In terms of global warming, almond milk seems to be about 4.6 times better than cow milk. On page 8 of [1], they claim that CO2-equivalent emissions are
0.36 kg/L almond milk, and 1.67 kg/L cow milk.
(Note: This is somebody's class report, not a peer-reviewed publication.)
There is some uncertainty in these numbers, of course. If you care more about water usage, then 1L of almond milk uses on the order of 1600 gallons of water, compared to under 100 gallons of water per liter of cow milk. Again, there is some uncertainty. And I think CO2-equivalent emissions is far more important.
Although trees generally conserve water much better than animals, you need to support the entire almond tree for a few almonds whereas the cow's entire body will be used for a variety of products. The water usage of the agricultural infrastructure supporting the cow may be higher in absolute numbers but a single cow is literally hundreds or thousands of pounds of useful meat and bone after it is no longer useful as a milking cow.
I was about to rebut you, but the facts remain: The largest supplier (by far) of almonds in the world is California. So yeah, if you drink almond milk it's likely sourced from CA using up precious water that is causing the CA central valley to literally sink [1], as much as several inches a month (ie, several feet so far).
However, almonds pale in comparison to cows or other livestock in terms of water usage (esp when used as meat) - while consuming large quantities of almonds may not be sustainable, it's a lot better than eating meat... just may be as water-unsustainable as drinking local milk (if you live in CA).
But meat cows and milk cows are not the same thing. You need to grow a whole cow to have the meat of one cow, but if you grow one milk-cow you have the life-time supply of one cow. The water to meat (weight) ratio may be in the thousands or ten thousands, but the water to milk ratio may be in the oughts or tens.
Milk cows carry a baby every year which puts more pressure on metabolism needs. Milk is more energy and water inefficient than meat ( same scale comparison).
