Water Leaking into trunk in 2013 Chevrolet Equinox

We have a 2013 Chevrolet Equinox, which we love. However, just recently, during a horrendous rainstorm, we got a flat tire. In the process of changing it, I noticed about 2” of water in the spare tire compartment. I vacuumed out the excess water, and dried the rest with a hair dryer, but two days later, the water had returned. I am totally baffled by this, but need to find the leak so it can be fixed, or we will have a vehicle filled with mildew and mold.
Has anyone had this same problem, and, if so, how did you resolve it?

Check for debris buildup on the top of the hatch around the gasket.