"Environmental" uses seems to mean they're just allowing the water to run naturally to maintain the environment. (This is the source Wikipedia cites: https://www.ppic.org/publication/water-use-in-california/). It's funny that they call that a use of water in California. If you remove that, then yes, agriculture uses 80% of the water.
Water that naturally flows into the state’s “wild and scenic” rivers, which are not connected to the state’s water system and can’t be under state and federal protections
Water required for maintaining fish and wildlife habitat within streams
Water that supports wetlands within wildlife preserves
Water needed to maintain water quality for agricultural and urban use