Distribution Of Hydraulic Parameters Research Articles

Effect of injection water ionic strength on estimating hydraulic parameters in a 3D sand tank using silica encapsulated magnetic DNA particles

We investigated the applicability of Silica encapsulated, superparamagnetic DNA particles (SiDNAmag) in determining aquifer hydraulic parameters at different ionic strengths (1 mM, 5 mM, and 20 mM phosphate buffer) of injection suspension. Thereto, in a homogeneous, unconsolidated sand tank we pulse - injected two uniquely sequenced SiDNAmag at two injection points. At 0.5 m and 0.8 m downstream from the injection points, we measured the concentration of SiDNAmags at three vertically distributed and two horizontally distributed sampling locations. We estimated the hydraulic parameter distributions from the SiDNAmag breakthrough curves through a Monte – Carlo approach and compared the parameter distributions with salt tracer breakthrough curves. Our results indicated that at all the ionic strengths, the times of peak concentrations, and the shapes of the breakthrough curves were similar to the salt tracer. As compared to the salt, a 1 – 3 log units reduction in the maximum effluent concentration of SiDNAmag was due to kinetic attachment. The attachment rate reduced from 1 mM to 5 mM phosphate buffer possibly due to competitive adsorption of phosphate onto the favourable attachment sites. SiDNAmag attachment rate further increased in 20 mM buffer suspension, possibly due to the compression of electric double layer and reduction in energy barrier for attachment. The parameter distributions of hydraulic conductivity (k), effective porosity (ne), longitudinal dispersivity (αL), vertical transverse dispersivity (αTV /αL) and horizontal transverse dispersivity (αTH /αL) estimated from the SiDNAmag and the salt tracer breakthrough curves were statistically similar. Our work contributes to the applicability of colloidal SiDNAmags for determining hydraulic parameters at different ionic strength conditions.

Comparison of Hydraulic Travel Time and Attenuation Inversions, Thermal Tracer Tomography and Geostatistical Inversion for Aquifer Characterization: A Numerical Study

For the characterization of heterogeneous aquifers, transient hydraulic tomography (THT) was proposed as a promising method to obtain the distribution of hydraulic parameters with satisfying spatial resolution using different approaches. These include hydraulic travel time, attenuation inversions, thermal tracer tomography, and geostatistical inversion with successive linear estimator (SLE). For the same hydrogeological test, different inversion methods tend to use different sub-data sets to obtain different hydraulic parameters. Up to now, however, few studies have focused on revealing the respective characteristics of these inversion methods and attempted to improve the accuracy of aquifer characterization by bridging the shortcomings of the inversion methods. The main objective of this study was to evaluate the utility of multiple inversion techniques on aquifer heterogeneity characterization. A series of warm water injection tests were first simulated in a fluvial aquifer analogue outcrop. The calculated head and temperature datasets from these tests were fully utilized to reveal the aquifer heterogeneity by using all of the four above-mentioned inversion methods. The results show that the thermal tracer tomography, hydraulic travel time, and attenuation tomography characterized the high permeability zones more accurately within the well area, whereas the geological statistical method tended to depict the overall distribution of K values for a larger area. By comparison analysis and combinations of the individual inversion results, the scientific and economic complementarity can be studied and some valuable advice for the choice of different inversion methods can be recommended for future practices.

Geostatistical analysis of high-resolution hydraulic conductivity estimates from the hydraulic profiling tool and integration with hydraulic tomography at a highly heterogeneous field site

Hydraulic profiling tool (HPT) and hydraulic tomography (HT) have been developed as promising techniques for the high-resolution characterization of surficial aquifer systems. HPT surveys can be rapidly conducted at a resolution of 1.5-cm, but provide only one-dimensional vertical profiles and require site-specific formulae to relate HPT measurements to K. Geostatistics-based HT can estimate three-dimensional distributions of hydraulic parameters, but may fail to provide detailed information and can be smooth when pumping/observation data density is sparse and usually are constrained to the area enclosed by the pumping and observation network. In this study, HPT and HT surveys were conducted at the North Campus Research Site (NCRS) in Waterloo, Ontario, Canada to characterize a glaciofluvial multi-aquifer-aquitard system with permeameter K values spanning nearly seven orders of magnitude. We first performed the geostatistical analysis of K values derived from 11 HPT surveys using the power-law model developed for the NCRS by Zhao and Illman (2022b). Then, the benefits of incorporating HPT K profiles into HT were evaluated for the reconstruction of hydraulic parameter fields. Results showed that the arithmetic mean of 11 HPT K profiles was nearly one order of magnitude higher than that of the 544 permeameter test K measurements. The K fields interpolated by ordinary kriging captured the vertical alternating layering patterns of aquifer and aquitard layers, while they over-predicted the values by nearly one order of magnitude than permeameter K for the top part of the aquifer system. By incorporating the kriged K values as prior means for the geostatistics-based HT, improvements were found in capturing spatial heterogeneity of K fields for areas both inside and outside the well cluster and in drawdown predictions than the inversion case using only pressure head data. The inclusion of vertical variation information of K derived from HPT into HT was also helpful in refining the vertical locations of estimated layer boundaries and introducing intralayer variation patterns of K for both aquifer and aquitard layers. This study demonstrates the potential ability of HT and HPT and advocates the joint use of both techniques for the characterization of subsurface heterogeneity at highly heterogeneous sites such as the NCRS.

Temperature homogenization control of parabolic trough solar collector field

The collector fields of large-scale commercial trough solar power stations often face inhomogeneities in environmental parameters and resistance to flow in the pipe network. Aiming at dealing with the problem of uneven distribution of hydraulic parameters and radiation in large collector fields, this study establishes a heat transfer model and a hydraulic model of the collector field and proposes a control strategy for the heat transfer fluid (HTF) flow in the parabolic trough collector (PTC) loops. Based on the proposed hydraulic model, the loop valve opening is directly calculated and fast control of the loop HTF flow is achieved. Simulation results show that the scheme significantly reduces the differences in HTF temperature at the outlet of the PTC loops.

Podzemní vody hluboké struktury regionálního rozsahu: Pasohlávky–Laa an der Thaya

The regions of South Moravia in Czech Republic and Lower Austria are well-known for their use of thermal mineral waters for balneological purposes. Mineral waters are exploited from a Jurassic aquifer by two about 1.5 km deep wells MUS-3G (Pasohlavky, Czech Republic) and Laa TH Nord 1 (Laa an der Thaya, Austria). This Jurassic aquifer buried below the Neogene foredeep overlies a crystalline basement of Bohemian Massif and continues to the southeast below the Western Carpathians. Jurassic sediments which are mainly composed of autochthonous carbonates increase their thickness in this direction due to the decline of the crystalline basement. Because of this decline, there are two developments of Jurassic sediments, the shallower on the northwest and the deeper on the southeast. The zone between these two developments is known as the Mušov transition zone. For sustainable mineral water resources development, a groundwater flow pattern and recharge are evaluated. This evaluation includes both the hydrogeologic structure of Jurassic carbonates and hydraulically continuous underlying and overlying rocks. Because of the considerable depth of this hydrogeologic structure, which ranges from 100 to 3 000 metres below sea level, this study was based mostly on archive reports related to deep wells at the study area. The extent of studied units was identified on well-log data and geophysical survey interpretation. The resulting groundwater level contour map is based on the spatial distribution of hydraulic heads ranging approx. from 180 to 220 metres above sea level (masl) that were derived from pressure and water density conditions at the Jurassic aquifer. The general direction of groundwater flow is from northwest and southeast to the drainage zone (hydraulic head approx. 170–190 masl) identified in the middle of the studied area, which is identical to a course of the Mušov transition zone and parallel to the course of Dyje river (water table 170–180 masl). The northwestern part of the studied hydrogeological structure also differs from the southeastern part in a lower total mineralization which indicates active inflow of fresh water. The study was also enhanced by a spatial distribution of hydraulic parameters of all modelled units. These parameters were derived from hydrodynamic tests. The hydraulic conductivity values for the major Jurassic aquifer range from 6.0 × 10-4 to 1.3 × 10-9 m/s. The occurrence of the higher hydraulic conductivity near the drainage zone indicates the presence of a well-developed drainage network.

Numerical investigation of hydraulic tomography for mapping karst conduits and its connectivity

Hydraulic tomography (HT) is a well-established approach to successfully describe subsurface hydraulic heterogeneity. This work explored the potential of HT and the simultaneous successive linear estimator algorithm to map the distribution and connectivity of karst conduits and their hydraulic parameters at the engineering scale. Three generalized synthetic karst conduit models, auxiliary conduit, cave and waterfall, were established. A series of pumping tests were conducted at different locations as forward simulations to collect hydraulic head responses. These responses were then used for the HT inversion analysis to estimate hydraulic parameter fields of karst aquifers under steady-state and transient conditions. Our results show that high-density observation wells substantially assist with interpreting the reliable spatial distribution of hydraulic parameters. With the increase in the number of pumping wells in the HT inversion, the estimates of hydraulic conductivity and specific storage became more accurate for the auxiliary conduit model, but for the cave and waterfall models, there was no significant improvement. The hydraulic conductivity (K) tomograms from transient hydraulic tomography (THT) better indicated the heterogeneity of the three karst models than those from steady-state hydraulic tomography (SSHT) because a large number of hydraulic head records were introduced into the THT inversion process. Moreover, when reliable geological data are available, the accuracy of the estimated hydraulic parameter maps can be greatly improved even if only infrequent hydraulic head measurements can be obtained, implying that a priori geological information may be extremely valuable in mapping karst conduit heterogeneity. Finally, the robustness of HT in mapping karst conduits is verified through the simulation of independent cross-hole pumping tests. This study proved that hydraulic tomography utilizing groundwater responses from a series of cross-hole pumping tests is an efficient and cost-effective way and provided a feasible method for accurate identification of hydraulic heterogeneity of karst aquifers.

CFD simulation on the transient process of coolant mixing phenomenon in reactor pressure vessel

The emergency coolant cooling system (ECCS) is designed to inject coolant into reactor pressure vessel (RPV) during loss of coolant accidents, ensuring the sufficient coolant inventory in the nuclear reactor core. During this process, the cold water mixes with high temperature coolant in the primary loop, making the wall of RPV and cold legs suffer severe pressurized thermal shock (PTS) and threatens the integrity of primary loop. In this study, coolant mixing phenomena in the experiment UPTF, which is a 1/1 full-scale model of the PWR with four coolant loops in Germany, was studied numerically using the CFD software Fluent. The best practice guideline for coolant mixing study using CFD method in the reactor primary loop and RPV, including the suitable turbulent model, geometry simplification and mesh conditions, was concluded. The detailed three dimensional thermal hydraulic parameter distributions were achieved and the effect of coolant injection rates on the mixing process is also obtained. Results show that the mixing effect is enhanced due to the existence of reverse flow at the core entrance sections. The high injection rate provides more timely coolant supplement and reduces the possible core exposure time. However, as the injection rate increases, more intensive disturbance on the temperature and velocity fields appear, which is more likely to cause the thermal fatigue.

Slope Erosion and Hydraulics during Thawing of the Sand-Covered Loess Plateau

Seasonal freeze-thaw processes have led to severe soil erosion globally. Slopes are particularly susceptible to changes in runoff, it can be useful to study soil erosion mechanisms. We conducted meltwater flow laboratory experiments to quantify the temporal and spatial distribution of hydraulic parameters on sandy slopes in relation to runoff and sediment yield under constant flow, different soil conditions (unfrozen slope: US; frozen slope: FS), and variable sand thickness. The results showed that sand can prolong initial runoff time, and US and FS have significantly different initial runoff times. There was a significant linear relationship between the cumulative runoff and the cumulative sediment yield. Additionally, hydrodynamic parameters of US and FS varied with time and spatially, as the distance between US and FS is linearly related to the top of the slope. We found that the main runoff flow pattern was composed of laminar flow and supercritical flow. There was a significant linear relationship between flow velocity and hydraulic parameters. The flow velocity is the best hydraulic parameter to simulate the trend of slope erosion process. This study can provide a scientific basis for a model of slope erosion during thawing for the Loess Plateau.

Scanning for water hazard threats with sequential water releasing tests in underground coal mines

Water hazards threat the safety of underground mining. A detailed characterization of hydraulic parameters is helpful for the design of engineering projects to prevent underground water hazards. Utilizing aquifer’s natural artesian condition, water releasing tests are often performed in China’s underground mines. In this research, we propose to interpret water releasing test data with hydraulic tomography (HT) technique. A 216-hour duration test was performed to localize water hazard areas in Ningtiaota underground coal mine. Groundwater was released with four sequential stages from 30 boreholes. HT analysis clearly shows that the study area has a potential water hazard region in southern part by only using data from the first two stages, which coincides with existing water inrush incident location. With the addition of more pressure responses from stages 3 and 4, it discovers low transmissivity and storativity values in northern part. Our numerical examples further demonstrate that sequential water releasing tests produce comparable hydraulic parameter distributions to tomographic tests. In the end, we conclude that water releasing tests aided by HT technique can leads to a high resolution characterization of water hazard aquifers.

Numerical Modeling of a Laboratory-Scale Waste Rock Pile Featuring an Engineered Cover System

Improved design to reduce contaminant mass loadings from waste rock piles is an increasingly important consideration. In certain cases, an engineered cover system containing a flow control layer (FCL) may be used to mitigate the release of metals out of a pile using capillary barrier effects (CBEs), diverting water away from reactive materials below. In this study, a reactive transport model was calibrated to observational data from a laboratory experiment designed to evaluate a cover system. The results show that the numerical model is capable of capturing flow rates out of multiple drainage ports and matching key effluent concentrations by including the spatial distribution of hydraulic parameters and mineral weathering rates. Simulations were also useful for characterizing the internal flow pathways within the laboratory experiment, showing the effectiveness of the cover in diverting the flow away from the reactive waste rock and identifying secondary CBEs between different rock types. The numerical model proved beneficial in building an improved understanding of the processes controlling the metal release and conceptualizing the system. The model was expanded to investigate the robustness of the cover system as a function of the applied infiltration rate, supporting that water diversion will occur with infiltration rates representative of field conditions.

Late Quaternary sequence stratigraphy as a tool for groundwater exploration: Lessons from the Po River Basin (northern Italy)

Sequence stratigraphy, typically used for hydrocarbon exploration in ancient strata, can be applied to late Quaternary successions to decipher complex spatial relations among their aquifers. Late Pleistocene–Holocene strata of the Po Basin were investigated using a sequence stratigraphic approach to produce a high-resolution model for guiding groundwater exploitation. Because facies tend to be diachronous across depositional basins, facies analysis was done within the conformable intervals of strata revealed by sequence stratigraphy to accurately interpret and map coeval lateral facies relations. Volumetric assessments, sand-distribution mapping, hydraulic characterization of facies, and spatial variations of hydraulic parameters revealed two aquifer systems: the lowstand systems tract (LST) and the highstand systems tract (HST) vertically separated by an aquitard, the transgressive systems tract (TST). The LST aquifer consists of amalgamated fluvial sands (average transmissivity: 3.5 E-3 m2/s [37.7 E-3 ft2/s]) with considerable width (>25 km [>16 mi]) preferentially elongated downstream. The widespread TST aquitard is dominated volumetrically (∼57%) by low-permeability estuarine deposits. The HST aquifer (average transmissivity: 5.4 E-5 m2/s [58.1 E-5 ft2/s]) is 5–10 km (∼3-6 mi) wide, elongated parallel to the modern shoreline. Sequence stratigraphic analysis at the parasequence scale revealed an almost unprecedented level of detailed insight into aquifer (or aquiclude) dimensions and the complex distribution of hydraulic parameters in the subsurface, showing that similar facies have different permeabilities depending on systems tract. In contrast, lithostratigraphic mapping obscures subsurface connectivity and directional trends and has minimal predictive power away from control. These insights should be useful for guiding correlation and mapping of the deep subsurface and for hydrocarbon reservoir modelers.

Gas network improvement proposal using numerical simulation

Simulation software packages are very useful tools for evaluating hydraulic conditions in gas systems, and therefore for supporting the design process, network maintenance and decisions about rerouting or modernisation of a network. In the range of this paper, a model of a real branched gas network covering 3 towns was created in the GAZNET software. At first, actual hydraulic conditions of gas flow in the pipes were simulated to evaluate distributions of flow velocity and pressure in the pipes. The obtained results indicated meaningful pressure drops and increase in flow velocity in some sections of the model, which not only constitutes a threat to provide required parameters of gas to consumers, but also forecloses connecting new consumers to the network. Thus, two variants of improvements were proposed: (1) expanding the network by building two additional sections or (2) increasing the number of gas sources by building additional pressure reduction and measuring unit. Conducted simulations indicated that changes of the network proposed in both variants clearly improve hydraulic conditions in the network model. However, the first variant was chosen as a better alternative, because distribution of hydraulic parameters in the model was more homogeneous than in the second variant, as well as because of economic considerations.

Application of HySpex hyperspectral images for verification of a two-dimensional hydrodynamic model

ABSTRACTThis research focuses on the use of HySpex hyperspectral images for verification of two-dimensional hydrodynamic modelling of open-channel flow over loose bed (CCHE2D) and assessment of water quality in the Zegrze Reservoir. The CCHE2D hydrodynamic model results show the distribution of hydraulic parameters of water flow and the sediment concentrations in the reservoir. HySpex images were used to obtain remote sensing indices of water quality. The images were compared to the hydrodynamic model results and field measurements. The analysis of hydrodynamic model results and hyperspectral image indices show the spatial distribution of the water’s physico-chemical properties in the reservoir, and poor mixing of the Bug River and the Narew River at their confluence. This study shows that there is synergy potential in using hydrodynamic modelling results and remote sensing indices of water quality for analysis of the reservoir’s water quality.

Determination of hyporheic travel time distributions and other parameters from concurrent conservative and reactive tracer tests by local‐in‐global optimization

AbstractThe complexity of hyporheic flow paths requires reach‐scale models of solute transport in streams that are flexible in their representation of the hyporheic passage. We use a model that couples advective‐dispersive in‐stream transport to hyporheic exchange with a shape‐free distribution of hyporheic travel times. The model also accounts for two‐site sorption and transformation of reactive solutes. The coefficients of the model are determined by fitting concurrent stream‐tracer tests of conservative (fluorescein) and reactive (resazurin/resorufin) compounds. The flexibility of the shape‐free models give rise to multiple local minima of the objective function in parameter estimation, thus requiring global‐search algorithms, which is hindered by the large number of parameter values to be estimated. We present a local‐in‐global optimization approach, in which we use a Markov‐Chain Monte Carlo method as global‐search method to estimate a set of in‐stream and hyporheic parameters. Nested therein, we infer the shape‐free distribution of hyporheic travel times by a local Gauss‐Newton method. The overall approach is independent of the initial guess and provides the joint posterior distribution of all parameters. We apply the described local‐in‐global optimization method to recorded tracer breakthrough curves of three consecutive stream sections, and infer section‐wise hydraulic parameter distributions to analyze how hyporheic exchange processes differ between the stream sections.

Theoretical bend-flow solutions and velocity-dip phenomenon

ABSTRACTFlow structure in an open-channel bend exhibits two specific features: (1) secondary flow caused by the channel curvature; and (2) typical occurrence of the maximum velocity below the water surface, known as velocity-dip phenomenon. To explain these features, this paper proposes a coupled model that provides theoretical three-dimensional bend-flow solutions. Considering the transverse distributions of hydraulic parameters as non-uniform and influenced by the side-wall stresses, the complete secondary circulation is obtained theoretically. Using a modified log-wake law, the velocity-dip phenomenon is analysed and found to exist in both primary and secondary flows.

3D fluid flow in fault zones of crystalline basement rocks (Poehla‐Tellerhaeuser Ore Field, Ore Mountains, Germany)

AbstractA comprehensive dataset for discrete groundwater inflows to mines in the Poehla‐Tellerhaeuser Ore Field and the mining scale fault zones has been compiled from unpublished data recorded by eastern German and Soviet hydrogeologists at the Soviet‐German stock company (SDAG) Wismut. This dataset has been analyzed to provide novel insights into the 3D distribution of preferential groundwater pathways and the impacts of faulting on the distribution of hydraulic parameters in crystalline rocks at site scale. The sampled 1030 discrete inflows include flow rates ranging from 1.7E‐8 to 3.7E‐2 m3 sec−1, which were transformed into mesoscale fracture transmissivity values ranging between 3E‐13 and 2E‐4 m2 sec−1. These mesoscale fracture transmissivities were spatially correlated with fault zones exhibiting trace lengths between 0.3 and 30 km, which were mainly formed during and reactivated several times since Variscan orogeny. The statistical correlations are based on a 3D geological model composed of 14 litho‐stratigraphic units and 131 mining scale faults, separated into five main strike directions. These fault zones strongly overlap and cover about 90% of the investigated rock mass volume with a decreasing percentage of overlap in the investigated depth range (0–900 mbgs). 97% of all inflows are located within fault damage zones, and most of the flow occurs within the overlap of multiple fault damage zones. A dimensionless hydraulic model for the distribution of flow Q as a function of the position x within mining scale fault zones has been derived as Q = 1.1e−4.5x (where x decreases from the fault core to the protolith and the exponent varies as a function of fault orientation). 75–95% of the flow occurs within the inner 50% of the damage zone, and mainly NW‐SE and NE‐SW striking mining scale faults are transmissive. The orientations of conductive mesoscale fractures within these damage zones show a larger variability than the corresponding mining scale faults.

Poor understanding of the hydrogeological structure is a main cause of hand-dug wells failure in developing countries: A case study of a Precambrian basement aquifer in Bugesera region (Burundi)

This study investigates a Precambrian basement aquifer in Bugesera region, a typical African rural area in northeastern Burundi. Domestic water supply relies on groundwater which is tapped through hand-dug wells. Despite several attempts to increase the number of water points in the area, the water demand is still far from being met as a result of the high rate of well failure. This paper seeks to understand whether the hydrogeological structure and the spatial distribution of hydraulic parameters can explain the low productivity and the high failure rate of hand-dug wells. The hydrogeological structure inferred from the interpretation of a large number of vertical electrical soundings (VES) reveals a typical sequence of geoelectrical layers, which is characterized by an overall upwards fining from the fresh basement, over the fractured/weathered basement, to the overburden or saprolite with a clay-rich layer on top. Whereas the overall aquifer potential mainly depends on the thickness of the weathered overburden, the aquifer potential for shallow hand-dug wells is determined by the hydraulic conductivity of the upper few meters of the saturated zone. This upper zone was investigated in the pumping tests. The spatial distribution of the specific capacity reveals a wide variation of hydraulic parameters, depending on the well’s position in the depth profile of the aquifer’s hydraulic conductivity. The thickness of the potential aquifer is highest in the central part of the study area (pegmatitic and granitic intrusions) which has the highest overall aquifer potential compared to the surrounding metasedimentary formations. However, a thick weathered overburden will increase the groundwater potential of an aquifer for deep boreholes, whereas for hand-dug wells, the productivity can only be high if the thickness of the weathered overburden is small enough, or the water table is deep enough, to allow to tap the coarse part at the base of the overburden and/or part of the weathered/fractured basement. This study reveals that the main cause of low productivity and failure of many hand-dug wells in Bugesera region is not to be linked to poor groundwater resource potential but rather stems from the inappropriate random siting of wells and from poor well construction expertise which does not take into account the hydrogeological conditions. The results of the investigation indicate that in the typical weathering profile of the Precambrian basement in Sub-saharan Africa, the coarse lower part of the weathered overburden and the fractured/weathered basement offer good prospects for water resource. Depending on the depth at which this layer is encountered, either shallow hand-dug wells or deep drilled wells are most appropriate.

Combining 3D Hydraulic Tomography with Tracer Tests for Improved Transport Characterization.

Hydraulic tomography (HT) is a method for resolving the spatial distribution of hydraulic parameters to some extent, but many details important for solute transport usually remain unresolved. We present a methodology to improve solute transport predictions by combining data from HT with the breakthrough curve (BTC) of a single forced-gradient tracer test. We estimated the three dimensional (3D) hydraulic-conductivity field in an alluvial aquifer by inverting tomographic pumping tests performed at the Hydrogeological Research Site Lauswiesen close to Tübingen, Germany, using a regularized pilot-point method. We compared the estimated parameter field to available profiles of hydraulic-conductivity variations from direct-push injection logging (DPIL), and validated the hydraulic-conductivity field with hydraulic-head measurements of tests not used in the inversion. After validation, spatially uniform parameters for dual-domain transport were estimated by fitting tracer data collected during a forced-gradient tracer test. The dual-domain assumption was used to parameterize effects of the unresolved heterogeneity of the aquifer and deemed necessary to fit the shape of the BTC using reasonable parameter values. The estimated hydraulic-conductivity field and transport parameters were subsequently used to successfully predict a second independent tracer test. Our work provides an efficient and practical approach to predict solute transport in heterogeneous aquifers without performing elaborate field tracer tests with a tomographic layout.

A sequence stratigraphic based geological model for constraining hydrogeological modeling in the urbanized area of the Quaternary Besòs delta (NW Mediterranean coast, Spain)

The Quaternary Besos delta is located on the Mediterranean coast in NE Spain. The Besos Delta Complex includes 3 aquifers constituted by 3 sandy and gravelly bodies, separated by lutitic units. These aquifers supply water for domestic and industrial use in this area. Management of groundwater has been problematic in the Besos delta since the 1960s, and continues to pose major problems for subsurface engineering works in this highly urbanized region. This study seeks to demonstrate the advantages of detailed geological characterization and modeling for designing and constructing a hydrogeological model. Available information of the subsurface was compiled, integrated and homogenized in a geospatial database. The interpretation of these data enabled us to delimit geological units by means of a sequence stratigraphic subdivision. A three-dimensional facies belt-based model of the Besos delta was built on the basis of this geological characterization. This model was used to constrain the distribution of hydraulic parameters and thus to obtain a consistent hydrogeological model of the delta, which was calibrated by data of water management and production over the last hundred years. The resulting hydrogeological model yielded new insights into water front displacements in the aquifer during the time-span considered, improving predictions in an attempt to optimize aquifer management.

Hydrogeological and hydrogeochemical investigation of a Precambrian basement aquifer in Bugesera Region (Burundi)

This study clearly shows that Bugesera region has genuine groundwater potential which could be circumscribed and tapped in order to provide enough drinking water to the inhabitants of the area. Thus, this study recommends further investigations and measures, including, geophysical investigations coupled to reconnaissance drillings, the installation of a network of piezometers to monitor the groundwater level variation, measurement of the discharge rate and water level fluctuation in the complex of marshlands and lakes, monitoring of groundwater quality and further pumping tests in order to rfine the distribution of hydraulic parameters in the study area.