The Grant County Public Utility District said the 2-inch wide crack had closed by nearly an inch Monday and a spillway pier that had bowed has moved back upstream by about an inch.
The utility says the measurements confirm the dam is more stable. It's still generating electricity.
The horizontal crack across a 65-foot wide spillway pillar was discovered underwater Feb. 26 and led the utility drop the reservoir by about 25 feet.
With the reservoir at historic lows, boat launches are closed and people along the shoreline are reminded not to dig for archaeological objects in the newly exposed areas.