Barbara Reichert

Separation of groundwater-flow components in a karstified aquifer using environmental tracers

Abstract Groundwater discharges from the intensively karstified Taurus Mountains to the Mediterranean Sea, either along the contact zone between the mountains and the Travertine Plateau (the Kirkgozler Springs, 15 m3/s), or through the travertine (e.g. the Dudenbasi Spring, 18 m3/s) and underneath it (unnamed submarine springs, unknown discharges). In an attempt to identify the hydraulic connections between the various outlet points, groundwater was analyzed for stable and radioactive isotopes, CFCs and He. The upgradient springs, belonging to the Kirkgozler–Dudenbasi system, were proven to be a mixture of recent and older water on the basis of their low 14C values (12–22.4 pmc), their exceptionally high He content (429–991 μcc/kg) and 3He:4He (R:Ra) ratios (1.471–2.602) and their measurable 3H and CFC contents (1.9–5.9 TU and 0.84 to 3.27 pmoles/kg, respectively). The older component probably contains an even lower amount of modern C. However, the undersaturation of the mixture with respect to calcite, its high CO2 content (up to 83 mg/L) and its enriched 13C values (−2.2 to −4.1‰) suggest intensive water/rock interactions, which would contribute 14C-devoid bicarbonates to the solution. Downgradient springs discharging along the Mediterranean coast contain groundwater contributions from higher altitudes, as evidenced by their depleted δ18O and δD composition with respect to the local precipitation; however, a larger portion of the recent water component could be contributed from direct precipitation on the travertine. This larger component is reflected in the increased 3H (3.4 to 8.4 TU) and 14C (32.7–63.6 pmc) contents, atmospheric He (43–82 pmoles/kg), R:Ra values (1.006–1.198) and CFC contamination of the water.

Fate of the herbicide glufosinate-ammonium in the sandy, low-organic-carbon aquifer at CFB Borden, Ontario, Canada

Abstract The herbicide glufosinate-ammonium was persistent in aerobic sandy aquifer material in laboratory batch and field in situ microcosms when added at concentrations of 50–400 μg L−1. In contrast, the compound is biotransformed relatively quickly in surface soil. Glufosinate transformation and metabolite (3-methylphosphinyl-propionic acid) production in carbonamended laboratory microcosms demonstrated that the aquifer system was carbon-limited with respect to glufosinate transformation. Microbiological test showed that flufosinateammonium and sodium-glufosinate was be used as a nitrogen source, in the presence of sufficient carbon. Glufosinate was not used by the native microorganisms as a source of phosphorus, nor metabolized as a sole carbon and energy source. Ammonium appeared to be preferred over glufosinate as a nitrogen source. When representative microbial strains isolated from the Borden aquifer were tested, most were glufosinate-ammonium tolerant. Complete inhibition of some isolates was demonstrated only at very high concentrations of 2–4 g L−1. The research suggests that in an aquifer with a relatively low clay content and little labile organic carbon, such as the sandy aquifer at the field site, glufosinate will be persistent and transport will be essentially unretarded. The availability of alternative nitrogen sources was also indicated as a parameter that can affect persistence.

Use of isotopes to study floodplain wetland and river flow interaction in the White Volta River basin, Ghana

Floodplain wetlands influence the timing and magnitude of stream responses to rainfall. In managing and sustaining the level of water resource usage in any river catchment as well as when modelling hydrological processes, it is essential that the role of floodplain wetlands in stream flows is recognised and understood. Existing studies on hydrology within the Volta River basin have not adequately represented the variability of wetland hydrological processes and their contribution to the sustenance of river flow. In order to quantify the extent of floodwater storage within riparian wetlands and their contribution to subsequent river discharges, a series of complementary studies were conducted by utilising stable isotopes, physical monitoring of groundwater levels and numerical modelling. The water samples were collected near Pwalugu on the White Volta River and at three wetland sites adjacent to the river using the grab sampling technique. These were analysed for 18O and 2H. The analysis provided an estimate of the contribution of pre-event water to overall stream flow. In addition, the variation in the isotopic composition in the river and wetland water samples, respectively, revealed the pattern of flow and exchange of water between the wetlands and the main river system.

Development of a hydrogeological conceptual wetland model in the data-scarce north-eastern region of Kilombero Valley, Tanzania

Understanding groundwater/surface-water interactions in wetlands is crucial because wetlands provide not only a high potential for agricultural production, but also sensitive and valuable ecosystems. This is especially true for the Kilombero floodplain wetland in Tanzania, which represents a data-scarce region in terms of hydrological and hydrogeological data. A comprehensive approach combining hydrogeological with tracer-based assessments was conducted, in order to develop a conceptual hydrogeological wetland model of the area around the city of Ifakara in the north-eastern region of Kilombero catchment. Within the study site, a heterogeneous porous aquifer, with a range of hydraulic conductivities, is underlain by a fractured-rock aquifer. Groundwater chemistry is mainly influenced by silicate weathering and depends on groundwater residence times related to the hydraulic conductivities of the porous aquifer. Groundwater flows from the hillside to the river during most of the year. While floodwater close to the river is mainly derived from overbank flow of the river, floodwater at a greater distance from the river mainly originates from precipitation and groundwater discharge. Evaporation effects in floodwater increase with increasing distance from the river. In general, the contribution of flood and stream water to groundwater recharge is negligible. In terms of an intensification of agricultural activities in the wetland, several conclusions can be drawn from the conceptual model. Results of this study are valuable as a base for further research related to groundwater/surface-water interactions and the conceptual model can be used in the future to set up numerical flow and transport models.RésuméLa compréhension des interactions eaux souterraines-eaux de surface dans les zones humides est. cruciale, car ces zones créent non seulement un haut potentiel pour la production agricole, mais encore des écosystèmes sensibles de grande valeur. Ceci est. spécialement vrai pour la zone humide de la plaine d’inondation de Kilombero en Tanzanie, qui est. une région pauvre en données hydrologiques et hydrogéologiques. Une approche globale associant hydrogéologie et des évaluations basées sur des traçages a été mise en œuvre pour développer un modèle hydrogéologique conceptuel de la zone humide autour de la ville de Ifakara dans le Nord-Est du bassin versant du Kilombero. Dans le domaine d’étude, un aquifère poreux hétérogène, avec une gamme de conductivités hydrauliques repose sur un aquifère rocheux fracturé. La chimie des eaux souterraines est. principalement influencée par l’altération des silicates et dépend du temps de séjour qui est. fonction des conductivités hydrauliques de l’aquifère poreux. Les eaux souterraines s’écoulent du versant collinaire vers la rivière durant la plus grande partie de l’année. Tandis qu’à proximité de la rivière l’eau de crue provient principalement du débordement du lit majeur, à une plus grande distance elle résulte des précipitations et de la décharge de la nappe souterraine. Les effets de l’évaporation sur l’eau de crue s’accroissent avec la distance à la rivière. En général, les contributions de l’eau de crue et du cours d’eau à la recharge de nappe sont négligeables. En termes d’intensification des activités agricoles dans la zone humide, plusieurs conclusions peuvent être tirées du modèle conceptuel. Les résultats de cette étude sont précieux comme base pour de nouvelles recherches relatives aux interactions eaux souterraines et eaux de surface et le modèle conceptuel peut être utilisé à l’avenir pour établir des modèles numériques d’écoulement et de transport.ResumenLa comprensión de las interacciones agua subterránea/agua superficial en los humedales es crucial porque ellos proporcionan no sólo un alto potencial para la producción agrícola, sino también por la sensibilidad y lo valioso de los ecosistemas. Esto es especialmente cierto para el humedal de la llanura inundable de Kilombero en Tanzania, que representa una región con escasos datos en términos de datos hidrológicos e hidrogeológicos. Se llevó a cabo un enfoque integral que combina evaluaciones hidrogeológicas con evaluaciones basadas en trazadores, con el fin de desarrollar un modelo hidrogeológico conceptual de humedales del área alrededor de la ciudad de Ifakara en la región nororiental de la cuenca de Kilombero. Dentro del sitio de estudio, un acuífero poroso heterogéneo, con una gama de conductividades hidráulicas, es subyacente a un acuífero de roca fracturada. La química del agua subterránea está influenciada principalmente por la meteorización de los silicatos y depende de los tiempos de residencia del agua subterránea relacionados con las conductividades hidráulicas del acuífero poroso. El agua subterránea fluye desde la ladera al río durante la mayor parte del año. Mientras que el agua de las inundaciones cerca del río se deriva principalmente del flujo de banco del río, el agua de la inundación a una mayor distancia del río proviene principalmente de la precipitación y de la descarga del agua subterránea. Los efectos de la evaporación en el agua de inundación se incrementan con el aumento de la distancia creciente al río. En general, la contribución de las inundaciones y de las corrientes de agua a la recarga de las aguas subterráneas es insignificante. En términos de una intensificación de las actividades agrícolas en el humedal, se pueden extraer varias conclusiones del modelo conceptual. Los resultados de este estudio son valiosos como base para investigaciones adicionales relacionadas con las interacciones agua subterránea/agua superficial y el modelo conceptual puede utilizarse en el futuro para establecer modelos numéricos de flujo y transporte.摘要了解湿地地下水/地表水相互作用至关重要,因为湿地不仅为农业生产提供了巨大的潜力,而且还提供了敏感和宝贵的生态系统。坦桑尼亚Kilombero河漫滩湿地尤其如此,这个湿地缺乏水文和水文地质数据。在此进行了基于示踪剂评价结果的水文地质和综合性研究,为了建立Kilombero流域东北部Ifakara市周围地区水文地质概念湿地模型。在研究区内,具有范围宽阔的水力传导率的异质孔隙含水层下伏着断裂岩含水层。地下水化学成分主要受到硅酸盐风化的影响,取决于与孔隙含水层水力传导率相关的地下水滞留时间。一年中大部分时间地下水从山坡流入河流。靠近河流的洪水主要来源于河流的漫滩流,而离河流较远的洪水主要源于降水和地下水排泄。洪水中的蒸发影响随着离河流的距离增加而增加。总的来说,洪水和河水对地下水补给的贡献微不足道。在强化湿地农业活动方面,可以从概念模型中得出几条结论。本研究结果作为进一步研究地下水/地表水相互作用的基础非常珍贵,概念模型将来可用于建立数值水流和运移模型。ResumoCompreender as interações entre águas subterrâneas/águas superficiais em áreas úmidas é crucial, pois áreas úmidas fornecem não só um alto potencial para a produção agrícola, mas também ecossistemas sensíveis e valiosos. Isto é especialmente verdadeiro para a área úmida da planície de inundação de Kilombero na Tanzânia, que representa uma região com escassez de dados em termos de dados hidrológicos e hidrogeológicos. Uma abordagem abrangente combinando avaliações hidrogeológicas com base em traçadores foi realizada, a fim de desenvolver um modelo hidrogeológico conceitual de áreas úmidas da área ao redor da cidade Ifakara na região nordeste da bacia hidrográfica de Kilombero. Dentro da área de estudo, um aquífero poroso, heterogêneo, com uma gama de condutividades hidráulicas, está subjacente a um aquífero de rocha fraturada. A química das águas subterrâneas é influenciada principalmente por intempéries de silicato e depende dos tempos de residência das águas subterrâneas, relacionadas as condutividades hidráulicas do aquífero poroso. As águas subterrâneas fluem da encosta para o rio durante a maior parte do ano. Enquanto a água da inundação perto do rio é derivada principalmente do fluxo excedente do rio, a uma maior distância do rio, a água de inundação é originada principalmente por precipitação e descarga subterrânea. Os efeitos da evapotranspiração na água de inundação aumentam com o aumento da distância do rio. No geral, a contribuição da água de inundação e água do curso d’agua é insignificante. Em termos de intensificação de atividades agrícolas na área úmida, várias conclusões podem ser extraídas do modelo conceitual. Os resultados desse estudo são valiosos como base para novas pesquisas relacionadas a interação entre águas subterrâneas/águas superficiais e o modelo conceitual pode ser usado no futuro para criar modelos numéricos de fluxo e transporte.

Redox Zones in the Plume of a Previously Operating Gas Plant

Within the framework of a current research program, the fate of BTEX has been investigated in a Quaternary porous aquifer below a former gas plant in south-west Germany. The investigation site is located in the Neckar valley and occupies an area of about 600 m by 400 m (Figure 16.1). Industrial activities in this area started in the year 1875 with the production of gas and other coal-derived oils and tars by hard coal carbonisation. After 1956 gas production was carried out on the basis of heavy oil; starting in 1964, light mineral oil products were used. There was a change from city gas production to the distribution of natural gas between 1969 and 1974.

Field Soil Gas Screening Methods for the Delineation of Subsurface Contamination

Delineation and remediation of subsurface contamination have become a major focus of environmental science during the past five years. Conventional technologies available for subsurface investigations (e.g. monitoring wells) always will be required to confirm and monitor subsurface contamination; however, quicker and less expensive techniques are useful for preliminary site evaluations. Soil-gas surveying is a technique that is applicable to a wide range of volatile organic compounds (VOCs) and other contaminants under a variety of geologic and hydrologic settings. This paper presents the results of the use of soil-gas surveys for evaluation of the magnitude and lateral extent of a BTEX contamination at a former gas plant in Southwest Germany.

Statusanalyse von Meerwasserintrusionen und Grundwasserhaushaltsmodellierung des oberen Küstenaquifers in Agadir, Marokko

ZusammenfassungDer durch Tourismus und exportorientierte Landwirtschaft erhöhte Wasserbedarf in der semi-ariden Küstenstadt Agadir führt seit Jahren zu einer Absenkung des Grundwasserspiegels. Diese führt zu Meerwasserintrusionen, die eine Verminderung der Grundwasserqualität zur Folge haben. Die Absenkung des Grundwasserspiegels wird mithilfe einer Grundwasserhaushaltsmodellierung bestätigt. Die positiven Bilanzposten werden von der Grundwasserneubildung durch Flussbettinfiltration, die negativen Bilanzposten von der Grundwasserentnahme zur Bewässerung dominiert. Über eine Sensitivitätsanalyse können die Parameter herausgestellt werden, die für weitere Modellierungen genauer untersucht werden sollten. Eine räumlich und zeitlich variable Intrusionsfront wurde unter anderem anhand von spezifischen Ionenverhältnissen, Chlorid-Gehalten und Salinitäten in Grundwasserproben ermittelt. Der Verlauf der Front folgt von Nordwesten nach Südosten grob der Küstenlinie. Im Vergleich zu 2005 liegt die Intrusionsfront 2010 jedoch weiter im Landesinneren. 2011 und 2012 kann ein tendenzieller Rückgang der Beeinflussung durch Meerwasserintrusion beobachtet werden.AbstractIn Agadir, a coastal town situated in the semi-arid south-western part of Morocco, irrigated agriculture and tourism are the primary economic activities. Both sectors require high volumes of fresh water. Over the last few decades, this constantly increasing demand has resulted in a significant drawdown of the water table, accompanied by seawater intrusion leading to a decrease in water quality. A groundwater storage model has verified the extensive drawdown. Positive terms in the flow balance equation are represented by groundwater recharge from bankfiltration, and by irrigation return flow. The negative terms are dominated by groundwater removal for irrigation. A sensitivity analysis reveals parameters which require further investigation. A spatially and temporally variable seawater intrusion front was identified using specific ion ratios, chloride concentrations and groundwater salinity. The intrusion front extends roughly from the northwest to the southeast, following the coast. Compared to 2005, the intrusion front had advanced further inland by 2010. In 2011 and 2012, the effects of seawater intrusion have tended to diminish.

Status analysis of sea water intrusion and groundwater balance modeling of the upper coastal aquifers in Agadir, Morocco.

ZusammenfassungDer durch Tourismus und exportorientierte Landwirtschaft erhöhte Wasserbedarf in der semi-ariden Küstenstadt Agadir führt seit Jahren zu einer Absenkung des Grundwasserspiegels. Diese führt zu Meerwasserintrusionen, die eine Verminderung der Grundwasserqualität zur Folge haben. Die Absenkung des Grundwasserspiegels wird mithilfe einer Grundwasserhaushaltsmodellierung bestätigt. Die positiven Bilanzposten werden von der Grundwasserneubildung durch Flussbettinfiltration, die negativen Bilanzposten von der Grundwasserentnahme zur Bewässerung dominiert. Über eine Sensitivitätsanalyse können die Parameter herausgestellt werden, die für weitere Modellierungen genauer untersucht werden sollten. Eine räumlich und zeitlich variable Intrusionsfront wurde unter anderem anhand von spezifischen Ionenverhältnissen, Chlorid-Gehalten und Salinitäten in Grundwasserproben ermittelt. Der Verlauf der Front folgt von Nordwesten nach Südosten grob der Küstenlinie. Im Vergleich zu 2005 liegt die Intrusionsfront 2010 jedoch weiter im Landesinneren. 2011 und 2012 kann ein tendenzieller Rückgang der Beeinflussung durch Meerwasserintrusion beobachtet werden.AbstractIn Agadir, a coastal town situated in the semi-arid south-western part of Morocco, irrigated agriculture and tourism are the primary economic activities. Both sectors require high volumes of fresh water. Over the last few decades, this constantly increasing demand has resulted in a significant drawdown of the water table, accompanied by seawater intrusion leading to a decrease in water quality. A groundwater storage model has verified the extensive drawdown. Positive terms in the flow balance equation are represented by groundwater recharge from bankfiltration, and by irrigation return flow. The negative terms are dominated by groundwater removal for irrigation. A sensitivity analysis reveals parameters which require further investigation. A spatially and temporally variable seawater intrusion front was identified using specific ion ratios, chloride concentrations and groundwater salinity. The intrusion front extends roughly from the northwest to the southeast, following the coast. Compared to 2005, the intrusion front had advanced further inland by 2010. In 2011 and 2012, the effects of seawater intrusion have tended to diminish.

Chemical Tracers and Stable Isotopes Mixing Models for Groundwater Quality and Recharge Study in the Moroccan High Atlas Mountains

A common global practice in the High Atlas Mountains is upstream water storage in dammed reservoirs that captures mountainous snowmelt, and downstream agriculture irrigation. However, the intensive use of water for irrigation, coupled with the effects of climate change, makes the region subject to high water stress. This implies the establishment of an integrated management system adapted to such water resources. Effective management of groundwater requires good control upstream of the different sources of supply and their contribution. Thus, we conducted a study on the contribution of the components snow and rain recharge of surface water and groundwater in the High Atlas, using chemical and isotope investigations. The isotopic results from the 2 sites upstream catchments (Souss and Tensift) compared to those obtained in the Draa basin highlight the importance of spatial and temporal variabilities of isotopic signal, which may impact quantifying the contributions of snowmelt to stream flow and groundwater. Using the stable isotope mixing model, the contribution of runoff derived from snowmelt (SN) ranges between 42 and 75% in the headwaters of the studied catchments, while the component of rainfall is 25–58%. The low mineralized waters from the High Atlas induce a dilution of the water salinity in the neighboring plains (Souss, Tensift and Draa). The results could be used to help refining hydrological conceptual models at various scales.

Statusanalyse von Meerwasserintrusionen und Grundwasserhaushaltsmodellierung des oberen Küstenaquifers in Agadir, Marokko@@@Statusanalysis and groundwater storage model of the upper coastal aquifer in Agadir, Morocco

ZusammenfassungDer durch Tourismus und exportorientierte Landwirtschaft erhöhte Wasserbedarf in der semi-ariden Küstenstadt Agadir führt seit Jahren zu einer Absenkung des Grundwasserspiegels. Diese führt zu Meerwasserintrusionen, die eine Verminderung der Grundwasserqualität zur Folge haben. Die Absenkung des Grundwasserspiegels wird mithilfe einer Grundwasserhaushaltsmodellierung bestätigt. Die positiven Bilanzposten werden von der Grundwasserneubildung durch Flussbettinfiltration, die negativen Bilanzposten von der Grundwasserentnahme zur Bewässerung dominiert. Über eine Sensitivitätsanalyse können die Parameter herausgestellt werden, die für weitere Modellierungen genauer untersucht werden sollten. Eine räumlich und zeitlich variable Intrusionsfront wurde unter anderem anhand von spezifischen Ionenverhältnissen, Chlorid-Gehalten und Salinitäten in Grundwasserproben ermittelt. Der Verlauf der Front folgt von Nordwesten nach Südosten grob der Küstenlinie. Im Vergleich zu 2005 liegt die Intrusionsfront 2010 jedoch weiter im Landesinneren. 2011 und 2012 kann ein tendenzieller Rückgang der Beeinflussung durch Meerwasserintrusion beobachtet werden.AbstractIn Agadir, a coastal town situated in the semi-arid south-western part of Morocco, irrigated agriculture and tourism are the primary economic activities. Both sectors require high volumes of fresh water. Over the last few decades, this constantly increasing demand has resulted in a significant drawdown of the water table, accompanied by seawater intrusion leading to a decrease in water quality. A groundwater storage model has verified the extensive drawdown. Positive terms in the flow balance equation are represented by groundwater recharge from bankfiltration, and by irrigation return flow. The negative terms are dominated by groundwater removal for irrigation. A sensitivity analysis reveals parameters which require further investigation. A spatially and temporally variable seawater intrusion front was identified using specific ion ratios, chloride concentrations and groundwater salinity. The intrusion front extends roughly from the northwest to the southeast, following the coast. Compared to 2005, the intrusion front had advanced further inland by 2010. In 2011 and 2012, the effects of seawater intrusion have tended to diminish.