I don't know, like I said, people lived in California before the arrival of colonists, it certainly wasn't a desert the way the Sahara was.
Nonetheless for some geographic reason, sure, it makes sense to send water there to grow things. The politics of it all are, if capitalism didn't deliver on efficiency in things that bring justice, like providing everyone with good food and shelter better than alternative governments, nobody would tolerate redirecting huge amounts of water to deserts in California or cities on Manhattan island.
Without capitalism, there would be something intrinsically valuable to pastoral, moneyless living, like the kind of farming people were doing when these reservoirs were built.
It's just ironic that, people have been living in the Americas doing just that, for at least millennia, and the same exact 1800s people and their descendants who felt they were entitled to do what they wanted with their upstate New York land, however inefficiently, will do nothing to remedy the same exact kind of losses for people who were there before them. Which is to say, just for the people who used to live on precolonized land, the "human costs" were not resolved by a free press, or laws, or money, it was resolved by simply ceasing to "account" for those costs.
Although, like I said, today you can go farm for subsidies if you wanted to, which is as good as a government-sponsored remedy will get, turning $1 tax into $0.10 of low cost of living and $0.90 in agricultural business income domiciled in... New York City.