ABSTRACT
This chapter discusses methods to measure velocity and stage to compute flow or to measure hydraulic residence time and mixing using dye tracers. Mechanical current meters are the most commonly used device for measuring point velocities. The principle of electromagnetic current meters is that voltage induced by water moving through a magnetic field perpendicular to the flow is proportional to the water velocity. Flows and other hydraulic characteristics are also available from organizations that operate water control structures such as dams, water intakes, outfalls, and other structures. Remote sensing has proven useful in large rivers, lakes and estuaries in providing qualitative definition of surface circulation patterns. The computation of discharge can be illustrated by the velocity-area method used in streams or rivers. Aside from concentration, a number of factors can affect the selection and use of fluorescent dyes and can affect the selection of a dye for a particular study.
