Subsurface Groundwater Research Articles

Land subsidence triggered by groundwater withdrawal under hyper-arid conditions: case study from Central Saudi Arabia

Natural and human-induced groundwater dynamics in hyper-arid aquifers play a crucial role in the evolution of the landscape. The area overlying the Saq Aquifer, in particular the Al-Qassim area within the central part of the Kingdom of Saudi Arabia, has witnessed numerous land deformation (land subsidence and fissures) events throughout the last two decades. An integrated remote sensing and hydrogeologic approach is adapted to identify areas affected by the land deformation and also to better understand the role of human-induced groundwater dynamics in the formation of these deformation features. A fourfold approach was implemented including: (1) conducting field surveys to collect observations and validate the reported deformation features, (2) applying a spatial correlation in a GIS environment for the reported damaged locations together with surface and subsurface geological features and groundwater extraction. (3) extracting the subsidence rates using SBAS radar interferometric technique using ENVISAT data sets, and (4) correlating these subsidence rates spatially and temporally with GRACE mass variations data. The results show that high subsidence rates of − 5 to − 12 mm/year along a northwest–southeast direction coincident with areas witnessing a significant drawdown in the fossil groundwater levels (up to 150 m) and a depletion (−10.1 ± 1.2 mm/year) in GRACE-derived terrestrial water storage. Findings from the present study draw attention to the quick responses of landscapes to human-induced groundwater dynamics under hyper-arid conditions.

Use of Landsat-8 OLI data for delineating fracture systems in subsoil regions: implications for groundwater prospection in the Waddai area, eastern Chad

The use of satellite images for mapping and analyzing linear structures and fracture systems in subsoil regions is essential to understand the subsurface groundwater path ways and traps. In this study, we apply Optimal Index Factor (OIF), principal component analysis (PCA), and directional filtering (Sobel) of several Landsat 8 bands for the wooded Waddai area in NE Chad. The application of the Sobel directional filter to these bands showed a robust performance for enhancing the discontinuity features and allowed better identification of the fault/fracture systems by the automated lineament extraction techniques. The results indicate that the ENE and WSW structural trends control the distribution and migration of groundwater, in good agreement with previous hydrological studies and published hydrogeological maps. New highly potential areas for groundwater exploration are identified on a lineament density map and verified by ground truth urban distribution.

The spatial component of integrative water resources management: differentiating integration of land and water governance

ABSTRACT Contemporary water-governance approaches lack an understanding of the differences revealed when land and water governance interact. Conflicts arise because the spatial component is less regarded in water-governance approaches. This explorative paper introduces an analytical framework for the common management of land and water along three frontiers: the vertical frontier concerns the interaction between subsurface groundwater and land uses on the surface; the horizontal frontier refers to coastlines or riverfronts; and the fluent frontier is about inundations and flood events. Rather than a panacea for all governance issues, this paper proposes a more differentiated perspective on integrative water-governance approaches.

The potential science and engineering value of samples delivered to Earth by Mars sample return

The potential science and engineering value of samples delivered to Earth by Mars sample return

GLOBAL SENSITIVITY ANALYSIS METHODS APPLIED TO HYDROLOGIC MODELING WITH THE SAC-SMA MODEL

ABSTRACT This study aimed to use global sensitivity analysis (GSA) methods to evaluate the sensitivity of the SAC-SMA hydrologic model parameters in the estimation of daily flows of the Piracicaba river basin. The study was carried out in three sections of flow monitoring of the Piracicaba river basin, with an area of 5,304.0 km2 and located in the State of Minas Gerais, Brazil. For the global sensitivity analysis of the SAC-SMA model, the Morris and Sobol methods were used. The model parameters showing high sensitivity were UZFWM, which represents the free water depth in the upper zone of the soil and interferes with the subsurface flow and groundwater aquifer recharge; ADIMP, which represents the additional impermeable area of the basin and interferes with the direct runoff generation; and LZPK, LZSK, LZFPM, and LZFSM, which are related to the base flow of the basin. The results showed that most of the SAC-SMA model parameters do not provide expressive variations in the output variable, most of the SAC-SMA model parameters with high sensitivity are the intervenient in the base flow, and the Morris method should be used as a preliminary analysis to the use of the Sobol method.

Improving thermal response tests with wireline temperature logs to evaluate ground thermal conductivity profiles and groundwater fluxes

A field method was developed to assess subsurface thermal conductivity profiles and groundwater fluxes from manual temperature logs using a wired probe lowered into a U-pipe during the recovery period of a thermal response test (TRT). Temperature and depth were recorded with a wired temperature and pressure data logger, which triggers a water level rise into a U-pipe. Depth correction methods were introduced and validated using subsurface temperature at equilibrium state measured into U-pipe. Wired temperature logs from recovery period after drilling operation were used to evaluate undisturbed subsurface temperature and during a conventional TRT to assess a thermal conductivity profile with approximately 1 m vertical spatial resolution. TRT analysis was improved by combining the infinite line source equation with the temporal superposition principle and slope method. The results reveal zones of higher apparent thermal conductivity identified as fractured zones in which Darcy’s flux has been quantified using the Peclet number analysis. The average subsurface thermal conductivity inferred with this method was 1.79 W m−1 K−1, similar to 1.75 W m−1 K−1 obtained using conventional TRT analysis. The estimated Darcy’s flux in the fracture zones is 3 × 10−9 to 1 × 10−8 m s−1. This method, based on wired temperature profiling along the borehole, provides a new approach using simple equipment and available analytical solutions to obtain more information from conventional TRT analysis.

The Effect of Geological Heterogeneity and Groundwater Table Depth on the Hydraulic Performance of Stormwater Infiltration Facilities

Urbanization has led to a substantial change in the hydrological cycle of urban catchments. Increased runoff and urban flooding, decreased direct subsurface infiltration and groundwater recharge, deterioration of water quality are among the major effects of this alteration. To alleviate these effects, Low Impact Development (LID) practices have been frequently adopted for stormwater management. Among LID infrastructures, infiltration facilities are particularly challenging to design and model due to the considerable amount of uncertainties related to the hydrogeological configuration of installation sites. To date, analysis on how soil heterogeneity, groundwater table depth, and thickness of the unsaturated zone affect the hydraulic performance of infiltration facilities are lacking. To address this knowledge gap, a series of numerical experiments under transient variably water saturated conditions were performed for a hypothetical infiltration facility. Numerical simulations showed that i) infiltration rates increase considerably as the initial depth of the groundwater table increases, ii) the contribution of the bottom of the facility to the infiltration of water is generally higher than the sides, iii) the presence of a less conducting soil layer at a short depth from the bottom of the facility reduces infiltration rates dramatically, iv) the complete clogging of the bottom of the facility has a dramatic impact on the hydraulic performance, v) the stochastic heterogeneity of the soil controls the overall stormwater infiltration process through the facility, and the hydraulic performance may largely deviate from the case when heterogeneity is absent.

Metatranscriptomes Reveal That All Three Domains of Life Are Active but Are Dominated by Bacteria in the Fennoscandian Crystalline Granitic Continental Deep Biosphere.

The continental subsurface is suggested to contain a significant part of the earth's total biomass. However, due to the difficulty of sampling, the deep subsurface is still one of the least understood ecosystems. Therefore, microorganisms inhabiting this environment might profoundly influence the global nutrient and energy cycles. In this study, in situ fixed RNA transcripts from two deep continental groundwaters from the Äspö Hard Rock Laboratory (a Baltic Sea-influenced water with a residence time of <20 years, defined as "modern marine," and an "old saline" groundwater with a residence time of thousands of years) were subjected to metatranscriptome sequencing. Although small subunit (SSU) rRNA gene and mRNA transcripts aligned to all three domains of life, supporting activity within these community subsets, the data also suggested that the groundwaters were dominated by bacteria. Many of the SSU rRNA transcripts grouped within newly described candidate phyla or could not be mapped to known branches on the tree of life, suggesting that a large portion of the active biota in the deep biosphere remains unexplored. Despite the extremely oligotrophic conditions, mRNA transcripts revealed a diverse range of metabolic strategies that were carried out by multiple taxa in the modern marine water that is fed by organic carbon from the surface. In contrast, the carbon dioxide- and hydrogen-fed old saline water with a residence time of thousands of years predominantly showed the potential to carry out translation. This suggested these cells were active, but waiting until an energy source episodically becomes available.IMPORTANCE A newly designed sampling apparatus was used to fix RNA under in situ conditions in the deep continental biosphere and benchmarks a strategy for deep biosphere metatranscriptomic sequencing. This apparatus enabled the identification of active community members and the processes they carry out in this extremely oligotrophic environment. This work presents for the first time evidence of eukaryotic, archaeal, and bacterial activity in two deep subsurface crystalline rock groundwaters from the Äspö Hard Rock Laboratory with different depths and geochemical characteristics. The findings highlight differences between organic carbon-fed shallow communities and carbon dioxide- and hydrogen-fed old saline waters. In addition, the data reveal a large portion of uncharacterized microorganisms, as well as the important role of candidate phyla in the deep biosphere, but also the disparity in microbial diversity when using standard microbial 16S rRNA gene amplification versus the large unknown portion of the community identified with unbiased metatranscriptomes.

The formation of irregular polygonal ridge networks, Nili Fossae, Mars: Implications for extensive subsurface channelized fluid flow in the Noachian

Roughly 16,000, ∼20–50 m wide, morphologically diverse, erosionally resistant ridges have been exhumed and mapped in Noachian-aged terrain across a large region in Nili Fossae and the Nilosyrtis Highlands. However, the formation of these landforms has been widely debated. Their morphology and geologic context suggest surface processes such as aeolian, fluvial, and glacial sedimentary deposition are unlikely candidates for their formation. Possible subsurface ridge formation mechanisms include: 1) volcanic dike intrusions along pre-existing fractures, 2) breccia dikes from impact cratering, 3) clastic dikes or deformation bands, and 4) chemical alteration or precipitation of minerals in or along pre-existing fractures or faults. The ridges are being exhumed from a phyllosilicate-bearing host rock, but whether the ridges themselves have an aqueous origin remains unknown. Although, previous studies used comparative morphology to assess their formation, each hypothesized formation mechanism implies different mineralogical suites possibly detectable in remotely sensed spectral data.Here we combine spectral and morphological analyses to assess the origin of a subset of ridges (n = 797) that have irregular polygonal ridge network morphology. We use observations from the Compact Reconnaissance Imaging Spectrometer for Mars (CRISM) and High Resolution Imaging Science Experiment (HiRISE), supplemented with Context Camera (CTX) imagery, to analyze the spectral signatures and geometry in order to 1) measure ridge morphology (orientation and intersection angles) and 2) isolate the spectral signatures of the ridges from their host unit to evaluate hypothesized ridge formation mechanisms. The irregular polygonal nature, near-orthogonal intersections, and lack of dominant orientation are characteristics consistent with fracture propagation under horizontal near-isotropic extensional stress in a physically heterogeneous host rock (inconsistent with impact- or volcanic-related features). Alternatively, very shallow clastic intrusion could produce similar ridge geometry.Our key findings are: 1) ridge orientation-frequency and distribution suggest mineralization or cementation of subsurface fractures or shallow clastic intrusions as favored formation mechanisms and 2) ridges share all the diagnostic spectral features of Mg-smectite (saponite) and/or mixed-layered talc-saponite clays of the host materials; however, ridges express weaker absorptions. If the CRISM spatial and/or spectral resolution has not limited our ability to detect a spectrally unique cementing agent, then both grain size or texture and visible to near-infrared inactive mineralogy could be responsible for the ridge's weaker spectral absorptions (such as quartz and silica, some oxide group minerals, and amorphous materials). Our results imply that shallow subsurface groundwater and hydrothermal activity was likely extensive prior to and during the opening of the Nili Fossae and played an integral role in the formation of the ridges observed throughout the region.

Water Quality Index and Microbial Population Assessment for Ground Water

Pollution of water sources have become a common problem these days, be it ground water source or surface water sources. The most important and major usage of ground water is for irrigation unfortunately groundwater is susceptible to pollutants that may enter into the subsurface ground water by runoff. Presence of microbes in drinking water is now common problems as majority of the ground water sources are being substantially polluted. the physico chemical and microbial properties of water was studied and was found that the treated water sample showed a better water quality rating than the raw sample. E.coli are indicators of microbial pathogens it indicates the presence of fecalcontamination in the water.

A case study of recurring slope lineae (RSL) at Tivat crater: Implications for RSL origins

The origin or origins of recurring slope lineae (RSL) on Mars are enigmatic. These seasonally dark, linear features correlate with temperatures appropriate for liquid water or brine. They also progress slowly downslope and fade (disappear) when inactive, similar to shallow subsurface groundwater flows that wick moisture to the surface. If liquid water or brine does indeed flow so near the surface and is sufficiently dilute, it could have profound implications for the modern habitability of Mars. We present the results of a case study at Tivat crater in the southern midlatitudes that provide new insights into RSL, including their potential origins at Tivat. These results include comprehensive maps of RSL extents in four Mars years, detailed RSL evolution across one growth season, rockfall markings, and dust devil tracks. In two well-constrained years, RSL and rockfall markings—which are more widely distributed than RSL—fade at the same time, suggesting a fading mechanism that acts across Tivat. Based on relative albedo analyses, RSL and rockfall markings at Tivat fade because their host slopes darken, which is most easily explained by the widespread removal of dust. Such a dry fading mechanism would favor a dry origin for RSL. We also present a wide range of other RSL observations, including highly variable growth, pooling-like behavior where slopes shallow to roughly 30°, and total areal extents that decrease each year across a span of five years. We discuss the implications of these observations for various RSL formation models, including a new conceptual model that primarily mobilizes dust. Taken together, our observations seem to favor a dry mass movement origin for RSL at Tivat, but significant challenges remain for each examined model.

Near-surface study of a hot spring site in Fiji

A geophysical investigation of a hot spring system located in Rabulu, Fiji, was carried out from October 2014 to March 2015. The investigation covered a survey area of 6075 m2. Self-potential (SP), ground temperature and soil carbon dioxide (CO2) concentrations were measured and investigated for their distribution characteristics and inter-linkages. Results indicated obvious anomalous zone at the hot spring discharge site. The SP profile analysis highlighted thermal water upwelling zones and elevation-driven subsurface groundwater pathways. Measurement of subsurface temperatures up to 1 m depths revealed increasing temperatures, indicating potentially high thermal gradients in the area. Surface soil CO2 distributions also agreed with SP and ground temperature results. The overall result of the study demonstrated that synchronised measurements of SP, ground temperature and soil CO2 can be instrumental in identifying anomalous zones near the hot spring sites. Other parameters such as spring water temperature, discharge rate and energy flux estimates from the spring were calculated and analysed. The high-dense multi-parameter data coverage allowed interpretation of geothermal features at a scale never conducted in Fiji before. The near-surface investigations reported in this study corroborate previously suggested steady geothermal activity in the region, deserving further detailed investigation.

An Open, Object-Based Framework for Generating Anisotropy in Sedimentary Subsurface Models.

The spatial distribution of hydraulic properties in the subsurface controls groundwater flow and solute transport. However, many approaches to modeling these distributions do not produce geologically realistic results and/or do not model the anisotropy of hydraulic conductivity caused by bedding structures in sedimentary deposits. We have developed a flexible object-based package for simulating hydraulic properties in the subsurface-the Hydrogeological Virtual Realities (HyVR) simulation package. This implements a hierarchical modeling framework that takes into account geological rules about stratigraphic bounding surfaces and the geometry of specific sedimentary structures to generate realistic aquifer models, including full hydraulic-conductivity tensors. The HyVR simulation package can create outputs suitable for standard groundwater modeling tools (e.g., MODFLOW), is written in Python, an open-source programming language, and is openly available at an online repository. This paper presents an overview of the underlying modeling principles and computational methods, as well as an example simulation based on the Macrodispersion Experiment site in Columbus, Mississippi. Our simulation package can currently simulate porous media that mimic geological conceptual models in fluvial depositional environments, and that include fine-scale heterogeneity in distributed hydraulic parameter fields. The simulation results allow qualitative geological conceptual models to be converted into digital subsurface models that can be used in quantitative numerical flow-and-transport simulations, with the aim of improving our understanding of the influence of geological realism on groundwater flow and solute transport.

Microbial Interactions With Dissolved Organic Matter Drive Carbon Dynamics and Community Succession.

Knowledge of dynamic interactions between natural organic matter (NOM) and microbial communities is critical not only to delineate the routes of NOM degradation/transformation and carbon (C) fluxes, but also to understand microbial community evolution and succession in ecosystems. Yet, these processes in subsurface environments are usually studied independently, and a comprehensive view has been elusive thus far. In this study, we fed sediment-derived dissolved organic matter (DOM) to groundwater microbes and continually analyzed microbial transformation of DOM over a 50-day incubation. To document fine-scale changes in DOM chemistry, we applied high-resolution Fourier transform ion cyclotron resonance mass spectrometry (FT-ICR MS) and soft X-ray absorption spectroscopy (sXAS). We also monitored the trajectory of microbial biomass, community structure and activity over this time period. Together, these analyses provided an unprecedented comprehensive view of interactions between sediment-derived DOM and indigenous subsurface groundwater microbes. Microbial decomposition of labile C in DOM was immediately evident from biomass increase and total organic carbon (TOC) decrease. The change of microbial composition was closely related to DOM turnover: microbial community in early stages of incubation was influenced by relatively labile tannin- and protein-like compounds; while in later stages the community composition evolved to be most correlated with less labile lipid- and lignin-like compounds. These changes in microbial community structure and function, coupled with the contribution of microbial products to DOM pool affected the further transformation of DOM, culminating in stark changes to DOM composition over time. Our study demonstrates a distinct response of microbial communities to biotransformation of DOM, which improves our understanding of coupled interactions between sediment-derived DOM, microbial processes, and community structure in subsurface groundwater.

Remediation of ammonia-contaminated groundwater in landfill sites with electrochemical reactive barriers: A bench scale study

Leachate plumes originating from leaking landfills often cause the contamination of groundwater in subsurface. Ammonia nitrogen in the contaminated groundwater is usually hard to be attenuated due to the hypoxic condition in subsurface environment. In this study, an active chlorine mediated electrochemical reactive barrier (ACM-ERB) consisting of inert electrodes is proposed for the remediation of ammonia-contaminated groundwater because an elevated level of chloride ions was often found in the groundwater polluted by leachate plumes. Bench-scale experiments were conducted to evaluate the prototype of this remedial technology and to study the variables affecting the performance of ACM-ERB. The results showed that ammonia in the simulated groundwater can be effectively converted into nitrogen rather than undesirable nitrite/nitrate. RuO2/Ti anode was better than PbO2/Ti anode for the sake of ammonia removal. In the presence of naturally occurring level of bicarbonate, the electrode arrangement with an upstream cathode offered weak alkaline pH and therefore favored the removal of ammonia in the initial stage of experiment. Higher current densities and bicarbonate concentrations were favorable to the removal of ammonia. An ammonia removal efficiency up to 70% was achieved for 20 mg/L NH4+-N influent, when the operating conditions were 250 mg/L chloride ions, 500 mA current, −80 mm water level and 6 mL/min flow rate. Polarity reversal could prevent the formation of scale on electrodes, thereby allowing the long-term operation of the ACM-ERB system in groundwater. Moreover, in the experiment using diluted leachate as influent solution, ammonia was preferentially removed relative to the organic contaminants. The present study demonstrates that ACM-ERB is a promising method to cope with the ammonia-contaminated groundwater in landfill sites.

Assessment of groundwater occurrence in Olomoro, Nigeria using borehole logging and electrical resistivity methods

The objective of this study was to assess the subsurface strata and groundwater situation of Olomoro, Nigeria using borehole logging and electrical resistivity techniques. The borehole logging consisting of resistivity and spontaneous potential logs were conducted by using the Johnson Keck logger on a drilled well in the study area. The electrical resistivity survey involving 17 vertical electrical soundings (VES) with a maximum current electrode spacing of 100 to 150 m was conducted using the Schlumberger electrode configuration. Analysis of the well cuttings revealed that the lithology of the subsurface consist of topsoil, clay, very fine sand, medium grain sand, coarse sand and very coarse sand. Results of the downhole logging also revealed that the mean electrical conductivity and the total dissolved solid of the groundwater was obtained as 390 μS/cm and 245 mg/cm3 respectively. These values are within the acceptable limit set by the Standard Organization of Nigeria (SON) for drinking water. The result of the vertical electrical sounding interpreted using the computer iterative modeling revealed the presence of four to five geoelectric layers which showed a close correlation with result from the lithology and downhole logging. Results further showed that the resistivity of the subsurface aquifer ranged between 1584 and 5420 Ωm while the aquifer depths varied between 27.8 and 39.3 m. Groundwater development of the area is suggested using the depth and resistivity maps provided in this study.

An Analysis of Hydraulic Properties of Soil Based on Soil Texture in Chiti Areas of Lamjung District In Nepal

Soil hydraulic properties play crucial role for having sustainable growth of vegetation and also required for carrying out environmental studies especially subsurface ground water. Since, its direct measurement is time consuming and therefore costly, indirect methods such as pedotransfer functions have been used to estimate hydraulic properties. Soil hydraulic properties: bulk density, available water, permanent wilting point, field capacity and water retention capacity and saturated hydraulic conductivity are essential to be studied. These factors affect soil productivity and the environment. The knowledge of soil water properties for different land-use and land cover types based on soil textural classes are important for re-growth of plants and agriculture crops and ultimately efficient soil and water management. The aim of this paper is to measure soil hydraulic properties based on soil textural classes for different land use types. Furthermore, the use of the soil texture triangle: hydraulic properties calculator has been assessed. The comparison of the soil hydraulic properties obtained from textural triangle for different land use land and cover types has also been analyzed. Moreover, an analysis of variance (ANOVA) of soil hydraulic properties among different land use types has been performed. The soil reaction (pH) value ranges from 4.69 to 6.69 and as a mean of 5.51 indicating slight acidic. The analysis showed barren land occupying 14.3 percent of total land use/land cover is found to be suitable for plant growth since it has loam texture having bulk density less than 1.6 g/cm3.The analysis of bulk density showed that barren land is significantly different at the 0.05 level from both agriculture and forest, whereas agriculture and forests are not different even at 0.05 significant levels. It verifies the fact that mean bulk density at the depth of 0.15 cm is affected by land use land cover types.The Geographical Journal of NepalVol. 11: 63-76, 2018

Litho-stratigraphic and hydrogeological evaluation of groundwater system in parts of Benin Metropolis, Benin City Nigeria: The key to groundwater sustainability

Previous studies revealed that soil properties play a significant role in aquifer contamination. Consequently, it is necessary to understand the nature and properties of soil in carrying out groundwater evaluation. This study evaluates the subsurface geology and groundwater flow direction in Okpagha, Iguomo, Ikhueniro and Okhuahe suburbs in Benin City, Nigeria. Six boreholes were drilled by means of manual (rotary) method in different parts of the study area and each borehole was logged in order to understand the lithology, depth to water table, static water level as well as flow direction. The results obtained show that aquifer within the study areas were confined, semi confined to unconfined and was dominated by sands with minor clay and lignite interbed. It was observed that aquifer becomes shallower towards eastern portion of the study areas with increase in sand and decrease in clay materials. It was also observed that groundwater flow map revealed a flow direction of North-West to South-East from North West to South East. The decrease in the depth of aquifer and increase in sand material could be explained by the closeness to sea level. This phenomenon can enhance the infiltration of contaminants into aquifer thereby contaminating the groundwater bodies. It is therefore necessary to constantly monitor the groundwater quality in this suburbs in order to be aware of the quality of water resources being consumed because poor water quality can impact public health negatively. Furthermore, the authors advise that boreholes should be drilled in the direction of groundwater flow for maximum yield Keywords : Groundwater, lithology, borehole, aquifer, water quality and contaminants

The Role of Frozen Soil in Groundwater Discharge Predictions for Warming Alpine Watersheds

AbstractClimate warming may alter the quantity and timing of groundwater discharge to streams in high alpine watersheds due to changes in the timing of the duration of seasonal freezing in the subsurface and snowmelt recharge. It is imperative to understand the effects of seasonal freezing and recharge on groundwater discharge to streams in warming alpine watersheds as streamflow originating from these watersheds is a critical water resource for downstream users. This study evaluates how climate warming may alter groundwater discharge due to changes in seasonally frozen ground and snowmelt using a 2‐D coupled flow and heat transport model with freeze and thaw capabilities for variably saturated media. The model is applied to a representative snowmelt‐dominated watershed in the Rocky Mountains of central Colorado, USA, with snowmelt time series reconstructed from a 12 year data set of hydrometeorological records and satellite‐derived snow covered area. Model analyses indicate that the duration of seasonal freezing in the subsurface controls groundwater discharge to streams, while snowmelt timing controls groundwater discharge to hillslope faces. Climate warming causes changes to subsurface ice content and duration, rerouting groundwater flow paths but not altering the total magnitude of future groundwater discharge outside of the bounds of hydrologic parameter uncertainties. These findings suggest that frozen soil routines play an important role for predicting the future location of groundwater discharge in watersheds underlain by seasonally frozen ground.

Probabilistic liquefaction-induced lateral spread hazard mapping and its application to Utah County, Utah

Earthquake-induced liquefaction may result in the lateral spread displacement of soil down gently sloping ground or towards a free-face, causing severe and costly damage to various facilities, bridges, buildings and other critical infrastructure. Despite the availability of analytical methods, most engineers currently use empirical or semi-empirical regression models to estimate liquefaction-induced lateral spread displacements at specific sites. However, the application of these regression models for regional mapping over a large geographic areas can be difficult because of challenges associated with the adequate characterization of subsurface soil and groundwater conditions, geotechnical properties, regional topography, and uncertainties associated with the causative seismic loading. To address these challenges, this paper presents a new and fully probabilistic procedure for regional hazard mapping of liquefaction-induced lateral spread displacement. The mapping process is demonstrated through an implementation in Utah County, Utah. To demonstrate the type of lateral spread displacement hazard maps possible, maps corresponding to return periods of 1033 and 2475years are developed for Utah County, Utah. The proposed procedure incorporates topographical data from airborne lidar surveys and geotechnical and geological data from available maps and subsurface explorations. It accounts for uncertainties in the soil properties, seismic loading, and the empirical models for predicting lateral spread displacement using Monte Carlo simulations.