“What about the emergency spillways?” Joe asked.
All major dams have emergency spillways around them just in case of such an event. These high-volume bypass channels were rarely used.
“Coming open now,” the supervisor said. He watched and counted: “… twenty-eight, twenty-nine, thirty. All gates are open. Also the Toshka Canal. Within ten seconds, we will be discharging maximum water volume. Four hundred thousand cubic feet per second.”
Joe heard and felt a great reverberation shaking the building from within. He looked out over the Nile down below. The water in the tailrace was churning like world-class rapids.
Thrown wide open, the spillways were dumping enough water to fill a supertanker every fifteen seconds. Maybe twice that amount was already flowing over the breach. Joe had a bad feeling it wouldn’t be enough. If Lake Nasser was full to the rim, it would take hours or even days to lower the water below the level of the breach. In that time, the gap would deepen and the process would continue. Joe feared they would never catch up.
As the flood raged, the multimillion-ton structure shook like a city in the grips of an earthquake. But instead of passing, the tremors held steady and grew worse.
Another huge section of the dam broke off and rumbled down the slope like an avalanche. In minutes the rushing water had swept it away, and now the breach stood two hundred feet wide. The outflow from it had to be ten times greater than all the other spillways combined. It looked like Niagara Falls.
Downriver, the flood swept onward, dragging boats and docks and anything in its path along for the ride. Barges and riverboats that took tourists on Nile cruises were torn from their moorings and flung downstream like children’s toys in the bath.
The water raced along the banks of the Nile, scouring out the walls in places, undercutting the rock and sandstone and causing landslides and collapses reminiscent of glaciers calving in the arctic.
It surged up over the banks and swept around the hotels and other buildings. Smaller buildings were obliterated as if they were made of toothpicks. One moment they were there, the next they were gone, replaced by rushing water. And this was only the beginning.
The supervisor stood silent. The major stood silent. Even Joe Zavala stood silent. They were powerless to do anything but watch.
Ninety percent of Egypt’s population lived within twelve miles of the Nile. If the whole dam gave way, Joe could see a disaster counting its victims in the millions. Even as the water spread out over the valley, sparing victims downstream from the destructive force, the aftermath might be worse than the flood.
Millions would be homeless. Half of Egypt’s farmable land would be flooded and at least temporarily destroyed. Dysentery, cholera and all the diseases that come with unsanitary conditions, and those spread by mosquitoes and other insects, would become epidemic.
It would only add insult to injury that the dam provided fifteen percent of Egypt’s electricity. But when piled on top of the nation’s other problems and its precarious political state, Joe feared a governmental implosion. He could see a nation of eighty million people falling into anarchy in one fell swoop.
“How long before total collapse?” he asked.
“Difficult to say,” the supervisor replied. “It depends on whether the core can hold.”
Joe noticed how the topside breach had widened substantially but hardly deepened at all. It was no longer a V shape, more like an extremely elongated U.
“What’s the core made of?” he asked, remembering how it had appeared to be a different material in the cross section of the model.
“Semiplastic, impermeable clay,” the supervisor said. “Concrete down below.”
If Joe was right the rushing water had scoured down through the aggregate and reached the core. The erosion rate had almost stopped. “Does it run the whole width of the dam?”
The supervisor nodded. “It’s dug into the rock on either side.”
“Can it hold the lake back?”
The supervisor thought about that for a moment. “The core won’t erode like the aggregate does, but as the back side of the slope is scoured away the amount of rock and stone keeping the core in place will be reduced steadily. At some point the weight of Lake Nasser will simply shove the core aside like a bus might push a small car.”
Joe looked out past the breach. The water was cascading over the top, plummeting and spreading. But the gentle thirteen-degree slope and the stone covering seemed to be helping, the covering was holding its own at least for now.
“I think the surface lining is holding up,” he said. “If the water level drops far enough, the core might save the day. And with the breach as wide as it is, that shouldn’t take more than a few hours.”
The supervisor nodded. “It’s possible,” he said, sounding like he didn’t want to get ahead of himself.
Major Edo pointed to something else, something Joe hadn’t seen before. A small geyser farther down below. All but lost in the greater flood, it was blasting outward like a water feature in some ornate garden. The spray soared and fanned into a fine mist that caught the illumination from the floodlights.
“What about that?” Major Edo asked.
Joe’s heart dropped. He remembered the mock-up in Yemen. The higher flood had come first, but the lower tunnel had caused the core to fail and the entire dam along with it.
“That’s a bigger problem,” Joe said.