Effects of rockfill dams and rock dumps on downstream water chemistry

Abstract

A number of potential negative effects on aquatic environments are associated with rockfills. However, in southwestern Norway, lakes and rivers downstream from large rockfills were among the very few sites where trout survived the acidification period. In this study, twelve rockfill dams, three rockfill dumps, several downstream locations and references were surveyed. The seepage water from the dams were found to have considerably elevated concentration of ions compared to the reservoir water. Despite a loss of alkalinity from oxidation of sulphide minerals, a net positive contribution to the downstream lakes was established. Simulations demonstrate a positive effect on the water chemistry downstream of the rockfills. The study suggest that this buffering effect has contributed to the survival of trout populations.