Daily baseflow values are required to characterize the environmental measurements being carried out in several basins in the Province of Genova, northern Italy. The main purpose of these measurements is the characterization of the environmental quality of the streams by means of the Extended Biological Index (EBI). The discharge values for the month preceding the EBI measurement are useful in distinguishing the different causes of index variation, which may be due to stage variations in a given period before measurement. Frequently, when the EBI was measured, the daily discharges were not known. The data at our disposal was limited to nearly 120 discharge measurements. Places and times of discharge measurement were different from those of EBI measurements. Information on the marginal distribution of daily flows, assumed to be a two-parameter log normal, was available for 16 other stations in the region, as well as for daily rainfalls at 20 stations. The research reported herein compares three different criteria used to obtain an estimate of the unknown daily flows and the mean discharge in the month preceding the EBI measurements.