The “River Memory” Effect: An Attempt to Understand and Model it

Abstract

Observations made by people working with retention reservoirs indicate that for standard, most common hydro-meteorological conditions, the majority of water in those lakes remains stagnant while almost all the discharge is carried by a relatively narrow current. This phenomenon is commonly called “the memory of the river” as that current appears often in locations close to the original bed of the river as it had been before the lake dam has been built. Such a behavior seems to appear not only when there are remnants of the old bed in the lake bathymetry, but also when there is no trace of the old bed. To the author’s knowledge, no theoretical study of this phenomenon exists so far. Hardly any articles about it can be found. The common intuition is that the formula for turbulent viscosity should be changed from Newtonian, linear one to something more sophisticated. In this article, the use of the Stribeck viscosity formula is proposed to explain water behavior for very small flow velocities (v ≤ 10⁻⁴ m/s) that normally occur in retention lakes. Physical justification, computational formulas changes proposals, and simplified simulation results are all presented.