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Residence time distributions in sinuosity‐driven hyporheic zones and their biogeochemical effects
Author(s) -
Gomez Jesus D.,
Wilson John L.,
Cardenas M. Bayani
Publication year - 2012
Publication title -
water resources research
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.863
H-Index - 217
eISSN - 1944-7973
pISSN - 0043-1397
DOI - 10.1029/2012wr012180
Subject(s) - biogeochemical cycle , sinuosity , watershed , hydrology (agriculture) , environmental science , hyporheic zone , residence time (fluid dynamics) , aquifer , hydraulic conductivity , soil science , geology , groundwater , geomorphology , surface water , ecology , environmental engineering , computer science , soil water , geotechnical engineering , machine learning , biology
Hyporheic exchange plays a key role in the biogeochemical evolution of water and in ecosystem functioning at the local, reach, and watershed scales. Residence time is a fundamental metric to describe the possible transformation taking place in this exchange zone. With this in mind, we use a simple conceptual model to explore the residence time distributions (RTDs) of sinuosity‐driven hyporheic zones (HZs) and to discriminate the individual effect of sinuosity ( σ ), valley slope ( J x ), hydraulic conductivity ( K ), aquifer dispersivity ( α L ), and the biogeochemical timescales (BTSs) that characterize the degradation of dissolved organic carbon in these hydrologic systems. We find that RTDs are characterized by one early mode and a late time power law behavior. For a given aquifer dispersivity, the shape of these distributions is stretched or compressed by changes in J x , K , and σ , having a strong influence on the net biogeochemical transformations within the HZ. Using BTSs proposed in previous studies and sensitivity analyses, we show the potential of σ , J x , and K to classify meander HZs as net sinks of nitrates or only modulators of the residence times in the subsurface where nitrate reduction is negligible. These findings can be used as predictive tools to quantify the potential of meanders as biogeochemical reactors at the watershed scale with the aid of remote sensing data and GIS processing techniques. These tools can guide experimental design, suggesting important locations to visit, sample, and/or instrument. Also, hyporheic restoration projects can use them for initial site selection and design of channel modifications.