Author(s): Zhi-Qiang Deng; Hoon-Shin Jung; Bhuban Ghimire
Linked Author(s): Zhiqiang Deng, Zhi-Qiang Deng
Keywords: VART Model; Solute Transport; Residence Time Distributions; Rivers
Abstract: Solute transport in natural rivers has been found to exhibit various long-tailed residence time distributions (RTDs) due to the hyporheic exchange between surface stream water and subsurface ground water. A newly developed Variable Residence Time (VART) model is utilized to simulate the long-tailed RTDs produced through tracer injection experiments conducted in hydraulically and geomorphically varied rivers. Simulation results show that (1) natural rivers may display a wide variety of RTDs switching from upward-curving patterns to a straight line (power-law distributions) and further to downward-curving lognormal distributions when plotted in log-log coordinates; (2) exponential RTDs often occur in streams with a shallow advection-dominated constant transient storage/hyporheic zone; (3) upward-curving RTDs may be formed in streams with an expanding transient storage area consisting of an upper advection-dominated hyporheic zone and a lower effective diffusion-dominated hyporheic zone; (4) lognormal RTDs are the most frequently occurring solute concentration breakthrough curves found in various rivers and streams with a contracting transient storage area consisting of an upper advection-dominated hyporheic zone and a lower effective diffusion-dominated hyporheic zone; (5) power-law RTDs are special cases of lognormal RTDs and commonly take place in small streams with a contracting transient storage area; and (6) the VART model provides a simple yet flexible tool for predicting solute dispersion and transport in natural streams and rivers. The results presented in this paper can improve understanding and modeling of longitudinal transport of pollutants and nutrients in rivers and streams and provide useful information for river restoration and management.
Year: 2009