Drought recovery in terrestrial and riverine ecosystems of the CONUS: Considering vegetation productivity and water quality

Drought has severe impacts on the structure and functionality of terrestrial and riverine ecosystems. The mechanism and duration of drought recovery are critical subjects that can have crucial ramifications for ecology, crop yield, carbon uptake, and ecosystem services, and it has not been thoroughly investigated. This study assesses drought recovery of terrestrial and riverine ecosystems for agricultural and hydrological droughts, respectively. Soil moisture simulations from Phase 2 of the North American Land Data Assimilation System (NLDAS-2) are employed to characterize agricultural drought, and streamflow data from the United States Geological Survey (USGS) are utilized for assessing hydrological droughts. Drought recovery for riverine ecosystems is studied considering both quantity and quality of streamflow. Water temperature, dissolved oxygen, and turbidity are the water quality variables considered in this study. Riverine drought recovery is assessed using a multi-stage framework that is applied to 400 streamflow stations across the CONUS for the study period of 1950-2016. On the other hand, terrestrial drought recovery is investigated utilizing ecosystem Gross Primary Productivity (GPP), a metric of photosynthetic activity, for the regions impacted by agricultural drought. GPP data is acquired from the Moderate resolution Imaging Spectroradiometer (MODIS) sensor onboard Terra satellite at 1km spatial resolution and 8-day temporal resolution across the CONUS during 2000 to 2015. The drought affected regions are assumed to be recovered when the post-drought GPP reverts to its regional average value. Results show that in general, riverine drought recovery takes about two months when considering water quality variables, whereas terrestrial drought recovery duration varies between 1 to 4 months depending on drought severity. Additionally, results indicate that drought recovery duration is positively correlated with drought severity.