Objectives of Turbidity Threshold Sampling:

• Reliably define the turbidity-suspended sediment relationship for each event
• Accurately estimate event loads from the continuous turbidity record.
• Automate data collection and sampling
• Limit the number of suspended sediment samples for each event

The ability to collect useful information about suspended sediment transport and water discharge is dependent on the timing and frequency of data collection during storms. All river systems, particularly smaller watersheds that respond very quickly to rainfall, benefit from automated data collection. In rain dominated regions most suspended sediment is transported during a small number of events.

Turbidity is an optical measure of the number, size, shape, and color of particles in suspension. A number of manufacturers offer turbidity probes that can be deployed on a continuous basis in streams. The optical properties of sediment, mainly size and shape, have a large influence on the magnitude of the turbidity signal.

A programmable data logger is required to make the sampling decisions. For remote locations, it is important that the data logger has low power requirements in order to preserve the battery's capacity. The Turbidity Threshold Sampling program only requires input information about stage and turbidity to decide what actions to take.

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