Preprints
https://doi.org/10.5194/egusphere-2024-2177
https://doi.org/10.5194/egusphere-2024-2177
02 Sep 2024
 | 02 Sep 2024

Delayed Stormflow Generation in a Semi-humid Forested Watershed Controlled by Soil Water Storage and Groundwater

Zhen Cui and Fuqiang Tian

Abstract. An analysis by Cui et al. (2024) of stormflow responses to rainfall in a mountainous forested watershed in the semi-humid regions of North China identified a distinct threshold for bimodal rainfall-runoff events, where delayed stormflow appeared to be influenced by shallow groundwater. This study further investigates the processes driving these bimodal events, focusing on the dynamics of soil water content (SWC) and groundwater level (GWL) during storm events. The results show that delayed stormflow is governed by the interplay between SWC and GWL. Delayed stormflow is initiated when SWC exceeds the soil’s water storage capacity, while its timing and volume are determined by GWL fluctuations. During rainfall, SWC increases rapidly; if it does not reach the soil's water-holding capacity, it stabilizes after the rainfall ends. Conversely, if SWC surpasses the soil's storage capacity, it decreases rapidly post-rainfall, with the excess rainwater infiltrating deeper to recharge groundwater, leading to a gradual rise in GWL. As GWL rises, increased hydraulic conductivity facilitates the movement of shallow groundwater into the stream channel, resulting in delayed stormflow. Simultaneously, the effective connection area between the stream channel and adjacent hillslopes expands vertically. At specific high GWL thresholds, GWL responses across the watershed converge, significantly increasing groundwater discharge and reducing lag times, often causing the delayed stormflow peak to merge with the direct stormflow peak. These findings enhance our understanding of delayed stormflow generation in similar regions and contribute to refining runoff generation theories.

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Zhen Cui and Fuqiang Tian

Status: final response (author comments only)

Comment types: AC – author | RC – referee | CC – community | EC – editor | CEC – chief editor | : Report abuse
  • RC1: 'Comment on egusphere-2024-2177', Anonymous Referee #1, 08 Nov 2024
    • AC1: 'Reply on RC1', Zhen Cui, 29 Nov 2024
  • RC2: 'Comment on egusphere-2024-2177', Anonymous Referee #2, 14 Nov 2024
    • AC2: 'Reply on RC2', Zhen Cui, 29 Nov 2024
Zhen Cui and Fuqiang Tian
Zhen Cui and Fuqiang Tian

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Short summary
This study investigates stormflow patterns in a forested watershed in North China, revealing that delayed stormflow is influenced by soil water content and groundwater levels. When soil moisture exceeds its storage capacity, excess water recharges groundwater, which then flows into streams more slowly. As groundwater levels rise, they enhance water movement and connectivity, causing a delayed stormflow peak to merge with the direct stormflow peak.