The overwhelming majority of the water does not go to Las Vegas (https://en.m.wikipedia.org/wiki/Colorado_River_Compact) — Nevada is only allocated 4% of the total water drawn from the Lower Colorado River. Las Vegas gets blamed due to its proximity to Lake Mead and the fact that it is in a desert, but it’s actually adopted aggressive water control measures over the years (see https://www.snwa.com/conservation/understand-laws-ordinances... for recent examples).

Also worth noting that while the colorizations of these satellite photos tend to paint the city in green, it is NOT very green at all. Clark County deprecated lawns ages ago by banning new ones and paying people to remove their existing lawns to replace with desert landscaping.

But that can only help mitigate the overdraw of the Colorado so much when 96% of the water is going to places that have much less stringent water conservation policy.

It looks like it's 20% smaller bounds-wise, but that's the top layer of the lake: the volume reduction must be at around 40-50%...