Transient water quality events in British Columbia coastal streams

Abstract

Transient events are rarely observed because of their aperiodic nature and short time duration. Often, it is not practical to sample these events using traditional methods. Typically, electronic instruments are required to gather sufficient data to observe transient events in streams and rivers. In many cases, data loggers equipped with water quality sensors offer the only reasonable opportunity to study these events. Data gathered at high frequency from two small streams illustrate some features of transient water events. These events illustrate the variety of changes observed in streams during both natural and man-induced events. Transient events may result from impacts on the entire watershed or from direct inputs to the stream channel. How a watershed responds to an event may be characteristic of ecosystem response to the disturbance. Events which affect the entire watershed differ in mechanism between the two study watersheds. This is a result of the different nature of the two ecosystems. Direct stream effects are more common in the urbanized watershed, and have properties which are distinct from the events affecting the entire watershed. The response of the system to transient impacts provides insight into the processes within the ecosystems. Data from a two month period in 1995 is used to illustrate observation and analysis techniques.