This study investigates stormflow patterns in a forested watershed in north China, highlighting the fact that delayed stormflow is governed by soil water content (SWC) and groundwater level (GWL). When SWC exceeds its storage capacity, excess water infiltrates, recharging groundwater and gradually elevating GWL. Rising GWL enhances subsurface connectivity and lateral flow, synchronizing watershed responses and, in extreme cases, causing a delayed stormflow peak to merge with the direct stormflow peak.