Drought assessment with a surface-groundwater coupled model in the Chesapeake Bay watershed

An integrated framework of surface and groundwater models is essential for the comprehensive understanding of impacts of droughts due to surface water and subsurface exchanges. We evaluate the response of soil moisture and groundwater dynamics during drought in the Northern Atlantic Coastal Plain in the Chesapeake Bay Watershed. The Variable Infiltration Capacity model coupled with MODFLOW (VICMF) was implemented and several variables were used in the Multivariate Standardized Drought Index (MSDI) that consider multivariate perspectives of droughts. Three drought indices were derived (MSDI_PSV, MSDI_PSM, MSDI_PWM) (PSV: Precipitation and Soil moisture from VIC; PSM: Precipitation and Soil moisture from VICMF, PWM: Precipitation and WTE from VICMF), and the accuracy of the results was verified using a performance measure (Drought area Agreement (%); DA) and a statistical test to evaluate spatial extent of the drought areas. The MSDI_PWM showed better results for predicting drought events as it captured overall drought conditions.