The Ambient Groundwater Geochemistry Program seeks to characterize the natural geochemistry of groundwater across Ontario. This release contains the data from the first 4 years of sampling, which covers all of southwestern Ontario and encompasses over 40 000 km². The data include detailed inorganic chemistry for more than 900 water samples. Parameters tested include dissolved gases, major ions, trace elements and field measurement of temperature, pH, redox potential and electrical conductivity. Isotopes of water were also tested and will be released at a later date. The data release includes

1. A single flat-file containing analytical data plus station data including well depth, type, deepest formation penetrated, etc.
2. A folder with precision and accuracy plots for all parameters
3. A folder with single-parameter maps for bedrock wells plotted over bedrock geology
4. A folder with single-parameter maps for overburden wells plotted over Quaternary geology
5. A support document with an explanation of the data and quality control methods and HTML links to all maps and plots.

Survey and sampling conducted from April 1, 2007 to June 30, 2014.