Although the amount of water is shrinking. The main issue for the Colorado is abuse from agriculture. Something like 80% is being used for farming in the middle of the fucking desert. And even worse their growing shit like avocados and almonds that need a shit ton of water.
The issue isn’t the game engine, it’s the texture files.
If you don’t care what it looks like, you cut 80-90% or more from any modern game subbing low quality textures.