The search for an ancient river valley

A contractor working for the Grand River Conservation Authority is going to drill test holes between mid-September and November is parts of the Grand River watershed as part of a search for an ancient river valley.
This is the third phase of a three-year study to find an ancient buried river valley. One earlier study showed that the valley may be 75 metres below sea level, which would make it about 140 metres below the surface of Lake Ontario.
The river valley could be millions of years old. Advancing glaciers reshaped the landscape more than 10,000 years ago and the ancient river valley was filled in.
When the glaciers melted, the water they released helped shape the modern landscape including the Grand River, said Gregg Zwiers, senior hydrogeologist with the GRCA, who is leading the study.
The first part of the study involved gathering existing data about the bedrock valley from water well records, gas well records, aerial photos and other studies. Researchers have also conducted geophysical gravity surveys to develop a cross-section of the valley. This led to the selection of the sites for the drilling.
“This research will give us more information to determine how stressed our water resources are. The investigation will help us with source water protection and our water budget,” Zwiers said.
The drilling is especially important to help discover the dimensions of the valley and what kind of material has filled it in. If it proves to be narrow, deep and filled with loose material, it could be a significant source of groundwater which could be tapped by municipalities.
Early next year all the research that has been compiled will be brought together to form as complete an understanding as possible of the river valley and an analysis of the potential source for municipal water supplies.
The GRCA has been working with geologists from the Ontario Geological Survey, a branch of the Ministry of Northern Development and Mines, which is contributing about $660,000.
Other agencies involved in the study include municipalities, provincial ministries, conservation authorities and universities.
SOURCE: GRCA