Yeah .. the arch should be pointing where the water is coming from the most.. it's like the defining purpose of an arch, to spread The Force (tm) throughout it

Not an engineer, but that may because we're used to seeing arches made out of materials with a lot of compressive strength, like stone and mortar. This is made out of steel, which has a lot of tensile strength. Sort of how suspension bridges are supported by thick cables.

Just a guess.

I just don't get why you would build it in an arch and not point the arch the correct direction, but yes I am also not an engineer