The Salt River Project has begun draining canals south of the Salt River for annual maintenance.
The canals running from Mesa to southwest Phoenix will remain empty through late December. After that, canals north of the Salt River will be drained and cleaned.
As part of the dry-up, SRP is removing and relocating thousands of algae-eating fish.
Crews will also be looking for signs of quagga mussels, a subspecies of mussel native to the East Coast that can clog up pipes and pumps.