Temporal and spatial scales of lake processes. Part 1: physical and ecological scales, non-dimensional parameters and flow regimes

Abstract

Scaling concepts, related to basic physical transport and mixing processes and other ecological
 aspects in lakes, are reviewed in an ecohydrodynamic perspective; the length and time scales as
 well as the non-dimensional parameters governing the various flow regimes and relevant to these
 processes are also presented, emphasizing the influence they have on lake ecosystems. The
 hierarchy of length scales is very important in determining both the turbulence structure, and in
 affecting the ecological processes occurring in lakes. Most of these scales are defined in terms of
 several basic parameters which, when combined properly, yield important dimensionless numbers,
 as: Rf, Ri, Pr, T, Ret, Frt, Grt, and Prt, the flux and gradient Richardson numbers, the Prandtl
 number, a dimensionless time, and the turbulent Reynolds, Froude, Grasshof and Prandtl numbers,
 respectively. A few more dimensionless numbers (as the Lake and Wedderburn numbers, LΝ, W,
 etc.) are also useful in characterizing the general dynamic behavior of lakes. Ratios of length or time
 scales may also provide similar useful parameters.