South Africa actually, remember the San Diego Zoological society isn't that great as far as geography? Though this might have been East Africa when the picture is taken.
I can't comment on how it is now, but in 2003, they had Lake Victoria defassa waterbuck (Kobus ellipsiprymnus adolfi-friederici) in the East Africa exhibit and ellipsen waterbuck (Kobus ellipsiprymnus ellipsiprymnus) in the South Africa exhibit, which if you were to have to locate those two subspecies, that would be the most accurate arrangement.
There is a White Rhinoceros in the far back, you can hardly see him, behind the third palm tree to the left; if that helps. I'm not sure if it would be a Northern or Southern one, but as there seems to be a second one down on the ground next to it, it might suggest the two Northern cows?
I know that this exhibit is South Africa now (I thought it's always been) This is the exhibit that you can see from the Cheetahs and where you start from on JiA.