降水强度对定海土壤饱和度、地表径流的定量影响

Quantitative Impact of Precipitation Intensity on Soil Saturation and Surface Runoff in Dinghai

摘要: 通过处理分析定海区2023年1月至2024年12月的日尺度土壤墒情(10 cm、20 cm、30 cm、40 cm深度)、降水量及城北水库水位，引入水库集雨面积和水面面积将水位变化转换为径流深，系统分析了降水强度、土壤饱和度与地表径流之间的定量关系。结果表明：(1) 表层土壤(10~20 cm)饱和度与径流深的相关性最高，深层土壤(30~40 cm)响应存在1~2天滞后；(2) 季节性差异显著：春季表层主导(10 cm)，夏季中层影响突出(20 cm)，冬季表层与深层同步(10 cm与40 cm)；(3) 基于168次产流事件的多元线性回归分析，得到最优关系式为：径流深 = 四日前降水量 × 0.40 + 土壤饱和度 × 0.15 − 0.77，其中土壤饱和度高度显著(p < 0.001)，四日前降水量为正但边际显著(p = 0.182)，表明径流主要受土壤饱和度控制，降水的影响存在约4天的滞后；(4) 典型事件分析验证了土壤饱和度的决定性作用：2024年5月13日4.37 mm降水在土壤饱和度高达40.9%时产生10.67 mm径流，而2023年11月27日101.5 mm降水因土壤饱和度仅1.7%未产流。研究成果可为定海城区洪涝预警、水库调度提供科学依据。

Abstract: Through processing and analysis of daily-scale soil moisture data (at depths of 10 cm, 20 cm, 30 cm, and 40 cm), precipitation records, and water level data of the Chengbei Reservoir in the Dinghai District from January 2023 to December 2024, this study quantitatively investigated the relationships among precipitation intensity, soil saturation, and surface runoff. By introducing the reservoir’s catchment area and water surface area, water level fluctuations were converted into runoff depth. The results indicate that: (1) The correlation between surface soil saturation (10~20 cm) and runoff depth is the highest, while the response of deeper soil layers (30~40 cm) exhibits a lag of 1~2 days. (2) Significant seasonal differences were observed: the surface layer (10 cm) dominates in spring, the middle layer (20 cm) has a prominent influence in summer, and the surface and deep layers (10 cm and 40 cm) show synchronized effects in winter. (3) Multiple linear regression analysis based on 168 runoff-generating events yielded the optimal relationship: Runoff Depth = (Precipitation from four days prior) × 0.40 + (Soil Saturation) × 0.15 − 0.77. In this equation, soil saturation is highly significant (p < 0.001), while precipitation from four days prior is positive but marginally significant (p = 0.182), indicating that runoff is primarily controlled by soil saturation, with the influence of precipitation exhibiting a lag of approximately 4 days. (4) Typical event analysis validated the decisive role of soil saturation: a 4.37 mm rainfall event on May 13, 2024, generated 10.67 mm of runoff when soil saturation was as high as 40.9%, whereas a 101.5 mm rainfall event on November 27, 2023, produced no runoff due to soil saturation being only 1.7%. The research findings can provide a scientific basis for flood early warning and reservoir operation in the Dinghai urban area.