Ballast water - water carried in tanks on ships to help provide stability and aid steering - is likely the single greatest source for introduction of non-native and invasive aquatic species. Ballast water is collected in one body of water and discharged into another body of water, usually large distances apart. At least one new invasive species is found in the Great Lakes every year, with Lake Superior being particularly at risk. Scientists from the U.S.
Effective groundwater management requires accurate knowledge about the water budget, which is the amount of water stored within the system in aquifers and the amount of water flowing through the overall hydrologic system including water flowing at the surface, water flowing from above ground down into aquifers, and water flowing between aquifers below the surface.