HYDROCHEMICAL CHARACTERISATION OF A COASTAL AQUIFER AT THE GERMAN NORTH-SEA COAST

In an ongoing project a Coastal Aquifer Testfield (CAT-Field) was installed for hydrological investigations at the German North Sea coast. Because of the partly coarse grained sediments the region seems to be suitable and may be interesting for future groundwater exploitation. To determine their possible influences is the aim of an interdisciplinary project. For the interpretation of the geochemical processes occurring in the salt- freshwater transition zone and during salinization, field data are compared with results from laboratory experiments and numerical calculations. Different types of groundwater are characterised by their geochemical pattern. Possible mechanisms for the formation of present NaHCO3 waters are Calcite precipitation and exchanger reactions during refreshening of the aquifer. These are briefly discussed with respect to results of column experiments, a twodimensional flow chamber experiment and their geochemical modelling with the computer programs PHREEQC (Parkhurst and Appelo, 1999) and Processing SHEMAT (Kühn and Chiang, 2000)

Joining participatory approach and spatially-based modelling tools for groundwater resource management.

Although a lot of science has been produced on Water Resource Management (WRM) in the Information and Communication Technology (ICT) sector, WRM is still poorly addressed via scientific means. Some reasons for this may be: the underrated importance given to this topic at political and decision-making level; the low-capacity of the research environment to transfer results; and missing numerical modelling capacities at agencies and governing authorities. ICT may provide tools for water planning and management, as discussed within the ICT4WATER cluster initiative. Among these, GIS-integrated numerical modeling is a robust method to represent hydrological systems and to provide answers to problems of protection of groundwater resources. Because these tools require a high level of knowledge pertaining to various disciplines, they are often disregarded as complex “tricky games” providing unrealistic results. This is a barrier to the uptake of technologies for water management. To overcome this issue, the application of ICT tools has been combined with an innovative participatory approach, and large capacity building activities, in the framework of the H2020 FREEWAT project (FREE and open source software tools for WATer resource management; www.freewat.eu). The major result of the project consists in an open source and public domain, QGIS-integrated modeling platform for promoting WRM. FREEWAT capabilities have been demonstrated at 14 case studies in EU and non-EU Countries, where the effectiveness of few measures foreseen in River Basin Management Plans for achieving good status of water bodies was tested. At each case study, a Focus Group (FG) participated by local stakeholders (e.g., river basin authorities, research institutions, environmental protection agencies, environmental associations) was formed and seven meetings were organized. During these meetings, the objective of each case study, the methodology to be adopted, including definition of the conceptual model and of data needed, were discussed. The FG also took decisions on scenarios to be simulated for testing the feasibility of the foreseen measures. FGs aimed at demonstrating that WRM may be performed with open source and public domain software and participants’ perception on using ICT tools for WRM was discussed. Some of the implemented models are now being used for operational purposes: Vrbansky plato (Slovenia), where FREEWAT is used to monitor remediation of heating oil spillage and the water supply company intends to maintain and use developed groundwater flow model for managed groundwater recharge with induced riverbank filtration; the Bremerhaven case study (Germany), where the local water authority intends to use the developed groundwater flow model for predictions; the Scarlino-Follonica case study (Italy), where the model will be used by the regional authority to manage private groundwater remediation projects in a large industrial contaminated site; the Gozo case study (Malta), where the model is being developed to support the assessment of good groundwater quantitative status as part of the implementation of the Water Framework Directive

Geochemische Prozesse in der Salz- Süßwasser Übergangszone.

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Three-dimensional model for multi-component reactive transport with variable density groundwater flow

PHWAT is a new model that couples a geochemical reaction model (PHREEQC-2) with a density-dependent groundwater flow and solute transport model (SEAWAT) using the split-operator approach. PHWAT was developed to simulate multi-component reactive transport in variable density groundwater flow. Fluid density in PHWAT depends not on only the concentration of a single species as in SEAWAT, but also the concentrations of other dissolved chemicals that can be subject to reactive processes. Simulation results of PHWAT and PHREEQC-2 were compared in their predictions of effluent concentration from a column experiment. Both models produced identical results, showing that PHWAT has correctly coupled the sub-packages. PHWAT was then applied to the simulation of a tank experiment in which seawater intrusion was accompanied by cation exchange. The density dependence of the intrusion and the snow-plough effect in the breakthrough curves were reflected in the model simulations, which were in good agreement with the measured breakthrough data. Comparison simulations that, in turn, excluded density effects and reactions allowed us to quantify the marked effect of ignoring these processes. Next, we explored numerical issues involved in the practical application of PHWAT using the example of a dense plume flowing into a tank containing fresh water. It was shown that PHWAT could model physically unstable flow and that numerical instabilities were suppressed. Physical instability developed in the model in accordance with the increase of the modified Rayleigh number for density-dependent flow, in agreement with previous research. (c) 2004 Elsevier Ltd. All rights reserved

A contribution to groundwater flow models in hydrothermal systems from North of Portugal

Geothermal resources are considered a sustainable and environmentally friendly alternative to produce energy. The north of Portugal seems to be a suitable area for the exploitation of geothermal resources due to its geothermal gradient and the occurrence of several thermal areas. A study based on 18O and 2H water isotope and geochemical data of shallow and deep geothermal aquifers was performed in selected seven hydrothermal systems located in the Cávado and Ave River watersheds, NW Portugal. The main goal of the study is the proposal of conceptual groundwater flow models, including information on recharge areas, groundwater flow paths, water-rock interaction, and mixing processes between water from different sources. The studied hydrothermal systems are ascribed to groundwater circulation in fractured granitic host rocks. Calcium is dominant cation in the thermal water of Caldelas, while sodium is dominant in the other studied thermal waters. Hydrogen carbonate is the dominant anion in the thermal water of Caldelas, Moimenta, Taipas and Vizela, while Cavadinho is represented by Cl-type water. The hydrothermal systems of Gestal and Eirogo are characterized by a mixed water type between chloride and hydrogen carbonate. The intensity of water-rock interaction suggests rather short residence times in the reservoir for the geothermal waters of Caldelas and Taipas compared to the other thermal waters. The 18O and 2H water isotope data indicate a dominant meteoric origin of the thermal waters. Considering the isotope altitude effect, the preferential thermal water recharge areas are located at altitudes between 315 and 585 m asl, which is coincident with the fault networks and could be a flow water circulation paths. Several geothermometers were applied, considering the geothermal gradient of the region, to estimate the reservoir depth and temperature. Estimated reservoir temperatures range from 40 °C for the Caldelas thermal area to 130 °C for the Vizela thermal area, indicating that correspond to low-temperature geothermal systems. The estimated temperatures suggest depths of the geothermal reservoirs between 0.8 and 3.3 km. Indications for mixing processes between upwelling geothermal waters and shallow aquifers were found at Vizela and Taipas area

transport with variable density groundwater

Three-dimensional model for multi-component reactiv