Abstract
(English)
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Short summary:
The goal of ALIANCE is to improve the investigation, characterisation and monitoring of coastal aquifers for vulnerability assessment. For this, ALIANCE proposes to develop a set of geophysical approaches for the quantitative evaluation of brine intrusion. This includes state-of-the-art geological, geochemical, petrophysical, logging and hydrological methods, and the design of 5 new geophysical and hydrodynamical logging/testing sensors yielding new data for model validation. Two end-member sites in terms of hydrogeological behaviour will be set up for long-term experimentation, the testing of the new tools, and the validation of site-specific experimental and modelling protocols from µm- to 100 m-scale. Active in-situ testing from short and longer-term injections with variable salinity fluids will simulate overdrafting or saline water intrusion. The electro-hydraulic coupling principle will be used to characterise and monitor water/brine hydrodynamics in coastal environments.
Scientific objectives and approach:
In order to mitigate the risks of saline water intrusion in coastal aquifers, an integrated, multi-scalar hydrogeological characterisation of subsurface structures and dynamics is required. The objective of ALIANCE is to develop a strategy for the quantitative description of fluid flow and storage in the shallow subsurface. A site-specific, detailed but cost-effective protocol will be implemented, leading to a site modeling capability associated with long-term monitoring from pressure and electrical fields. This includes state-of-the-art geological, geochemical, petrophysical, geophysical logging and hydrological methods, and the design of 5 new downhole sensors yielding new data for model validation. Two end-member sites in terms of hydrogeological behavior will be set up for long-term experimentation, the testing of the new tools, and the validation of site-specific experimental and modelling protocols from µm- to 100 m-scale. Active in-situ testing from short- and longer-term injections with variable salinity fluids will simulate over-drafting or saline water intrusion. In addition to pressure and fluid electrical conductivity, the electro-hydraulic coupling principle will be used to characterise and monitor water/brine hydrodynamics.
Problems to be solved:
Salt intrusion in coastal aquifers, either from natural or anthropogenic source, is often related to over-drafting due to agricultural use, or a high density of population, or the effect of droughts in arid regions. While the physical processes associated with salt water intrusion are still being discussed, more field data are needed to assess the predictive models developed for long-term management and vulnerability assessment of groundwater resources in this context. This research focuses on the development of new geophysical logging, hydrological testing and long-term monitoring methods to describe and monitor saline intrusion processes.
Expected Impacts:
ALIANCE aims to improve the long-term management of brine intrusion in coastal aquifers from detailed field description and hydro-electrical monitoring. The research will provide (1) a new geophysical and hydrological protocol to characterize shallow aquifers in an integrated manner, (2) new logging and testing sensors to investigate shallow aquifers, (3) geophysical and hydrological data at 2 end-member sites to validate existing numerical codes, (4) a test for new in-situ monitoring techniques of salt water intrusion in coastal aquifers.
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