Temporal Variation of Drought Indices: A Case Study in Egirdir Lake Basin

Abstract

From the past to the present, many climate changes have occurred and have affected the world in a very large way. Especially towards the end of the 20th century, climatic changes and temperature increases. As a result, it brought various disasters with it. Drought has been one of the slowest and most dangerous disasters. Various calculation methods have been found for long-term drought. As one of the drought types, hydrological drought lasts for a long time; it poses more danger than other drought types. Since the importance of hydrological drought starts when the plant is planted in the soil and covers its life during the harvest, water is an effective parameter here. Therefore, hydrological drought is discussed in this study. One of the frequently used indexes in calculating hydrological drought is the Standard Precipitation Index (SPI) method developed by McKee et al. In a drought assessment made taking into account the Standardized Precipitation Index values, the period when the index is constantly negative is defined as the dry period. The first month in which the index falls below zero is considered the beginning of the drought, while the month when the index rises to a positive value is considered the end of the drought. The study area was obtained from Isparta Regional Meteorology General Directorate and rainfall data between 1929 and 2019 were taken. A total of 90 years of data were used. 12-month data sets were prepared. These data sets were organized and studied according to the type of calculation. According to the total drought classes of the average 90-year data of Isparta central district and the average annual drought of all months, drought was experienced for a period of 20 years.