This chapter focuses on the parameters most commonly monitored by drinking water practitioners in streams (i.e., it is assumed, for illustration and discussion purposes, that the water source is a surface water stream). Drinking water monitoring refers to water quality monitoring based on three criteria: ensure to the greatest extent possible that the water is not a danger to public health, ensure that water provided at the tap is as aesthetically pleasing as possible and ensure compliance with applicable regulations. State and local water quality practitioners as well as volunteers have been monitoring water quality conditions for many years. In fact, until the past decade or so (until biological monitoring protocols were developed and began to take hold), water quality monitoring was generally considered the primary way to identify water pollution problems. Standard methods prescribe all phases of procedures and calculations for Biochemical oxygen demand (BOD) determination. A BOD test is not required for monitoring water supplies.