The effect of flow regime and turbidity on periphyton in a laboratory system
Birkett, Clayton Lamar
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This study was to design and develop a laboratory system for studying flow regime and turbidity interactions on periphyton development under three turbidity regimes. The flume was configured to create areas of distinct flow regime by using multiple roughness conditions and an in-channel weir. The one dimensional hydraulic model HEC-RAS was useful for modeling channel velocities and related properties, although the abrupt channel geometry and narrow channels appeared to cause some discrepancies in depth predictions. The results suggest that turbidity should be kept between 100 mg/l and 200 mg/l for periphyton growth, tending to confirm the 250 mg/l limit in the literature. Mean velocity was a fairly good predictor of live biomass (chlorophyll a) and filament length. The turbulent RMS velocity was the better predictor of dead biomass (pheophytin). Chlorophyll a concentration at the 100 mg/l sediment concentration was greatest, most likely due to periphyton compensation to turbidity-induced shading.