Standardized Groundwater Level Index refers to a groundwater drought index proposed by Bloomfield and Marchant (2013) as a standardized level that shows whether ground water level is higher or lower than the normal year value and the index is used to discern the drought level of non-supplied areas, which mainly rely on groundwater for water sources. A value lower than 0 means lower ground water level than the previous year.

SPI(Standardized Precipitation Index) is defined as a meteorological drought index. SPI3 is used to estimate the impact of each water source on drought by calculating rainfall deficit in units of three months for each observation station. SPI has an intensity scale in which both positive and negative values are calculated, which correlate directly to wet and dry events. Drought events are indicated when the results of SPI, for whichever timescale is being investigated, become continuously negative and reach a value of −1. The drought event is considered to be ongoing until SPI reaches a value of 0.

SPI(Standardized Precipitation Index) is defined as a meteorological drought index. SPI6 is used to estimate the impact of each water source on drought by calculating rainfall deficit in units of three months for each observation station. SPI has an intensity scale in which both positive and negative values are calculated, which correlate directly to wet and dry events. Drought events are indicated when the results of SPI, for whichever timescale is being investigated, become continuously negative and reach a value of −1. The drought event is considered to be ongoing until SPI reaches a value of 0.

PDSI(Palmer Drought Severity Index) is commonly used around the world. This index is calculated using monthly temperature and precipitation data along with information on the water-holding capacity of soils. It takes into account moisture received (precipitation) as well as moisture stored in the soil, accounting for the potential loss of moisture due to temperature influences. Since the index is used around the world, the code and output are widely available. Scientific literature contains numerous papers related to PDSI. The use of soil data and a total water balance methodology makes it quite robust for identifying drought.

SMI(Soil Moisture Index) represents drought conditions according to the effective water percentage of soil moisture. This is mainly used for agricultural drought estimations because it is calculated using precipitation, temperature, wind speed, humidity, soil, and physical characteristics data. The value of -1 indicates a weak drought state, and the lower the index value is, the more severe the drought condition is.

MSWSI(Modified Surface Water Supply Index) is used to supplement SWSI (Surface Water Supply Index) for considering hydrological droughts in Korea, a country which has complex terrain conditions and various water supply characteristics. The index is calculated using the amount of storm water, inflow of dam, river flow, and groundwater level of useful data among the hydrological parameters observed in Korea. Taking into account the full water resources of a basin provides a good indication of the overall hydrological health of a particular basin or region.

Drought Status