Emerald ash borer (EAB) ( Agrilus planipennis Fairmaire), an invasive, phloem-feeding beetle native to Asia, has killed millions of ash ( Fraxinus spp.) trees in North America since it was detected in southeast Michigan in 2002. Consistently high mortality of black ash ( Fraxinus nigra) and green ash ( F. pennsylvanica) which often occur in riparian forests is a concern given their role in regulating soil moisture and shallow groundwater levels. We monitored hydrologic processes in a riparian forest in southwest Michigan to assess impacts of EAB invasion and subsequent ash mortality. From 2018-2022, we recorded soil moisture, depth to groundwater and meteorological variables at 15-min intervals throughout the growing season in a canopy gap following EAB-caused ash mortality and in adjacent, unaffected forest in the Augusta Creek riparian zone. Groundwater contributions to evapotranspiration (ET _G) were estimated using a groundwater level fluctuation (WLF) method. Significant differences in volumetric soil moisture content (16-26% higher in the gap than forest), average depth to water (10 cm in the gap vs 70 cm below land surface in the forest) and mean daily ET _G (0.6 in the gap vs 3.0 mm per day in the forest) persisted across four growing seasons. Within the gap, prolonged saturation of the near surface may be contributing to a shift from a forested riparian ecosystem to herb and sedge-dominated wetland. These differences have implications for an array of riparian zone ecosystem services, a concern given the extent of ash mortality already sustained in much eastern North America.