Water management in the 12th century

I am beginning to get an inkling of how sussed they were in mediaeval times as regards water management. What is becoming clear to me that is that the site is not just a place where a moat was dug but rather some very sophisticated management of aquifers and geology to maintain a site water table a metre or so above the stream in order to keep the moat and carp pond full of water. I am now keen to pursue a plan for the entire site rather than just focus on the moat. The survey has shown us that the carp pond and moat are hydrologically continuous and basically you can't raise the water levels in one without impacting the other.