources in urban areas. In conclusion, electrical resistivity tomography is an effective tool for characterizing subsurface aquifer systems, while derivative analysis of pumping tests is crucial for highlighting aquifer system heterogeneities. These methods offer a more practical interpretation compared to traditional drawdown versus time curve approaches, making the results invaluable for groundwater usage monitoring and management.

Optimizing Recharge Area Delineation for Small- to Medium-Sized Groundwater Systems through Coupling Methods and Numerical Modeling: A Case Study of Linfen City, China

In previous investigations, the demarcation of capture zones within a specific research area predominantly relied on a singular method, leading to pronounced limitations and uncertainties. To address this challenge, an extensive field survey was conducted, focusing on the systematic classification of water sources in the Linfen City region. Building upon this classification, an intricate fusion of a hydrogeological analysis and formulaic methodology was employed. This integrated approach, coupled with independent numerical simulation methods, was applied to delineate recharge areas for both alluvial fan pore water in piedmont regions and exposed karst water in small- to medium-sized water sources. Simultaneously, precise spatial interpolation was carried out on water quality monitoring data from supply wells within the water source area for the year 2020. This meticulous analysis facilitated the determination of the spatial distribution characteristics of hydrochemical elements. To assess the water quality within the capture zone, the class III groundwater quality standards of China were employed as a pivotal tool for validating the results of the delineation of water source recharge areas. In the final analysis, a comparative study between the integrated coupling method and numerical simulation outcomes revealed the successful delineation of the boundaries for the water supply areas of Tumen and Caojiapo in Linfen City, covering areas of 5.5 km2 and 22.29 km2, respectively. Simultaneously, the combination of the three methods accurately outlined the boundary of the Hexi water supply area, encompassing an area of 2.5224 km2. These results vividly illustrate that the amalgamation of various methodologies proves more beneficial for the precise delineation of capture zones, particularly in diverse types and scales of groundwater sources. The synergy exhibited by these three methods underscores their collective efficacy, providing a more comprehensive and intuitive delineation of the recharge areas for small- to medium-sized water sources. Consequently, these findings significantly enhance the practical application value of the study and hold promise in making substantial contributions to local groundwater security and management initiatives.

Occurrence and Formation Mechanisms of High-Fluoride Groundwater in Xiong’an New Area, Northern China

While extant research has predominantly focused on elucidating the mechanisms of fluorine (F−) enrichment in groundwater within the North China Plain, the occurrence and formation mechanisms of high-F− groundwater in Xiong’an New Area remain unexplored. Consequently, 365 groundwater samples (172 from shallow groundwater, 193 from deep groundwater) were collected from Xiong’an New Area. Hydrochemical analysis, geochemical modeling, and statistical analysis were used to explore the occurrence and formation mechanisms of high-F− groundwater. The results reveal that the highest F− concentrations in shallow and deep groundwater were up to 3.22 mg/L and 1.79 mg/L, respectively. High-F− groundwater was primarily located at the eastern part of the study area. The distribution area of high-F− shallow groundwater was much greater than that of deep groundwater. F-bearing minerals dissolution and ion exchange were the principal formation mechanisms of high-F− groundwater in both shallow and deep aquifers. Moreover, competitive adsorption, evaporation, and the impacts of Ca2+ and Mg2+ dissolution equilibrium on F-bearing dissolution were crucial to the formation of high-F− groundwater in shallow aquifers. Desorption in an alkaline environment, evaporites dissolution and salt effects were vital to the formation of high-F− groundwater in deep aquifers. These findings can contribute to the support of local groundwater security and management.

Identification of the Pollution Mechanisms and Remediation Strategies for Abandoned Wells in the Karst Areas of Northern China

Abandoned well pollution is a critical component of global environmental issues and a historical legacy issue of national development. Despite this, the specific mechanisms by which abandoned wells pollute groundwater remain unclear, particularly in the karst regions of Northern China, where no scientifically effective remediation methods exist. To address this gap, this study focuses on Yangquan City in Shanxi Province and employs field investigations, the analytic hierarchy process, high-definition deep-well logging technology, and qualitative analysis to assess the pollution risk of all abandoned wells in the study area, identifying those with high pollution risk. Through the analysis of extensive image and video data for these high-risk wells, we propose a conceptual model of cross-strata channels in abandoned wells and elucidate the mechanisms by which they pollute groundwater. The results show that, from a single-well perspective, the pollution mechanism is cross-strata pollution. From a regional perspective, the pollution mechanisms are hydraulic connectivity and solute migration and transformation. Based on these findings, we present a scientifically effective remediation strategy tailored to the typical characteristics of abandoned wells in the study area, offering a viable solution to the abandoned well pollution problem in Yangquan City. This research not only augments the theoretical framework in the domain of groundwater pollution but also advances sustainable groundwater security and management strategies. Moreover, the study furnishes theoretical foundations and pragmatic solutions for the remediation of abandoned wells in Yangquan City, which are crucial for the sustainability of the groundwater ecosystem.

Application of hydrogeophysics and diagnostic plots in setting up a sustainable managed aquifer recharge scheme, West Coast, South Africa

The lack of using hydrogeophysics and hydraulic data in setting up a sustainable managed aquifer recharge scheme leads to challenges in operations and maintenance of such infrastructures. Managed aquifer recharge is an engineering and technological based water management approach that is used to maximize storage and improve groundwater security. However, this approach is under-utilized in many countries and South Africa is no exception. This study aimed at improving knowledge on aquifer dynamics for managed aquifer recharge scheme using hydrogeophysics and diagnostic plots. This study argued that integrating hydrogeophysics data and diagnostic plots for setting up managed aquifer recharge schemes lead to improved operations and maintenance through improved scientific knowledge on the dynamics of the aquifer. SkyTEM and electrical resistivity tomography data were used to delineate subsurface structures. Pumping test data were used to develop diagnostic plots, for identifying flow regimes and boundary conditions in the proposed managed aquifer recharge area. Results from geophysics investigation inferred pathways for potential managed aquifer recharge and areas to avoid. The integration of hydrogeophysics and diagnostic plots provided a more practical interpretation for the study area. It is recommended that hydrogeophysics investigation should be carried out before and after setting managed aquifer recharge scheme as it leads to enhanced decisions on groundwater usage, monitoring and management.

Newspaper coverage of water security issues in the water‐stressed Northern Province of Sri Lanka: An explorative study of three Tamil dailies

AbstractNewspapers remain as an effective medium for circulating information among the public in the North of Sri Lanka and have the potential to influence public opinion and people's behavior regarding sustainable use of groundwater. This study investigated the extent and scope of newspaper coverage on the subject of water security in the Northern Province of Sri Lanka. Three newspapers, namely, Yarl Thinakkural, Uthayan, and Valampuri were chosen on the basis of readership, circulation in print form, and for being daily local or regional papers in Tamil. The content analysis of 1214 articles published in 2019 and 2020 in the three papers indicated that as much as 80% of space in the papers was allocated to reporting general news items and events in the community related to new water projects, rain and floods or drought events and announcements of allocation of irrigation water for farming. Only 20% of newspaper space was taken up by non‐news articles including advertisements related to water. We conclude by saying that the effect of these newspapers on their audiences would merely be to inform rather than to set agendas or frame the discourse in society, let alone persuade readers enough to make changes. The study revealed the significant potential that exists for newspapers to shift their culture of simply reporting of facts in a dispassionate way to one of environmental journalism with a degree of advocacy in view of the critical nature of the security of groundwater in the Northern Province.

Groundwater security indicators and their drivers: An assessment made in a region of tropical climate (Paraopeba River basin, Brazil)

Groundwater helps overcoming periods of drought buffering their effects on water supply to people, natural ecosystems and the economy. Following the latest Conference of the Parties (COP27), groundwater research gained renewed impulse because the Parties committed themselves to invest on environmental dimensions of water security related with aquifer characterization and protection. In that context, the purpose of this study was to help providing an integrated assessment to some fundamental issues about groundwater security, summarized as the three “how”s: how much, how ready and for how long can groundwater be delivered from watersheds? A complementary goal was to identify and quantify the role of watershed characteristics controlling these “how”s. The methodology combined hydrologic modeling and GIS and the results for the test site (Paraopeba River basin, Brazil) were: (1) the studied river tributaries mostly drain regolith aquifers with short hydrologic turnover times (1.3–23.7 yr) and small aquifer mobile storages (0.1–1.3 m), but high specific yields (0.2–8.2 m/yr), being generally prone to hydrologic droughts; (2) the specific discharge is primarily elevation controlled (via precipitation increases with altitude), but relates positively with drainage density as well; (3) the mobile storage in the Quadrilátero-Ferrífero mountain is larger than elsewhere, being influenced by a local geomorphologic setting (higher coverage with concave hillslopes); (4) the groundwater contribution to streamflow discharge is high (> 50 %, on average), being improved with the coverage of argisols; (5) vulnerability to droughts could be alleviated through expansion of water-retention infrastructure in specific regions, as well as through land use conversions targeting reduced evapotranspiration or sustainable land management of argisol and concave surface landscapes. Although applied to a specific catchment, our results stand on a site-independent methodological framework. Thus, the understanding about groundwater security gained with this study can be inspiring to other workers dealing with tropical climate landscapes.

SD-DSS model of sustainable groundwater resources management using the water-food-energy security Nexus in Alborz Province

Unbalanced development of Alborz Province in recent years has amplified groundwater security crisis as well as water stress. This study conducted dynamic decision support system modelling of sustainable groundwater resources management based on water-food-energy security nexus (WFESN-SD-DSS). Using the results, the scenarios were designed in three categories of solutions: 1- Groundwater resources security; 2- Groundwater resources security; and 3- Groundwater resources security. The WFEN-SD-DSS model findings implied that combined policies represented the best solution and these included: Aquifer artificial recharge of 10 million cubic meters per year; control of well water usage; exploitation and reuse of graywater to supply 10% of agricultural water; 10% development of irrigation efficiency using novel irrigation systems; 10% reduction of agricultural waste; 10% development of the performance of agricultural products by modifying seeds, conserving plants; 5% reduction of electrical energy dissipation in combined cycle power plants; and development of solar water pump systems in agriculture sector.

Investigating the effect of soil cracks on preferential flow using a dye tracing infiltration experiment in karst in Southwest China

AbstractSoil cracks significantly affect the preferential flow, and various uncertainties are associated with the effect of soil cracks on preferential flow in karst areas in Southwest China. This study investigated soil crack properties (inclusions, width, and configuration) by applying ground‐penetrating RADAR (GPR) to pedons. Blue dye‐tracing experiments were designed based on the geophysical detection results to assess the influences of crack inclusions (sand grains and rock fragments), crack widths (1, 1.5, and 2 cm), and configurations (I‐shape, V‐shape, and Λ‐shape) on preferential flow. The following results were obtained: (1) the GPR envelope can describe the configuration of isolated soil cracks; (2) soil cracks can accelerate infiltration and increase the maximum dye‐penetration depth, cumulative infiltration, and wetting‐front depth by averages of at least 5.2%, 63.2% and 4.4%, respectively; and (3) the I‐ and Λ‐shaped soil crack configurations contributed to preferential flow, but the preferential flow was not observed along the V‐shaped‐configuration‐crack pore paths despite the retardation of brilliant blue FCF. The I‐shaped configurations, with a crack width of 1.5 cm, were filled with rock fragments and had higher preferential flow ratios (18.2%–52.3%) and length indices (4.0%–33.8%) compared to the other configurations. In summary, inclusions, crack width, and configuration significantly influence the preferential flow (p < 0.05), and the influence of these soil crack properties on preferential flow cannot be neglected during vegetation restoration and groundwater security operations in karst areas.

Ground truthing global-scale model estimates of groundwater recharge across Africa

Groundwater is an essential resource for natural and human systems throughout the world and the rates at which aquifers are recharged constrain sustainable levels of consumption. However, recharge estimates from global-scale models regularly disagree with each other and are rarely compared to ground-based estimates. We compare long-term mean annual recharge and recharge ratio (annual recharge/annual precipitation) estimates from eight global models with over 100 ground-based estimates in Africa. We find model estimates of annual recharge and recharge ratio disagree significantly across most of Africa. Furthermore, similarity to ground-based estimates between models also varies considerably and inconsistently throughout the different landscapes of Africa. Models typically showed both positive and negative biases in most landscapes, which made it challenging to pinpoint how recharge prediction by global-scale models can be improved. However, global-scale models which reflected stronger climatic controls on their recharge estimates compared more favourably to ground-based estimates. Given this significant uncertainty in recharge estimates from current global-scale models, we stress that groundwater recharge prediction across Africa, for both research investigations and operational management, should not rely upon estimates from a single model but instead consider the distribution of estimates from different models. Our work will be of particular interest to decision makers and researchers who consider using such recharge outputs to make groundwater governance decisions or investigate groundwater security especially under the potential impact of climate change.

Use of Hyperspectral Reflectance and Water Quality Indices to Assess Groundwater Quality for Drinking in Arid Regions, Saudi Arabia

Combining hydrogeochemical characterization and a hyperspectral reflectance measurement can provide knowledge for groundwater security under different conditions. In this study, comprehensive examinations of 173 groundwater samples were carried out in Makkah Al-Mukarramah Province, Saudi Arabia. Physicochemical parameters, water quality indices (WQIs), and spectral reflectance indices (SRIs) were combined to investigate water quality and controlling factors using multivariate modeling techniques, such as partial least-square regression (PLSR) and principal component regression (PCR). To measure water quality status, the drinking water quality index (DWQI), total dissolved solids (TDS), heavy metal index (HPI), contamination degree (Cd), and pollution index (PI) were calculated. Standard analytical methods were used to assess nineteen physicochemical parameters. The typical values of ions and metals were as follows: Na2+ > Ca2+ > Mg2+ > K+, Cl− > SO42− > HCO3− > NO3− > CO32−; and Cu > Fe > Al > Zn > Mn > Ni, respectively. The hydrogeochemical characteristics of the examined groundwater samples revealed that Ca-HCO3, Na-Cl, mixed Ca-Mg-Cl-SO4, and Na-Ca-HCO3 were the main mechanisms governing groundwater chemistry and quality under the load of seawater intrusion, weathering, and water-rock interaction. According to the WQIs results, the DWQI values revealed that 2.5% of groundwater samples were categorized as excellent, 18.0% as good, 28.0% as poor, 21.5% as extremely poor, and 30.0% as unfit for drinking. The HPI and Cd values revealed that all groundwater samples had a low degree of contamination and better quality. Furthermore, the PI values showed that the groundwater resources were not affected by metals but were slightly affected by Mn in Wadi Fatimah due to rock–water interaction. Linear regression models demonstrated the significant relationships for the majority of SRIs paired with DWQI (R varied from −0.40 to 0. 75), and with TDS (R varied from 0.46 to 0.74) for the studied wadies. In general, the PLSR and PCR models provide better estimations for DWQI and TDS than the individual SRI. In conclusion, the grouping of WQIs, SRIs, PLSR, PCR, and GIS tools provides a clear image of groundwater suitability for drinking and its controlling elements.

Environmental tracers and groundwater residence time indicators reveal controls of arsenic accumulation rates beneath a rapidly developing urban area in Patna, India

Groundwater security is a pressing environmental and societal issue, particularly due to significantly increasing stressors on water resources, including rapid urbanization and climate change. Groundwater arsenic is a major water security and public health challenge impacting millions of people in the Gangetic Basin of India and elsewhere globally. In the rapidly developing city of Patna (Bihar) in northern India, we have studied the evolution of groundwater chemistry under the city following a three-dimensional sampling framework of multi-depth wells spanning the central urban zone in close proximity to the River Ganges (Ganga) and transition into peri-urban and rural areas outside city boundaries and further away from the river. Using inorganic geochemical tracers (including arsenic, iron, manganese, nitrate, nitrite, ammonium, sulfate, sulfide and others) and residence time indicators (CFCs and SF6), we have evaluated the dominant hydrogeochemical processes occurring and spatial patterns in redox conditions across the study area. The distribution of arsenic and other redox-sensitive parameters is spatially heterogenous, and elevated arsenic in some locations is consistent with arsenic mobilization via reductive dissolution of iron hydroxides. Residence time indicators evidence modern (<~60–70 years) groundwater and suggest important vertical and lateral flow controls across the study area, including an apparent seasonal reversal in flow regimes near the urban center. An overall arsenic accumulation rate is estimated to be ~0.003 ± 0.003 μM.yr−1 (equivalent to ~0.3 ± 0.2 μg.yr−1), based on an average of CFC-11, CFC-12 and SF6-derived models, with the highest rates of arsenic accumulation observed in shallow, near-river groundwaters also exhibiting elevated concentrations of nutrients including ammonium. Our findings have implications on groundwater management in Patna and other rapidly developing cities, including potential future increased groundwater vulnerability associated with surface-derived ingress from large-scale urban abstraction or in higher permeability zones of river-groundwater connectivity.

Health risk assessment of groundwater nitrogen pollution in Yinchuan plain

High nitrogen concentration of groundwater poses a threat to human health. This study evaluated the potential health risk of nitrogen pollution in Yinchuan plain by geostatistical analysis and triangular stochastic model considering different land use types, and identified the uncertainties of the parameters. 163 samples were collected from groundwater wells in different land use types. The results show that the concentration of NO3−-N ranges from 0.059 to 450 mg/L, with an average of 22.439 mg/L. Approximately 32% of the samples exceed Grade III threshold (20 mg/L of N). The concentration of NH4+-N ranges from 0.011 to 11 mg/L, with an average of 0.456 mg/L. The concentration of NO2−-N ranges from 0.003 to 9.09 mg/L The NO3−-N and NH4+-N concentration in the groundwater of the unutilized land use is significantly lowest among all the land types. The concentration of nitrogen is highest in farmland use. The ranking of non-carcinogenic risk under different land types for infants, children, adult males and females is: farmland use > residential land use> unutilized land use. The non-carcinogenic risk value of farmland use is three times as much as that of the residential land use. Drinking groundwater can be potentially harmful to human health, and nitrogen pollutants pose an even greater threat to infant. At the same time, considering the impact of different land use types on groundwater would avoid overestimating or underestimating regional risk value. Triangular stochastic model is more sensitive to data changes and can reduce uncertainty. The contribution rate of nitrate concentration to risk is more than 83%, indicating that random sampling is needed to improve the reliability of evaluation results. The research results of this study will provide a new way to solve the uncertainty in groundwater security management.

Identification of Artificial Recharge Sites for Nand Samand Catchment

Abstract: Security of groundwater is widely regarded as a serious impediment to India's economic and social progress. According to the Central Ground Water Board's (CGWB) assessment, India's groundwater tables are plummeting at an alarming rate, with reserves in some regions reaching critical levels. Unregulated groundwater use in southern peninsular India has also resulted in excessive extraction, lowering the 'critical' threshold. With over 30 million groundwater structures in use, India is on the verge of a disaster of over-extraction that will leave 60% of all aquifers in critical condition within the next two decades. To resolve the issue, a variety of renewable groundwater solutions must be implemented. Artificial recharge is a procedure that augments groundwater at a pace that is significantly greater than the rate of replenishment under natural conditions, which may give a solution. The current study is for the Nand Samand catchment in the district of Rajasthan. The investigation of artificial groundwater recharge sites is being conducted using an integrated Remote Sensing and Geographic Information System (GIS) approach. Thematic maps such as topographic elevation, post-mosoon groundwater level, recharge, slope, transmissivity and soils map are created, and weighted overlay analysis is used to identify areas suitable for artificial recharge. Keywords: Nand Samand catchment, artificial recharge zone, thematic map, remote sensing, GIS

A groundwater security model based on hydraulic turnover times and flow compartments

Starting with a log-linear relationship between groundwater discharge per unit drainage area (Q/Ab), hydraulic turnover time (t) and aquifer mobile storage (z), this study builds a groundwater security method at catchment scale. The method embeds previously published approaches to calculate Q/Ab, t and z, and relies solely on stream flow discharges and watershed areas. The ability to build a method on a couple of variables is remarkable. The method recasts the calculated variables as aquifer security indicators (SQ, St and Sz), relating SQ with yield capacity, St with self-depuration capacity and Sz with resilience. Groundwater security is the weighted product of SQ, St and Sz. The method is validated with stream flow discharges and drainage areas concerning 294 hydrometric stations and their watersheds, located in continental Portugal. The results revealed a majority of moderately to highly secure watersheds, especially as regards St (> 62%), while 7–10% were classified as very highly secured in general (SQ-St-Sz). The least secured basins are located in the more arid regions of continental Portugal (Northeast and south regions), as expected. The method can be easily transposed to any other region worldwide, with the necessary adaptions to regional climate, geological and topographic settings.• Compile stream flow discharge data and organize them as natural logarithms and logarithmic variations as function of time, to estimate Q, t and z;• Recast the Q, t and z values as SQ, St and Sz ratings, respectively, using the appropriate reclassification scales, and estimate watershed security levels, namely average security or customized (weighted) securities that highlight the contributions of Q/Ab (watershed yield), t (aquifer's self-depuration capacity) or z (aquifer's resilience);• Use the results to draw illustrative diagrams and spatial distribution maps.

基于探地雷达的滨河带藤本和次生乔木林土壤优先流特征

PDF HTML阅读 XML下载 导出引用 引用提醒 基于探地雷达的滨河带藤本和次生乔木林土壤优先流特征 DOI: 10.5846/stxb202103260800 作者: 作者单位: 作者简介: 通讯作者: 中图分类号: 基金项目: 国家自然科学基金（32071839） Characteristics of preferential flow of liana and secondary arbor forests along riverside based on Ground Penetrating Radar Author: Affiliation: Fund Project: 摘要 | 图/表 | 访问统计 | 参考文献 | 相似文献 | 引证文献 | 资源附件 | 文章评论 摘要:滨河带是河流生态系统和森林生态系统的过渡带，该区域林分的土壤优先流特征对流域的地表水文过程会产生重要影响。探究土壤异质性与优先流的关系，为当地地下水安全和河流上下游水生态安全提供参考。本研究以永定河滨河带的藤本和次生乔木林两种植被为研究对象，结合传统亮蓝（Brilliant Blue FCF）染色示踪法，利用探地雷达（Ground Penetrating Radar，GPR）技术进行测线扫描。提取探地雷达图像的单道波形图，对反射波各参数与染色面积比进行拟合，并结合优先流染色特征进行分析。染色形态特征表明，藤本样地土壤染色形态呈现断离式零散分布，优先流发育带为土壤表层以下5-30 cm的土层深度，而次生乔木林土壤呈现大面积斑块状分布，优先流发育较为迟缓，其发育带为土壤表层以下10-25 cm的土层深度，且平均染色面积比藤本小1.68%。探地雷达测线表明，土层深度为0-15 cm时，最大振幅和总振幅面积均随土层的深度增加而下降，土层深度为15-35 cm时，两参数开始波动变化，且藤本样地的最大振幅和总振幅面积大于次生乔木林样地。经拟合发现，染色面积比与最大振幅呈y=25.104lnx+25.137（R2=0.8697）的对数关系，染色面积比与总振幅面积呈y=23.874lnx-26.862（R2=0.6173）的对数关系。以上分析可知，次生乔木林地土壤比藤本覆盖下的土壤紧实度更好，其电磁波在经历物理过程中损失的电磁信号较少，而藤本样地的电磁信号波动较大，可见藤本覆盖下土壤层次间结构差异变化比次生乔木林更明显，从而导致藤本覆盖下的土壤优先流程度更高。为保护地下水安全，对于滨河床地带和丘前的低洼地这类排水不良的区域，可对藤本植被茂盛的地带采取适当适量的伐藤措施来抑制藤本覆盖下的优先流过度发育，同时也可通过避免强降雨前施肥降低藤本植被覆盖下的地下水污染。 Abstract:The riparian zone is a transition zone between river ecosystem and forest ecosystem. The characteristics of preferential flow in forest belt along riverside have an important influence on the surface hydrological process of the watershed. Therefore, study of the relationship between soil heterogeneity and preferential flow is of great significance to local groundwater security and water ecological security of upstream and downstream rivers. In this paper, using the technique of Ground Penetrating Radar (GPR) combined with the traditional staining tracing method, the liana and secondary arbor forest sample plots along Yongding Riverside (the junction of Beijing and Hebei) were detected. The single channel oscillogram of the GPR image was extracted, and then the parameters of reflected wave and dye area ratio were fitted. Finally, the key step was to analyze the preferential flow staining features. The staining morphological characteristics showed that the preferential flow segment of liana sample plot was 5-30 cm below the soil surface, while the secondary arbor forest sample plot was 10-25 cm below the soil surface. The average dye area of the secondary arbor was 1.68% smaller than that of liana. The GPR lines results showed that the maximum amplitude and the total amplitude area decreased with the increase of soil depth at 0-15 cm. At 15-35 cm below the soil surface, the two parameters began to fluctuate. The maximum amplitude and total amplitude area of liana plot both were larger than that of secondary arbor plot. It was found that the dye area ratio was logarithmic with the maximum amplitude and the total amplitude area. The logarithm relationship between the dye area ratio and the maximum amplitude was y=25.104lnx+25.137 (R2=0.8697), and the logarithm relationship between the dye area ratio and the total amplitude area was y=23.874lnx-26.862 (R2=0.6173). The soil compactness of secondary arbor forest was better than that of liana. Therefore, there was less electromagnetic signal lost in the secondary arbor forest during the physical process. The electromagnetic signal of liana plot fluctuated greatly and lost more signals. It could be seen that the difference of soil structure between different layers of liana vegetation was more distinct than that of the secondary arbor, which led to preferential flow more frequently under liana coverage. In order to protect the safety of groundwater, it is necessary to cut down lianas appropriately and moderately in areas with poor drainage such as riverside bed zone and low-lying depression in front of hills. It could inhibit the over-development of preferential flow in soil under lianas coverage. 参考文献 相似文献 引证文献

GIS-based modelling of climate variability impacts on groundwater quality: Cape Flats aquifer, Cape Town, South Africa

The need to improve groundwater security remains critical, especially in urban areas where demand for groundwater as an alternative source of water supply is increasing following unprecedented population growth. Climate change continues to threaten groundwater resources in such areas. This study assessed and analysed data from a variety of sources that required holistic analytical tools to demonstrate the impacts of climate change on groundwater quality at the local level. We evaluated how climate conditions affect groundwater quality using a hydrological model (WaterWorld model) in a GIS context. The Cape Flats Aquifer in the city of Cape Town in South Africa was chosen as a case study. The WaterWorld model was used to calculate hydrologic scenarios based on climate change factors and groundwater quality parameters for the period 1950–2000. Mean annual precipitation and temperature were simulated using the multi-model mean and Representative Concentration Pathway 8.5 for the years 2041–2060. Simulation results showed that annual precipitation will increase until 2041 and then decrease until 2060. A significant temperature increase of 1.9 °C–2.3 °C was predicted. Water balance simulations showed a decrease of about 8.6% per year under the future dry climate. ArcGIS 10.3 was used to combine geospatial data and develop a groundwater vulnerability map. Modelling analysis based on GIS showed that the southern and central suburbs of the study area are more susceptible to groundwater contamination and have high surface runoff and higher average temperatures. The groundwater vulnerability index and electrical conductivity concentrations showed a strong positive correlation when the model was validated using linear regression analysis (R2 = 0.99, P < 0.05). In this article, we recommend the use of the WaterWorld model in a GIS environment to simulate hydrologic scenarios on climate change and groundwater quality parameters to provide practical and feasible insights for actions to improve groundwater management.

Drying increases organic colloidal mobilization in the karst vadose zone: Evidence from a 15‐year cave‐monitoring study

AbstractUnderstanding the hydrological processes of colloids within the karst vadose zone is vital to the security of karst groundwater and providing appropriate paleohydrological explanations of colloid‐facilitated metals in speleothem. This study addresses the mobilization mechanisms driving colloidal organic matter (COM) transport in the karst vadose zone using a 15‐year long monthly monitoring dataset from a cave drip point (HS4) in Heshang Cave, Qingjiang Valley, China. Variations in COM concentrations were reported as the fluorescence difference values of raw and filtered (&lt;0.22 μm) samples at an excitation wavelength of 320 nm and emission wavelength of ~400 nm. A fluorescence humification index (HIX) lower than 0.8 and an autochthonous index (BIX) higher than 1.2 indicated that the origin of COM was mainly from the karst vadose zone, rather than the soil zone. The COM concentration varied from 0.001 to 0.038 Raman Unit (RU), with evident seasonal fluctuations. Rising limbs for COM values occurred prior to rising limbs within a dripwater hydrograph; moreover, the COM peak values corresponding to the beginning of the increasing hydrograph generally suggested that the mobilization of COM reflected the movement of the air–water interface (AWI) in the karst vadose zone rather than rainfall intensity or flow velocity. COM peak values were positively correlated with the antecedent drying duration and negatively correlated with HIX values. These phenomena may be explained by the increased amount of organic matter that was aggregated and absorbed on the surface of carbonate in the karst vadose zone during a longer drying duration. Moreover, the longer drying duration was also beneficial to autochthonous biological activity, which subsequently decreased the HIX value of the organic matter in the karst vadose zone. The movement of AWI and the drying duration are both controlled by the outside weather conditions. This study is therefore conducive to evaluating the security of karst groundwater in response to climate change, and challenges prevailing paleoclimate interpretations of colloid‐facilitated metal abundance timeseries reported from speleothems.