JWARP  Vol.2 No.11 , November 2010
Pool Effects on Longitudinal Dispersion in Streams and Rivers
Abstract: Surface storage (pools, pockets, and stagnant areas caused by woody debris, bars etc) is very important to solute transport in streams as it attenuates the peak of a spill but releases the solute back to the stream over a long time. The latter results in long exposure time of biota. Pools as fundamental stream morphology unit are commonly found in streams with mixed bed materials in pool-riffle or pool-step sequences. Fitting the transient storage model (TSM) to stream tracer test data may be problematic when pools present. A fully hydrodynamic 2-D, depth averaged advection-dispersion solute transport numerical simulation study on hypothetical stream with pool reveals that a pool can sharply enhance longitudinal spreading, cause a lag in the plume travel-time and radically increase solute residence time in the stream. These effects fade like a “wake” as the solute plume moves downstream of the pool. Further, these effects are strongly influenced by a dimensionless number derived from the 2-D transport equation ? or , which outlines the relative transverse mixing intensity of a stream or river, where, of the stream reach concerned, W is the flow width, Q0 is the volumetric flow rate, q is the longitudinal flux density, and Dt is the transverse turbulent diffusion coefficient. The breakthrough curves (BTCs) downstream of a pool may be “heavy tailed” which cannot be modeled accurately by the TSM. The internal transport and mixing condition (including the secondary circulations) in a pool together with the pool’s dimension determine the pool’s storage effects especially when >> 1. Results also suggest that the falling limb of a BTC more accurately characterizes the pool's storage because the corresponding solute has more chance to sample the entire storage area.
Cite this paper: nullW. Zhang and M. Boufadel, "Pool Effects on Longitudinal Dispersion in Streams and Rivers," Journal of Water Resource and Protection, Vol. 2 No. 11, 2010, pp. 960-971. doi: 10.4236/jwarp.2010.211114.

[1]   S. H. Keefe, L. B. Barber, R. L. Runkel, J. N. Ryan, D. M. McKnight, and R. D. Wass, “Conservative and reactive solute transport in constructed wetlands,” Water Resources Research, Vol. 40, W01201, 2004, pp. 12.

[2]   J. G. M. Derksen, G. B. J. Rijs and R. H. Jongbloed, “Diffuse Pollution of Surface Water by Pharmaceutical Products,” Water Science and Technology, Vol. 49, No. 3, pp. 213-221, 2004.

[3]   M. Velicu and R. Suri, “Presence of steroid hormones and antibiotics in surface water of agricultural, suburban and mixed-use areas”, Environ Monit Assess, Vol. 154, 2009, pp. 349-359.

[4]   H. B. Fisher, E J. List, R. C.Y. Koh, J. Imberger and N.H. Brooks, “Mixing in inland and coastal waters,” Academic Press, 1979.

[5]   J. R. Webster and T. P. Ehrman, “Solute Dynamics,” In: F. R. Hauer and G. A. Lamberti, ed., Methods in Stream Ecology, Academic Press, Inc., San Diego, Calif., 1996, pp. 145 -160.

[6]   R. Runkel, D. M. McKnight and H. Rajaram, “Modeling hyporheic zone processes”, Advance Water Resources, Vol. 26, No. 9, 2003, pp. 901-905.

[7]   G.I. Taylor, “The dispersion of matter in turbulent flow through a pipe,” In: Proceedings of the Royal Society London Series A, Vol. 123, 1954, pp. 446-468.

[8]   H.B. Fischer, “The Mechanics of Dispersion in Natural Streams,” Journal Hydraulics Division Proceedings, ASCE, Vol. 93, No. 6, 1967, pp.187-216.

[9]   H.B. Fischer, “Dispersion Predictions in Natural Streams,” Journal Sanitary Engineering Division, ASCE, Vol. 94, No. SA5, 1968, pp. 927-943.

[10]   E. L Thackston, and K. B Schnelle, “Predicting effects of dead zones on stream mixing”. Journal of the Sanitary Engineering Division. Proceeding of The American Society of Civil Engineering, Vol. 96, No. 2, 1970, pp. 319- 331.

[11]   K. E. Bencala and R. A. Walters, “Simulation of solute transport in a mountain pool and riffle stream: a transient storage model,” Water Resources Research, Vol. 19, No. 3, 1983, pp. 718-724.

[12]   C. F. Nordin and B. M. Troutman, 1980. “Longitudinal dispersion in rivers: the persistence of skewness in observed data,” Water Resources Research, Vol. 16, No. 1, 1980, pp.123-128.

[13]   E. M. Valentine, and I. R. Wood, “Longitudinal dispersion with dead zones”. Journal of the Hydraulics Division, Vol.103, No. HY9, 1977, pp. 975-991.

[14]   R. L. Runkel, “One-dimensional transport with inflow and storage (OTIS): a solute transport model for streams and rivers (WRIR 98-4018),” US Geological Survey, Denver, CO 73 pp. 1998.

[15]   Y.Ge and M. Boufadel, “Solute transport in multiple-reach experiments: Evaluation of parameters and reliability of prediction,” Journal of Hydrology, Vol. 323, No. 1-4, May 2006, pp. 106-119.

[16]   M. Gabriel, “The role of geomorphology in the transport of conservative solutes in streams. M.S. thesis, Temple University, Philadelphia, 2001.

[17]   P. A. Carling and H.G. Orr, “Morphology of riffle-pool sequences in the river severn,” England. Earth Surface Processes and Landforms, Vol. 25, No. 4, 2000, pp. 369- 384.

[18]   A.Chin, “The periodic nature of step-pool mountain streams,” American Journal of Science, Vol. 302, February 2002. pp. 144-167.

[19]   DHI Water and Environment, 2003. MIKE 21- Coastal Hydraulic and Oceanography(Hydrodynamic Module: Scientific Documentation; Advection-Dispersion Module: Scientific Documentation).

[20]   J. C. Rutherford, “River mixing,” John Wiley and Sons, New York, 1994.