Variability of Darcian Flux in the Hyporheic Zone at a Natural Channel Bend
Channel bends are one of the most important characteristic features of natural streams. These bends often create the conditions for a hyporheic zone, which has been recognized as a critical component of stream ecosystems. The streambed vertical hydraulic conductivity (Kv), vertical hydraulic gradien...
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doaj-3b389cd120d84908b798de084ad82def2020-11-24T22:51:24ZengMDPI AGWater2073-44412017-02-019317010.3390/w9030170w9030170Variability of Darcian Flux in the Hyporheic Zone at a Natural Channel BendShaofeng Xu0Jinxi Song1Weiwei Jiang2Guotao Zhang3Ming Wen4Junlong Zhang5Ying Xue6College of Urban and Environmental Sciences, Northwest University, Xi’an 710127, ChinaCollege of Urban and Environmental Sciences, Northwest University, Xi’an 710127, ChinaCollege of Water Sciences, Beijing Normal University, Beijing 100875, ChinaCollege of Urban and Environmental Sciences, Northwest University, Xi’an 710127, ChinaCollege of Urban and Environmental Sciences, Northwest University, Xi’an 710127, ChinaCollege of Urban and Environmental Sciences, Northwest University, Xi’an 710127, ChinaCollege of Urban and Environmental Sciences, Northwest University, Xi’an 710127, ChinaChannel bends are one of the most important characteristic features of natural streams. These bends often create the conditions for a hyporheic zone, which has been recognized as a critical component of stream ecosystems. The streambed vertical hydraulic conductivity (Kv), vertical hydraulic gradient (VHG) and Darcian flux (DF) in the hyporheic zone were estimated at 61 locations along a channel bend of the Beiluo River during July 2015 and January 2016. All the streambed attributes showed great spatial variability along the channel bend. Both upward fluxes and downward fluxes occurred during the two test periods, most of studied stream sections were controlled by downwelling, indicating stream water discharge into the subsurface. The average downward flux was higher at the downstream side than at the upstream side of the channel bend, especially in July 2015. The distribution of streambed sediment grain size has a significant influence on the variability of Kv; high percentages of silt and clay sediments generally lead to low Kv values. Higher Kv at the depositional left bank at the upstream site shifted toward the erosional right bank at the downstream site, with Kv values positively correlated with the water depth. This study suggested that the variabilities of Kv and VHG were influenced by the stream geomorphology and that the distribution of Kv was inversely related, to a certain extent, to the distribution of VHG across the channel bend. Kv and VHG were found to have opposite effects on the DF, and the close relationship between Kv and DF indicated that the water fluxes were mainly controlled by Kv.http://www.mdpi.com/2073-4441/9/3/170hyporheic zoneDarcian fluxchannel bendvertical hydraulic conductivitystream topographygrain sizeporosity |
collection |
DOAJ |
language |
English |
format |
Article |
sources |
DOAJ |
author |
Shaofeng Xu Jinxi Song Weiwei Jiang Guotao Zhang Ming Wen Junlong Zhang Ying Xue |
spellingShingle |
Shaofeng Xu Jinxi Song Weiwei Jiang Guotao Zhang Ming Wen Junlong Zhang Ying Xue Variability of Darcian Flux in the Hyporheic Zone at a Natural Channel Bend Water hyporheic zone Darcian flux channel bend vertical hydraulic conductivity stream topography grain size porosity |
author_facet |
Shaofeng Xu Jinxi Song Weiwei Jiang Guotao Zhang Ming Wen Junlong Zhang Ying Xue |
author_sort |
Shaofeng Xu |
title |
Variability of Darcian Flux in the Hyporheic Zone at a Natural Channel Bend |
title_short |
Variability of Darcian Flux in the Hyporheic Zone at a Natural Channel Bend |
title_full |
Variability of Darcian Flux in the Hyporheic Zone at a Natural Channel Bend |
title_fullStr |
Variability of Darcian Flux in the Hyporheic Zone at a Natural Channel Bend |
title_full_unstemmed |
Variability of Darcian Flux in the Hyporheic Zone at a Natural Channel Bend |
title_sort |
variability of darcian flux in the hyporheic zone at a natural channel bend |
publisher |
MDPI AG |
series |
Water |
issn |
2073-4441 |
publishDate |
2017-02-01 |
description |
Channel bends are one of the most important characteristic features of natural streams. These bends often create the conditions for a hyporheic zone, which has been recognized as a critical component of stream ecosystems. The streambed vertical hydraulic conductivity (Kv), vertical hydraulic gradient (VHG) and Darcian flux (DF) in the hyporheic zone were estimated at 61 locations along a channel bend of the Beiluo River during July 2015 and January 2016. All the streambed attributes showed great spatial variability along the channel bend. Both upward fluxes and downward fluxes occurred during the two test periods, most of studied stream sections were controlled by downwelling, indicating stream water discharge into the subsurface. The average downward flux was higher at the downstream side than at the upstream side of the channel bend, especially in July 2015. The distribution of streambed sediment grain size has a significant influence on the variability of Kv; high percentages of silt and clay sediments generally lead to low Kv values. Higher Kv at the depositional left bank at the upstream site shifted toward the erosional right bank at the downstream site, with Kv values positively correlated with the water depth. This study suggested that the variabilities of Kv and VHG were influenced by the stream geomorphology and that the distribution of Kv was inversely related, to a certain extent, to the distribution of VHG across the channel bend. Kv and VHG were found to have opposite effects on the DF, and the close relationship between Kv and DF indicated that the water fluxes were mainly controlled by Kv. |
topic |
hyporheic zone Darcian flux channel bend vertical hydraulic conductivity stream topography grain size porosity |
url |
http://www.mdpi.com/2073-4441/9/3/170 |
work_keys_str_mv |
AT shaofengxu variabilityofdarcianfluxinthehyporheiczoneatanaturalchannelbend AT jinxisong variabilityofdarcianfluxinthehyporheiczoneatanaturalchannelbend AT weiweijiang variabilityofdarcianfluxinthehyporheiczoneatanaturalchannelbend AT guotaozhang variabilityofdarcianfluxinthehyporheiczoneatanaturalchannelbend AT mingwen variabilityofdarcianfluxinthehyporheiczoneatanaturalchannelbend AT junlongzhang variabilityofdarcianfluxinthehyporheiczoneatanaturalchannelbend AT yingxue variabilityofdarcianfluxinthehyporheiczoneatanaturalchannelbend |
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