Irrigation channel seepage investigations

Abstract

Most irrigation channels in Australia are earth lined and leak water to the surrounding terrain. The cost of lost water can be high in economic and environmental costs. The solution is to completely line the canals or replace them with pipes, both expensive options. An alternative is to focus on areas of highest seepage. In this study we trialed a dipole-dipole resistivity array towed behind a dinghy in the canal. The approach followed trials using electromagnetic techniques in previous years that showed conductivity changes below and around the canals in part reflected seepage. We inverted the resistivity results to sections and statistically analysed the data from various depths in the ground by correlating the resistivity against pondage seepage results. Our conclusion was that the resistivity worked best where there was a diffuse seepage from the canal. The greatest effect was around the watertable. Where seepage rates were low there was no correlation with resistivity. The correlations improved with increasing seepage particularly where the inverted sections indicated the seepage rates were uniform along the channel.