Evaluation of a continuous flow-proportional real-time streamflow sampler using a computer controlled hydrograph generator

This study investigated the problems with current streamflow sampling techniques and resulted in the design and evaluation of a continuous, flow-proportional, real-time streamflow sampling unit. The sampling unit was evaluated against a commercially available pumping type sampler to determine which sampler more accurately represented both constituent mass movement and the timing of constituent movement. The samples were taken from test streams produced by a computer-controlled hydrograph generator. Potassium bromide was injected into these streams with both constant and dynamic feed rates. Samples taken by each sampler were analyzed for bromide concentrations using a selective ion probe.

Results of this study indicated that a sampling unit that continuously extracts a flow proportioned sample and stores the sample in a discrete container provided more accurate information on both constituent mass movement and timing of movement than a sampler that took discrete samples at fixed time intervals. The sampler that collected samples at timed intervals was susceptible to missing sudden spikes in concentration and in overestimating the actual characteristics of the test stream when a sudden spike in concentration was detected. The continuous real-time sampler extracted a sample that was representative of the actual constituent characteristics of the test streams.

Results of this study indicated that continuous, flow-proportional, real-time sampling is an effective method of acquiring water quality data. This type of sampling provides the ability to obtain high quality information on total constituent mass movement as well as when the movement actually occurred.