From what I have read, the Dam has is leaking. The more pressure on the dam, the more errosion from the leak. The reason to keep the dam lower is to minimize the pressure, thus minimize the amount of errosion until they can fortify the leak area plus all of the like area. This dam has held this amount of water and more in the past and I do not think they are worried about it busting today. They are more concerned with what may happen in the future if it goes unchecked. I would also imagine there is a cost to the currrent structure based on the intrution for the repairs. I would hope they would have factored in this sort of short term situation in their plans.