DEAR WATERSHED EXPERT: What’s the leading cause of water pollution in Minnesota?
DEAR WONDERING WATER-LOVER: You might be surprised to learn that mercury from the air is, by far, the leading cause of pollution in our lakes and rivers. When power plants burn coal to create electricity, they release mercury into the atmosphere. The mercury eventually falls out into lakes and ends up in the fish. There are 1650 lakes in Minnesota with too much mercury in the water or the fish. So, it may not be safe to eat fish from these lakes more than once a week or once a month.
Last month, former WCCO weatherman Paul Douglas spoke about global climate change to a crowd of about 250 people at St. Andrew’s Lutheran Church in Mahtomedi. During his presentation, he talked about the changing weather patterns he’s witnessed during his career as a meteorologist and the impacts we are starting to see here in Minnesota and around the world due to rising sea levels, more frequent extreme weather events, and warmer air and water temperatures.
Within the worlds of stormwater and water resources management, climate change has been a big topic in recent years. Cities are struggling to adapt their existing stormwater pipes and ponds to account for more frequent large rainstorms – the kinds that wash out culverts and flood roads. We used to call them 100-year storms, but lately they happen more like once every five years. In fact, southern Minnesota was hit by three “1,000-year storms” in less than a decade in 2004, 2007 and 2010. Climatologists are finding that we’re getting the same amount of rain per year as we used to, but it’s coming down in a few big storms rather than gradually over the course of many drizzly days. As a result, stormwater infrastructure is getting stressed and more water is flowing downstream to rivers instead of soaking into the ground to replenish shallow and deep aquifers. Scientists around the world agree that increasing levels of carbon dioxide in the air from the burning of fossil fuels like coal, oil, and natural gas are to blame for global climate change.
The fuels we burn to create electricity and power our cars contribute to climate change but there are other connections between water and energy in Minnesota as well. Power plants intake massive amounts of water for cooling and to create steam; likewise, water plants use large amounts of electricity to draw in and treat water. Most of the water used for power generation is considered non-consumptive because it is eventually piped back into a river or lake. However, approximately two gallons of water are lost to evaporation for every kilowatt hour (kWh) of electricity consumed (National Renewable Energy Laboratory 2003). The average Minnesota household uses 100,000 gallons of water per year and 10,800 kWh of electricity, which is equivalent to an additional 21,600 gallons of water.
Even worse, energy production creates pollution that often makes its way into our air and water. Remember those 1650 lakes in Minnesota with unsafe levels of mercury? It turns out that 99% of that mercury comes from atmospheric deposition. As a result, even some of our most pristine Boundary Waters lakes suffer from mercury impairments because air travels everywhere. The good news is that Minnesota has reduced its mercury emissions by 70% since 2000 and there have been reductions across the U.S. (45% less between 1990 and 1999) and worldwide (20% less between 1990 and 2000) as well.
Coal burning power plants continue to be the largest source of mercury emission in Minnesota (46% of emissions), while taconite processing contributes about 20% of the emissions. To combat this problem, many coal-burning power plants across the U.S. are converting to natural gas, which releases less mercury and less carbon dioxide when burned. However, astute readers will note that there are plenty of connections between natural gas and water as well, particularly when natural gas is mined through a process known as fracking. Not only does fracking require large volumes of water and create contamination on site, but it also has the potential to impact local water resources in Minnesota and Wisconsin where companies mine silica sand to use in fracking operations.
So, what can you do to help protect Minnesota’s lakes and rivers? Turn out the lights when you leave the room and run the air conditioning less this summer. After all, you won’t need either when you’re sitting on a dock with your toes in the water and pole in your hand. By the way, as long as you’re heading to the lake, you might as well walk there and get some exercise.