There’s some bitter irony to the problem of too much water menacing the Golden State. California has suffered through a long and severe drought, at times driving Governor Jerry Brown to institute stringent—critics say draconian—water controls. This winter has seen much more snow and rain, which is good news for the parched state, but bad news for the Oroville Dam, where huge amounts of water are collecting. The lake rose 50 feet in a matter of days. Earlier in February, as operators let water over a concrete spillway to reduce the pressure, a crater appeared in the spillway. Faced with too much water in the lake, they continued to use the spillway anyway, and the damage got worse. On Friday, the crater was 45 feet deep, 300 feet wide, and 500 feet long.

There’s a backup for the concrete spillway, an auxiliary spillway that had never been used. It’s really just a hillside sloping down from the reservoir, covered in brush and trees. As the situation became more dire last week, crews starting clearing the slope for its first baptism. Managers hoped pressing the auxiliary spillway into service would give them time to patch up the concrete spillway over what’s expected to be a drier season. (That could be easier said than done: Snowpack upstream is 150 percent of normal for this time of year, meaning there’s going to be more melt headed downstream than normal.)

Initially, that seemed to do the trick: The water level in Lake Oroville was dropping, and the danger seemed to be abating. On Sunday, however, officials noticed the auxiliary spillway was starting to erode—at the same time that huge amounts of water continued to flow into the lake. The fear is that if the spillway gives out, a wall of water could push down out of Lake Oroville and toward lower ground. Workers are trying to shore up the emergency spillway with bags of rocks, including dropping them from helicopters. If it gives way, the Feather River would flood downstream, and might wash out other levees farther down the river. Meanwhile, debris from erosion also forced the state Department of Water Resources, the dam’s operator, to shut down its power plant, which could have helped to release some additional water. And there’s rain forecast for later this week.

How did the situation get so dire? One part of that is the seesaw state of the drought, with the weather moving from dry to saturated in a matter of months. (While droughts are a normal part of the globe’s climate, scientists say human-caused climate change has exacerbated them, increasing the severity of California’s drought by as much as 20 percent.)

Dam operators can’t control the weather, but they can try to prepare for unexpected events like the sudden inundation of Lake Oroville with consistent maintenance. One question in this case is whether the Oroville Dam has been adequately maintained.