Variability of Darcian Flux in the Hyporheic Zone at a Natural Channel Bend

Water 2017, 9(3), 170; doi:10.3390/w9030170

Author 

Shaofeng Xu ¹

, Jinxi Song ^1,2,* , Weiwei Jiang ³

, Guotao Zhang ¹

, Ming Wen ¹

, Junlong Zhang ¹

 and Ying Xue ¹

¹

College of Urban and Environmental Sciences, Northwest University, Xi’an 710127, China

²

State Key Laboratory of Soil Erosion and Dryland Farming on the Loess Plateau, Institute of Soil and Water Conservation, Chines Academy of Science and Ministry of Water Resources, Yangling 712100, China

³

College of Water Sciences, Beijing Normal University, Beijing 100875, China

^*

Author to whom correspondence should be addressed. 

Academic Editor: Karl-Erich Lindenschmidt

Received: 13 December 2016 / Revised: 11 February 2017 / Accepted: 12 February 2017 / Published: 27 February 2017

View Full-Text   |     Download PDF [7180 KB, uploaded 27 February 2017]   |    

 Browse Figures

 

Abstract 

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 (K_v), 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 K_v; high percentages of silt and clay sediments generally lead to low K_v values. Higher K_v at the depositional left bank at the upstream site shifted toward the erosional right bank at the downstream site, with K_v values positively correlated with the water depth. This study suggested that the variabilities of K_v and VHG were influenced by the stream geomorphology and that the distribution of K_v was inversely related, to a certain extent, to the distribution of VHG across the channel bend. K_v and VHG were found to have opposite effects on the DF, and the close relationship between K_v and DF indicated that the water fluxes were mainly controlled by K_v. View Full-Text

Keywords: hyporheic zone;  Darcian flux;  channel bend;  vertical hydraulic conductivity;  stream topography;  grain size;  porosity

▼ Figures

Figure 1

This is an open access article distributed under the Creative Commons Attribution License which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. (CC BY 4.0).

For further details log on website :
http://www.mdpi.com/2073-4441/9/3/170