Author(s)

M. M. Portela & J. F. Santos

Abstract

In mainland Portugal, the measurement of stream flows started later than the measurement of the majority of the other hydrologic variables. Also the former measurements were not carried out systematically, thus resulting in stream flow series not only with several faults, but also with reduced length, circumstances that often compromise their utilization either for research or design purposes. Based on the records at sixteen Portuguese climatologic stations it is stressed that the sequential water budget technique applied to the Thornthwaite potential evapotranspiration may provide a monthly stream flow evaluation model having in view the fulfilment but, especially, the extension of monthly flow data. As the number of parameters and the data requirements of the previous technique and model are relatively modest it is possible, by that way, to estimate monthly stream flows even in regions with scarce hydrologic information. Keywords: sequential water budge, Thornthwaite and Penman-Monteith potential evapotranspirations, evaluation of monthly stream flows. 1 Introduction: scope of the study In Portugal mainland, the extensive and systematic measurement of stream flows started later than that of the majority of the other hydrologic variables. Furthermore, the corresponding series of flow records present not only frequent sporadic flaws but also long interruptions thereby limiting their use for both

Keywords

sequential water budge, Thornthwaite and Penman-Monteith potential evapotranspirations, evaluation of monthly stream flows.