DEVELOPMENTS IN HYDROGEOPHYSICAL RESEARCH

SUMMARY Measurement of groundwater physical properties of porosity and hydraulic conductivity in porous or fractured rock environments, and assessing water quality generally requires drilling a borehole. Boreholes provide accurate information at a point source, and a combination of boreholes can be used to infer regionalscale (i.e. 2 to1500 km) characteristics. However, is there a better way to fill in the gaps? Electrical and electromagnetic geophysical techniques are sensitive to electrical properties of the subsurface. Movement of electrical charges (usually in the form of charged chloride and sodium ions) can provide an analogue for amount of water contained in pores, and to a lesser extent, to the movement of water through the environment. In addition, the interaction of electrical charges with porous sediment grains and within fractures can be used to determine fluid flow without ever drilling a hole. APPROACH The primary challenge for geophysicists is to link observations of electrical properties uniquely with hydraulic properties. Such geophysical methods must be fast, repeatable, and cover large spatial areas to make them a practical alternative to traditional hydrogeological approaches. The Hydrogeophysics Group at the University of Adelaide are developing the following approaches, tools and techniques to do this in a number of ways: