Is the fresh water supply to your pond muddy too? If it is you can create a couple small pools before the creek reaches your pond to trap sediments, but it would have to be slow moving to let the particles settle. Vegetation where the stream empties in would help too. Ive heard of Fish and Wildlife people in my area spraying chemicals onto the surface of a pond that bind to the suspended sediments and sink. The government does it, but I don't know how the fish would like it.