Our pond is almost 2 mnths old. Our "No Shade" temps were getting upwards of 95F (mid-depth) w/ solar radiation >1300 w/m^2. Because of those temps, we delayed introducing fish.
To help regulate temps at mid-depth (15"), we added various lilies. After fanning out, covering roughly 1/3 surface, the mid-depth temps were significantly reduced, <93F with solar radiation still >1300 w/m^2. We have noticed our Koi and Shubies now come out of the "deep" to feed in the late morning.
After noticing higher solar radiation levels (in the morning) preceding the afternoon max pond temps, we planted 2 young 18' Weaping Willows 20' east of the pond, providing shade in the summer mornings, while allowing direct radiation in the winter.
Now we just have to wait for the willows to fan out.
Our max pond temp goal at 15" depth is <92F.