Generally do tipping bucket rain gauges measure rainfall only once per day?

Match the rainfall mechanisms

A core of sandstone is brought into the laboratory and a Darcy experiment is done on the on the core to determine the hydraulic conductivity (K). See experimental set up below.

The following was recorded: core diameter (D) 10 cm; core length (L) 20 cm; steady state flow (Q) was recorded at 5 ml/min; h₁ = 20 cm; h₂ = 5 cm.

a)  Using Darcy’s law, determine the hydraulic conductivity (K) of the core in the units of [m/s] and report to two decimals.

b) Assuming that the fluid used in the experiment is fresh water at 25 °C, determine the intrinsic permeability (k) for the sandstone in [m²] and report to 1 decimal.  

What is the term below referred to and how is it derived?

If I compute the evaporation using a Class A pan (shown below), will I overestimate the evaporation from the surrounding area?