Regionalization Of Hydrologic Information: Establishment Of Flow Series At Ungauged Watersheds
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M. M. Portela & A. C. Quintela
In previous papers the authors have shown that the mean annual flow expressed as water depth over the watershed—mean annual flow depth, H —provides an accurate measure of the temporal variability (within the year and throughout the years) of the natural flow regime in Portuguese rivers and therefore can be adopted as a regionalization parameter of hydrologic information. The analysis then presented focused mainly on the annual and monthly flows, the daily flow temporal variability having been only briefly mentioned. In this paper the flow series regionalization subject is more deeply developed, not only at the monthly level—by including a considerably large number of results—but especially by presenting new results at the daily level. Additional approaches that confirm the relationship between the characteristics of the daily flow series and H are presented and procedures that enable the establishing of mean daily flow series at ungauged watersheds are included. Keywords: mean annual flow depth, temporal relative variability of flow series, hydrologic information regionalization, mean daily flow, ungauged watershed. 1 Introduction: previous works of the authors Portela and Quintela ,  and  showed that the mean annual flow expressed as water depth over the watershed – mean annual flow depth, H – is closely related with the relative temporal variability (within the year and among the years) of the flow regime in Portuguese rivers, providing a powerful parameter that enables flow regionalization and, therefore, the establishment of flow series at ungauged watersheds.
mean annual flow depth, temporal relative variability of flow series, hydrologic information regionalization, mean daily flow, ungauged watershed.