Palmer's drought indices revisited

Palmer's Hydrological and Meteorological Drought Severity Indices are reviewed along with a number of recent modifications that help reduce ambiguity from decision concerning the beginning and ending of drought conditions. Based on data from Regina, Saskatchewan, it is shown that the Meteorological Index, due to its greater sensitivity, responds at least one month faster to changing moisture conditions than the Hydrological Index and is consequently recommended for forward planning in water resource management and agriculture. Assumptions regarding differences in available water capacity of up to 100 mm resulted in maximum absolute differences of up to 0.30 in the Hydrological Index and 0.36 in the Meteorological Index, both evaluated as statistically non‐significant.