Water levels at Lake Powell have dropped to their lowest level since the huge reservoir was filled more than 50 years ago, another sign of the ongoing drought’s toll on the Colorado River. The reservoir fell to 3,555.09 feet above sea level Friday and continued to drop through the weekend, according to the U.S. Bureau of Reclamation. As of late Sunday, water levels stood at 3,554.72 feet. The previous low mark, set in 2005, was 3,555.10 feet. Friday’s low water mark comes barely a month after Lake Mead, the largest reservoir on the river, reached a record low. Federal officials are expected next month to declare a water shortage on the Colorado River, triggering cutbacks next year in Arizona and Nevada.