{"title":"实地测量土壤层中夹带的孔隙气压和地下水位上升的影响","authors":"Sho Iwagami, Shoji Noguchi, Takanori Shimizu, Tayoko Kubota, Shin'ichi Iida","doi":"10.1002/hyp.15235","DOIUrl":null,"url":null,"abstract":"<p>Unsaturated soil contains pore air, some of which becomes entrapped in the soil layer during the infiltration process. Such entrapped pore air in the soil layer inhibits infiltration, decreases hydraulic conductivity, and causes erroneous estimates of groundwater response. Experimental studies suggest an effect of compressed entrapped pore air on stream discharge. However, few studies have investigated the behaviour of pore air in the field, and no method for measurement of pore-air behaviour has been established. We measured pore-air pressure (<i>P</i><sub><i>air</i></sub>) with a simple handmade probe, combined with atmospheric pressure (<i>P</i><sub><i>atm</i></sub>) and groundwater level. The entrapment and compression of pore air were detected based on the pressure difference (<i>ΔP</i> = <i>P</i><sub><i>air</i></sub> – <i>P</i><sub><i>atm</i></sub>). Observations were conducted for approximately 1 year in two small headwater catchments (TC and HA, which have differences in soil depth and groundwater level dynamics) in Ibaraki Prefecture, Japan. Positive responses of <i>ΔP</i> during some rainfall events were confirmed at both TC and HA. Pore-air entrapment occurred even during weak rainfall events with rainfall intensity of <10 mm/h. During a typhoon event in October 2019, a maximum <i>ΔP</i> of 3.9 kPa was observed at HA. The pore pressure increase recorded by the tensiometer was mostly explained by the increase in <i>ΔP</i>, which was supported by the soil moisture data. Therefore, we concluded that our handmade measurement system could successfully measure <i>P</i><sub><i>air</i></sub> and detect pore-air entrapment in the field. This showed that <i>P</i><sub><i>air</i></sub> is not negligible. Total event rainfall was related to the maximum <i>ΔP</i>. It also showed that the rise in the groundwater level plays a significant role in pressurization of the entrapped pore air. We present the first field data demonstrating the effect of groundwater level rise on the pressurization of entrapped <i>P</i><sub><i>air</i></sub>.</p>","PeriodicalId":13189,"journal":{"name":"Hydrological Processes","volume":null,"pages":null},"PeriodicalIF":3.2000,"publicationDate":"2024-07-09","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":"0","resultStr":"{\"title\":\"Field measurement of entrapped pore-air pressure and the effect of rising groundwater level in the soil layer\",\"authors\":\"Sho Iwagami, Shoji Noguchi, Takanori Shimizu, Tayoko Kubota, Shin'ichi Iida\",\"doi\":\"10.1002/hyp.15235\",\"DOIUrl\":null,\"url\":null,\"abstract\":\"<p>Unsaturated soil contains pore air, some of which becomes entrapped in the soil layer during the infiltration process. Such entrapped pore air in the soil layer inhibits infiltration, decreases hydraulic conductivity, and causes erroneous estimates of groundwater response. Experimental studies suggest an effect of compressed entrapped pore air on stream discharge. However, few studies have investigated the behaviour of pore air in the field, and no method for measurement of pore-air behaviour has been established. We measured pore-air pressure (<i>P</i><sub><i>air</i></sub>) with a simple handmade probe, combined with atmospheric pressure (<i>P</i><sub><i>atm</i></sub>) and groundwater level. The entrapment and compression of pore air were detected based on the pressure difference (<i>ΔP</i> = <i>P</i><sub><i>air</i></sub> – <i>P</i><sub><i>atm</i></sub>). Observations were conducted for approximately 1 year in two small headwater catchments (TC and HA, which have differences in soil depth and groundwater level dynamics) in Ibaraki Prefecture, Japan. Positive responses of <i>ΔP</i> during some rainfall events were confirmed at both TC and HA. Pore-air entrapment occurred even during weak rainfall events with rainfall intensity of <10 mm/h. During a typhoon event in October 2019, a maximum <i>ΔP</i> of 3.9 kPa was observed at HA. The pore pressure increase recorded by the tensiometer was mostly explained by the increase in <i>ΔP</i>, which was supported by the soil moisture data. Therefore, we concluded that our handmade measurement system could successfully measure <i>P</i><sub><i>air</i></sub> and detect pore-air entrapment in the field. This showed that <i>P</i><sub><i>air</i></sub> is not negligible. Total event rainfall was related to the maximum <i>ΔP</i>. It also showed that the rise in the groundwater level plays a significant role in pressurization of the entrapped pore air. We present the first field data demonstrating the effect of groundwater level rise on the pressurization of entrapped <i>P</i><sub><i>air</i></sub>.</p>\",\"PeriodicalId\":13189,\"journal\":{\"name\":\"Hydrological Processes\",\"volume\":null,\"pages\":null},\"PeriodicalIF\":3.2000,\"publicationDate\":\"2024-07-09\",\"publicationTypes\":\"Journal Article\",\"fieldsOfStudy\":null,\"isOpenAccess\":false,\"openAccessPdf\":\"\",\"citationCount\":\"0\",\"resultStr\":null,\"platform\":\"Semanticscholar\",\"paperid\":null,\"PeriodicalName\":\"Hydrological Processes\",\"FirstCategoryId\":\"89\",\"ListUrlMain\":\"https://onlinelibrary.wiley.com/doi/10.1002/hyp.15235\",\"RegionNum\":3,\"RegionCategory\":\"地球科学\",\"ArticlePicture\":[],\"TitleCN\":null,\"AbstractTextCN\":null,\"PMCID\":null,\"EPubDate\":\"\",\"PubModel\":\"\",\"JCR\":\"Q1\",\"JCRName\":\"Environmental Science\",\"Score\":null,\"Total\":0}","platform":"Semanticscholar","paperid":null,"PeriodicalName":"Hydrological Processes","FirstCategoryId":"89","ListUrlMain":"https://onlinelibrary.wiley.com/doi/10.1002/hyp.15235","RegionNum":3,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":null,"EPubDate":"","PubModel":"","JCR":"Q1","JCRName":"Environmental Science","Score":null,"Total":0}
Field measurement of entrapped pore-air pressure and the effect of rising groundwater level in the soil layer
Unsaturated soil contains pore air, some of which becomes entrapped in the soil layer during the infiltration process. Such entrapped pore air in the soil layer inhibits infiltration, decreases hydraulic conductivity, and causes erroneous estimates of groundwater response. Experimental studies suggest an effect of compressed entrapped pore air on stream discharge. However, few studies have investigated the behaviour of pore air in the field, and no method for measurement of pore-air behaviour has been established. We measured pore-air pressure (Pair) with a simple handmade probe, combined with atmospheric pressure (Patm) and groundwater level. The entrapment and compression of pore air were detected based on the pressure difference (ΔP = Pair – Patm). Observations were conducted for approximately 1 year in two small headwater catchments (TC and HA, which have differences in soil depth and groundwater level dynamics) in Ibaraki Prefecture, Japan. Positive responses of ΔP during some rainfall events were confirmed at both TC and HA. Pore-air entrapment occurred even during weak rainfall events with rainfall intensity of <10 mm/h. During a typhoon event in October 2019, a maximum ΔP of 3.9 kPa was observed at HA. The pore pressure increase recorded by the tensiometer was mostly explained by the increase in ΔP, which was supported by the soil moisture data. Therefore, we concluded that our handmade measurement system could successfully measure Pair and detect pore-air entrapment in the field. This showed that Pair is not negligible. Total event rainfall was related to the maximum ΔP. It also showed that the rise in the groundwater level plays a significant role in pressurization of the entrapped pore air. We present the first field data demonstrating the effect of groundwater level rise on the pressurization of entrapped Pair.
期刊介绍:
Hydrological Processes is an international journal that publishes original scientific papers advancing understanding of the mechanisms underlying the movement and storage of water in the environment, and the interaction of water with geological, biogeochemical, atmospheric and ecological systems. Not all papers related to water resources are appropriate for submission to this journal; rather we seek papers that clearly articulate the role(s) of hydrological processes.