I think it’s pretty likely that the main cause is it’s being diverted for agricultural use. Things like diversions into cities will also contribute, but genera

I think it’s pretty likely that the main cause is it’s being diverted for agricultural use. Things like diversions into cities will also contribute, but generally gets dwarfed by agricultural use. The Colorado river flow for example is 80% agricultural. 20% for all other uses, including the bare trickle that actually makes it to the ocean