Groundwater Research Articles

Impact of Irrigation Source on the Dissemination and Persistence of Coliforms and Foodborne Pathogens in Fresh Tomato High Tunnel-dripline System from Small Specialty Crop Farms

This study investigated the impact of irrigation sources (pond, stream, and well) in high tunnel-dripline systems on the dissemination and persistence of foodborne pathogens (Escherichia coli O157, Listeria monocytogenes, Campylobacter spp., Salmonella spp., and the ‘big six’ Shiga toxin-producing E. coli [STEC]) in small specialty crop farms (SSCFs). Ten SSCF-growing fresh tomatoes using high tunnel-dripline systems were sampled between January and November 2022. Selective enrichment combined with PCR was used to detect the selected foodborne pathogens in the irrigation water (n = 240), soil (n = 240), and tomato fruits (n = 120). Overall, surface-originated water sources (streams and ponds) having potential contact with farm animals or wildlife harbored higher pathogen burden (cumulative prevalence of all the pathogens) compared to subsurface water source (well and underground spring water). STEC O26, O45, and O103 were detected at high frequency (up to 88% per SSCF per time point) in the water source and associated dripline irrigation system of 4/6 SSCFs using stream and pond water. Other foodborne pathogens (especially, L. monocytogenes) were detected in 6/10 SSCFs, but at low frequency (<25% per SSCF per time point). The prevalence of foodborne pathogens in the 10 SSCFs over time was positively correlated with the length of high tunnel and planting date (r2 = 0.93 and 0.79, respectively; P < 0.006). Our study highlighted that dripline irrigation systems may allow the long-distance transport of foodborne pathogens from the contaminated water source to the field. Risk assessment and mitigation measures should be implemented to assure the quality of the water source used for irrigation in SSCF.

Dissimilatory Iodate-Reducing Microorganisms Contribute to the Enrichment of Iodine in Groundwater.

Iodate reduction by dissimilatory iodate-reducing microorganisms (DIRMs) plays a crucial role in the biogeochemical cycling of iodine on Earth. However, the occurrence and distribution of DIRMs in iodine-rich groundwater remain unclear. In this study, we isolated the dissimilatory iodate-reducing bacteriumAzonexus hydrophilusstrain NCP973 from a geogenic high-iodine groundwater of China for the first time. The analysis of genome, transcriptome, and heterologous expression revealed that strain NCP973 uses the dissimilatory iodate-reducing enzyme IdrABP1P2 to reduce dissolved or in situ sediment-bound iodate to iodide. The location of IdrABP1P2 in the conjugative plasmid of strain NCP973 implies that IdrABP1P2 could be spread by horizontal gene transfer and allow the recipient microorganisms to participate in the enrichment of iodide in aquifers. Based on the global iodine-rich groundwater metagenomes and genomes, the identification of idrA showed that phylogenetically diverse DIRMs are widely distributed not only in geogenic high-iodine groundwater of China but also in radionuclide-contaminated groundwater of USA as well as in subsurface cavern waters in Germany and Italy. Moreover, the abundance of idrA was found to be higher in groundwater with a relatively high iodine content. Collectively, these results suggest that terrestrial iodine-affected groundwater systems are another important habitat for DIRMs in addition to marine environments, and their activity in aquifers triggers the mobilization and enrichment of iodine in groundwater worldwide.

Global patterns in vegetation accessible subsurface water storage emerge from spatially varying importance of individual drivers

Global patterns in vegetation accessible subsurface water storage emerge from spatially varying importance of individual drivers

Presenting a transdisciplinary robust approach for comprehensive assessment of large-scale underground water resources in western Indo-Gangetic Basin

Overexploitation, pollution, and anthropogenic activities threaten the sustainability of groundwater resources in the western Indo-Gangetic Basin. Meanwhile, distinguishing regions prone to contamination and understanding the natural and anthropogenic factors affecting groundwater quality is challenging due to the heterogeneous nature of aquifer systems and the lack of high-resolution spatial and temporal data on aquifer protective hydrogeological layers. This study presents a transdisciplinary robust approach combining regional electrical resistivity surveys, hydrogeological data, physicochemical analyses, and geospatial datasets to identify regions prone to contamination and understand the impacts of natural and anthropogenic factors on groundwater resources. This approach involves three key steps: evaluating the geohydraulic nature of aquifer protective hydrogeological layers, mapping the aquifer vulnerability index (AVI), and conducting comparative analyses of potentially vulnerable areas with groundwater quality index (GWQI) and hydrological factors. Firstly, model-based inversion of ID Vertical Electrical Sounding (VES) data provides insights into geoelectrical indices such as depth, thickness, apparent resistivity, longitudinal conductance, transverse resistance, and longitudinal resistivity of aquifer protective hydrogeological layers. Second, the Artificial Neural Network (ANN) model is used as a multilayer perceptron network to simulate hydraulic conductivity (K) using geoelectrical indices of aquifer protective hydrogeological layers. Subsequently, by considering ANN-derived K and VES-derived h of aquifer protective hydrogeological layers, the dynamic hydraulic resistance to the vertical flow of wastewater through the protective hydrogeological layers evaluated the index of the potentially vulnerable areas. Comparative analyses of potentially vulnerable areas with GWQI and hydrological factors (e.g., digital elevation model, soil, drainage density, lineament density, slope) enhance understanding regions prone to contaminants and land surface stress. Findings show that the ANN approach to simulate K, reducing effort with costs associated with slug testing is significant for AVI assessment. Furthermore, the geohydraulic characteristics, vulnerability indexing, and comparative analyses assist in identifying contamination-prone areas, improving groundwater resource protection and exploration activities.

Estimation and Comparison of Deflouridation of Flouridated Ground Water Using Four Natural Adsorbents: Multani Mitti, Chalk Powder, Orange Peel Powder and Ragi Powder

This study highlights the global issue of fluoride contamination in drinking water, affecting approximately 260 million people in 30 countries, with India facing significant challenges as endemic fluorosis impacts around one million individuals across 17 states. The elevated fluoride levels are primarily attributed to fluoride-bearing minerals in local rocks and soils. The World Health Organization recommends maintaining fluoride concentrations near 1 mg/L to balance dental health benefits while preventing fluorosis. In response, various defluoridation methods—such as precipitation and adsorption—are implemented in India to adjust fluoride levels to optimal ranges. Given the essential role of water in physiological processes for humans, animals, and plants, understanding the variable quality of surface and groundwater is crucial. This variability is influenced by local geological factors and the presence of contaminants, necessitating effective management strategies for safe drinking water access.

Electromagnetic and Radon Earthquake Precursors

Earthquake forecasting is arguably one of the most challenging tasks in Earth sciences owing to the high complexity of the earthquake process. Over the past 40 years, there has been a plethora of work on finding credible, consistent and accurate earthquake precursors. This paper is a cumulative survey on earthquake precursor research, arranged into two broad categories: electromagnetic precursors and radon precursors. In the first category, methods related to measuring electromagnetic radiation in a wide frequency range, i.e., from a few Hz to several MHz, are presented. Precursors based on optical and radar imaging acquired by spaceborne sensors are also considered, in the broad sense, as electromagnetic. In the second category, concentration measurements of radon gas found in soil and air, or even in ground water after being dissolved, form the basis of radon activity precursors. Well-established mathematical techniques for analysing data derived from electromagnetic radiation and radon concentration measurements are also described with an emphasis on fractal methods. Finally, physical models of earthquake generation and propagation aiming at interpreting the foundation of the aforementioned seismic precursors, are investigated.

Impact of organic mulch and exposure to shallow groundwater levels on Cnidoscolus aconitifolius in a tropical wetland, South Sumatra, Indonesia

Agricultural land in Indonesia is decreasing due to its conversion for various non-agricultural interests, which are economically more profitable. The remaining land available for agricultural activities is a suboptimal wetland. The reduction in cultivable areas has led to the evaluation of alternative crops in suboptimal land conditions. Chaya (Cnidoscolus aconitifolius) is a fast-growing perennial plant, its leaves are edible and rich in vitamins, minerals, and dietary fiber. However, the chaya plant has not been intensively tested for its adaptation to shallow groundwater tables in tropical lowlands. This study aimed to assess chaya’s adaptability to shallow groundwater table conditions and the benefits of using organic mulch. This research consisted of two separate parts, one part was related to organic mulch benefits (planting media without watering, with organic mulch but not watered, and with organic mulch and watering), while the other one was related to shallow groundwater table tolerance. The study followed a randomized complete block design consisting of three replications. Results showed that chaya plants negatively responded to the shallow groundwater table conditions. Growth retardation due to shallow groundwater levels is reflected in the averages of leaf length, leaf width, leaf area, canopy diameter, and canopy area; fresh and dry weight of stem, petiole, and leaf blade; development of roots; SPAD value at 7 weeks after transplanting and it was based on visual appearance. However, despite the increase in substrate humidity due to the application of organic mulch, the effects were not significant on most of the measured morphological traits. In conclusion, chaya plants are not able to adapt to shallow groundwater levels and do not require organic mulch on the soil surface.

Simulating controlled drainage and hydrological connections in a cultivated peatland field

AbstractCultivated peatlands are increasingly regarded as hot spots due to climate change and other environmental concerns. Flexible water management, such as controlled drainage, is proposed to optimize cultivation and reduce environmental risks in peatland fields. The hydrological and environmental implications of controlled drainage depend on site‐specific variables, and it is unclear how controlled drainage should be implemented in various conditions. Simulation models are a promising approach to systemically study the field hydrology, as models can capture the complete water balance, which is difficult through experimental studies alone. We calibrated and validated the spatially distributed model FLUSH to describe the hydrology of a field block with a shallow peat cover and controlled drainage in central western Finland. The objectives were to analyze the hydrological effects of controlled drainage and detect hydrological connections between the field and an adjacent upslope forest area. The results showed how inflow from the forest can induce high observed drain discharge but impacted the block groundwater tables only in the proximity of the forest (distance &lt;25 m). The effect of controlled drainage on groundwater tables was on average 0.15 m and seasonally varying. Controlled drainage reduced drain discharge, and the reduction was larger with the forest area included in the model. While controlled drainage effects on groundwater levels and soil moisture were insensitive to groundwater influxes from adjacent areas, the water balance impact highlights the role of hydrological connections in the hydrology of cultivated peatlands under controlled drainage.

Modern legal problems of human health protection: from complex approaches to practical solutions

The article analyzes the state of social relations on the protection of human health by means of environmental and legal regulation as an important direction of the state environmental policy and policy in the field of health protection, the development of legal practice, the identification of shortcomings and gaps in the current legislation, as well as making proposals for its improvement in view of international legal and European approaches to the regulation of the specified relations. Obtaining ecologically significant information about the state of human health, carrying out other investigations within the framework of the study of its determinants will contribute to the development of the mechanism of legal regulation of relevant relations in Ukraine. The subject of the research is the provisions of environmental and other branches of legislation, as well as scientific-theoretical and practical ideas, views and approaches to solving legal problems of protecting human health and environmental protection, ensuring ecological, food, nutritional safety, developing the methodology of conducting scientific research in environmental and legal and other areas. The object of the research is social, environmental and other legal relations that arise in today’s conditions under the influence of military threats and the requirements of martial law, as well as social and legal prerequisites for the formation and development of determinants of health through the prism of the legal, in particular, environmental and legal mechanism. The effectiveness of environmental law is largely determined by the implementation of the main and most important goal - the direct protection of a person and his right to life and health in general. The global community’s fight against excessive environmental pollution, the development of rational use of natural resources, care for people and all of humanity are fundamental vectors of the development of international cooperation. In most of the developed countries of the world, solving the problem of ensuring environmental safety is assigned to the competence of specially created government institutions, which determine the appropriate directions of international cooperation, vectors of development. It is necessary to make it impossible to ignore the natural-scientific paradigm, according to which the environment that affects the human body is not only nature, but also everything that is outside the body. The attention of scientists should not be limited to the analysis of the consequences of a polluted environment, but should also be directed to the study and forecasting of changes in the environment that surrounds a person, the conditions of human existence and their impact on the health of a person as a biosocial being. The range of these changes is very wide - from innovations in the structure of nutrition to transformations of culture and ethics, development of legal culture, healthy lifestyle at the social and individual levels. Human health should be considered as a complex socio­economic, ecological and hygienic indicator that integrates demographic, social and biological processes characteristic of human society, reflects the level of its economic and cultural development, the state of medical care, bears the imprint of historical and ethnographic traditions and natural and climatic changes. Along with the culture of work, life, thinking, behavior, communication, adaptive culture, today it is proposed to highlight the culture of health, which in fact determines the further development of all types of cultures and should become a prerequisite for the formation of a person as a complete individual, covering all aspects of life. Preserving the health of the nation is a social necessity today. The process of forming an ecological culture through a system of educational activity measures, in addition to direct ecological culture, also covers the formation of a culture of a healthy lifestyle, hygienic skills, a caring attitude towards the environment, etc. It is equally important to ensure a balanced and safe diet for the entire population. Considering the complexity of the specified problem, it is necessary to involve specialists of various specialties in this work. The set tasks actualize the issue of researching the content of the concept of «human health» defined by the Law of Ukraine «On the Public Health System». The term «ecological determinants of health» as the level of pollution of the natural environment (locality) where a person lives: the level of pollution of surface and underground water, land plots, atmospheric air, etc., needs legislative consolidation.

Wastewater flooding risk assessment for coastal Communities: Compound impacts of climate change and population growth

The study introduces a wastewater modeling framework that evaluates the compound impacts of intense rainfall, groundwater infiltration, sewer aging based roughness and population growth on wastewater systems. It integrates property and city-level flooding risk assessment and wastewater treatment plant (WWTP) capacity analysis into a single methodological approach. The framework applied to the coastal city of Charlottetown, whose population increased from 30,887 in 1981 to 42,440 in 2023, but the wastewater system did not expand accordingly, resulting in frequent sewer backups, street and basement flooding, as witnessed during the extreme wet weather event of September 2, 2021. Using PCSWMM (Personal Computer Storm Water Management Model), the study assessed that the city-wide wastewater flooding risk in Charlottetown, based on 2023 population data and historical IDF curves, affects 13.31% of the network during a 2-year storm and 18.38% during a 100-year storm. These risks increase to 14.5% and 22.6% under future IDF scenarios, reaching 17.89% and 26.4% by 2060 with projected population growth. The WWTP capacity is exceeded by 27.8% during peak wet weather flows from a 2-year storm and by 86.3% during a 100-year storm, based on 2023 population and historic IDFs. Under future IDF scenarios for 2060 population, exceedances rise to 103.6% and 169.1% respectively, for a 2-year and 100-year storm. Basement flooding risk affects 13.35% of basements during a 2-year storm and 18.31% during a 100-year storm, for 2023 population and historic IDFs. Future IDF scenarios indicate risk increasing to 17.77% and 25.80% by 2060 for a 2-year and 100-year storm respectively. The hydraulic modeling results indicate that GWI is not currently impacting the study area, nor is it expected to in near future, because the groundwater table is over 10 m deep, while wastewater pipes are no deeper than 6 m. The framework and study have significant social implications and benefits, including protecting public health, enhancing the resilience of urban infrastructure, and safeguarding the environment, ultimately improving the quality of life for residents in coastal communities like Charlottetown.

Climate change and ecological assessment in Europe under the WFD – Hitting moving targets with shifting baselines?

The Water Framework Directive (WFD) sets the fundamental structure for assessing the status of water bodies in the European Union. Its implementation is currently entering its fourth six-year cycle assisted by a total of 38 guidance documents. The principal objective is to ensure good status for surface and ground waters. The functioning of the WFD is based on detecting the impact of human pressures on biological, physico-chemical, or hydromorphological parameters, and reducing these causal pressures through a program of measures to achieve good status. Climate change can exert a significant influence on ecological status by directly altering parameters monitored, pressure interactions, or influencing the effectiveness of programs of measures. Aquatic systems respond holistically to climate change with different pressures having additive, synergistic, or antagonistic interactions. The challenge is how to adapt the framework to manage aquatic systems in the context of climate change while maintaining focus on implementing measures to tackle key pressures. This paper examines potential approaches, including reassignment of waterbody type, quantifying the portion of Ecological Quality Ratio (EQR) driven by climate change, and creating an assessment module of climatic pressures and ecological responses. The overall purpose is to stimulate discussion and explore ways to incorporate climate change into the WFD structure.

Forecasting the groundwater levels in the Baltic through standardized index analysis

In regions where groundwater forms the primary source of drinking water, comprehending the prospective availability of subsurface water resources due to climate change is of paramount importance.This study evaluates the impact of climate change on groundwater levels in the Baltic States until the end of this century. It employs link between surface and subsurface standardized indices. For forecast it uses various Representative Concentration Pathways (RCP) alongside different Regional Climate Models (RCM).By linking historical groundwater drought episodes with calculated surface drought indices and accumulation periods observed during defined climate Normals, we project groundwater levels for the short, medium, and long-term future. The study incorporates 13 EURO-CORDEX RCMs under three RCP scenarios.Our analysis reveals that, compared to the recent climate Normals, an overall increase in groundwater levels is expected at most study sites. However, lower groundwater levels are estimated in the near future. The projected impacts show no significant seasonal bias or spatial conformity. Although these findings are specific to the Baltic region, the methodologies described can be readily adapted for global application.

Assessment and identification of potential of ground water potential zones at industrial coastal location using remote sensing, GIS and SWAT

Assessment and identification of potential of ground water potential zones at industrial coastal location using remote sensing, GIS and SWAT

Geophysical investigation of the ground fissures and ground subsidence near Karla lake (eastern Thessaly basin, Greece)

Ground fissures have occurred in the last four decades across the eastern Thessaly basin (Greece) resulting in damage to the villages of the area. Several studies for the area refer to the over-pumping of ground water as the main reason for their occurrence, causing sediment compaction due to the reduction of the aquifer level. In this paper, we depict the results of a joint geophysical survey trying to determine the subsurface regime of the basin and the exact reasons contributing to the existence of the ground fissures. The focal part of the survey includes gravity measurements for deeper investigation, combined with existing and already presented geoelectrical and electromagnetic data. Several borehole data have also been used for the calibration of the geophysical interpretation. The differential GNSS data of the gravity campaign revealed the ground subsidence of the area, reaching up to 9.16 m. The alpine basement of the area is comprised mainly of metamorphic rocks, such as marbles, mica schists and gneiss-schists, covered by thick fluviοterrestrial and alluvial deposits. Several structural maps were generated in order to delineate the lateral density variations that could be related to fault zones along with the interpretive sections for geological modelling. The alpine bedrock was adumbrated in relatively great depths, with a large anticline of NW-SE direction, rising and separating the basin in two parts. In the east part, the fluvioterrestrial deposits, which are expected to play an important role in the compaction due to their water aquifer, are located only west of this anticline. At the east part, where the old lake Karla was hosted, the alluvial deposits lay directly on the alpine basement in smaller depths. This complicated regime is responsible for differential sediment compaction and the ground subsidence of the surface.

Nitrate source analysis of underground drinking water sources in Zhangjiakou main urban area and its health risk assessment

&lt;p style="line-height:200%;text-align:justify;text-justify:inter-ideograph;"&gt;&lt;span lang="EN-US"&gt;In order to investigate the main pollution factors of underground drinking water sources in semi-arid agricultural areas in China, and to reveal the threatening influence of pollutants on the normal water security of local society. Single-factor evaluation index, principal component analysis, basic data statistics are used to clarify the main pollution indicators of underground drinking water sources in Zhangjiakou main city and discuss the main influencing factors of the change of their pollution concentration, and evaluate the degree of health threat of its pollution to the drinking water of local residents. The results show that: the water sources of Taobeiying and Gushi are deeply affected by human activities, and nitrate, as the only exceeding substance under drinking water standards, is the most important indicator of groundwater pollution; and the nitrate con-centration of groundwater is higher in the pasture and nearby agricultural activities; nitrate contamination levels in groundwater are within the health acceptability range for the vast majority of the population, with only newborns in the Taobeiying drinking water source being exposed to a non-carcinogenic risk of nitrate. The results of the study will help to maintain a stable groundwater environment.&lt;/span&gt;&lt;/p&gt;

Heavy metal contamination of the Nigerian environment from e-waste management: A systematic review of exposure pathway and attendant pathophysiological implications

Nigerian environment has become a depository of worrisome levels of toxicants including heavy metals. Electrical and electronic equipment which leads to the generation of e-waste is one of the considerable sources of environmental contaminants in Nigeria. This systematic review deployed Preferred Reporting Items for Systematic Reviews and Meta-Analysis (PRISMA) method to analyze various empirical and quantitative outputs on heavy metal components of e-waste management sites in Nigeria and investigated the distribution of heavy metals in several environmental matrices such as soil, water, surface dust, plant and blood of e-waste scavengers. Also, the probable environmental multi-transformation that ultimately potentiates the susceptibility of humans to the pathophysiological effects and genetic related disorders of exposure to heavy metal component of e-waste was discussed. The relative abundance of metals in soils due to inappropriate e-waste handling is given as follow: Fe>Cu>Pb>Zn>Mn>Co>Cr>Ni>As>Cd, in underground and surface water: Zn>Fe>Cu>Cr>Mn>Pb>Hg>Ni>Co>Cd>As; in surface dusts: Fe>Zn>Pb>Cu>Mn>Cr>Ni>Cd>Co; in plants: Pb>Cu>Mn>Zn>Ni>Cr>Cd obtained from the Nigerian environment. Moreso, the estimated abundance of heavy metals in the blood of e-waste scavengers is Nigeria is given as Cr>Cd>Hg>Zn>As>Pb>Cu>Mn>Fe. Conclusively, this study does not only show that various matrices of Nigerian environment is contaminated with heavy metal but also that the pattern of abundance differ in the environment and in biological systems with the latter having the abundance of Pb, Cr and Cd and the former having the abundance of Cu, Zn and Fe.

Hobli wise hydro geomorphological evaluation of the groundwater prospects mapping

ABSTRACT Numerous studies highlight the urgent issue of groundwater depletion due to overexploitation. The United Nations’ World Water Development Report (2023) warns that if current extraction rates persist, many regions could face severe groundwater shortages in the coming decades. A 2021 study in Nature reports that about one-third of the world’s largest groundwater basins are depleting faster than they are replenished, escalating the risk of critical shortages. In Chickballapur District, excessive agricultural activity has led to an imbalance between groundwater loss and recharge. To address this challenge, a weighted overlay analysis of spatial layers in QGIS was employed to identify potential groundwater zones. This methodical approach involved mapping topographic features and integrating six spatial layers: slope, geomorphology, lithology, drainage, lineament and land use/cover. Each subcategory was ranked and scored based on expert opinion and existing literature. The Central Ground Water Board data was used to validate the resulting groundwater prospect map. The study further included an assessment of groundwater prospects across administrative units by superimposing the administrative boundaries on the final map. Calculating the percentage of land within each groundwater prospect category is crucial for effective groundwater management at the administrative level.

CATALOG OF LANDSLIDES OF THE CITY OF ZENICE WITH SPECIFIC CAUSES

As part of its activities, the Federal Institute of Geology carries out mapping of active landslides in the territory of the Federation of Bosnia and Herzegovina, and my task is to map instability in the area of the City of Zenica. A very large number of landslides were registered during the catastrophic rainfall that occurred in 2014. Following these phenomena and certain records, detailed mapping of unstable slopes and records of unstable surfaces was started. The cadastre is defined in such a way that it displays all input data with location polygons in GIS. Not in the field, quite recognizable causes were observed, which are always a combination of bad geological and hydrogeological conditions with a significant anthropogenic factor. The slope of the terrain is also very unfavourable, and gravity also played a significant role in the instability of these slopes. Almost all registered landslides have unregulated water (surface, underground, waste). The frequent occurrence of earthquakes on this section also significantly threatened the stability of slopes and buildings, and on the spot, the consequences of cracking and shearing of buildings were evident as a result of the earthquake. A special review will be given to the activation of mudflows during extensive rainfall in this area, which is not rare. A significant share in the formation of mudflows belongs to heavy precipitation, which over time formed the so-called "watersheds" where water was transported from higher to lower parts of the slope. However, during the climate changes, there was a significant increase in the amount and frequency of precipitation, which carried the surface cover and rock blocks that were moved down the steep slopes. Road approaches to the villages, as well as a significant number of buildings, made artificial dams and cut cuts that were a natural way of draining water. So you have a significant number of buildings built exactly on these "watersheds" that represent the dam. In the newly created situation, by changing the natural paths of movement of surface and underground water, it would be necessary to regulate the water below and around the road strip, as well as the drainage of water around buildings. Only after the water has been drained, certain geotechnical procedures can be carried out to stabilize the slope and to permanently rehabilitate it, so that the inhabitants of these villages do not constantly fear during rainfall.

The departure of sperm whales (Physeter macrocephalus) in response to the declining jumbo squid (Dosidicus gigas) population in the central portion of the Gulf of California.

As sperm whales are important predators that control energy flux in the oceans, changes in their population can be used as a sentinel to measure of ecosystem health. The present study conducted a sperm whale survey of the eastern Midriff Islands Region in the Gulf of California over the course of nine years, recording sightings and collecting photographs of the fluke of sperm whale individuals. A photo-identification catalog was compiled, while individual recapture data were used to estimate the population size in the central portion of the Gulf of California, using a Jolly-Seber POPAN open population model. The results obtained show a yearly population of between 20 and 167 sperm whales, with a super population of 354 sperm whales observed between 2009 and 2015. However, from 2016 to 2018, no sightings of the species were recorded, which coincides with the decline observed in landings of their main prey, the jumbo squid, in the region. General additive model conducted on sperm whale sightings per unit of effort vs jumbo squid landings obtained an adjusted R2 of 0.644 and a deviance explained of 60.3%, indicating a good non-linear relationship between sightings of this odontocete and its prey availability. This evidence suggests that sperm whales departed the region between 2016 and 2018, due to a documented fishery collapse alongside changes of their main prey into its small phenotype, possibly as the result of increase warming conditions in surface and subsurface waters in the Gulf of California in the last three decades.

Determining Groundwater Table in Slopes with Horizontal Drains and Design Framework for Length and Spacing

ABSTRACT Horizontal drains (HDs) are commonly implemented in slope stabilization to reduce the pore water pressure (PWP); however, they also cause complex three-dimensional (3D) variations in the groundwater table (GWT), which require intricate 3D flow models. To address this challenge, we propose a novel semi-empirical method based on a series of numerical simulations validated through numerical and field studies to determine the GWT of a slope with HDs. Subsequently, the proposed method was extended to calculate the average PWP (U) acting on a predefined slip surface via linear integration. The decrease of U (ΔU) resulting from HDs can be used to evaluate the performance of HDs. To create design charts that consider the impact of length and spacing of HDs on ΔU for a specific slope, we developed a Python-based computer program. Two case studies were conducted, which showed that ΔU increases with longer HDs and shorter spacing. The results also indicated that extending the HDs beyond a particular length does not significantly affect ΔU; it is highly sensitive to the spacing in short HDs and not sensitive in long HDs. Furthermore, we found that the total length of HDs required to achieve a target ΔU is less in wide spacings than in short spacings. In conclusion, long HDs with wide spacings are more effective and economical. Owing to the unique nature of each slope stability problem, this study offers a practical tool for analyzing the effectiveness of HDs instead of providing a general guide.