Soil moisture thresholds for runoff generation: depth sensitivity and mechanistic controls
- 1Department of Hydraulic Engineering, State Key Laboratory of Hydroscience and Engineering, Tsinghua University, Beijing 100084, China
- 2Key Laboratory of Hydrosphere Sciences of the Ministry of Water Resources, Tsinghua University, Beijing 100084, China
Abstract
A compound wetness index combining antecedent soil moisture and event rainfall (S 0 = ASI 0 + P) is commonly used to analyze threshold-based runoff responses. However, it remains unclear how the depth of soil moisture integration affects threshold detection and predictive performance. Here, we examined the relationship between runoff thresholds and maximum integration depth (MID) across four experimental catchments spanning diverse climates and runoff generation mechanisms. Using segmented regression across multiple MIDs and monitoring sites, we identified runoff thresholds and evaluated the explanatory power of S 0 for stormflow using post-threshold coefficients of determination (R h 2 ). Thresholds were consistently detected across integration depths, but explanatory power varies strongly among catchments. In storage-controlled systems, R h 2 increased with depth, indicating that deeper soil moisture integration better captured subsurface storage controls on stormflow initiation. In contrast, in connectivity-limited or shallow flow-dominated systems, shallow integration depths performed better because near-surface wetting controlled preferential flow or infiltration-excess runoff, whereas deeper integration included hydrologically inactive storage. These results show that the optimal integration depth is catchment dependent and closely linked to dominant runoff generation processes. Accounting for this depth dependence can improve threshold-based runoff analysis and support more process-consistent soil moisture monitoring and hydrological modeling
Related
- Critical soil moisture thresholds reveal contrasting ecosystem responses across the tropics
- Cumulus parameterization controls simulated rainfall more than microphysics, but not at heavy thresholds: a 3 * 2 factorial WRF study over the Western Himalaya
- Hydroclimatic controls and interaction-driven sensitivity of reference evapotranspiration across Indian climate regimes
- Next-generation Metop ASCAT surface soil moisture datasets from EUMETSAT H SAF
- Controls on natural hydrogen generation during serpentinization of mantle rocks
BibTeX
@article{cui2026soil,
title = {{Soil moisture thresholds for runoff generation: depth sensitivity and mechanistic controls}},
author = {Zhen Cui and Fuqiang Tian},
journal = {Journal of Hydrology},
year = {2026},
month = jun,
doi = {10.1016/j.jhydrol.2026.135827},
url = {https://doi.org/10.1016/j.jhydrol.2026.135827},
note = {CC BY},
}
RIS
TY - JOUR
TI - Soil moisture thresholds for runoff generation: depth sensitivity and mechanistic controls
AU - Zhen Cui
AU - Fuqiang Tian
PY - 2026
DA - 2026/06/03
JO - Journal of Hydrology
DO - 10.1016/j.jhydrol.2026.135827
UR - https://doi.org/10.1016/j.jhydrol.2026.135827
AB - A compound wetness index combining antecedent soil moisture and event rainfall (S 0 = ASI 0 + P) is commonly used to analyze threshold-based runoff responses. However, it remains unclear how the depth of soil moisture integration affects threshold detection and predictive performance. Here, we examined the relationship between runoff thresholds and maximum integration depth (MID) across four experimental catchments spanning diverse climates and runoff generation mechanisms. Using segmented regression across multiple MIDs and monitoring sites, we identified runoff thresholds and evaluated the explanatory power of S 0 for stormflow using post-threshold coefficients of determination (R h 2 ). Thresholds were consistently detected across integration depths, but explanatory power varies strongly among catchments. In storage-controlled systems, R h 2 increased with depth, indicating that deeper soil moisture integration better captured subsurface storage controls on stormflow initiation. In contrast, in connectivity-limited or shallow flow-dominated systems, shallow integration depths performed better because near-surface wetting controlled preferential flow or infiltration-excess runoff, whereas deeper integration included hydrologically inactive storage. These results show that the optimal integration depth is catchment dependent and closely linked to dominant runoff generation processes. Accounting for this depth dependence can improve threshold-based runoff analysis and support more process-consistent soil moisture monitoring and hydrological modeling
SN - 0022-1694
SN - 1879-2707
ER -