What is/are the method(s) to determine Infiltration?

Flooding-Type Infiltrometer(ff)
As the flooding-type infiltrometer measures the infiltration characteristics at a spot only, a large number of pre-planned experiments are necessary to obtain representative infiltration characteristics for an entire watershed.
Rainfall Simulators(fr)
Rainfall simulators are one of the most popular research devices for studying the impacts of rainfall on the activation of runoff, infiltration, and sediment transport mobilization in the landscape.
Rainfall simulator type infiltrometers give lower values than flooding type infiltrometers. This is due to the effect of the rainfall impact and turbidity of the surface water present in the former. i.e ff > fr
Hydrographic Analysis: This method involves analyzing hydrographs, which are charts that plot river discharge over time.
By studying the base flow and direct runoff components of a hydrograph after a rainfall event, scientists can estimate infiltration rates indirectly.
Hydrographic analysis helps understand how much rainfall infiltrates the soil versus how much runs off.