The conference in Christianopolis had been convened to discuss strategies to deal with this situation. Nadia had done what she could to get influential people down to it, including meteorologists, hydrologists, and engineers, and the possibility of Sax, whose return was imminent. The problem of crater flooding was to be only the initial point of discussion for the whole question of watersheds, and the planetary hydrological cycle itself.
The crater problem specifically was to be solved as Nadia had predicted: plumbing. They would treat the craters like bathtubs, and drill drains to empty them. The brecciated pans under the dusty crater floors were extremely hard, but they could be tunneled through robotically; then install pumps and filters and pump the water out, keeping a central pond or lake if one wanted, or draining it dry.
But what were they going to do with the water they pumped out? The southern highlands were everywhere lumpy, shattered, pocked, cracked, hillocky, scarped, slumped, fissured, and fractured; when analyzed as potential watersheds, they were hopeless. Nothing led anywhere; there was no downhill for long. The entire south was a plateau three to four kilometers above the old datum, with only local bumps and dips. Never had Nadia seen more clearly the difference between this highland and any continent on Earth. On Earth, tectonic movement had pushed up mountains every few-score million years, and then water had run down these fresh slopes, following the paths of least resistance back to the sea, carving the fractal vein patterns of watersheds everywhere. Even the dry basin regions on Earth were seamed with arroyos and dotted with playas. In the Martian south, however, the meteoric bombardment of the Noachian had hammered the land ferociously, leaving craters and ejecta everywhere; and then the battered irregular wasteland had lain there for two billion years under the ceaseless scouring of the dusty winds, tearing at every flaw. If they poured water onto this pummeled land they would end up with a crazy quilt of short streams, running down local inclines to the nearest rimless crater. Hardly any streams would make it to the sea in the north, or even into the Hellas or Argyre basins, both of which were ringed by mountain ranges of their own ejecta.
There were, however, a few exceptions to this situation. The Noachian Age had been followed by a brief “warm wet period” in the late Hesperian, a period perhaps as short as a hundred million years, when a thick warm CO2 atmosphere had allowed liquid water to run on the surface, carving some river channels down the gentle tilts of the plateau, between crater aprons diverting them this way and that. And these watercourses had of course remained after the atmosphere had frozen out, empty arroyos gradually widened by the wind. These fossil riverbeds, like Nirgal Vallis, Warrego Valles, Protva Valles, Patana Valles, or Oltis Vallis, were narrow sinuous canyons, true riverine canyons rather than grabens or fossae. Some of them even had immature tributary systems. So efforts to design a macro-watershed system for the south naturally used these canyons as primary watercourses, with water pumped to the head of every tributary. Then there were also a number of old lava channels that could easily become rivers, as the lava, like the water, had tended to follow the path of least resistance downhill. And there were a number of tilted graben fractures and fissures, as at the foot of the Eridania Scopulus, that could likewise be turned to use.
In the conference, big globes of Mars were marked up daily to display different water regimes. There were also rooms full of 3-D topo maps, with groups standing around different watershed systems, arguing their advantages and disadvantages, or simply contemplating them, or fiddling with the controls to change them, restlessly, from one pattern to another. Nadia wandered the rooms looking at these hydrographies, learning much about the southern hemisphere that she had never known. There was a six-kilometer-high mountain near Richardson Crater, in the far south. The south polar cap itself was quite high. Dorsa Brevia, on the other hand, crossed a depression that looked like a ray cut out from the Hellas impact, a valley so deep that it ought to become a lake, an idea that the Dorsa Brevians naturally did not like. And certainly the area could be drained if they cared to do it. There were scores of variant plans, and every single system was strange looking to Nadia. Never had she seen so clearly how different a gravity-driven fractal was from impact randomness. In the inchoate meteoric landscape, almost anything was possible, because nothing was obvious— nothing except for the fact that in any possible system, some canals and tunnels would have to be built. Her new finger itched with the desire to get out there and run a bulldozer or a tunnel borer.
Gradually the most efficient, or logical, or aesthetically pleasing plans began to emerge from the proposals, the best for each region being patched together, in a kind of mosaic. In the eastern quadrant of the deep south, streams would tend to run toward Hellas Basin and through a couple of gorges into the Hellas Sea, which was fine. Dorsa Brevia accepted a plan to have their town’s lava tunnel ridge become a kind of dam, crossing a watershed transversely so that there was a lake above it and a river below it, coursing down to Hellas. Around the south polar cap, snowfall would remain frozen, but most of the meteorologists predicted that when things stabilized there wouldn’t be much snowfall on the pole, that it would become a cold desert like Antarctica. Eventually of course they would end up with a largish ice cap, and then part of it would pool down into the huge depression under the Promethei Rupes, another partially erased old impact basin. If they didn’t want too large of a southern ice cap, they would have to melt and pump some of the water back north, into the Hellas Sea perhaps. They would have to do some similar pumping in Argyre Basin, if they decided to keep Argyre dry. A group of moderate Red lawyers was even now insisting on this before the GEC, arguing that one of the two great dune-filled impact basins on the planet ought to be preserved. It seemed certain this claim would receive a favorable judgment from the court, and so all the watersheds around Argyre had to take this into account.