Sounds like a trout pond?
If spring-fed, does your outlet pipe run all summer? If so, you should set up your pipe to draw from the surface, or just below, to pass the warmest water through the outlet.
Another option would be to deepen the pond. More thermal mass leads to lower summer temperatures, just based on the lag in warming the average temperature of the pond.
Another option would be some floating islands of water plants. That should provide some shade, perhaps a little cooling from transpiration, and the plants will take up some of the nutrients that might otherwise go to algae growth. Further, the dangling roots would be a new micro-environment for zooplankton and some of your forage fish.
The search function should turn up some of the past threads on floating islands.
Also, you could build a dock from land, or a floating dock for swimmers if either of those was in your long-term plans. That would provide a tiny amount of shade in the pond.
Finally, do you have AC electricity at the pond? There are some aerial water sprayers for aeration of the water, but they are mostly decorative. (It is much more efficient to use bubble aeration in the water column to add oxygen to your pond water.) I would assume that type of sprayer creates some evaporative cooling in the atmosphere above your pond. (Which would cool the air ABOVE your pond, but would IMHO have very little effect on your water temps.) Perhaps if you turned that type of sprayer sideways (or created your own sprayer) and directed it at the pond surface, then you might get the evaporative cooling to occur right at the surface of the pond. (However, I think this would not give you much cooling for the cost and effort.)
If you are trying to make the pond more amenable for the survival of trout, I believe most of our trout people on Pond Boss do add a little water column aeration in their ponds. Slightly warmer water with more oxygen is better for trout that would otherwise be struggling in the low dissolved oxygen conditions that come with the warmer water temperatures of summer.
Good luck with your pond! I hope some of my wild ideas trigger a few good thoughts on your end that might actually apply to your conditions.
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