By Larry Jensen (February 20, 2018, 5:03 PM EST) -- Since President Donald Trump took office just over one year ago, much has changed at the U.S. Environmental Protection Agency. In this Expert Analysis series, former EPA general counsels and agency members discuss some of the most significant developments and what they mean for the future of environmental law in the U.S. Larry Jensen Since 1972, the Clean Water Act has regulated the discharge of pollutants and the placement of fill into "navigable waters," which are defined by the act as "the waters of the United States." What has never been clear is the extent to which certain non-navigable waters, like ephemeral tributaries to navigable waters, or certain aquatic features, like wetlands, may be considered "waters of the United States." Hoping to resolve the issue once and for all, the Obama administration in June 2015 published the "Clean Water Rule: Definition of Waters of the United States," which is known as the WOTUS rule.[1] However, the courts almost immediately stayed the effectiveness of the WOTUS rule, and, in one of his first official acts, President Donald Trump ordered the WOTUS rule rescinded and replaced. Regardless of the outcome of the Trump administration's replacement effort, the 46-year controversy over the meaning of the phrase "waters of the United States" is likely to continue for many years to come....