Tests of the SGW-NMR technique within two aquifer characterization projects in the Iberian Peninsula

The management of GroundWater (GW) resources implies, ahead of any exploitation scenario, an inventory and characterization of such resource. This is a multidisciplinary task, in which a whole array of techniques are used but the Surface version of the GroundWater Nuclear Magnetic Resonance teclmique (SGW-NMR) appears to have a potential role. NMR techniques are used in state-of-the-art applications such as medical imaging, chemical structure analysis and hydrocarbon resources exploration and quantification. The SGW-NMR technique is an implementation of this technology for the purpose of non-invasive investigations of groundwater from the earth's surface. The SGW-NMR technique has been described, among others, by Goldman et al. (1994) and Lieblich et al. (1994). The introduetion of a commercial SGW-NMR system by IRIS Instruments in the Spring of 1996, marketed under the name of NUMIS PMR, was followed with interest at ITC and elsewhere. Such interest is based on the potentialof this non-invasive technique in the domain of groundwater exploration and quantification. In fact, of high interest to us is its capacity to identify the hydrostratigraphy of the flow system, to quantify the effective porosity and to provide information related to pore size distribution and therefore to hydraulic conductivity of in-situ subsurface materials from surface measurements only (i.e. without using boreholes). This information is available in a sounding mode (i.e. as a function of depth) and is measured over a large volume of materials (106 to 107 m') so that seale effect, as observed with point souree hydraulic determinations i.e. pumping tests, are minimized (Lubczynski et al, 1997).