Assessment of meteorological and hydrological drought; a case study in Kirindi Oya river basin in Sri Lanka

A desk study was conducted to detect the changes in drought, their frequencies and trends in the Kirindi Oya river basin in Sri Lanka using standardised precipitation index (SPI) and streamflow drought index (SDI). The frequency of drought events was assessed using SPI and trend of SPI was also determined using Mann-Kendall and Sen's slope. The results based on SPI analysis indicated that hydrological years 1989-1990, 1991-1992, 2000-2001 and 2013-2014 were drought years and the year 1991-1992 was identified as a severe drought year in the Kirindi Oya river basin. The significant negative trend of SPI (-0.055) during July to September time scale indicates the increasing drying tendency of the entire basin. However, frequency of being dry of the basin in annual and April to September period is only 16% for the entire basin. Based on SDI, 2000-2001 and 2003-2004 were identified as hydrological drought years especially for the October to December period both at Thanamalwila and Wellawaya gauge stations in the basin.