Most of the water in the ogallala aquifer came from glaciers that melted thousands

The correct answer is - rainfall.

The Ogallala Aquifer is a very large aquifer. It traces its origins at the end of the last ice age, where the water from the melting glaciers filled it up. After that initial filling of from the water of melting glaciers, the Ogallala Aquifer has been reliant on the water from the rainfall to fill it, and replenish the lost water.

Since the humans started to use it though, this aquifer has been constantly experiencing decrease in its water levels. The reason for that is that the humans use more water from the aquifer than what the rainfall can replenish, and that is especially a big problem because the aquifer is located in an area where there isn't a lot of precipitation.

Harmful mutations may cause genetic disorders or cancer. A genetic disorder is a disease caused by a mutation in one or a few genes. A human example is cystic fibrosis. A mutation in a single gene causes the body to produce thick, sticky mucus that clogs the lungs and blocks ducts in digestive organs.
There are several well-known examples of beneficial mutations. Here are two such examples: Mutations have occurred in bacteria that allow the bacteria to survive in the presence of antibiotic drugs, leading to the evolution of antibiotic-resistant strains of bacteria.
In fact, the G-T mutation is the single most common mutation in human DNA. It occurs about once in every 10,000 to 100,000 base pairs -- which doesn't sound like a lot, until you consider that the human genome contains 3 billion base pairs.