PLANE SOURCE INJECTOR DESIGN FOR RIVER DISPERSION STUDIES

A device that injects a planar, spike input of tracer and accommodates irregular stream cross-sections was designed and held tested. The inj ector is based on a modular support and electrical system that can eas ily be modified in the field. The tracer is distributed to the water f rom self-emptying packets made of latex tubing. These packets resist p remature breakage and contribute no litter to the stream. The packets empty after applying a current to the electrical system. Instream asse mbly of the tracer injector is possible from a boat. A two-dimensional input of tracer significantly shortens the initial mixing period for streams that are wide and deep. During the initial period, the tracer cloud becomes well-mixed vertically and laterally. After the initial p eriod is satisfied, the variance of the tracer cloud grows linearly wi th time, and longitudinal dispersion can be measured easily. The use o f a plane source injector significantly reduces the duration of the in itial period.