In 1943 I watched the USGS measure the flow in the Run by timing an orange as it floated along a measured course (the current was too sluggish to turn the standard current meter). They operated from a boat because the bottom of the run was too soft to stand on. In 1990, I devised a way to precisely measure depth and current velocity. I think of it as “fishing for numbers”. It has evolved and I have become more astute over the 32 years of practice.