Hydrological drought assessment in Northern Victoria, Australia

Drought forecasting plays an important role in the planning and management of water resources. Drought Indices based on meteorology (rainfall) are the most popular tool for monitoring, assessing and predicting drought events. Standardized Hydrological Drought Index (SHDI) is a recently developed index with a greater potential to use in water management due to simplicity and applicability across time and spatial scales. The aim of this study is to assess the hydrological drought defined by SHDI, at 8 hydro-meteorological stations in Northern Victoria of Australia over the period 1970 -2010. The popular meteorological drought index, the Standardized Precipitation Index (SPI) which is similar to SHDI is used as the reference drought index. SPI and SHDI values were calculated at 3 month and 12 month time steps. The study showed that all sub-catchments experienced moderate, severe or extreme drought events in 1971-73, 1976-77, 1982-83, 1994-95, 1996-97, 2001-03 and 2006-08 periods based on both indices. SHDI showed a delay in drought onset and termination compared to SPI during the major drought events. Severity of the hydrological drought is higher than that of the meteorological drought when the drought condition is prolonged as in the Millennium drought (2001-09). The greatest drought intensity was recorded during the 1982-83 drought events in all stations. Hydrological processes such as runoff, infiltration and evapotranspiration which depend on catchment physiographic characteristics define the relationship between the meteorological drought and the hydrological drought.