Ann: Lulo Kimberlite Exploration Update, page-63

Geologically speaking, you are correct, but one can often infer what has happened.

ref LOM 21-12-15:

"Lucapa notes that the L165, L166, L167, L170 and L171 cluster of kimberlites in the south western partof the concessionarepartofatopgraphicdividebetweenthelowersouth-westflowingtributariesoftheCacuiloRiver andthenorthwestflowingCanguigitributary,whichhadbeencapturedanddivertedintotheCacuilo,southor upstreamoftheE46resource/miningarea. "

So it seems there is a good chance over the years, flow would have been towards the mining blocks.

Cheers,  bbd