Surface and groundwater drought impact on natural vegetation growth and drought recovery.

Droughts' persistent impact and growing use of surface water and groundwater will likely exacerbate hydrological droughts. Variations in precipitation patterns worsen the effects in particular catchment regions as a result to climate change. The end result is less groundwater recharge and multi-year droughts that impact vegetation and rivers.

An essential factor to better understand the recovery in catchments affected by drought is to understand the interaction between water availability and vegetation dynamics. At the same time, the vegetation recovery in terms of growth and productivity can also be assessed with this framework. In this study, we focus on natural catchments of central Chile which have experienced drought and multi-year drought periods with severe impacts on surface water and groundwater.

We collected 250 tree ring samples of 5 species that are susceptible to droughts in central Chile in natural catchments, and used CAMELS-CL for statistical analysis. Cross correlation analysis between surface, groundwater and vegetation dynamics was performed for each catchment to quantify the interaction between these factors. To further determine the influence of drought events on vegetation, the compound NDVI correlation and SPEI at a catchment level were used. Finally, the drought termination framework was applied to understand the recovery response of surface, groundwater and vegetation.

Our analysis identifies the typical time lag between droughts in surface water, groundwater and  their impact on vegetation growth. This is done on an annual time scale as we are looking at multi-year events. We find that the typical response time varies throughout the country, depending on the local natural water availability. These findings highlight that the multi-year drought impact on vegetation and its recovery is not uniform and should be better understand in light of climate change and the global increase in multi-year drought events.