It takes a very long time for water to be exchanged in the Great Lakes. If all the inputs of water to the lakes were stopped, it would take about 400 years for the water to drain out (like a bathtub that was full and you turned off the faucet and waited for the tub to empty out the drain). This is because of the huge amount of water we are talking about - 18% of the world's entire surface freshwater - and the fact that the "drain" is the St Lawrence River, which can only drain so fast. The larger the lake, the longer it takes to replenish the water - For Lake Superior, it is 190 years! For Lake Michigan, it is about 100 years.

Dear Lotte,

To prevent toxic chemicals from being spread within the Great Lakes, we must prevent them from being emitted to the environment. We have to close the barn door BEFORE the horse gets out! This requires greater efforts to evaluate chemicals and products before they come to market for their toxicity and their environmental persistence, and requires a more precautionary approach - erring on the side of caution about a chemical rather than assuming it is "innocent" until proven "guilty", by which time the chemical can't be pulled back from the environment if it is found to be harmful.

Once chemicals get into the Great Lakes, it is hard to remove them because of the immense size of the lakes and the volume of water. So it is up to natural processes to take care of removing them - these include bacterial breakdown, or volatilization back to the air (gets them out of the water but only puts them in another part of the environment...) or burial in sediments after the chemicals sorb to particles or algae in the water. The chemicals you hear the most about, like PCBs or flame retardants or pesticides, are very persistent so they don't break down, and it takes decades to centuries to clean the water by waiting until they get buried in sediments. It is much better to prevent them from entering the environment in the first place!

Dear Rahul,

No, I think because we made progress in the 1970s and 1980s, people take the Great Lakes for granted. Back in the 1960s it was public outrage at the environmental problems they saw that led to the Clean Water Act, the Clean Air Act, the Great Lakes Water Quality Agreement and the formation of the US EPA. We need to make people aware that while progress has been made there is still much to do to protect them, to be good stewards of the Great Lakes.

In Minnesota, about 40% of our lakes and streams are considered to be below water quality standards by federal and state law, and almost all of these "impaired" lakes and streams suffer from excess nutrients (phosphorus and nitrogen), or eutrophication. The problem occurs more in the SE, SW, and NW parts of the state, mostly because of land use and population density. The excess nutrients come from agricultural runoff in rural areas, and from storm water runoff and development in suburban and urban areas. Also, Minnesota lakes are generally shallow and they are more susceptible to the impacts of excess nutrients.

Hi Heather,

I have several favorite spots on the Great Lakes, but if I had to choose, I would say that the north shore of Lake Superior is a big favorite, by Grand Marais and of course Isle Royale, and Sleeping Bear Dunes on the eastern shore of Lake Michigan is a beautiful spot. But then there is Georgian Bay in Lake Huron, Point Pelee park in Lake Erie, and the Thousand Islands in Lake Ontario....so many to choose from!

The Clean Water Act was first passed in 1972, and it has been extremely effective at protecting our water resources from point discharges, such as industrial effluents, through a permitting process. It also has been effective at reducing nutrient discharges from waste water treatment plants, which are also point discharges. Where the Clean Water Act has not been so effective is controlling what are called non-point discharges, which come from larger areas and not a specific discharger. These include storm water run-off, and run-off from croplands and confined animal feeding operations. The run-off from these includes nutrients and other pollutants, an dis not well controlled or regulated through the Clean Water Act.

1 - re-establish the integrity of science and its use in decision making in all federal agencies. There are excellent scientists in these agencies, and excellent external scientific advisors, that have been ignored in recent years, and they need to be given their voice and respect back.

2 - incorporate climate change considerations in all areas of policy making - from endangered species considerations to dredging considerations to water policies - it is or will be affecting our environment, our health, and our economy and we need to consider climate change holistically.

3 - use environmental policy to stimulate economic recovery, by upgrading and replacing aging infrastructure in the wastewater and drinking water sector, and encouraging green energy and manufacturing policies and job development.

I firmly believe that the change in administration will have a large impact on the US participation in global environmental efforts, particularly on global warming policy and green energy policy. Pres-elect Obama has indicated that this is a priority for his presidency, and it is reflected already in his nominations for his cabinet and other officers, and their statements made during their confirmation hearings (Chu, Energy and Jackson, EPA have already had their hearings). Not only does the new administration value science and wish to see it used to inform policy, they are very educated and informed about the issues. Be optimistic!