Author details

5. Conclusions

stations of Table 1.

Figure 5.

Average and standard-deviation of EVP and EV0 (mm)

Average and standard-deviation of EVP and EV0 (mm)

correlated.

102

The main conclusions of this study are as follows:

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i. The method of Thornthwaite yields to monthly potential evapotranspirations clearly smaller than those resulting from the Penman-Monteith method, thus confirming that the former method underestimates the potential

0

Averages and standard deviation of the monthly series of EVP, EV0, HP, and H0 in some of the climatologic

50

100

150

**Vila Real (06K/01)**

> **Viseu (10J/01**

Average and standard-deviation of HP and H0 (mm)

Average and standard-deviation of HP and H0 (mm)

Current Practice in Fluvial Geomorphology - Dynamics and Diversity

Average and standard-deviation of EVP and EV (mm)

> Average of EVP Standard-deviation of EVP Average of EV0 Standard-deviation of EV0 Average of HP Standard-deviation of HP Average of H0 Standard-deviation of H0

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**Alcobaça/E. Fruticultura (16D/06)**

Average and standard-deviation of HP and H0 (mm)

evapotranspiration in Mainland Portugal. Nevertheless, the Thornthwaite and

evapotranspiration of Thornthwaite slightly higher than those resulting from

coefficients between surface runoffs obtained via one or the other potential

Penman-Monteith monthly potential evapotranspirations are highly

ii. For most of the studied climatological stations, the Thornthwaite water balance model resulted in monthly surface runoffs based on the

the Penman-Monteith evapotranspiration. However, the correlation

iii. The differences between monthly surface runoffs obtained by the water balance model considering the Thornthwaite or the Penman-Monteith potential evapotranspirations are much smaller than the differences between those evapotranspirations and may even become negligible, particularly in

According to the previous results, one may conclude that, despite its poor data requirements, the potential evapotranspiration of Thornthwaite combined with the simplest water balance model provides a feasible and accurate approach (i) to fill in the gaps of monthly flow series, (ii) to increase the spans of such series, and (iii) to

evapotranspiration are most of the time very high.

the wetter areas of Portugal.

estimate monthly flows at ungauged catchments.

Maria Manuela Portela<sup>1</sup> \*, João Santos<sup>2</sup> and Ticiana Marinho de Carvalho Studart<sup>3</sup>

1 Civil Engineering Research and Innovation for Sustainability (CERIS), Instituto Superior Técnico/Lisbon University (IST/UL), Lisbon, Portugal

2 Department of Engineering, ESTIG, Beja, Portugal

3 Department of Hydraulics and Environmental Engineering, Federal University of Ceará, Fortaleza, Ceará, Brazil

\*Address all correspondence to: maria.manuela.portela@ist.utl.pt

© 2019 The Author(s). Licensee IntechOpen. This chapter is distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/ by/3.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.
