The monitoring of each type of drought has been based on index that attempt to encapsulate then on regional and temporal basis. The results of those mathematical models on drought implications are associated with choosing the correct time scale that each drought concept should be analyzed. The study was based on monthly and ten day period precipitation average and its standard deviation, and the Kolmogorov-Smirnov test. The paper also compared the index departures with climate water balance parameters. The importance of using the correct time scale, when meteorological drought index (PDSI adap and SPI) or agricultural drought index (IPER) are been used was shown. While the study of the meteorological drought implications has to be done on times scales equal or bigger than the monthly, the agricultural impacts, has to be analyzed based on parameters that are directly associated with actual evapotranspiration of the crops and, even on shorts times scales, the establishment of an expected value of those parameters, that allow the quantification of an crop water surplus deficit, could be detected.
drought index; water surplus deficit; actual evapotranspiration
