Kiv knelt by the northern edge of Chaska’s chalk map and traced his broad thumb along the double line she had drawn beneath the Quiet Spring.
“Wait a minute,” Kiv said, his brow furrowing. “If we break the lower sill here to turn the upper vein into that dry limestone fault, the head-pressure drops three feet.”
“Four feet,” Chaska corrected, tapping the elevation mark with her chalk. “That’s the whole point. We have to drop the water below the lake chute.”
“If you drop the head-pressure four feet,” Kiv said, looking up toward the crate of translucent salamanders and the flat baskets of blind crabs, “the Quiet Spring drains dry to the gravel bed. Every warm shelf up there goes cold in an hour.”
The cavern went quiet except for the hiss of the steam vent behind Lilt’s tail.
Nobody had missed the math once Kiv pointed at the sill mark. The Quiet Spring was not just an empty puddle they had happened to camp beside; its deep, warm mineral blend was the only water in the upper valley that kept the displaced Cradle nursery creatures from dying of shock after the central basin collapse, and its steady warmth was the only soak that had eased the iron ache in Pip’s skull. They could not keep that pool full and use its current to starve Veyt’s bell at the same time.
