Civil engineers can do a lot, but for these ancients, the Y1K megadrought that they faced was more than they could handle.
When colonists from the Wari state arrived in the remote Moquegua Valley in southern Peru, they built their towns on high, dry land and erected canals and aqueducts that carried water much farther than any previously attempted in the region. Such innovative hydraulic engineering enabled Wari—which some scholars argue was South America's first empire—to expand and thrive for some 400 years despite an often dry, drought-prone climate. But archaeologists studying Wari's rise and fall confront a puzzle. The state's collapse about 1000 years ago appears to have coincided with a severe drought. How could drought have doomed a society that had been built on learning to take maximum advantage of limited water?
Lizze Wade, "Engineering an empire" 368 (6488) Science 234-237 (April 17, 2020). DOI: 10.1126/science.368.6488.234