A Simplified Model to Simulate pH and Alkalinity in the Mixing Zone Downstream of an Acidic Discharge

Research output: Contribution to journalArticle


A modelling methodology was developed that simulates the resulting pH and alkalinity in the mixing zone when acidic water is discharged into a river. The input to the model are the: pH, alkalinity, flow, and temperature of both the river water and the acidic discharge. Two different scenarios were simulated: (1) a change of pH in the acidic discharge, assuming constant flow; and (2) a change in the flow of the acidic discharge, assuming constant pH. The model incorporates the effect of carbonic acid and the modelled values agree well with the laboratory results. The model setup was subsequently used to predict the anticipated effect of contamination of the Zambezi River in Mozambique. The results indicate that the river will be impacted if the average pH of the water in the tributaries coming from the mining area is below 3. The model could be used by water managers to predict the potential impact of acidic discharges in poorly monitored rivers.


External organisations
  • Eduardo Mondlane University
Research areas and keywords

Subject classification (UKÄ) – MANDATORY

  • Water Engineering


  • Acid mine drainage, Modelling, River flow, Water quality
Original languageEnglish
Pages (from-to)552-564
JournalMine Water and the Environment
Issue number3
Early online date2018 Jan 23
Publication statusPublished - 2018 Sep
Publication categoryResearch