That all depends on the shape of your pond liner if one hole at the bottom would drain the entire pond because it is pitched to one side then your good. but odds are your going to need a whole bunch of penitrations to allow the water to drain . No sitting water will equal no smell . Go to any active land fill on a rainy day and the pleasurable aroma is one you won't forget. Go to a caped sight and you'd never know it was a landfill as one time.
In short the faster the water drains away the less problems you will have.
In short the faster the water drains away the less problems you will have.