Many years ago the city of Denver had a problem. The land east of the Rocky mountains is dry, rain is sparse and the aquifers were being depleted. The city was growing rapidly, still small by today’s standard, but they were thinking big and looked for a really good water supply. There was one fairly nearby: the Colorado river. There was only one small problem, it was on the other side of the continental divide. They were building a railroad tunnel under the continental divide anyway, so for a few million dollars extra they added a water tunnel, with a capacity of 36 m3/s of water flow, and it has been draining water from the Colorado River basin since 1936.
As an engineering feat it was quite impressive, and the population west of the Rocky Mountains was minuscule. This has changed and the demand for water in the Southwest is enormous and increasing. Las Vegas alone is now about the same size as the City of Denver. (The Denver Region is about 5.5 million)
Much of the water in the Colorado River basin is used for agricultural purposes.
This is important: The Colorado River water is all spoken for. It never reaches the Gulf of California. Once upon a time there was a good shrimp harvest at the mouth of the Colorado River. No more.
Time to shut down the Moffat Tunnel.