Ever since I downloaded DG the water streams running through WR have been completely untextured, only untill I jump into them do they become loaded, and then every time I look away, and look back there unloaded.

That happened before DG in Markarth. It was fixed by loading the save again. Did you try reloading a save?

Yes this happened to me before Dawnguard was even released, usually it just takes a minute or two and it should be fine, try moving towards it and it should appear.

Still happening :/

Try clearing the cache, probably won't work but that's the usual suggestion when things like this happen. Btw do you have the game installed to your HDD ?