Query: Spatial distribution of hydrogeology

title: A comparative analysis of statistical and machine learning techniques for mapping the spatial distribution of groundwater salinity in a coastal aquifer
abstract: Groundwater salinity in an aquifer system is typically measured through field studies (e.g. groundwater sampling, and direct current resistivity method) The field based measurements are costly and time consuming when they are applied over a large domain. In this study, a methodology was developed and evaluated based on available hydrogeology and hydrometeorology data and statistical and machine learning techniques to map the groundwater salinity in the southern coastal aquifer of the Caspian Sea. First, variables affecting groundwater salinity (aquifer transmissivity, distance from the sea, the mean annual precipitation, the mean annual evaporation, elevation, and the depth to the water table) were determined, and the dataset was randomly divided into three subsets of training, testing, and verification. Next, the relationship between groundwater salinity and its controlling factors was established using three methods namely extreme gradient boosting (EGB) deep neural network (DNN) and multiple linear regression (MLR) and the models were evaluated by comparing the measured values and the predicted values using the statistical criteria (R squared, Nash Sutcliffe efficiency (NSE) and normalized root mean square deviation (NRMSD) Finally, the optimum model was applied to the set of known input variables to map the spatial variation of the groundwater salinity across the entire southern coastal plain of the Caspian Sea, and the final map was verified using the verification subset. Results showed that consideration should be given to the EGB method, considering its higher performance on the testing subset (R squared 0.89, NSE 0.87, NRMSD 0.45) In depth analysis of the variables showed that the aquifer transmissivity is the most crucial parameter affecting groundwater salinity in the region. The adopted approach could potentially be used for groundwater management purposes in the study area and similar settings elsewhere.

title: Environmental and artibicial tracers in hydrogeology title: Groundwater blow system in the Nakano shima Island, Japan, based on the spatial distribution of major components, CFCs, and 3H

title: Relation of the spatial and temporal distribution of water quality parameters to hydrogeology at Indian River Bay, Delaware: field observations and modeling

title: Calculating Energy and Its Spatial Distribution for a Subsurface Urban Heat Island Using a GIS Approach
abstract: In urban areas, the human influence on the city ecosystem often results in a Subsurface Urban Heat Island (SUHI) which can be used geothermally. Unfortunately, a model of a SUHI does not consider the geology and hydrogeology of the subsoil. These can vary significantly over short distances, and are of considerable importance for the energy balance. In this work, we calculated the energy and its density stored in the subsoil via a SUHI. For this so called energy SUHI (e SUHI) we evaluated the geology and its physical parameters for the first 20 m below ground level in the German city of Nuremberg and linked them to measured underground temperatures in a GIS application. This approach revealed stored energy of 1.634 x 1010 MJ within the soil and water for the study area with an area of 163 km2 and a volume of 3.26 x 109 m3. It corresponds to an average energy density of 5.0 MJ/m3. The highest energy density of 16.5 MJ/m3 was found in the city center area and correlated well to increases in subsurface temperature. As expected, our model reacts sensitively to thickness changes in the geological layers and the unsaturated zone.

title: Discussion on 'Utilization of X ray computed micro tomography to evaluate iron sulphide distribution in roofing slates' Quarterly Journal of Engineering Geology and Hydrogeology, Vol. 51, 2018, pp. 169 178
abstract: The paper presented by Vavro et al (2018) is an interesting application of a relatively new technique, X ray computed micro tomography (MCT) for the determination of iron sulphides in roofing slates. Once the slate shingles are installed on a roof, these iron sulphides may oxidize, creating unattractive red stains running along the roof surface. This pathology is considered to be the main technical problem for the roofing slate industry (Cardenes et al 2016 a In their paper, Vavro et al (2018) explain how the use of MCT allows quantification of the amount, size and spatial distribution of the iron sulphides on two samples of roofing slates. However, their work misses some important

title: A vectorial method for the study of the spatial distribution or morphological features applied to the needs of hydrogeology
abstract: The purpose of this computerized processing is to create a database of morphological features in vectorial form with an access by index. The file system is independent of the type and format of the initial documents. It allows work both with objects of various sizes and recomposition of maps by superposing and juxtaposing the information. A practical example showing maps of major directions or frequencies of orientations by mesh, explains how heterogeneous data are linked together and managed dynamically in memory. The methodology used here, can be transposed easily to any other type of counting, for example in order to determine the fractal dimension of a river network.

title: Investigation of sinkholes spatial distribution using the weights of evidence method and GIS in the vicinity of Karapinar (Konya, Turkey)
abstract: There are many sinkholes (182) in the vicinity of Karapinar. Approximately 20 large sinkholes 10 m in diameter) were formed within the Obruk Plateau between 1970 and 2012. The formation of sinkholes is the most important geological hazard in the study area because they can damage engineering structures, settlements, agricultural areas, and eventually be a source of casualties. To date, no study has been conducted on the distribution of sinkholes in this region. In this study, the spatial distribution of the sinkholes and the factors controlling sinkhole development were studied through the use of geographical information systems using a sinkhole inventory and a spatial database containing information on the topography, geology, hydrogeology, and land use. Initially, 182 sinkholes were identified in the area by examining the digital elevation model produced for this study. The sinkholes were verified in the field. Thirty two factor maps were produced to investigate their relationship with sinkholes using the weights of evidence method. The sinkholes are mainly related to dissolution of the Neogene age lacustrine Insuyu Formation, consisting of limestone and clayey limestone. Sinkhole frequency increases in the vicinity of drainages (2000 3000 m) and faults

title: Geo Electric Study in Hydrogeology According to the Axis Hassi Naga Hassi Khebi of Tindouf (Southwestern Algeria)
abstract: The hydrogeological environment of the Saharan North East region of Tindouf is of utmost interest, particularly in agriculture. In fact, exploitation and exploration processes must be analysed to ensure sufficient water production. This study demonstrates the value of spatial processing and exploitation of geoelectric and geological data in the study area and facilitates interpretation. The results of the electrical survey and the spatial analysis of the data allowed us to design a complete model that met the needs of hydrogeology. The applied methodology consists in breaking down our subject into three (3) classes of entities: geomatics, geophysics and hydrogeology. Synthetic mapping based on continuity is the result of studying two sites (Hassi Naga and Hassi Khebi) for geological analysis. Knowing that the electrical resistivity is between 0 and 3000 Ohm meter, we were able to construct thematic maps showing the spatial distribution of the facies and the probable positions of the boreholes. The study provided with a geo spatial model highlighting the impact of measurements in hydrogeology of the area considered that was called SIHE (Information System for Environmental Hydrogeology)

title: Multiple Point Statistical Simulation of rock fracture network as a key control on the hydrogeology and salinity: a case study from the Qarabagh area, West Azarbayjan Province, Iran
abstract: Modeling and characterization of the geometry and distribution of Rock Facture Networks (RFNs) are essential in applications such as hydrogeological or environmental evaluations. It is widely accepted that RFNs are potentially associated with the hydrogeological (thus salinity) characteristics of the surrounding environments. Despite the complexity and inaccessibility of RFNs, stochastic methods provide a functional framework to predict their characteristics in the subsurface. An efficient tool for modeling RFNs is the Discrete Fracture Network (DFN) which also includes a number of geostatistical techniques that consider spatial variability structure. The advantages of these techniques are: realistic results, ease of application, and uncertainty assessments. Multiple point geostatistics/statistics (MPS) is a modern and effective geostatistical tool for realistically simulating RFNs. In the present study, we modeled the RFNs in a location near the Qarabagh area, in the western Urmia Lake; in this regard, we used the Single Normal Equation Simulation (SNESIM) algorithm of the MPS geostatistical method using Training Images (TIs) instead of variograms. The required datasets and information for this modeling was provided using the field measurements of the fracture orientations and dips, as well as the outcrop photographs. The outcomes of these models can be used in predicting the salinity distribution in the surrounding area Therefore, through the SNESIM algorithm, TIs obtained from the outcrop photographs, and direct measurements, 100 RFN realizations were generated at each station. These realizations were then averaged to predict the locations with higher and lower fracture probabilities and to assess the general trend of the fracture distributions.

title: Modeling of temporal and spatial distribution of groundwater level in the water table fluctuant belt of the lower reaches of Heihe River: application of FELLOW software.
abstract: The groundwater level plays an important role in determining the pattern and distribution of vegetations that stabilize riverine environments.Presently,models simulating distribution of groundwater level become important tools in the groundwater research field.Based on the field investigation of geology and hydrogeology,conductivity and water supply capacity of the aquifer were determined in this study.After spatializing the relative parameters inputted,FEFLLOW software was run and a series of temporal and spatial distribution maps of groundwater level were obtained.By analyzing these maps,we could draw some conclusions:(1) Comparing the estimated and measured values,the mean error was 0.54m in 31 stations with mean minimum error 0.04m and mean maximum error 1.17 m;(2) Spatially,the lowest groundwater table appeared in southern mountain and northern parts between east lake and west lake.Generally,the groundwater level is between 1 m and 4 m in the most parts of the study area.Temporally,variation of groundwater level is not significant;(3) The groundwater level has gradually descended from initial stage of simulation in the study area due to decrease of runoff form the middle reaches of Heihe River.However,the Chinese Government initiated the environmental restoration project in the Heihe River basin in 2000 with water diversions from the Zhengyi gorge reservoir to the lower reaches.From 2000 to 2002 there were 6.8x10~8 m~3 each year has been releases to the lower reaches.The groundwater level has thus risen from 2002.However,the trend of ground level change was different in different parts.The ground level has mounted up in the upper and lower parts of the study area,but dropped in the middle part.