Well, one thing at a time. He had the dam to worry about, for if power failed, that would be the end of all this! And he only had, really, two working hours coming up. Repair a dam that size in two hours? Ow!
The maps came. One was a sketch the Chinese engineers had lately made. They had put the village location in. They had done a sketch map of the lake and aside from the Chinese character notations and numbers, it was all quite nice and comprehensible. They had even taken soundings.
He looked at the defense map and noticed for the first time that it was “copied from the original survey.” And from the Psychlo dates, the original survey was nearly eleven hundred years ago. By means of a glass he read the original dam data.
The original Kariba dam, as modified by the Psychlos when they first took over and installed this defense installation, was shown to be about two thousand feet long. The structure height was about four hundred and twenty feet, backed by a lake one hundred seventy-five miles long and about twenty miles wide at its widest point. A truly big dam. It had even had a road for vehicles running all along the top of it.
Jonnie compared the maps. The original had no place for any village! What was this? Had the planet changed its face?
He grabbed a man-map of the area. The river had been named the “Zambesi,” about twenty-two hundred miles long and one of the world's major rivers. It had flowed through "Kariba Gorge” and here it had been dammed for hydroelectric power, an immense undertaking. The sides of the gorge at this place had been steep too. No place for any village! He compared the maps.
The top of the dam that had been a road, even before the ship hit the lake, had been awash.
Then Jonnie knew what had happened.
The floods of the Zambesi, year after year for eleven hundred years, had been silting up this lake.
No wonder the water level had dropped so incredibly fast. The crash must have blown a million tons of silt over the dam. And now there was not enough water flow to replace it so fast for there wasn't that much lake! It was now only about one hundred twenty miles long, and the water at the dam itself was only about a thousand feet wide. The rest had been mud.
He said to Chong-won and the Chinese engineer, “This dam had six generator intake ports where the water entered from the lake, fell through the dam, and turned the generators. Right now, I want all six of them closed. The instant they are through firing, in about twenty-five minutes, we're going to cut all power. Do that, then close the ports. When they need electricity to start firing again we will omit lake defense cable to get rid of its power drain and we will open up only two generator ports. Can you do this?”
“Ah, yes!” Then a repeat. “You want us to shut off all power in about twenty-five minutes, close all generator ports, and about two hours later omit defense cable at the lake and open only two ports to the generators. We will also close all spillways?”
Jonnie nodded. The excess dam water hadn't ever before gone over the top of this dam. It spilled through spillways under the dam and reentered the river far below. Conserve water. That wouldn't handle the whole situation but it might help.
Thor was there. “Get Dwight!" Jonnie said.
“He's in the hospital. Broken arm, bashed up.”
“He was also our best explosives man at the lode,” said Jonnie. “Get him.”
They were still firing at the console but he could use this time to organize.
Dwight came. He had two black eyes and a plaster cast on his arm. He was limping. But he was grinning like a lighthouse.
Jonnie wasted no time. “Dwight, collect two one-thousand-foot rolls of blast cord, about three one-hundred-pound drums of liquid explosive, three of those port-a-pack drill rigs with a hundred feet of shaft for each, and fuses and things.”
“What are you going to do?” asked Thor. “Blow up the planet?”
Jonnie said, “You, Thor, collect every man here we had with us at the lode and a lot of Chinese.”
Stormalong was there. “Get ready to transport explosives and men across that lake,” Jonnie told him. “The instant they are through with this first hour's firing, we've got to be ready to roll.”
He scribbled a note for a communicator to give to Angus the instant he was finished with firing boxes: “You are going to lose all power for two hours. Inform us when you are through with this first run as we'll be running motors and blasting. Don't start firing again until you get an all-clear from us. Communicate with me by mine radio.”
Men were being sent through the passage to the outside. Some of them were veterans from the raid, and hospital cases. Dr. Allen looked on with disapproval, especially at Jonnie. But he said nothing.
Jonnie got outside. It was daylight now, thank heaven. He could see what he was doing. He looked at the dam. Yes, indeed. Silt! There was silt splattered all over the place. What a muddy job this would be. Where the top of the dam had been broken, piles of silt lay there. There was silt all up the cliff sides. Splattered as if with a gigantic paintbrush. Wet silt. One of the biggest dangers here was slipping and sliding.
He had his mine radio on so he could be told when they were done with the first hour's firing. Men were running dollies out of deep magazines, getting explosives to a plane. Pilots were standing by. Two mine passenger planes were loading personnel. A dozen Chinese raced into the powerhouse equipped with big wrenches: they would need them to move levers and controls frozen in place for a thousand years.
Jonnie walked to the dam edge and looked up the lake.
He couldn't believe his eyes. He would have thought the plunge through the atmosphere would have destroyed more of it than that.
There was the capital ship, a gigantic wreck, dug sideways into the silt five miles uplake from the dam.
And it was contributing its share to the disaster.
The twisted, charred hulk was blocking fresh water flow to the dam! Above it, a new lake was forming.
He got Dwight. “You pick about three men. Put them on a flying platform. Lay blast cord on the east side of that wreck and blow a new water channel around it. I’ll give you the time to fire the cord. Get it laid and come back to me.”
Dwight rushed off to find his men and more explosives.
Jonnie walked over to a point where he could see the opposite end of the dam. It was a very curved dam, its lake side jutting into the lake like a half-moon. Yes, there sure was water escaping. Because of the shape of the dam, a hard push of concussion against it would cause the ends to thrust much more strongly into the banks. The far end over there was firm enough against the cliff, but the bottom of the dam must have moved. Water was roaring out under that far edge like a gigantic fire hose.
Possibly ancient cracks at the far base had been filled with silt until now. But the blast had torn them open. The only thing that would plug that was about half a million tons of rock dumped upstream from it. And this was no time to be dumping rock with blade scrapers and cranes.
The half-formed plan he had made had been right. He looked at the cliffs on the far side of the gorge. If he blew one of them down to fill the breach, would the concussion also rip out the rest of the dam?