I'm sure it could be done, but it would cost a fortune. My understanding is the canals were built to distribute water to farmers, and conservation/evaporation wasn't really much of a consideration because California had plenty of water back then.

BTW, I used to swim in those same canals around Modesto and Turlock as a kid. So gross.

At least $16 billion for 45 miles. See https://www.deltaconveyanceproject.com/about-the-delta-conve... and https://en.wikipedia.org/wiki/Delta_Conveyance_Project