The importance of hydraulic gradient, lineament trend, proximity to lineaments and surface drainage pattern for yield of groundwater wells on Askøy, West Norway.

Abstract

Groundwater and lineament studies were made on Askøy, an island northwest of Bergen. In addition to field measurements of lineaments and associated fractures, a total of 2695 photolineaments and 409 topolineament were analysed in realtion to yield of drilled groundwater wells. The results of statistical analyses in geographical information systems (GIS), as well as numerical modelling of groundwater flow, highlight two parametres that affect yield of groundwater wells. These factors are proximity of groundwater wells. These factors are proximity of groundwater wells to lineaments and lineament trends.The results indicate that, on Askøy, NE-SW-trending lineaments, and those that strike subparallel to the slope of the topography, area most likely to provide high-yield groundwater wells. Although the statistical significanse in these analyses is not high, the results indicate that the metods may be generally very useful, particularly for areas with a large number of drilled wells. The surface drainage pattern on Askøy is partly controlled by lineaments and other tectonic elements. In particular, the streams commonly follow topographic lineaments, many which are fault zones, individual fractures, contacs or other mechanical dsicontinuities in the rock mass. We include that by combining data on lineament trends and surface drainage, it may be possible to characterise hydraulic differences between lineaments of different trends.