Three tracer tests were carried out by slug injection of fluorescein, amino-G-acid, and bromide at piezometers with 0.4 m long intake zones located 5 m distant from an 80 m deep pumping borehole. The piezometer intake zones were about 2 m (Tests 1 and 2) and 18 m below static water level, and the pumping borehole was sealed using a packer at about 11 m (Tests 1 and 2) and 19 m below static water level. Analytical expressions were used to interpret the data. Test 2 was unsuccessful. Four pathways were discernible from the Test 1 tracer breakthrough curves. These pathways were interpreted as being due to three dominantly fracture routes and one dominantly intergranular flow route. The earliest (sharp) peak arrived after a few hours, and the last (broad) intergranular flow peak arrived after around 40 hours. Fluorescein was delayed slightly (retardation factor = 1.4) relative to the other tracers. In the deeper Test 3, three pathways were discernible, with concentration peaks at about 9, 25, and 78 hours. Fluorescein was delayed relative to amino-G-acid (retardation factors = 1.25 and 1.5) in the second and third pathways. As with the first test, the last peak was very broad, suggesting a variety of intergranular routes through the rock, and possibly the effect of diffusion. The tests clearly demonstrate the importance and complexity of fracture flow over short distances in the Triassic sandstones, the complexity of the intergranular flow routes, and that different retardation factors can be associated with different pathways.
. Bringing groundwater models to LIFE: a new way to assess water resource management options. Hydrological Sciences Journal, 59 (3-4), 578-593.Abstract If management of water resources is to fully take into account the requirements of the environment, it will benefit from quantitative predictions of the ecological effects of river flow alterations. A significant relationship between flow reductions caused by groundwater abstraction and ecological conditions (as measured by relevant biotic indices) has been shown in streams in the midlands of England. In this article, we combine this relationship with hydrological indices derived from calibrated regional groundwater models to assess river reaches that are likely to be ecologically impacted by abstraction and might consequently be at risk of failing to meet EC Water Framework Directive standards. We demonstrate the application of this method within the framework of the Ecological Limits of Hydrologic Alteration (ELOHA) approach to making water resource decisions. We provide examples of how this approach can be used to assess the implications of different groundwater abstraction scenarios for river water bodies.Key words hydro-ecology; groundwater model; low flows; macro-invertebrates; abstraction Faire VIVRE les modèles hydrogéologiques-une nouvelle façon d'évaluer les options de gestion des ressources en eau Résumé Si la gestion des ressources en eau doit prendre pleinement en compte les besoins de l'environnement, elle bénéficiera des prévisions quantitatives des effets écologiques des altérations des écoulements en rivière. Une relation significative entre les réductions de débit causées par les prélèvements en eau souterraine et les conditions écologiques (telles que mesurées par des indices biotiques pertinents) a été démontrée pour des cours d'eau du centre de l'Angleterre. Dans cet article, nous combinons cette relation avec des indices hydrologiques issus de modèles hydrogéologiques régionaux, calés de manière à déterminer les tronçons de rivière susceptibles d'être impactés écologiquement par les prélèvements et qui, par conséquent, pourraient présenter le risque de ne pas répondre aux normes de la Directive cadre sur l'eau. Nous décrivons l'application de cette méthode dans le cadre de l'approche ELOHA (Ecological Limits Of Hydrologic Alteration-limites écologiques liées aux modifications hydrologiques) pour la prise de décision sur les ressources en eau. Nous fournissons des exemples sur la façon dont cette approche peut être utilisée pour évaluer les conséquences de différents scénarios de prélèvement d'eau souterraine sur les cours d'eau.
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