Drought Propagation in the Lindis Catchment, Central Otago, New Zealand: An Event Based Analysis of Historical and Future Climate

Drought, which is recognized as a slowly evolving natural hazard occurring globally in all climates regardless of precipitation patterns, has the potential to lead to societal disruptions, economic and agricultural impacts and ecosystem breakdowns. Future projections show precipitation patterns changing and drought worsening in many parts of the world from rising temperatures due to climate change. Drought propagation refers to the transmission of water deficits from one part of the hydrological cycle to another. Here, the focus is on the propagation of meteorological (i.e. precipitation) drought water deficits (MD) into hydrological (i.e. streamflow) drought (HD) in the Lindis catchment, Central Otago. The Lindis Catchment lies on the eastern side of the Southern Alps in the rain shadow and as a result, the lower catchment is one of the driest parts of New Zealand. Using a daily precipitation threshold of 5 mm, combined with percentiles of daily streamflow, the coincidence of MD and HD events is analyzed according to their timing, magnitude, and duration. An analysis is conducted to observe how these may be modified under late-century (2080-2096) climate change scenarios relative to a baseline period (2006-2022). The HBV-Light rainfall runoff model is employed to simulate the Lindis catchment for this purpose using downscaled data for the SSP 2-45 scenario from a series of GCMs for 2080-2096. Along with increases in precipitation, temperature, and the amplification of the seasonal runoff cycle observed in previous studies, drought propagation dynamics exhibit a shift toward a quicker propagation from meteorological to hydrological drought within the Lindis Catchment. Mild streamflow drought occurrence increases by more than double and propagation time is decreased by more than two weeks at moderate drought thresholds. The study highlights the complex ways in which precipitation deficits of different characteristics can combine to influence streamflow under both present and future climates – findings that have important implications for managing water allocation, ecological health, and possible climate change adaptation options.