Groundwater sources throughout the Great Lakes basin need to be better monitored and mapped. The work is needed to determine how quickly the sources recharge and the potential impact that contaminants in groundwater could have on water quality in the basin.
That’s according to a report recently released by the Canadian and US governments under the Great Lakes Water Quality Agreement.
Contaminants can work their way down the water table and impact groundwater and the quality of surface waters. The recent groundwater report indicates that this can impact fish populations, and ultimately the fish further up the food chain that we eat. Drinking water from groundwater and surface water sources can be impacted too, and excess nutrients in groundwater -- from sources like septic systems, manure, fertilizer, leaking wastewater pipes and concentrated animal feeding operations -- may contribute to algal blooms in lakes.
Because it can take anywhere from a few days to decades for groundwater to reach the surface, depending on the local geology and soil makeup, water quality managers may have to deal with these contaminants for years to come, long after their initial sources may have been cleaned up.
The groundwater report makes several recommendations on the science front. The authors suggest tracking groundwater as it moves into streams and the Great Lakes, and compiling locations of known and suspected sources of groundwater contaminants.
The report also recommends improving groundwater quality monitoring and surveillance to help fill information gaps. For instance, scientists want to know more about the interaction between groundwater and surface water on local-scales when it reaches the “transition zone” between the two.
It wasn’t until the 2012 amendment to the Great Lakes Water Quality Agreement that Canada and the United States committed to coordinating groundwater science and management actions. Under the amendment, an “Annex 8 subcommittee” of experts from both countries was formed to identify groundwater impacts on the chemical, physical and biological integrity of the lakes, and analyze other issues. While the topic of groundwater has been a part of the agreement since 1978, progress reports weren’t required until 1987.
The vast majority of groundwater connects to surface streams, creeks and other waterways in the Great Lakes basin. According to a 2010 report from the IJC’s Great Lakes Science Advisory Board, 8.2 million people in the Great Lakes basin rely on groundwater to drink, including 82 percent of the rural population; it also provides 43 percent of agricultural water (and this proportion is increasing) and 14 percent of industrial water in the basin.