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.
[1] http://www.environment.ucla.edu/perch/resources/images/cow-v...
https://www.theguardian.com/lifeandstyle/shortcuts/2015/oct/...
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).
[1] https://www.theguardian.com/us-news/2015/nov/28/california-c...