It’s that time of year: When Lake Lanier drops another inch, another boat ramp closes. Thursday, Lake Lanier’s water level dropped just below 1,063.02 feet above sea level, more than 3 feet lower than it was this time last year. With the change, boat ramps at Burton Mill, Duckett Mill and Bethel Park all closed, according to Pat Robbins, a spokesman for the U.S. Army Corps of Engineers in Mobile, which manages the lake.