Ref: Obviously "rain" is a very attractive hypothesis for the source of water at Giza but still the problem is the limited catchment area and the inability to hold significant amounts between rain events.
Many ancient societies harvested rain. Why would the AE be any different, unless they had an abundance of stream water. Has there been a notable ground radar of areas that might contain a water ditch or canal. And, if so, to what extent?
Where did they look?