Galster et al. (2006) use questionable data for two Pennsylvanian streams to misconstrue the dependence of streamfl ow on watershed area and urbanization. Their fi rst equation, Q = kA c , relates fl ow rate 'Q' (m 3 /s) to drainage area 'A' (m 2), using 'k,' "a measure of river base fl ow (m/s)" and 'c', "the scaling power dependency" (Galster, et al., 2006, p. 713) Their Table 3 reports both positive and negative values for k, and redefi nes its units as m 3 /s. Instead, Equation 1 requires that k be positive because both Q and A are positive, and that k has inconsistent units that depend on c. Because Table 3 reports that c ranges from 0.32 to 1.61 for different hydrographs in Sacony Creek (cf. Figure 1), k's units must vary from m +2.36 /s to m-0.22 /s. Such implausible and inconsistent units are one of many problems that arise when empirical relationships and log-log plots are misused in hydrology. The values Galster et al. list for k in Table 3, e.g.,-2.25 to +1.37 for Sacony Creek, actually are values of log k. Because the scale is logarithmic, this represents a >4,000 fold range for k, rendering it useless as a measure of base fl ow. Also, the various fi ts of Equation 1 to their data are poor and confl icting (Figure 1). Dates of occurrence are not reported for most discharge events used by Galster et al., and when they are, inconsistencies abound. Their Figure 2 caption states that the results are for "December 2004 to January 2005," yet their x-axis encompasses only June and July, 2005. None of the points shown in Figure 2 correspond in any way to Table 3, which is referenced

The problem involves turbulent diffusion of momentum, sensible heat, and water vapor in the lower atmosphere when a neutral, dry air mass encounters a warm, wet surface. The water surface temperature is specified, and the surface roughness is taken to be constant over land and water. The turbulent fluxes are formulated by a semiempirical turbulence theory with the Businger‐Dyer form of the Monin‐Obukhov similarity functions, a water vapor buoyancy term in the Obukhov stability length, and Blackadar's scaling height in the mixing length. The resulting solution of the equations of conservation shows that the stability discontinuity at the leading edge can greatly affect the mean rate of evaporation and that the vertical vapor flux can greatly contribute to the atmospheric stability. The solution is relatively insensitive to the exact form of the Monin‐Obukhov similarity functions or to the exactness of Reynolds' analogy or von Karman's constant. For large fetches and near‐neutral conditions the solution becomes similar to that obtained in Sutton's problem and with Harbeck's empirical formula.

The melt from a ripe snowpack due to sensible and latent heat flux is considered. The problem is two‐ dimensional; the snow field has a well‐defined leading edge. The equations that describe the airflow over the snow are the conservation of momentum, sensible heat, and water vapor. The turbulent diffusion is formulated by semi‐empirical turbulence theory. The solution shows the manner in which the point melt varies downwind from the leading edge and the average melt varies with the fetch of the snowpack for varying degrees of atmospheric stability conditions. The results indicate that a reasonably accurate estimate of total melt can be achieved by using the one‐dimensional formulae with temperature, humidity, and velocity measurements taken over the central part of the snow field.

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