Influencing mechanism and hydrogeological implications of water level fluctuation of lakes in the northern Qaidam Basin,Qinghai-Tibet Plateau

The Qaidam Basin(QB)is a concentrated distribution area and chemical industrial bases of salt lakes in China.Lakes in the QB have been expanding during the past 20 years.Rapid lake expansion resulted in some considerable scientific issues on the protection of salt lake resources and infrastructure,and monitoring of hydrological processes at the lake-basin scale.Although the spatial-temporal trends of lake changes on the Qinghai-Tibet Plateau(QTP)have been well documented,the underlying influencing mechanism and hydrogeological implications of rapid lake changes in the QB are not well understood.Three lakes in the northern QB were selected to investigate lake water level fluctuations on different time scales based on extensive in-situ monitoring and satellite observations.The influencing mechanism and hydrogeological implications of rapid changes of terminal lakes were discussed in combination with the reported increasing precipitation rate and mass balance of glaciers in the northern QTP.Results reveal the following:(1)the fluctuation pattern of Sugan Lake was asynchronous and out of phase with that of Xiao Qaidam and Toson lakes during the monitoring period;(2)Sugan Lake water rose gradually,and the rise interval was from late April to early July.In contrast,Xiao Qaidam and Toson lakes took on a rapid and steep rise,and the rise intervalwas from late July to September;(3)the influencing mechanisms for rapid lake fluctuations are controlled by different factors:glacier and snow melting with increasing temperature for Sugan Lake and increasing precipitation for Xiao Qaidam and Toson lakes;(4)in accordance with different intervals and influencing mechanisms of rapid lake expansions in the QB,hydrological risk precaution of lakes and corresponding river catchments was conducted in different parts of the basin.This study provided an important scientific basis for assessing the hydrological process and hydrological risk precaution,and protection of salt lake resources along with rapid lake expansions in the arid area.

Modelling of the Hydrogeological Behaviour of the Tassette Aquifer: Study of the Possibilities of Exploiting This Aquifer as an Alternative against the Limestone Problem in the Commune of Thies

Senegal’s drinking water supply comes on the one hand from groundwater and mainly from Maastrichtian and Paleocene aquifers. The Tassette area included in the Thies region has such potential that the Paleocene is currently exploited to cover a certain part of Dakar’s important water needs. In addition, the city of Thies is itself confronted with the problems of limestone present in its drinking water and generally creating problems of scaling pipes. A water transfer is therefore a possible option to deal with this situation. This study will consist of modelling the Tassette aquifer to determine if it will cover Thies’ water needs over a period of 20 years. To assess the responses of the groundwater to pumping at this level and the changes that may occur, a numerical hydrogeological model is necessary. In order to have a better overview of the area, boreholes and piezometric tests were carried out, highlighting the different characteristics of the aquifer and the water it contains. Based on these, the model was developed according to a mesh system and more precisely by discretization and simulation according to the finite difference method from the Visual Modflow Flex software. The results observed for this modelling show that the city of Thies cannot be supplied as a whole. This mining model also causes brackish water intrusion. On the other hand, the additional withdrawal of a certain quantity of water compared to the current situation does not have as great negative impacts and would still partially meet the expectations of this modelling.

Assessing Future Flooding Risk in a Coastal Lagoon Using Hydrogeological Approaches and Analysis of the 2021 Flood Event: A Case Study of Tasi-Tolu Lagoon, Dili, Timor-Leste

This study aims to apply a hydrogeological approaches and analysis of the 2021 flood event of Tasi-Tolu Lagoon to achieve four specific goals. Firstly, the study seeks to determine the natural characteristics of the lagoon, which include factors such as size, depth, water quality, and ecosystem composition. Secondly, the influence of precipitation on the water volume in the lagoon will be examined. This analysis involves assessing historical rainfall patterns in the region, as well as the amount and frequency of precipitation during the 2021 flood event. Thirdly, the hydrogeologic and geologic conditions of the lagoon will be evaluated. This involves examining factors such as the type and structure of the soil and bedrock, the presence of aquifers or other underground water sources, and the movement of water through the surrounding landscape. Finally, the study seeks to assess the risk of future flooding in Tasi-Tolu Lagoon, based on the insights gained from the previous analyses. Overall, this study’s goal is to provide a comprehensive understanding of the hydrogeological factors that contribute to flooding in Tasi-Tolu Lagoon. This knowledge could be used to inform flood mitigation strategies or to improve our ability to predict and respond to future flooding events in the region.

Hydrogeological Investigations of Groundwater and Surface Water Interactions in the Berg River Catchment, Western Cape, South Africa

The Berg River Catchment based in the Western Cape Province,South Africa services the greater Cape Town area with water,subsequent to supplying the vast agricultural activities that exist in the middle and the lower reaches.This study thus investigates the hydrogeochemical interactions between surface and groundwater in the Berg River Catchment with the aim of establishing trends and transfer of constituents between the surface and groundwater systems,investigates the role that geology plays in water chemistry as well as identifies the geochemical processes controlling surface and groundwater chemistry in the catchment.This study was carried out using three types of research designs namely i)experimental research design;ii)field research design and meta-analysis research design.Furthermore,the study made use of hydrochemical data ranging from 2003 to 2013 obtained from the National Water Monitoring Database owned and maintained by the Department of Water and Sanitation and data that were sampled in 2016 by authors and analyzed using the ICP-MS Technique Ground Water Chart,Arc-GIS and Geosoft(Oasis Montaj)were further employed to model the data.The results indicated that:i)in the Upper Berg there is not much interaction and transfer of constituents between surface and groundwater;ii)the Middle Berg,however,indicated a degree of interaction with the sharing of constituents between the two water systems and iii)the Lower Berg indicated only NaCl water type also noting that the area situated near the river mouth whereby there is the mixing of river and seawater.

Main progress and prospect for China’s hydrogeological survey

This paper reviewed the main achievements of hydrogeological survey in China,summarized the significant progress of hydrogeological survey over the past decade,and forecasted the key responsibilities for hydrogeological survey in the“14th Five-year Plan”.The significant progress includes:China established the 1:50000 standard hydrogeological survey system with Chinese characteristics and produced the new generation of highquality hydrogeological maps;the national groundwater monitoring project was completed and accepted,which marks China taking the leading position in groundwater monitoring internationally;fruitful results were achieved in the national groundwater quality survey,and groundwater quality background values were basically identified and checked;hydrogeological and environmental geological survey was continuously promoted in karst areas and the ecological restoration of rocky desertification achieved remarkable results;China strengthened layer exploration techniques for groundwater,integrating the key and practical techniques of layer exploration and monitoring;the exploration of groundwater in the poverty-stricken regions and old revolutionary base areas were effectively promoted to strongly guarantee the poverty alleviation and drinking water safety;the mystery of desert groundwater was uncovered,making up for the shortage of 1:250000 hydrogeological survey in the Badain Jaran Desert;and more efforts were made to conduct survey on the water resources in the basin,and to finish the unified measurement of national-scale groundwater level.

Hydrogeological Study of the Aquifer System in Central Tunisia: New System Structuring of Horchane Aquifers

Hydrogeological investigations, tectonics and seismic reflection show the complexity of the Horchane groundwater and drainage possibilities with neighboring groundwater in central Tunisia. Seismic reflection lines intersecting the region show the role of halokinetic movements, by the intrusion along preexisting faults, in the restructuring of the hydrogeological basin. The salt domes associated with a chaotic facies at the base of outcrops, that limit the Horchane basin, puch to outcrops the areas of recharge area. Geoelectric section shows the anisotropy and the importance of Mio-Plio-Quaternary (MPQ) sediment along the gutters, between the outcrops of El Hafay and Kebar on the one hand, and outcrops of Kebar and Majoura on the other. These gutters are communicated with channels that facilitate drainage of the Horchane complex groundwater by that Gammouda in North-East and Braga in East. The results of this study clearly indicate the important role of the geology in the restructuring of groundwater basins, through early halokinetic movements. (i.e. halokinetic movements). The aquifer geometry is controlled by the ascent of Triassic salt material, from the Middle Jurassic, in central Tunisia.

The application of resistivity tomography to hydrogeological exploration

Resistivity tomography, an advanced technique reconstructing resistivity image from a series of potential survey of electrode arrays is quite different from the non linear inversion of wave problems. The main problem in the resistivity reconstruction is how to solve the Poisson′s equation of direct current fields in voluminous media and to complete the inversion iteration efficiently. A mathematical idea of cascade algorithm proposed by Shima (1992), as an example, is introduced briefly in this paper. The emergence of water flood in tunnels in Wennan Coal Mine, Shandong Province, gave us chances to carry out hydrogeological exploration twice using resistivity tomography in 1995～1996. Three profiles with a total length of 5832 m and a maximum depth of 120 m in tomograms are completed. The series of resulting tomograms distinctly reveal the distributions of stratigraphic structure, mined out areas, fracture zones, crack belts and piping water loss zones. These results from tomograms are verified by drill records and then successfully adopted in the followed hydrogeological engineering in the coal mine. Finally, the authors discussed the technical method and existing problems in resistivity tomography.

Hydrogeological and Hydrochemical Assessment of Basin Granitoids in Assin and Breman Districts of Ghana

Hydrogeological and hydrochemical assessments were carried out in Assin and Breman districts of Ghana. A multi-criteria approach was used in the assessment of the basin granitoids including;electrical resistivity survey, pumping test and water quality analysis. A total of twenty-five (25) representative boreholes were drilled, developed and pumped;obtaining data for aquifer hydraulic parameters estimation. Correlation analysis was used to determine relationships that exist between aquifer hydraulic parameters. Schoeller, Piper, Stiff plot and Gibbs diagrams were used to determine the hydrogeochemical facies, water types and the mechanism that control groundwater quality. The statistical analysis determined that aquifer hydraulic parameters discharge rate (Q), hydraulic conductivity (K) and Transmissivity (T) showed a strong positive correlation with specific capacity (Q/Sw) with R value 0.8462, 0.8738 and 0.8332 respectively. The K and T were respectively between 0.02 - 0.90 m/day and 0.36 - 13.47 m2/day with mean of 0.24 m/day and 3.03 m2/day respectively. The K values indicate a hydrogeological condition of aquiclude with relatively low permeability and medium water bearing capacity. The aquifer T magnitude is very low to low, groundwater potential is adequate for local water supply with limited and private consumption. All physicochemical parameters were within the permissible limits of Ghana Standards Authority (GSA) and World Health Organisation (WHO) except for apparent colour, pH, Fe and Mn. Distribution of major ions in groundwater samples was calculated and the general trend among cations and anions was found to be Ca2+ > Na+ > Mg2+ and Cl? > HCO3? > SO42? respectively. The study area shows five main water types namely;Ca-HCO3, Na-Mg-HCO3-SO4, Ca-SO4, Na-Cl and Mg-Na-Cl. Weathering of rock-forming minerals as the mechanism controlling the groundwater chemistry. Microbiological parameters were above the permissible limits. Groundwater is suitable for drinking after treatment with chlorination, aeration and slow sand filtration methods.

Corrosion assessment for spent nuclear fuel disposal in crystalline rock,using variant cases of hydrogeological modeling

This paper presents a corrosion assessment of copper spent nuclear fuel disposal canisters in crystalline rock,using hydrogeological modeling.A simplified approach is considered,to avoid complex and time-consuming computer simulations.This simplified case is presented as a base case,with changes in the hydrogeological parameters presented as variant cases.The results show that in Taiwan’s base case,decreasing the hydraulic conductivity of the rock or decreasing the hydraulic conductivity of dikes results in a shorter transport path for sulfide and an increase in corrosion depth.However,the estimated canister failure time is still over one million years in the variant cases.

Perimeters of Protection Demarcation for New Boreholes of Bonoua Aquifer (Southeastern, Côte d’Ivoire) through Hydrogeological Modeling

Located in the southeastern of C&#244te d’Ivoire, Bonoua aquifer contains an enormous groundwater potential. The new boreholes have been realized in this region to support the water supply of the populations. Moreover, in this region, agriculture is the main activity, whose pesticides used to guarantee the productivity, constitute a threat for groundwater. Thus, this study was undertaken in order to design a hydrogeological model able to simulate the piezometry of the Bonoua aquifer and determine the perimeters of protection for the new boreholes. The model, carried out under the Visual Modflow interface, was designed in steady-state mode and calibrated manually from the piezometry of the year 2000. The value of the standardized root mean squared residual of 4.86% (<10%) allows to say that the calibration obtained is considered satisfactory. Also, the correlation coefficient between observed and simulated heads of 0.95 permits to confirm a good calibration of the model. Perimeters of protection values were determined by simulating the paths of the virtual particles of water from the calibrated model. The simulations show that generally, the groundwater of Bonoua aquifer flows from north to south and the piezometric levels obtained vary between 65 m in the north and 5 m in the south. Upstream radius of the closed perimeters of protection calculated from the model varies from 172 to 482 m. However, those of distant perimeters of protection vary from 2877 to 6441 m.

Study on standards of 1:50000 hydrogeological maps in China

In compilation of 1: 50 000 hydrogeological map, Some principles which are suitable for hydrogeological characteristics in China have been defined. Groundwater development and protection have been regarded as equally important. Some key problems such as classification of water-bearing formation, water yield property, color system and color scale of water yield property of water-bearing formation, expression of groundwater system, expression of hydrogeological parameters have been solved. This standardizing work can lay solid foundation for integration of 1: 50 000 synthetic hydrogeological map achievement and data, so as to broaden the service areas of hydrogeological survey.

Relationship between Hydrogeological Structure and Groundwater Exploitation Capacity in Aquifer of the Basin of Cai Phan Rang River, Ninh Thuan Province, Viet Nam

This article presents the results of dividing the hydrogeological structure zones in aquifer of Cai Phan Rang river basin, Ninh Thuan province, Viet Nam, and the relationship between parameters of hydrogeological structure zones with water storage capacity of hydrogeological structure. Research results divided hydrogeological structure of Cai Phan Rang River Basin into four zones, including three zones with depression bedrock and one zone with slope bedrock, and the results assessed： （1） specific discharge of exploitation well is proportional to zone area of hydrogeological structure; （2） specific discharge of exploitation well is inversely proportional to slope of bedrock surface, slope of water level in zone and area of drainage surface of hydrogeological structure zone; （3） water level fluctuation in zone is proportional to slope of bedrock surface, slope of water level in zone and inversely proportional to distribution area of zone; （4） total mineralization of water is proportional to bedrock surface slope and water level slope in zone, and inversely proportional to drainage surface area of zone and volume of structural depression. Research results are practical significance in solutions proposal to increase exploitation capacity for various water use purposes.

Compilation of hydrogeological map of China

Hydrogeological map is one of the important carriers of groundwater related information.It directly reflects the hydrogeological conditions and previous investigation and research results of a mapping area.The hydrogeological map of China is a map reflecting the characteristics of hydrogeology and groundwater dynamics on a national scale.On the basis of the hydrogeological map of China(1:4000000)compiled in 1988,this map compilation attempted to update and enhance the existing map,with the latest survey results from the project of National Investigation and Evaluation of Groundwater Resources and Environmental Problems led by China Geological Survey.Task of the mapping program included redefining groundwater types,quantifying the classification standard of the groundwater and adding the pore-fissure water in laterite layer of hilly basin.The multilayer structures for porous,karst and porous-fractured groundwater and their water-rich grades are reflected on the map.Based on the comprehensive summary of the latest hydrogeological data of China,this research conducts an in-depth analysis of the regional distribution characteristics of groundwater in China,utilizes a digital mapping process and establishes a cartographic database for the purpose of further use.With the enrichment of the content and the continuous improvement of cognitive level,mapping content can be updated quickly,which has practical significance for the concept of surveying and mapping and scientific popularization.

Hydrogeological Framework and Groundwater Balance of a Semi-arid Aquifer, a Case Study from Iran

Climate changing and associated factors combined with considerably increases in water demand have been accompanied by severe depletion of reservoir storage of the most groundwater supplies of Iran. Shahriar aquifer in west of Tehran is a representative aquifer of these kinds. In order to meet water demand of the area and protecting groundwater from quantity and quality deterioration, precision recognition of geology, hydrologic and hydrogeologic characteristics of the aquifer is first step. The basic objective of this study is to develop the hydrogeological framework of the groundwater system in Shariar, Iran and to estimate groundwater balance as a scientific database for future water resources delevopment programs. Based on this research lateral groundwater inflows, direct infiltration of rainfall, stream bed infiltration, irrigation return and surplus drinking and industrial water are the recharging factors of the aquifer. Subsurface outflows, domestic and industrial pumping wells and agricultural abstraction are the main parameters discharge the aquifer system. Water balance in the Shahriar aquifer system is in disequilibrium and a deficit of about 24.7 million cubic meters exists.

Recognition of the hydrogeological potential using electrical sounding in the Khemisset-Tiflet region, Morocco

The low recharge of reservoirs and the increasing demand for water limit the potential of mobilized resources, especially in arid to semi-arid areas like Morocco. Integrated management is essential to safeguard this resource. In respect with this perspective, this work provides the analysis of hydrogeological potential of Khemisset-Tiflet region, which falls within the action area of the Sebou Hydraulic Basin Agency. The basis of our studies was as follows:(1) The interpretation of the existing geoelectric data;(2) application of geophysical methods for non-destructive reconnaissance and their integration into a Geographic Information System(GIS). The analysis demonstrates that: The map of the isohypses and the geoelectric cross-section of the substratum of the superficial roof aquifer show clearly a plunge associated with development of the Paleozoic roof in the South and the direction of flow of the surface water is from south to north, from the upper zone to the north of the El Kansera dam. These conclusions constitute very useful contribution for any resource management projects in this area.

Lineaments Extraction from Gravity Data by Automatic Lineament Tracing Method in Sidi Bouzid Basin (Central Tunisia): Structural Framework Inference andHydrogeological Implication

The gravity method may be used in the exploration of deep sedimentary basins. It allows the structuring and the lateral and vertical extent of sedimentary fill to be determined. This study has concerned a qualitative and quantitative gravity analysis of Sidi Bouzid Basin in Central Tunisia. Bouguer anomaly analysis and Gravity data filtering allows us to emphasize the structures affecting the basin. The Automatic Lineament Tracing method helps to quantify the different gravity responses of faults located in the shallow and deep sedimentary sections and in the basement. The elaborated structural map of the study area constitutes a useful document for rationalizing the future groundwater exploration in the arid area of central Tunisia since it shows faults dipping and deep hydrogeologic sub-basin delineation.

Hydrogeological Hazards and Control Measures in Engineering Geological Exploration

For engineering geological investigation, hydrographic surveys are particularly important. By operating the equipment, relevant technicians analyze hydrogeological data around the project. A series of corresponding measures were taken to ensure the smooth completion of the project. However, due to the inadequate completion of hydrogeological survey work, it has great harm to the later stage of engineering work, and even will lead to the final failure of the project. Based on this, this paper explores the hazards and prevention measures of hydrogeology in engineering surveys.

Hydrogeological Comparison of Three Wells with a Basin Approach in the Nandaime-Rivas Aquifer, 2021

In general, the content of this study is aimed at presenting a comparative analysis of the hydrogeological results of three underground sources. The points or sources of analysis are the Dolores 01, Dolores 02 and Mecatepillo wells, which are registered at the following coordinates: East 610561, North 1292576, East 610234, North 1293090, East 611482, North 1293881, respectively, according to the UTM WGS system 84 Zone 16N, the analysis is done with a basin approach in the Nandaime-Rivas aquifer. According to the above, bibliographic resources have been consulted that help to further understand the comparative criteria such as transmissibility, storage coefficient, a radius of influence and thickness of the aquifer, providing complementary and additional information.