Advanced modelling of time domain electromagnetic data with updated hydrogeological interpretations

Numbers of Paleozoic and Cretaceous intracratonic basins are recorded in Northeast Africa that are formed related multi-rifting forces. High rainfall and/or large water bodies in and/or near it causes accumulation of groundwater with good potentialities. Wadi Arab Basin southeast Egypt has selected for testing their impacts. It depends on huge data sets of topography, satellite images, TRMM, geomorphology, morphometric analyses, geology, structure, geophysics, hydrogeology, field observations and measurements, sediment and water samples, chemical analyses, ARC-MAP Program, and softwares. Muti-rifing forces led to the presence of three morphotectonic depressions in the basin with huge thickness reach 1400 m south Gebal Dahmit. Investigations of data sets reveal new information about subsurface geology and discovering four high potential aquifers belonging Cretaceous and Paleozoic with fresh and brackish water quality. They recharged from Lake Nasser through deep faults and occasionally from watershed areas. Deep groundwater wells were recommended for evolution the groundwater aquifers. Results could potentially highlight for rising fresh water demands for sustainable development in similar tectonic and hydrologic settings.

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: 4 000 000) 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.

Beneath the great state of Texas, there is water. Texas has nine major aquifers and 21 minor aquifers underlying the state. These aquifers are a vital water supply source in Texas, providing approximately 60 percent of the 16.1 million acre-feet of water used in the state annually.[2] These underground waters also sustain surface water flow in rivers across Texas; thus, they are integral to the health of watersheds throughout the state and the economies that depend on this water. When W.H. Auden wrote, “Water is the soul of the Earth,” he must have been referring to groundwater.
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\nIn Texas, groundwater is regulated on the local level by groundwater conservation districts (GCDs), whose regulatory authority over subsurface aquifers is generally confined by county boundary lines rather than hydrogeological ones. In 1917 after devastating drought, voters approved the Conservation Amendment to the Texas Constitution, which provided the authority for the Texas Legislature to establish GCDs to conserve the state’s groundwater resources.[3] Chapter 36 of the Texas Water Code governs the powers and duties of GCDs in Texas.
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\nTexas landowners own the groundwater beneath their land as private property.[4] While a landowner is entitled to drill for and produce groundwater below the surface of his property, the Texas Supreme Court has held that he is subject to reasonable regulation through GCDs.[5] In GCD-managed areas, a landowner’s right to pump groundwater is tempered by the Water Code’s goals of protecting property rights in groundwater and the groundwater resource. Groundwater regulation ideally prevents one landowner from pumping to such an extent that nearby wells are impacted.
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\nNot all areas of Texas, however, are controlled by a GCD. Approximately one-third of the surface area of Texas is not regulated by a GCD. These areas where a GCD does not exist are depicted on the map below as areas without color. Out of the 254 counties in the state, 174 counties are either fully or partially within a confirmed or unconfirmed GCD.[6] In unprotected areas, there is no regulatory authority to monitor the rate and amount of groundwater withdrawal, and the rule of capture permits landowners to pump unlimited amounts of groundwater, even if doing so dries up neighboring landowners’ wells. Unregulated areas in Texas are the final frontier — the last remaining, lawless parts of the state where groundwater protection is nonexistent.
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\nDuring a time of unparalleled pressure on groundwater resources across the state, the lack of groundwater protection in some areas of Texas is undermining important areas of law and policy — from property rights and natural resource protection, to groundwater management and regional water planning.

The importance of background levels is clearly stressed by the GWD for the reason that wherever elevated background levels of substances or ions or their indicators occur due to natural hydro- geological reasons, these background levels in the relevant body of groundwater shall be taken into account when establishing groundwa- ter quality standards. However, to accurately determine background concentrations, free of anthropogenic influence, it is important to take into consideration original data quality for background analysis, us- ability of method(s), representation of the background - is it true or ambient background values of concern, any potential sources of con- tamination near the sampling points etc. Traditionally, geochemical background is often regarded as a fixed value (mean or median), that represents a hypothetical background concentration without taking into account natural variability. However, it was proved in many cases that background groundwater quality very often varies both in space and time as a result of the variations in the climate, rainfall compo- sition, hydrogeological and hydrogeochemical processes, as well as due to the impact of human activities. In the paper it is demonstrated that background values of selected inorganic parameters should be determined on the scale of the particular study because these values are site specific. To treat adequately multimodal or skewed data distri- bution, resulting from more than one processes involved in the gener- ation of the original data set, the model-based objective methods, the iterative 2-σ technique and the calculated distribution function, were used. Geochemical data from the groundwater of Samobor aquifer were subjected to the quantitative partitioning by which outliers were removed from the original data sets. Ambient background concentra- tions are then defined, resulting from the long term human impact on the groundwater quality in this area.

Magnetic Resonance Sounding (MRS or Surface Nuclear Magnetic Resonance (SNMR)) is a geophysical technique used for direct groundwater detection and aquifer characterisation. the technique is based upon the nuclear magnetic resonance (NMR) method, most well known in medical imaging. the technique was developed in the early 1980’s but commercial systems only became available in the late 1990’s. the technique has been trialled in Australia previously, but the method has not been fully adopted into common use. the main impediment of the technique is in detecting a very small signal typically 8-10 orders of magnitude less than the background electromagnetic noise. with the advent of new system designs and modern processing technologies the latest developments in MRS have greatly improved the success of the technique. CSIRO is undertaking a study to test the latest in MRS instrument design- the Vista Clara GMR system in Australian settings. As part of the study a trial site over the Tamala Limestone in Western Australia was undertaken as part of a larger hydrogeological study of this particular limestone which provides a groundwater resource to the Perth area, Western Australia. in this project MRS soundings were collected at 3 sites. Following the surface measurements, sonic drilling was performed, and each hole was logged with an NMR tool. in addition laboratory NMR and permeability tests were performed on recovered samples. This paper discusses the results of the three scales of measurements and demonstrates how MRS provides a non invasive method for characterising aquifers.

Salt water intrusion is a critical challenge for the management of fresh water resources on small oceanic islands like those in the lower Florida Keys, which have extensive coastal development including construction of canals. We present the use of the Direct Current Resistivity (DCR) method for investigating the location of the fresh water, saline water (FW/SW) interface. A Super-Sting R1 28-electrode resistivity imaging system was used to investigate the subsurface geology and the FW/SW interface on Big Pine Key. the survey consisted 54m long profile in the center of the island and a 250m long roll along profile extending inland from the western shore. in the center of the island, resistivities range from 40 – 250 ohm-m near the surface and correspond to the freshwater lens which extends to a depth of 6 m below sea level. Below this depth, values of 20-30 ohm-m indicate brackish groundwater. On the western shore of the island, resistivities of 1-3 ohm-m corresponding to sea water are found at the surface and extend 25 m inland. Farther inland, resistivities increase to 50 ohm-m indicating a 2-3 m thick fresh water lens. the FW/SW interface slopes landward and 250 m inland from the shore, brackish resistivity of ~20 ohm-m extend to 4 m below sea level and saline found at 8 m depth. Observed geoelectrical data were compared with a 2-D salinity profile simulated from the USGS SEAWAT model .Analysis of the data show that the largest depth to FW/SW interface occurs at 8m depth in the middle of the island with a gradual decrease in the FW towards the saline zone on the shore of the island and this is generally consistent with the geophysics. Ultimately, both geophysical methods and hydrogeological model Tools like SEAWAT can predict island sea water intrusion with reasonable accuracy.

Over the past 15 years Douglas County, NV has removed production wells in northern Carson Valley from use due to relatively high arsenic concentrations (Carl Ruschmeyer, January 2013, Douglas County Public Works Director, verbal communication). To maintain the supply of water to the public, the town of Minden has been providing water to Douglas County and Carson City. Due to the projected increases in municipal demand, water resource managers are concerned that increasing pumping rates from wells in Minden may change groundwater chemistry and degrade the resource by potentially drawing in arsenic enriched water. Long-term exposure to arsenic can cause illnesses ranging from skin discoloration to various cancers including those of the bladder, skin, and kidney (U.S. Environmental Protection Agency, 2012). Naturally occurring arsenic is one of the most common contaminants in groundwater in the western United States. Arsenic found in basin-fill aquifers is oftentimes associated with alluvial/lacustrine sedimentary deposits derived from the weathering of volcanic rocks and geothermal waters (Welch and others, 1988). The primary aquifers beneath Carson Valley are comprised of quaternary aged basin-fill deposits of weathered granitic and volcanic material (Welch, 1994). Factors contributing to increasing arsenic concentrations in groundwater include, but are not limited to, proximity to arsenic bearing rocks, relatively long groundwater flow paths, the application of phosphate containing fertilizers, and leaching from soils in irrigated areas (Busbee and others, 2009; Anning and others, 2012). The vulnerability of groundwater resources to contamination is influenced by the physical properties of the aquifer, pumping rates, locations of wells and screened intervals relative to the groundwater flow system, and geochemical environment (Focazio and others, 2002). Arsenic mobility and transport through the subsurface is largely controlled by the interaction of groundwater with aquifer sediments. Arsenite (As(III)), the reduced form of inorganic arsenic, usually exhibits greater mobility in groundwater than the oxidized form, arsenate (As(V)) largely due to the greater attraction of As(V) to aquifer sediments relative to that of As(III) at pH values exceeding 8.5 (Smedley and Kinniburgh, 2002). Arsenic speciation (form) is influenced by the relative redox condition of the aquifer environment. For example, in the vicinity of the Douglas County Airport, where arsenic speciation has been characterized, arsenic in groundwater collected at depths greater than 250 feet below land surface was found to be primarily As(III); however, in the upper 150 feet of the aquifer As(V) predominated (Paul and others, 2010). This data set provides a spatial and temporal assessment of available chemical and physical data from local, county, state, and federal databases for the Carson Valley, near Minden, Nevada. Critical data gaps will be identified and, if necessary, additional sample collection and monitoring under conditions of routine groundwater pumping from both municipal and agricultural supply wells will be suggested. Data included as part of this data set, are data provided by the USGS and Carson Valley water purveyors with the support of the Carson Water Subconservancy District and Nevada Division of Environmental Protection to evaluate arsenic mobility and transport in Carson Valley. These data are water quality samples and water-level observations

Geothermal energy and in particular low temperature re- sources, have a rising worldwide importance. Ground-Source Heat Pumps (GSHP) have been used increasingly because they are among the cleanest and most energy efficient heating and cooling systems for buildings. Simulation models can be applied for a more effective use of the subsoil for geothermal purposes. In fact they are useful tools for the design of efficient systems considering also the need to avoid abnormal temperature distributions in soil and aquifers. In the hydrogeology field MODFLOW/MT3DMS are the most widespread programs to face environmental problems and to fore- cast quantity and quality impacts on groundwater resources. Al- though MODFLOW/MT3DMS are used to represent open circuit heat pumps, they are hardly used to represent borehole heat exchang- ers (BHE). The aim of this study is to simulate BHEs through two computer codes. The first one is TRNVDSTP, coupled to TRNSYS, which is often used in GSHP design in pure conduction cases. A methodology to take groundwater flow into account was added to TRNVDSTP, but a validation is still missing. The second one is MODFLOW/MT3DMS, suitable for groundwater flow and transport models, but whose reliability in BHE simulation is today unknown. The two software have been compared in terms of predicted ex- changed energy and temperature distribution in the aquifer.

In most regions of the world, safeguarding groundwater resources is a serious issue, particularly in coastal areas where groundwater is the main water source for drinking, irrigation and industry. Water availability depends on climate, topography and geology. The aim of this paper is to evaluate aquifer recharge as a possible strategy to relieve water resource scarcity. Natural aquifer recharge is defined as the downward flow of water reaching the water table, increasing the groundwater reservoir. Hydro-meteorological factors (rainfall, evapotranspiration and runoff) may alter natural recharge processes. Artificial aquifer recharge is a process by which surface water is introduced with artificial systems underground to fill an aquifer. As a consequence of global warming that has increased the frequency and severity of natural disasters like the drought, the impacts of climate change and seasonality, the artificial recharge has been considered as a viable option. Different direct and indirect techniques can be used, and the choice depends on the hydrologic characteristics of a specific area. In Italy, Legislative Decree no. 152/06 plans artificial aquifer recharge as an additional measure in water management, and Decree no. 100/2016 establishes quantitative and qualitative conditions for recharge. Many projects examine aquifer recharge, such us WADIS-MAR in the southern Mediterranean region, WARBO in Italy and municipal wastewater treatment project in Apulia, a southern Italian region. However, aside from groundwater recharge, the community must foster a spirit of cooperation to manage groundwater as a sustainable resource.

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.

Rock engineering problems related to underground hydrocarbon storage

Groundwater development in weathered and fractured hard rock aquifers is a more complex and dynamic as compared with that in unconsolidated alluvial stratum or in soluble carbonate rocks. The fact is that the aquifers classified under hard rocks are discontinuous, anisotropic and have only secondary porosity. However, in India more than 65% of the region is covered by hard rocks, particularly in the southern part of the country which is dominated by basaltic lava flows. The farmers in this part of the region are always facing conditions of hydrologic extremes due to the uncertainty in the rainfall pattern added with climatic changes. In this context, it is highly essential to develop reliable and well-conceived models for estimating the groundwater availability and to guide the society for adapting to the worst scenario of water scarcity from time to time. For sustainable development, it is necessary to take up soil and water conservation techniques in each watershed, taking a sub-basin as the unit for planning. Therefore in the present study Malaprabha sub-basin in northern region of Karnataka has been studied systematically for groundwater hydrological parameters like rate of infiltration and Hydraulic conductivity varies with respect to land use and the lithology. The rate of infiltration in the forest area is high 13% compared hard and compact rock similarly the Hydraulic conductivity varies from 0.2 cm/hr in the barren land to 5.8 cm in the Forest area. Therefore these two factors mainly affect the groundwater recharge and movement with this experimental values conceptual model has been developed and found that in the upper part of the basin the rate of infiltration is high and groundwater occurs in the unconfined aquifers and in the middle part of the basin the groundwater occurrence is low and in lower portion the groundwater occurrence is considerably higher.

During fiscal years 1990-92, the water-resources activities of the U.S. Geological Survey in Louisiana consisted of hydrologic data collection and interpretive investigations and research. Data collection activities involved the operation of statewide stream gaging, ground-water, and quality-of-water long-term monitoring networks. Interpretive investigations and research addressed specific hydrologic concerns such as potential organic chemical contamination in the lower Calcasieu River, water quality of the Barataria basin and Mermentau River basin, water quality and flood characteristics of streams, quality and quantity of freshwater in aquifers, and evaluation of ground-water resources. This report briefly describes the problem, objective, approach, progress, and plans for each project. It also includes a description of the District's organization and a list of cooperators.

The Bureau of Reclamation is developing a water-resource project, the Closed Basin Division, in the San Luis Valley of south-central Colorado that is designed to salvage unconfined ground water that currently is discharged as evapotranspiration. The water table in and near the 130,000-acre Closed Basin Division area will be lowered by an annual withdrawal of as much as 100,000 acre-feet of ground water from the unconfined aquifer. The legislation authorizing the project limits resulting drawdown of the water table in preexisting irrigation and domestic wells outside the Closed Basin Division to a maximum of 2 feet. Water levels in the closed basin in the northern part of the San Luis Valley historically have fluctuated more than 2 feet in response to water-use practices and variation of climatically controlled recharge and discharge. Declines of water levels in nearby wells that are caused by withdrawals in the Closed Basin Division can be quantified if water-level fluctuations that result from other water-use practices and climatic variations can be estimated. This study was done to evaluate water-level change at selected observation wells in and near the Closed Basin Division. Regression models of monthly water-level change were developed to predict monthly water-level change in 46 selected observation wells. Predictions of monthly water-level change are based on one or more of the following: elapsed time, cosine and sine functions with an annual period, streamflow depletion of the Rio Grande, electrical use for agricultural purposes, runoff into the closed basin, precipitation, and mean air temperature. Regression models for five of the wells include only an intercept term and either an elapsed-time term or terms determined by the cosine and sine functions. Regression models for the other 41 wells include 1 to 4 of the 5 other variables, which can vary from month to month and from year to year. Serial correlation of the residuals was detected in 24 of the regression models. These models also include an autoregressive term to account for serial correlation in the residuals. The adjusted coefficient of determination (Ra2) for the 46 regression models range from 0.08 to 0.89, and the standard errors of estimate range from 0.034 to 2.483 feet. The regression models of monthly water- level change can be used to evaluate whether post-1985 monthly water-level change values at the selected observation wells are within the 95-percent confidence limits of predicted monthly water-level change.

Anecdotal evidence, mostly from the United States, suggests that it has become increasingly difficult to find well-trained, entry-level ground water hydrologists to fill open positions in consulting firms and regulatory agencies. The future prospects for filling positions that require training in ground water hydrology are assessed by considering three factors: the market, the numbers of qualified students entering colleges and universities, and the aging of the existing workforce. The environmental and water resources consulting industry has seen continuous albeit variable growth, and demand for environmental scientists and hydrologists is expected to increase significantly. Conversely, students' interest and their enrollment in hydrology and water resources programs have waned in recent years, and the interests of students within these departments have shifted away from ground water hydrology in some schools. This decrease in the numbers of U.S. students graduating in hydrology or emphasizing ground water hydrology is coinciding with the aging of and pending retirement of ground water scientists and engineers in the baby boomer generation. We need to both trigger the imagination of students at the elementary school level so that they later want to apply science and math and communicate the career opportunities in ground water hydrology to those high school and college graduates who have acquired the appropriate technical background. Because the success of a consulting firm, research organization, or regulatory agency is derived from the skills and judgment of the employees, human resources will be an increasingly more critical strategic issue for many years.