A three-dimensional hydro-geochemical model to assess lake acidification risk

© 2014 Elsevier Ltd. Biogeochemical and hydrological fluxes from riparian zones to lake environments can be significant, particularly for shallow systems experiencing large variations in water level, yet they are not considered in water quality models. To address this challenge we dynamically coupled a three-dimensional surface water model with a soil hydro-geochemical model of the riparian zone and used the coupled system to simulate the impacts of acid sulfate soils on the water quality of a morphologically complex coastal lake system in South Australia. A 3-yr simulation was undertaken to capture a period of exposure and re-flooding of pyrite-bearing sediments and acid fluxes to the lake. Model performance was assessed against data from several acidification events that occurred and the simulations reproduced the observed spatio-temporal variation in the expression of soil and water acidity. The model approach introduced here has potential for simulating systems where the terrestrial-aquatic linkage is important in shaping water quality.