Wasteload allocations(WLA) and total maximum daliy load(TMDL) determined with the lowest streaflow(e.g., 7Q10) may violate water quality standards as streamflow increases. Traditionally, streamflow increase is considered to monotonically improve the worst water quality (e.g., dissolved oxygen) which occurs at the lowest streamflow. This conventional worst case assumption might not be held because of parameter changes with streamflow increase which include increased non-point source discharges, varying decay (k₁ and reaeration (k₂ coefficients and reduced residence times. These parameter changes were hypothetically tested here to see the possible violation of the assumption. The results of this study indicate that unless the dependence of decay coefficient on streamflow is high and positive($gt;0.11), the worst case assumption will be valid in most natural channels. However, in highly regulated and polluted streams, the possibility of the violation was also observed. Since some of our major streams are well regulated for many purposes and sometimes observed highly polluted, the study results suggest that use of the lowest streamflow might be inappropriate for wasteload allocations. Rather, a trial and error approach is suggested. The approach develops wasteload allocation plans; tests them for a number of low streamflow conditions; and finds a best one. For this, computer models will be iteratively used.