Wetland creation: Why and how?

I have been playing with the idea of creating a few small wetlands on our property. It seems to me that it would be beneficial to install a wetland above the existing pond, to slow down and warm up the water entering the pond (it is REALLY cold snowmelt), and to add nutrients to the water flowing into the pond (the water is so cold and fast moving that it doesn't seem to support much life, rendering the pond sterile). Is this the right line of thinking, or am I missing the point of wetland creation? Is there a better way to incorporate wetlands into my land, besides putting one up near the creek entrance to the pond?

Meandering the inflow of cold snowmelt will warm it up.
I would just add some animals and their waste to create nutrient load.