Spatial synchrony, temporal clustering and dominant driver of streamflow droughts in Peninsular India

Abstract Understanding the spatio-temporal evolution of streamflow droughts and their relationship with potential causative processes is critical for effective drought management. This study assesses spatial synchrony and temporal clustering of streamflow droughts in six major river basins of Peninsular India. The importance of baseflow, rainfall deficits, soil moisture deficits and high temperatures in triggering streamflow droughts is also investigated to identify the dominant driver during the period 1981–2015. Spatial synchrony of streamflow droughts is investigated using multivariate Ripley’s K function and temporal clustering is evaluated using univariate Ripley’s K at various timescales. The interactions of streamflow droughts with potential causative processes are investigated using event coincidence analysis. At regional scale, streamflow droughts in peninsular catchments show strong spatial synchrony even at longer timescales. However, at basin scale, droughts in the catchments show strong spatial synchrony only at smaller timescales, behave independently of each other and achieve asynchrony with time, especially at longer timescales. Streamflow droughts show the strongest temporal clustering at smaller timescales and the strength of clustering decreases after a 3 year timescale. Rainfall deficits primarily control streamflow droughts in Peninsular India at a range of lags, except just before the onset of drought events where baseflow dominates. In addition, trigger coincidence rates of baseflow are lower than rainfall deficits but higher than soil moisture deficits and high temperatures at longer time lags.