Using Standardized Groundwater Index and Standardized Precipitation Index to Assess Drought Characteristics of the Kaoping River Basin, Taiwan

In the present study, long-term monitoring data were collected from the study area of the Kaoping River Basin, Taiwan. Specifically, data from six selected groundwater level stations and six precipitation stations in the vicinity were collected between 1997 and 2014. The standardized groundwater index (SGI) and standardized precipitation index (SPI) were then used to analyze the region's drought characteristics. The results revealed that continuous droughts occurred in the river basin from 2003 to 2005. The trend for 2014 further indicated that the drought situation in the region would worsen in terms of severity. After calculation and analysis of the cross correlation function between the SGI and the SPI, a positive correlation was identified between the maximum cross correlation function (q(max)) and the duration of the drought event. The larger the q(max) value, the longer was the duration of the drought, and vice versa. The study also found that the q(max) value varied with geographical locations: it was smaller for the various measuring stations located along the Qishan and Laonong rivers, but it tended to be larger for stations located beyond the Ailiao River. Thus, this study reckoned that if a drought event were to occur in the latter area in the future, its duration would be relatively longer. The findings of this study could also serve as future reference for the water resources management of the Kaoping River Basin.