The observed acidification of lakes and forest soils in Sweden has raised concem over the future of groundwater resources. Many of the processes which effect groundwater quality occur above the water table in the insaturated soil. Models of the hydrology and chemistry in this zone were developed and the results of that work are presented in this report. The overall objective of this project was to obtain a better understanding of the chemical and hydrological processes involved in the acidification of soil and groundwater in order to estimate future changes due to changes in acid deposition in relation to other acidifying processes.

This work concluded of this report is that the groundwater in Sweden is vulnerable to acid deposition and that drastic reductions in emissions are necessary to protect this water. The model development provides a set of tools which are generally applicable to the hydrochemistry of acidification. They demand limited calibration and the requirements for input data and parameter values can usually be met. This makes it possible to use the models for assessment of groundwater acidification. The spatial and climatic variabilities of parameters and driving variables, however, are large. The uncertainties introduced by this variability must be considered when the results are used for decision making.