Why is the fact that the Tigris and Euphrates rivers cross international boundaries on their path to the Persian Gulf a problem potentially greater than the one that exists on the Colorado River?

Answer 1

There is very little water in Southwest Asia. There are disputes over building dams on the Euphrates and Tigris River. Turkey wants to use the power of the rivers to create hydroelectric power, but the dams would limit the water-flow to countries further downstream like Syria and Iraq. Additionally, dams tend to prevent the flow of silt, dirt with key nutrients for plants, leading to a lower level of fertility in downstream water. The disputes between the power-hungry Turkey and the resource-deprived Syria and Iraq could erupt in war.

The Colorado River is almost entirely within the United States and the states within the US can amicably discuss water allocation, especially since no US State has an army that it can use to attack another state and all US States recognize the authority of federal dispute resolution mechanisms.