Harnessing El Nino in 1000AD

By studying clues such as discarded agricultural tools, plant remains and field locations, the team determined that farmers selectively used the canals to direct El Niño floodwaters to fields farther from the rivers, beyond the reach of their typical river-water irrigation. 

Amazing the ingenuity of ancient farmers. Every time we discover the work that they have done, we realize that they got far more out of the landscape than we had thought possible with techniques available at the time.

https://www.scientificamerican.com/article/ancient-peruvian-farmers-harnessed-el-nino-floodwaters/