COLD REGIONS HYDROGEOPHYSICS: PHYSICAL CHARACTERISATION AND MONITORING

Abstract

The use of geophysical methods to characterize distribution of continuous and discontinuous permafrost has been widely applied (e.g. Arcone et al., 1998; Sullivan et al., 2000; Hauck et al., 2001; Hinkel et al., 2001; Moorman et al., 2003) including ground penetrating radar (GPR), electrical resistivity (ER) and electromagnetic (EM) sounding. Different methods have been employed to study water movement in frozen soils: time domain reflectrometry (TDR), electrical resistivity (ER), EM soundings and self potential (SP). In this chapter the main focus is on the use of geophysical methods to solve hydrological problems in areas with frozen conditions, but also includes examples of characterisation of structures in the permafrost which have an importance for hydrogeological processes in these regions. Frozen and thawed structures in the subsurface may cause water and contaminant pathways which are not intuitively based on traditional soil stratification procedures. Because these structures are temperature dependent there may also be a need to monitor spatio-temporal changes in these structures in order to assess how they may affect flow paths in the ground. Time-lapse measurements may hence be required. To study changes in the soil water system under frozen or partially frozen conditions can be a challenge; soil water sampling equipment may freeze and destructive methods such as conventional soil sampling is impossible under frozen conditions. The objective of conducting various geophysical methods in a hydrological perspective is to describe flow paths and to improve models for water and solute transport under partially frozen conditions. The next section of this chapter describes the physical properties of permafrost, seasonally frozen soils and glaciers, and is followed by descriptions of how these affect the hydrology in the respective systems. A description of applicable geophysical methods and properties obtained under frozen conditions are given in part 2. Some of the methods are described in more detail than others due to limited space. A new book on application of geophysical methods on glacial and periglacial terrain edited by Hauck and Kneisel