Estimation of monthly stream flows based on the sequential water budget technique applied to the Thornthwaite potential evapotranspiration

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.