Quantitative definition and spatiotemporal distribution of little water season (LIWAS) in Korea

Like other continental climatic regions Korea has a period around the spring when agricultural activities are interrupted frequently by a shortage of available water resources during the season. This season, which is termed the Little Water Season (LIWAS) in this study, has important implications for many socio-economic activities but the scientific definition of this season remains vague. In this study, the onset and termination dates, as well as the characteristics of the LIWAS have been defined based on the Available Water Resources Index (AWRI). Based on the proposed definition of LIWAS, the implications on hydrological conditions over a range of geographic scales and their inter-annual variations on the water resource environments in Korea have been assessed. To develop an appropriate index for LIWAS based on AWRI, the criterion value (CV) for LIWAS was set as the lowest 25th percentile of the AWRI values averaged for 30 years (1981-2010). Therefore, the Little Water Season for Korea (LIWAS_K) was considered as the period when the daily averaged AWRIs were successively lower than the CV (143.7 mm). Based on this, the mean onset and end date of LIWAS_K, was 9 February and 11 May which also reflected the period in the spring season when the available water resources are expected to the lowest. Moreover, a number of seasonal characteristics of the water availability during the LIWAS, such as the Little Water Intensity (LWI), Water Deficit Amount (WDA) and Water Deficit Intensity (WDI) have been defined for the particular study region. Based on our results, we aver that the proposed season classification of the LIWAS can be better analyzed using the concept of usable water resources as a classification of dry period instead of using temperature and raw rainfall datasets