We get 10" of precipitation a year on average. We are the second driest state in the United States next to Nevada holding the number 1 spot. We get snow but most of the time our snow is so dry you can't even make a snow ball out of it. We also have more sunny days than most of the country. On average we have over 230 sunny days per year!
Really nice looking deck and beautiful pond.
For most people having that 2 x 4 material directly in contact with the ground is going to be an issue - not so much if you live in the desert.
The 2" PT lumber sold at the big box stores is not rated for ground contact (says so right on the tag) and may rot very quickly if used that way.
The 4" material, like fence posts, is rated for ground contact and will last a long time. It's a little more expensive, but if you live in anything other than a very dry climate it would be a much better choice.
I guess it really all depends on your climate, how much you want to spend, and how long you want it to last.
I wish I could get away with that method here because I love the way yours looks, but in wet FL it wouldn't last very long at all. And that would be the case in large parts of the U.S.