Good video. This is along the lines of what I've always felt GP1 was initially intended for: water resource management.
Keep in mind that the surface area of GP's 4 sides is vastly immense and reaches up into the air off the floor of the plateau. Also, due to the thermal mass of the structure, as well as its white tura cladding, it's surface temperature would remain fairly constant through day and night. This would allow the pyramid to literally pull moisture from the atmosphere via condensation every day, regardless of season, and in potentially significant amounts.
So you have rain, condensation, and ground water all being directed by the pyramid into the relatively small volume enclosure that surrounds its base. Pretty smart folks.