2025-03-09 中国科学院（CAS）
＜関連情報＞
- https://english.cas.cn/newsroom/research_news/earth/202503/t20250310_903500.shtml
- https://agupubs.onlinelibrary.wiley.com/doi/10.1029/2024GL112674
- https://www.sciencedirect.com/science/article/abs/pii/S0022169424015063
高頻度土壌水分モニタリングによる複雑な地形を持つ小規模丘陵斜面における土壌厚による優先流の制御 Regulation of Preferential Flow by Soil Thickness on Small Hillslopes With Complex Topography Through Intensive High-Frequency Soil Moisture Monitoring
Jun Zhang, Sheng Wang, Zhiyong Fu, Fa Wang, Kelin Wang, Hongsong Chen
Geophysical Research Letters Published: 04 March 2025
DOI:https://doi.org/10.1029/2024GL112674
Abstract
Preferential flow (PF) is a relatively rapid water movement that significantly impacts geophysical processes. However, identifying PF and its environmental control mechanisms remains challenging, primarily due to soil spatial heterogeneity. In this study, 20 sensors were installed on two hillslopes with distinct soil thicknesses to monitor moisture at 5-min intervals. PF types were identified based on moisture response sequence to rainfall across layers, and relationships among PF frequency (PFF), soil depth, and rainfall characteristics were determined. Macropore flow was the main PF type, followed by soil‒bedrock interface flow. On the hillslope with deep soil cover, PFF was significantly negatively correlated with soil depth. Comparison, on the hillslope with shallow soil cover, PFF was not influenced by soil depth but more notably controlled by rainfall intensity and antecedent soil moisture. Accordingly, these findings highlight the critical roles of the soil thickness in shaping PF characteristics.
Key Points
- Both macropore and soil‒bedrock interface lateral preferential flows (PFs) were identified by soil moisture sensors
- A linear relationship between the soil depth and PF frequency was observed on a hillslope with an average soil thickness of 60 cm
- PFs are more notably affected by rainfall characteristics on hillslopes with shallow soil cover than on those with deep soil cover
Plain Language Summary
Preferential flow is a crucial type of soil water movement that allows water to follow priority paths through macropores or along interfaces with varying permeabilities, thereby bypassing the soil matrix to reach deeper layers or flow laterally. In karst regions, notable dissolution of carbonate rocks leads to highly spatially heterogeneous soil development, rendering the mechanisms underlying PF difficult to identify. Thus, our understanding of the pace of karst hydrological processes is limited. In this study, moisture sensors were employed for high-frequency, high-density dynamic observations of soil moisture on hillslopes, the type of PF was identified on the basis of response sequences, and the relationships among PF, soil depth, and rainfall characteristics were analyzed. Our study revealed the influence of the spatial distribution of the soil depth, which is a key surface parameter, on PF. The findings offer mechanistic insights into geophysical processes in complex hillslope regions, such as runoff and solute transport, and thus may facilitate the improvement in regional water management and flood control efforts.
複雑な丘陵斜面における急速な浸透プロセスの特性化： 降雨イベントに対する土壌水分応答からの洞察 Characterizing rapid infiltration processes on complex hillslopes: Insights from soil moisture response to rainfall events
Jun Zhang, Sheng Wang, Zhiyong Fu, Kelin Wang, Hongsong Chen
Journal of Hydrology Available online: 29 September 2024
DOI:https://doi.org/10.1016/j.jhydrol.2024.132110
Highlights
- Soil moisture response time to rainfall lengthens with topography uplift.
- Soil infiltrate in shallow soil hillslope faster than thick soil hillslope.
- Rainfall traits’ effect on soil moisture response exceeds antecedent moisture.
- Shallow soil-covered hillslopes are more influenced by rainfall characteristics.
Abstract
Evaluating the soil moisture response characteristics to rainfall events is valuable for understanding eco-hydrological effects in the context of global climate change. However, the effects of soil thickness and rainfall characteristic indicators on soil moisture responses remain unclear, especially in the karst hillslopes characterized by highly complex topography. This study examined the soil moisture response to 35 rainfall events at 5-min intervals by deploying 20 sets of monitoring devices across two hillslope plots (5 × 20 m) with distinct mean soil thicknesses. The response metrics included the soil moisture response time (Tp2p) and wetting front velocity (Vwf), whereas indicator factors considered were soil thickness distribution, slope position, and rainfall characteristics. Overall, the results showed that Tp2p increased from downslope to upslope, as well as from the surface to deep layers. Surprisingly, the mean Vwf (1373 mm h−1) in this study site was significantly higher than that in non-karst regions (17–610 mm h−1). This suggests that rainwater can rapidly infiltrate the soil profile and contribute to subsurface runoff generation. Rainfall characteristics are the primary controlling factors influencing the soil moisture response to rainfall, with their contribution priority (44.3–63.9 %) higher than that of antecedent soil moisture conditions (26.1–35.2 %). The variation in soil moisture response metrics in shallow soil cover hillslopes was more affected by rainfall indicators (41–64 % vs. 31–47 %), thereby potentially weakening the potential influence of topography and soil properties. These findings highlight the effect of refined monitoring in characterizing soil moisture heterogeneity in response to rainfall and emphasize the potential impact of rapid responses on karst eco-hydrological processes.
