Which one ?
Graphs -> Lake Powell, then select “All Time Lake Levels” from the pull-down menu at the bottom of the page.
When its working, it gives a single-line trace of the lake level since 1963; right now it gives (me) the graph posted earlier.
Though, you can get a tabular approximation by clicking on one of the “dates” in the table on the main page; that will give you the level on that date for every year since 1963. From there, you can maneuver around to different days.