Final answer:
The Colorado River is losing river elevation due to sedimentation, which is causing Lake Mead to fill up. The exact amount of river elevation lost each year varies depending on factors like the river's flow rate and sedimentation rate.
Step-by-step explanation:
The Colorado River is losing river elevation due to sedimentation. As the river flows into Lake Mead, sediment settles out of the water, causing the lake to fill up. Recent studies show that sedimentation is occurring at a rate that could fill Lake Mead entirely within the next few hundred years. The exact amount of river elevation lost each year will vary depending on factors such as the river's flow rate and the rate of sedimentation.