Abstract

LOZADA, Beatriz I  and  SENTELHAS, Paulo C. Relationships between water deficits and water surplus estimated by the normal and serial climatic water balance. Bioagro [online]. 2003, vol.15, n.3, pp.209-216. ISSN 1316-3361.

The climatic water balance, estimated with normal or average potential evapotranspiration and rainfall data, does not consider the inter-annual variability of these parameters, then eventually water deficits and water surplus could not be detected respectively in humid and dry climates when this method is used. In this study, it was determined the possible variation and the relationship between water deficits and water surplus estimated by the normal and serial climatic water balance. Climatic data from seven localities in Venezuela were used, ranging the records from 21 to 53 years. The water balance was estimated by Thornthwaite and Mather method. The results showed that most of the water deficits and water surplus values were underestimated when normal water balance was used. In this case, the water deficits values were lower than 25% of probability and the water surplus were between 25% and 50% of probability. When the averages of water deficits and water surplus were determined by the serial climatic water balance they were near or higher than 50% of probability, showing a better estimation of the actual conditions. These results were used to establish the relationship between the variables estimated by both methods (normal and serial water balance) being found a very good fit: r² = 0.986** for water deficits and r² = 0.947** for water surplus.

Keywords : Climate; hydrology; inter-annual variability; Thornthwaite and Mather.