Comparative study of methods of preparing hydraulic-head surfaces and the introduction of automated hydrogeological-GIS techniques

Construction of hydraulic-head surface (HHS) maps is the most commonly used technique for groundwater evaluation. A review of methods used for constructing HHS maps showed that, of the manual methods, the hydrogeological interpretative technique produces a better surface than the equally spaced approach. Geostatistical methods gave similar surfaces to the manual methods; they share the problem of groundwater contours intersecting surface contours and the inability to identify groundwater discharge areas. The results showed that the automated hydrogeological-GIS (geographical information system) techniques, which take into account the hydrogeomorphic and topographic controls, produced the most realistic surfaces. Groundwater contours follow the hydrogeomorphic trends, do not intersect surface contours and can properly identify areas of groundwater discharge. The major advantage of the hydrogeological-GIS technique is the ability to prepare HHS maps with a small number of data points. It is also possible to use regressions from other catchments to prepare HHS maps for catchments with similar hydrogeomorphic characteristics and elevation ranges but which have no data.