The importance of groundwater as a resilient water supply has increased in recent years, and efforts are underway to achieve groundwater sustainability and reduce overdrafts in aquifers. However, understanding climate-groundwater feedbacks in coupled natural-human systems are complex given the groundwater response time to environmental drivers and challenges in quantifying recharge. In this talk, I will provide an overview of groundwater lag time and recovery to droughts across the Continental US using groundwater level observations from anthropogenically unaffected aquifers.  Next, I will focus on approaches for characterizing groundwater recharge in high-elevation mountainous critical zones, where mountain-valley aquifer connectivity is poorly understood.