What has made the dry areas of the Columbia Basin usable for agriculture?

Question

I need this answer for a study guide and i can't seem to find anything.

please help!!

Answer 1

The columbia basin has soil that is largely influenced by volcanic dust and ash. This works well with water that is provided by irrigation.  But, irrigation alone would not have been enough.

The benches that are the best for farming are all volcanic material, and are well drained. Roots can go deep to get both water and nutrients.

Answer 2

Irrigation

EDIT:  Yes,donflect the volcanic soil, it's nutrients and drainage made the basin excellent potential agricultural land.  But that land is arid, high desert.  It was a steady supply of water that made agriculture possible.