Abstracts

natural or anthropogenic hazards and water quality risk prediction. A minimum suite of
parameters including the 7 major ions, pH, redox and certain dissolved gases, in addition
to any health-related parameters of interest, provides much more information than the
sum of their individual contributions.
A full-matrix groundwater geochemical sampling program has been completed in southern
Ontario at an unmatched scale, density and degree of analytical completeness. 2300
samples collected at 1850 stations at a uniform sample density across the 96,000 km 2 area
allows the mapping of groundwater geochemical regimes in most of southern Ontario for
the first time. Dozens of phenomena and processes have been identified at all scales, many
of which were previously unknown. A few examples of the processes Identified include: (1)
wide regions of biogenic shale gas, (2) a 1400 km 2 breathing well zone expelling hypoxic
gases, (3) stagnant flow zones, (4) provincial-scale patterns in the distribution of tritium in
groundwater, (5) regions where iodine in potable water exceeds seawater by many times,
(6) decadal-scale trends in aquifer recovery and depletion, (7) the replacement of ancient
water in aquifers with modern water due to pumping, (8) provincial-scale regions of natural
fluoride hazard (9) areas of systemic bacterial occurrence in aquifers, and (10) widespread,
discreet zones of karstic groundwater flow. Most of these discoveries could not have
been anticipated when the program began 8 years ago, which demonstrates the efficacy of
primary data collection and geological mapping in the support of groundwater studies.
207 - A study of flow system dynamics utilizing a diverse set of
isotopic and geochemical methods; Oak Ridges Moraine, Ontario
Lori Labelle & Shaun Frape
Department of Earth and Environmental Science, University of Waterloo, Waterloo, Ontario,
Canada
Rick Gerber
Oak Ridges Moraine Hydrogeology Program, Toronto, Ontario, Canada
The Oak Ridges Moraine (ORM) is a 160-km long ridge a mixture of sand, silt and gravel
deposits north of Lake Ontario, and extends west to east from the Niagara Escarpment to
Peterborough and the Trent River. Understanding the complex flow system is complicated by
the regional geology, which includes aquifers in the bedrock valleys, till aquifers, and eroded
tunnel channels separated by aquitards. The Oak Ridges Moraine is recognized as a regionally
significant groundwater recharge area and is an important source of domestic water for
the Greater Toronto Region, along with providing base flow to hundreds of local streams.
This regional study examines a diverse moraine complex, consisting of sediments ranging
from earlier glaciations (~130k) to considerably younger materials from recent glacial
events (~20k) (Barnett et al. 1998). This results in a very complex flow system within
the Oak Ridges Moraine, consisting of multiple aquifer/aquitard units and end members
causing multiple potential mixing scenarios. To assess this complicated hydrostratigraphy
a diverse range of age dating and isotopic methods have been used in the study. Naturally
occurring stable isotopes can be used to trace groundwater flow paths and provide direct
evidence of the vulnerability of an aquifer; as well as provide insight into flow systems at
56 IAH-CNC 2015 WATERLOO CONFERENCE