引用本文:王承书,杨晓楠,孙文义,穆兴民,高 鹏,赵广举,宋小燕.极端暴雨条件下黄土丘陵沟壑区土壤蓄水能力和入渗规律[J].土壤学报,2020,57(2):296-306. DOI:10.11766/trxb201902190602
WANG Chengshu,YANG Xiaonan,SUN Wenyi,MU Xingmin,GAO Peng,ZHAO Guangju,SONG Xiaoyan.Soil Water Storage Capacity and Rainwater Infiltration in Hilly-Gully Loess Region under Severe Rainstorm[J].Acta Pedologica Sinica,2020,57(2):296-306. DOI:10.11766/trxb201902190602
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极端暴雨条件下黄土丘陵沟壑区土壤蓄水能力和入渗规律
王承书1, 杨晓楠1, 孙文义1, 穆兴民1, 高 鹏1, 赵广举1, 宋小燕2
1.西北农林科技大学土壤侵蚀与旱地农业国家重点实验室;2.西北农林科技大学水利与建筑工程学院
摘要:
黄土高原退耕还林还草工程实施后,下垫面环境条件的变化可能对流域水文过程、水文通量、水量平衡以及生态系统产生十分重要的影响。研究极端暴雨条件下剖面土壤蓄水能力和入渗规律,对于阐明流域产汇流过程和影响机制具有重要的科学价值。采用土壤墒情仪对陕北“7•26”特大暴雨事件下黄土丘陵沟壑区草地剖面土壤水分进行了实时动态监测,分析了极端暴雨条件下剖面土壤水分的动态变化和蓄水过程,利用Horton入渗模型模拟了剖面土壤水分湿润锋的运动过程,揭示了极端暴雨条件下剖面土壤水分的入渗规律。结果表明:(1)极端暴雨条件下,黄土丘陵沟壑区坡面草地不同深度层次土壤水分与降雨过程的响应不同,具有层次性和明显的滞后效应,其中,0~140 cm是影响该地区土壤水文过程的关键层次;(2)土壤水分再分配结束时,湿润锋最深深度达140 cm,土壤蓄水量达225.99 mm,较降雨前95.37 mm增加了1.37倍;(3)极端暴雨过程中湿润锋的运动随时间呈对数递减关系,其稳渗速率随容重增加而减小,呈指数函数递减;(4)极端降雨过程中该地区坡面草地的产流机制仍以超渗产流为主,对于揭示流域的产汇流机制和完善水文预报模型具有重要的科学意义。
关键词:  黄土丘陵沟壑区  7∙26极端暴雨  入渗过程  产汇流机制
基金项目:国家重点研发计划项目(2016YFC0402401)和国家青年科学基金项目(41501293)
Soil Water Storage Capacity and Rainwater Infiltration in Hilly-Gully Loess Region under Severe Rainstorm
WANG Chengshu1, YANG Xiaonan1, SUN Wenyi1, MU Xingmin1, GAO Peng1, ZHAO Guangju1, SONG Xiaoyan2
1.State Key Laboratory of Soil Erosion and Dryland Farming on the Loess Plateau, Northwest A&F University, Yangling;2.College of Water Resources and Architectural Engineering, Northwest A&F University, Yangling
Abstract:
【Objective】 Revegetation of the Loess Plateau, especially since the implementation of large-scaled “Grain for Green” projects, has brought about great changes in land surface coverage and underlying surface (or subsoil layer) of the plateau and altered significantly physical properties (soil structure, porosity, etc.) of the soil. Such dynamic changes in the environment may generate very important impacts on hydrological processes, hydrological fluxes, water balance, and ecosystems at a watershed scale. In recent years, rainfall-infiltration-runoff processes and their mechanisms as affected by global warming have become a hot topic in the field of hydrology. Therefore, the study to explore water storage capacity of and rainwater infiltration processes in soil profile under severe rainstorm may help expose processes and mechanisms of soil hydrology, soil erosion and surface runoff, and hence is of great scientific value to elucidation of processes of runoff generation and convergence and their influencing mechanisms. 【Method】In this paper, a real-time dynamic soil water monitoring system was used to monitor soil moisture layer by layer at 10 cm intervals in 2 m soil profiles in a tract of grassland in a hilly and gully loess region during the “7•26” severe rainstorm event in northern Shaanxi Province. Data of the rainfall event was obtained from the meteorological station of the region. Both rainfall data and soil moisture data were extracted at 1-hour intervals. Based on analysis of the rainfall and soil moisture data, dynamic changes, distribution characteristics and soil water storage capacity of the soil water in the profiles during the severe rainstorm event were acquired. And with the aid of the Horton infiltration model, movement and infiltration processes of the soil moisture wetting front in the grassland profiles were simulated. 【Result】Results show: (1) the response of soil moisture in the profile to the rainfall varied with process of the rainfall and depth of the soil layer. The soil profile could be divided into three layers, i.e. soil moisture quick-changing layer (0~ 60 cm), soil moisture active layer (70~ 140 cm) and soil moisture stable layer (150~ 200 cm), with soil water varying in the range of 15.49~ 16.72 mm, 2.01~13.27 mm and 0.22~ 0.44 mm, respectively; (2) The 0~140 cm soil layer is critical to the soil hydrological process in the profile, with average water storage being 26.49% higher than that of the 150~ 200 cm soil layer. The soil water storage of that layer could reach as high as 225.99 mm, 1.37 times its initial water storage capacity (95.37 mm). Thereinto, the 0~100 cm soil layer is the one with available soil water closely related to its grass cover; (3) In this area, soil infiltration depends on physical properties of the soil. Soil steady infiltration rate decreases with increasing soil bulk density, and the decrease declines in magnitude with risng bulk density, too;and (4) Rainwater infiltration rate on grassland hillslopes (P< 0.01) shows a decreasing trend with the time going. The attenuation is high in rate in the initial period and turns low. The infiltration rate varies exponentially with time. Cumulative infiltration (R2= 0.99, P< 0.01) shows a logarithmic relationship with wetting front movement process (R2= 0.99, P< 0.01) along the time series. The Horton infiltration model is suitable for simulation of the infiltration process (R2= 0.97, P< 0.01) as affected by severe rainstorm. 【Conclusion】During the severe rainstorm event, the mechanism of runoff generation is still dominated by infiltration excess runoff on hillslopes of the region. The increase in infiltration can reduce runoff volume and delay runoff generation to a certain extent, which has a significant impact on the mechanism of runoff generation.
Key words:  Hilly and gully loess region  7∙26 severe rainstorm  Infiltration process  Mechanism of runoff generation and convergence