The Well Acacia. The Brytewood Chronicles, #4

Seventeen and restless, Caleb Brytewood thought he'd found his calling when his family saved the Hearthwood Oak. But each tree since taught him how little he truly understood. A merchant's western expedition promises extraordinary profit and access to a legendary guardian tree-the Well Acacia, buried somewhere in the desert provinces beyond the edge of every reliable map. It's the kind of opportunity that doesn't come twice: practical trade funding sacred purpose, adventure married to duty.
But the western territories aren't waiting to be saved. Villages cluster around failing wells while a powerful family hoards the water that should flow freely. Ancient trade routes have become paths of desperation as drought tightens its grip on the region. And in the jewel city of Mesaqat, where the Well Acacia should stand as beacon of hope, corrupt guardians have diverted the sacred tree's lifeblood to their own cisterns-leaving the tree dying and the Veil between worlds dangerously thin.
With Eli-the young Keeper of the Chronicle Pine from the northern mountains-and the irrepressible trader Thaddeous, Caleb ventures into the Serran Reach, where the maps end and the land itself seems to ache with ancient calling. But this time, restoration may require more than courage and a Keeper's touch. Sometimes the price of healing a broken world is the one thing you can't afford to give. And sometimes, by the time you understand what's really at stake, you're already too far down the road to turn back.