Hydrogeological Situation Research Articles

To what extent do improved irrigation technologies extend aquifer life?

World financial support for Yemen has concentrated on improved irrigation technology as the primary means to reduce the rate of overexploitation of Yemen’s aquifers. An analysis of the impact of such investments on cumulative water abstraction, water savings and the life of an aquifer is presented. It shows that these investments have limited potential to extend aquifer life. The returns are highest in areas with significant remaining resources, and are not attractive in the most severely stressed areas. The analysis also shows that improved irrigation technologies increase the profitability of pumping for the farmer, exacerbating problems of over-abstraction. Finally, it shows that water savings depend on the hydrogeological situation. The policy implications of these findings are discussed in relation to Yemen, an exceptionally water-short country where most of the aquifers in groundwater-irrigated areas are severely over-drafted.

Analysis of groundwater-level fluctuation in a coastal confined aquifer induced by sea-level variation

Groundwater responses to tide fluctuations in different hydrogeological situations have been investigated for many years. Various solutions have been derived using the assumption that tides are composed of sinusoidal components, neglecting non-periodic variables. This approach has resulted in the introduction of some inaccuracy in predictions of groundwater responses to sea-level variation. To resolve this problem, this study used the Fourier sine transform method to derive an analytical solution based on the measured sea-level boundary. Compared with an analytical solution based on a sinusoidal assumption and a numerical solution generated by MODFLOW, this solution provided better performance in groundwater-level prediction in a coastal confined aquifer in Zhuhai City, China. The hydrogeological parameters estimated by the three aforementioned methods fitted well with those estimated by field surveys and pumping tests. The introduced analytical solution not only reflects the physical mechanisms of tide-induced groundwater-level fluctuation, but also reveals the non-periodic fluctuation of groundwater level caused by sea-level variation. This solution may also be used to evaluate groundwater responses to random mechanical stresses.

GEO-ENVIRONMENTAL STUDIES ON WADI QENA, EASTERN DESERT, EGYPT. BY USING REMOTE SENSING DATA AND GIS.

Geographic information system (GIS) and remote sensing data confirmed by field checks have been used to investigate the geoenvironmental characteristics at Wadi Qena area. The study area is mainly covered by sedimentary rock units (Paleozoic to Cenozoic) and a small basement exposure in its northeastern corner. It exhibits different types of structural elements represented by anticlines (Wadi Qena and Wadi Hamama) and synclines (El Serai and Abu Had) and four main fault trends (NE-SW, NW-SE, ENE-WSW and N-S). The basin analysis studies show that the most dangerous risk area is located at the southern part of the wadi drained by Wadi El-Jurdi and Wadi Shahdeen. Quantify the hydrogeologic situation, land-use map and a plane for flood risk protection of the investigated area are delivered to support the decision-making processes. However, many locations are suggested for new cities along Wadi Qena which accommodates the residential and the industrial activities required for developments. The most dangerous zones are located at the downstream of Wadi El-Jurdi and Wadi Shahdeen. So, the entire development plan should avoid this buffer zone.

Influence of precipitation and deep saline groundwater on the hydrological systems of Mediterranean coastal plains: a general overview

The increasing water demand is a concern affecting many regions in the Mediterranean Basin. To overcome this situation rim countries resorted during the last decades to a massive mobilization of their water resources, often resulting in excessive water exploitation. In such a context, understanding the effects of present recharge and aquifer salinization is crucial for correct water management. Understanding the present hydrogeological situation of coastal plains requires the knowledge of both their past morphologic conditions and their recent geological evolution. Within this framework, this paper presents a review of water related problems in the Mediterranean Basin. It suggests a conceptual model for groundwater resources in Mediterranean coastal plains, deriving from the present and past recharge processes. Special attention is paid to providing a better understanding of climate change impacts on water quantity and quality, and conservation of ecological diversity. Citation Re, V. & Zuppi, G. M. (2011) Influence of precipitation and deep saline groundwater on the hydrological systems of Mediterranean coastal plains: a general overview. Hydrol. Sci. J. 56(6), 966–980.

Relation between hydrogeological setting and swelling potential of clay-sulfate rocks in tunneling

In this study, an approach to estimate the swelling potential of clay-sulfate rocks in tunneling is presented. Swelling of clay-sulfate rocks leads to damage in tunnels that is difficult and costly to repair. Swelling is caused by the transformation of the sulfate mineral anhydrite into gypsum, which involves an increase in rock volume in a system open to water flow. Knowledge of the hydrogeological situation and the groundwater flow systems at the tunnel is essential to better understand the swelling processes. The present study was conducted for the Chienberg tunnel in Switzerland. It investigates the hydrogeological situation of four zones in this tunnel crossing the Triassic Gipskeuper formation. In two of them, heavy swelling occurred after tunnel excavation, while in the other two no swelling occurred. In addition, the groundwater flow systems before and after tunnel excavation are investigated based on numerical flow modeling. The findings suggest that in certain situations after tunnel excavation, depending on geological and changing hydraulic conditions, the excavation damaged zone around the tunnel provides a “hydraulic short circuit” between the weathered Gipskeuper and the anhydrite-bearing strata of the unweathered Gipskeuper. As a result, water from the weathered Gipskeuper gets in contact with anhydrite, triggering its transformation into gypsum and, thus, rock swelling. The results of the study may also contribute to improved swelling experiments in the laboratory and a more reliable planning of restoration measures in tunnels that are damaged by rock swelling.

Implementation of the Italian hydrogeological cartographical guidelines (CARG Project).

This work is aimed to contribute to the revision of the Italian hydrogeological cartographical guidelines, after the last field-testing promoted by the Geological Survey of Italy (now ISPRA – Land Resources and Soil Protection Dept.) in representative hydrogeological situations of the Italian territory, taking into account that a good quality hydrogeological map has to be based on the collection of field survey measurements, in order to allow a characterization of quantitative and protection management aspects of groundwater resources.The current Italian guidelines propose to distinguish the hydrogeological complexes based on relative permeability degree using a colour scale following a chronological criterion. But in this way, the complex ages and not the hydrogeological features are evidenced and, thus, the use of a colour scale strictly related to the permeability degree of the hydrogeological complexes is here proposed.The official guidelines suggest the representation of surface and spring waters based on annual mean discharge. This rule, as a suitable long time of discharge measurements to calculate the annual mean discharge is not always available in the Italian territory sites, may be modified allowing the representation of both surface and spring waters also by mean discharge values, obtained after field measurement surveys.It is also significant to evidence the opportunity of including in the guidelines some specific symbols for: i) boundary of suspended aquifer recharge areas; ii) open (i.e., allowing hydraulic exchange) and closed (i.e., not allowing hydraulic exchange) groundwater divide; iii) groundwater drainage process; iv) lake monitoring station; v) linear spring; vi) area affected by intense tectonic lamination.

Development of genetic algorithm-based optimization module in WHAT system for hydrograph analysis and model application

Many hydrologic and water quality computer models have been developed and applied to assess hydrologic and water quality impacts of land use changes. These models are typically calibrated and validated prior to their application. The Long-Term Hydrologic Impact Assessment (L-THIA) model was applied to the Little Eagle Creek (LEC) watershed and compared with the filtered direct runoff using BFLOW and the Eckhardt digital filter (with a default BFI max value of 0.80 and filter parameter value of 0.98), both available in the Web GIS-based Hydrograph Analysis Tool, called WHAT. The R 2 value and the Nash–Sutcliffe coefficient values were 0.68 and 0.64 with BFLOW, and 0.66 and 0.63 with the Eckhardt digital filter. Although these results indicate that the L-THIA model estimates direct runoff reasonably well, the filtered direct runoff values using BFLOW and Eckhardt digital filter with the default BFI max and filter parameter values do not reflect hydrological and hydrogeological situations in the LEC watershed. Thus, a BFI max GA-Analyzer module (BFI max Genetic Algorithm-Analyzer module) was developed and integrated into the WHAT system for determination of the optimum BFI max parameter and filter parameter of the Eckhardt digital filter. With the automated recession curve analysis method and BFI max GA-Analyzer module of the WHAT system, the optimum BFI max value of 0.491 and filter parameter value of 0.987 were determined for the LEC watershed. The comparison of L-THIA estimates with filtered direct runoff using an optimized BFI max and filter parameter resulted in an R 2 value of 0.66 and the Nash–Sutcliffe coefficient value of 0.63. However, L-THIA estimates calibrated with the optimized BFI max and filter parameter increased by 33% and estimated NPS pollutant loadings increased by more than 20%. This indicates L-THIA model direct runoff estimates can be incorrect by 33% and NPS pollutant loading estimation by more than 20%, if the accuracy of the baseflow separation method is not validated for the study watershed prior to model comparison. This study shows the importance of baseflow separation in hydrologic and water quality modeling using the L-THIA model.

Análise da Vulnerabilidade do Lençol Freático à Contaminação por Hidrocarbonetos em Cenário de Vazamentos na Área do Oleoduto Orsul II, Refap-Copesul, RS

This study used concepts derived from the DRASTIC methodology (Aller et al.1987) to evaluate the potential of natural vulnerability(PNV) for groundwater contamination on the route of the ORSUL II pipeline which connects Alberto Pasqualini Refinery (REFAP) to the Petrochemical Complex of the South (COPESUL), in the metropolitan region of Porto Alegre, Rio Grande do Sul. The geographic information system (GIS) was used to generate information plans for the variables used to evaluate and cross- match these plans and obtain the potential vulnerability index (PVI). The use of a flux model allowed the generation of the aquifer recharge map from the hydraulic loads observed and the creation of scenarios of leaks in the pipe, showing the advective displacement of contamination. The evaluation model for the potential of natural vulnerability was tested considering the hypotheses of small leaks and large short duration spills. In the latter, the potential vulnerability of the aquifer was evaluated inverting the scores of the depth factor of the N.A., obtaining the map of contamination opportunities by mass injection. The approach used in this study identified different hydrogeological situations along the pipeline. They must be known in order to plan preventive measures, contingency plans and monitoring

Relations between vegetation and soil in initial succession phases inpost-sand excavations.

Rahmonov O., Szymczyk A.: Relations between vegetation and soil in initial succession phases in post-sand excavations. Ekologia (Bratislava), vol. 29, No. 4, p. 412–429, 2010. open-mined sand exploitation always leads to the total liquidation of vegetation and soil cover. The given study presents the relations between vegetation appearing in the excavation and soil development in the initial phases of succession. investigations were carried out in the kuznica Warezynska sandpit, located in the Silesian Upland in southern Poland. results obtained indicate that at uncovered sands, due to exploitation in unreclaimed places, spontaneous regeneration of vegetation-soil cover occurs. in the succession series observed in the excavation, 3 stages were distinguished (primary, secondary and terminal), which were divided into 6 phases. The oldest observed succession stage was made by communities from the Dicrano-Pinion connection. The duration of succession of the oldest surfaces is estimated at 25 years. Considering morphology, the forming soil differs at every succession stage. in respect to observed soil formation processes, advancing soils, even the oldest surfaces, have initial character; they are poor in nutrients and characterized by acidic, slightly acidic to alkaline pH-reaction. Physico-chemical properties of soil, forming in the area of the sandpit, are conditioned most of all by the ground water level, its chemical composition and the duration of succession. investigations proved that the course of succession at habitats fed mainly by waters, originated from the seepage of waters of deep circulation, and this differs from this those in places fed by the precipitation of waters. These differences appear most of all in the first phase of optimum stage. The sandpit is also characterized by a large differentiation of vegetation, resulting from the mosaic character of habitats. Habitat differentiation of the sandpit bottom is connected with its diversified relief and hydrogeological situation.

Quality of underground water and hydro-geological situation caused by oil exploitation in the area of Kikinda

Numerous oil fields were discovered in the area of North Banat and its regional centre, the city of Kikinda. These oil fields were explored and exploited in the second half of the XX century. Oil rigs in the area of the city zone can endanger the environment, as well as the quality of life of the citizens. In order to discover the presence of polycyclic aromatic hydrocarbon we have applied GC/MSD technique, whereas we have applied GC/MSD Purge and trap. technique to discover the presence of aromatic hydrocarbon. Chemical analyses of water samples from the area of Kikinda did nit prove that underground water was polluted with oil. .

The Combined Approach When Assessing and Mapping Groundwater Vulnerability to Contamination

In early 1980’s, the Italian scientific community, together with a number of institutional decision-makers, realized how urgent it was to protect natural and environmental resources. They agreed that an adequate level of scientifically organized knowledge allows the accurate planning and development of environment systems through the management and direction of the effective development process, but without stopping it. Since the special VAZAR1 project was first set up in 1984, as part of the GNDCI-CNR2 scientific context it has been the cardinal center point of Research National Program “Aquifer Vulnerability Assessment”. The problem of groundwater contamination was examined in this program for the very first time in Italy in an organic and extensive manner as a key for forecasting and prevention purposes. The Italian approaches to assessing and mapping groundwater vulnerability to contamination are essentially based on two main methodologies: 1) the GNDCI Basic Method [1,2] a HCS type approach that can be used for any type of Italian hydrogeologic situation, even where there is a limited number of data. A unified legend and symbols are also defined for each hydrogeologic level. 2) The SINTACS method [2,3], a PCSM developed for use prevalently in areas with a good data base coverage. The methodological approaches described in this paper now make up the Italian standard which has been dealt with in the recent very important Italian Law (152/993) and which are now ratified in the national guidelines [4] produced by ANPA, the Italian National Agency for Environment Protection. The methods, besides Italy [5] have been applied in several other Countries [6–10] and others.

The fresh water-seawater contact in coastal aquifers supporting intensive pumped seawater extractions: A case study

The construction of desalination plants along the Mediterranean coast that are supplied with seawater via pumped boreholes in coastal aquifers has given rise to novel hydrogeological situations. At the experimental site on the Andarax delta (SE Spain), a monitoring system has been set up, consisting of piezometer clusters. Piezometric level and electrical conductivity are monitored continuously at various depths in the aquifer. The data obtained allow the response of the aquifer to the intensive saltwater extraction to be assessed. Under a natural regime, the situation is highly stable and only the influence of the tides is detected. Under a regime of seawater extraction, the response becomes very dynamic, with pronounced falls in water level in the deepest piezometers and a marked descent in the position of the interface (25 m). This leads to a gradual decline in electrical conductivity in the slotted piezometers situated at the interface as a result of ingress of fresh water via slotted portions of the production boreholes.

Assessment of Holocene surface hydrological connections for the Ounianga lake catchment zone (Chad)

A hydrological perspective to the recent sedimentary analysis conducted at Lake Yoa (Ounianga region, NE Chad) is proposed. The complex hydrological and hydrogeological situation alters the climatic stress. The potential paleo-water network and lake levels have been computed based on SRTM elevation information and ArcGis software. Results show that Lake Yoa is situated in a favorable location, and in addition to continuous input from the Nubian Sandstone Aquifer System (NSAS), it could benefit from river input from distant recharge areas, including the Tibesti Mountains and a large catchment area in the Erdis. Water budgets for 6000 cal yr BP reconstructed conditions show that the maximum lake level (40 m above its present level) was probably maintained relatively easily by surface and subsurface water.

The cenozoic aquifer system of the Lower Tagus Basin: a description of the hydrogeological situation in the Almada region (Portugal)

A conceptual hydrogeological model of the Mio-Pleistocene deposits in the Almada region, located in the Cenozoic aquifer system of the Lower Tagus Basin (Portugal), has been developed. Though numerous studies have been conducted on its geological features, there have not been enough hydrogeological investigations to define the origin, flow path and the groundwater quality and to understand the coexistence of overlapped interacting aquifers. Therefore, a study is presented here on the occurrences and features of groundwater resources in the Almada region based on an inventory in the field (wells, springs and boreholes), physical and chemical analyses, geologic setting, and tectonic and geomorphologic observations. This aquifer system has long been a source of concern because of the high level of extraction over the last few decades, as well as the progressive degradation of the water quality. Available groundwater resources have been affected by intensive agricultural and industrial activity, as a consequence of incorrect or non-existent hydrogeological knowledge.

Modelling groundwater contamination above the Asse 2 medium-level nuclear waste repository, Germany

The medium-level radioactive waste deposited in the Asse 2 salt mine, Germany, has a total activity of 1.2 × 1015 Bq (1 January 2002). The waste lies in a former mining chamber on the −511 m mining level close to the contact between the Mesozoic country rock and the Zechstein salt dome. The Mesozoic country rock is strongly faulted but the geometry of the fault pattern is incompletely known. Two tectonic cases are considered: a pessimistic case, which assumes that the radioactive source is linked to the surface by a single fault, and an optimistic case, which assumes that the radioactive source is not connected to any fault at all. The potential groundwater contamination by radioactive fluids expelled from the cavity is simulated with the TOUGH2 code for periods of up to 6,000 years, when the potential contamination reaches its greatest vertical extent. Two types of driving forces are considered: convergence of the rock salt surrounding the cavity and generation of H2 gas by the corrosion of iron, steel and other metallic components of the waste at low O2 fugacities. Rock-salt creep has the greatest potential impact, as it leads to a radioactive plume whose 1 Bq/L activity contour rises up to 240 m below the surface in the pessimistic tectonic case. The value of the model for the assessment of the environmental risk is limited. The knowledge of the hydrogeological situation is incomplete and the pessimistic tectonic case may not be pessimistic enough for a realistic worst-case scenario.

A monitoring programme for 1,3‐dichloropropene and metabolites in groundwater in five EU countries

1,3 Dichloropropene (1,3-D) is a preplanting soil fumigant for the control of cyst and free-living nematodes and is currently undergoing a resubmission under Annex 1 listing of Directive 91/414/EEC. The characteristics of 1,3-D are such that the risk of it or its soil metabolites leaching through the soil profile cannot be excluded. As such, groundwater monitoring programmes were established in five EU countries representing a wide range of agricultural, climatic and hydrogeological situations, covering a range of groundwater vulnerability scenarios. All monitoring was conducted in areas where there has been historical use of 1,3-D. Over 5000 groundwater samples were analysed for the presence of 1,3-D and its metabolites over a 2 year period. Almost all analyses (for parent and metabolites) yielded concentrations of <0.1 microg L(-1). There were just two detections of >0.1 microg L(-1) (0.12 microg L(-1) and 0.4 microg L(-1)) for the 3-chloroacrylic acid metabolite in shallow groundwater samples of the alluvial gravels of the River Tiétar in the Caceres region of Spain. Groundwater monitoring programmes have been conducted in the EU in five countries. These have demonstrated that there is negligible contamination of groundwater with 1,3-D or its metabolites across a range of agroclimatic regions where 1,3-D is known to have been used for a number of years. Local scientific knowledge of geological features, hydrology, agricultural practice and specific local issues was essential to the conduct of the study.

FATORES CONDICIONANTES DA QUALIDADE E DA VARIAÇÃO DO NÍVEL DAS ÁGUAS SUBTERRÂNEAS NO MUNICÍPIO DE MERUOCA, CEARÁ

This work describes the Meruoca&rsquo;s water supply and discusses the factors that have influenced thequantity and quality of groundwater. Four hydrogeological situations in the area were considered: alteration mantle andfractured crystalline rocks, whose structure is good to storage water; no fractured crystalline rocks, represented bygranites and volcanic rocks, that aren&rsquo;t good to storage water. The Meruoca&rsquo;s groundwater supply is achieved mainly bydug wells (87%), followed tube wells (9%) and natural sources (4%). Dug wells water levels were monitored during 3years and was verified that the water table changes from 1.0 m up to 6,0 m. Was observed that the water level in the dugwells has immediate response during the rain, attesting the condition of an unconfined aquifer. Nine samples werecollected to complete chemical analysis and eighteen (18) samples to partial analyses, including the nitrogenous seriescompounds (NH4, NO2 e NO3). The chemical results indicated Na-HCO3 and Na-Cl water type. The quality of water isgood to human supply, in most of the cases.

Correlation between nitrate concentration in groundwater and parameters affecting aquifer intrinsic vulnerability

This paper is the result of a study which was carried out in order to verify if the traditional methods to evaluate the intrinsic vulnerability or vulnerability related parameters, are able to clarify the problem of nitrate pollution in groundwater. In particular, the aim was to evaluate limitations and problems connected to aquifer vulnerability methods applied to nitrate contamination prevision in groundwater. The investigation was carried out by comparing NO3− concentrations, measured in March and November 2004 in the shallow aquifer, and the vulnerability classes, obtained by using GOD and TOT methods. Moreover, it deals with a comparison between NO3− concentrations and single parameters (depth to water table, land use and nitrogen input). The study area is the plain sector of Piemonte (Northern Italy), where an unconfined aquifer nitrate contamination exists. In this area the anthropogenic presence is remarkable and the input of N-fertilizers and zootechnical effluents to the soil cause a growing amount of nitrates in groundwater. This approach, used in a large area (about 10,000 km2) and in several monitoring wells (about 500), allowed to compare the efficiency of different vulnerability methods and to verify the importance of every parameter on the nitrate concentrations in the aquifer. Furthermore it allowed to obtain interesting correlations in different hydrogeological situations. Correlations between depth to water table, land use and nitrogen input to the soil with nitrate concentrations in groundwater show unclear situations: in fact these comparisons describe the phenomenon trend and highlight the maximum nitrate concentrations for each circumstance but often show wide ranges of possible nitrate concentrations. The same situation could be observed by comparing vulnerability indexes and nitrate concentrations in groundwater. These results suggest that neither single parameters nor vulnerability methods (GOD and TOT) are able to describe individually the complex phenomena affecting nitrate concentrations in soil, subsoil and groundwater. In particular, the traditional methods for vulnerability analysis do not analyze physical processes in aquifers, such as denitrification and nitrate dilution. According to a recent study in the shallow unconfined aquifer of the Piemonte plain, dilution can be considered as the main cause for nitrate attenuation in groundwater.

The Italian way to prevent groundwater contamination risk

In the early 1980's the Italian scientific community, together with a number of institutional decision-makers, realized how urgent it was to protect natural and environmental resources. They agreed that an adequate level of scientifically organized knowledge allows the accurate planning and development of environmental systems through management and direction of the actual development process, without hindering it. Since the special project was first set up in 1984, as part of the GNDCI-CNR (National Group for the Defence against Hydrogeologic Disasters, of the Italian National Council of Research) scientific context, it has been the cardinal point of Research Line 4 “Assessment of Aquifer Vulnerability”. The problem of groundwater contamination was examined in this project for the very first time in Italy in an organic and extensive manner as a key for forecasting and prevention purposes. The Italian approaches to assessing and mapping groundwater vulnerability to contamination are essentially based on two main methodologies:- The GNDCI Basic Method a HCS (Hazard Contamination Source) type approach that can be used for any type of Italian hydrogeologic situation, even where there is a limited amount of data. A unified legend and symbols are also defined for each hydrogeologic level.- The SINTACS [Soggiacenza (depth to groundwater); Infiltrazione (effective infiltration); Non saturo (unsaturated zone attenuation capacity); Tipologia della copertura (soil/overburden attenuation capacity); Acquifero (saturated zone characteristics); Conducibilità (hydraulic conductivity); Superficie topografica (Slope)] method, a PCSM (Point Count System Model) developed for use prevalently in areas with good data base coverage. The methodological approaches described in this paper now make up the Italian standard which has been set in the recent very important Italian Law (152/99) and which has now been ratified in the national guidelines produced by ANPA, the Italian National Agency for Environment Protection. In this paper the structure of the Research Line, the progress obtained by the 21 Research units (over 100 researchers) in 20 years of activity, the results gained etc. are briefly highlighted.

Ground water origin and movement in the upper Yarmouk Basin, Northern Jordan

The Upper Yarmouk basin in northern Jordan has become an increasingly important groundwater resource in recent years. Despite this, studies of groundwater recharge and movement in the area are limited, and mostly parts of larger scale regional data syntheses. Detailed analysis of the hydrogeology, hydrochemistry and isotopic data indicate a more complex system than previously presented. Whereas earlier studies suggested that groundwater is derived from a single aquifer, this study suggests abstraction from multiple aquifers. Moreover, faults and lineaments in the area may be causing segmentation and limited flow within individual aquifers. The isotopic and hydrochemical data suggest that local recharge plays a significant role in the hydrogeologic situation in the study area. This appears to be mostly happening in the hilly zone in the central part of the study area.