Why naval mines were cached deep inside Sudan

Why were naval mines stored far inland on the Nile at the outbreak of the Mahdist War?

They were forward-positioned during Anglo-French rivalry, and secret local recordkeeping allowed some caches to be forgotten.

The inland naval mines are linked to contingency planning during Anglo-French rivalry. Both powers placed weapon caches where they might be needed in a future confrontation. Some locations were passed between local commanders without being recorded on maps that an opponent could find. When commanders departed without preserving that knowledge, the locations could be lost.