Influence of Hyporheic Exchange on Solute Transport in a Highly Hydropower Regulated River

Set in the downstream riparian zone of Xin’an River Dam, this paper established a 2D transversal coupling flow and solute transport and reaction model by verification within situ groundwater level and temperature. The denitrifying methods and principles in the riparian zone from the perspective of hyporheic exchange were explored, which provided a basis for the engineering techniques for river ecological restoration. Our studies have shown that under the condition of water level fluctuation, a biological method such as adding denitrifying bacteria biomass to a fixed degree (the same below) can greatly increase the denitrifying rate (1.52 g/d) in the riparian zone; chemical methods such as adding organic carbon into the surface water or groundwater can increase the total riparian nitrate removal (8.00–8.18 g) and its efficiency (19.5–20.0%) to a great extent; hydrogeological methods such as silt cleaning of the aquifer surface or local pumping around the contaminated area can increase the total riparian nitrate removal (1.06–14.8 g) to some extent, but correspondingly reduce the denitrifying efficiency (0.95–1.4%); physical methods such as designing the bank form into gentle slope or concave shape can slightly increase the total riparian nitrate removal (0.22–0.52 g) and correspondingly improve the denitrifying efficiency (0.25–0.85%). At the application level of river ecological restoration, integrated adopting the above methods can make the riparian denitrifying effect “fast and good”.

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Impact of dam operations on hyporheic exchange in the riparian zone of a regulated river

Hydrological Processes ◽

10.1002/hyp.7324 ◽

2009 ◽

Vol 23 (15) ◽

pp. 2129-2137 ◽

Cited By ~ 114

Author(s):

Audrey Hucks Sawyer ◽

M. Bayani Cardenas ◽

Ashleigh Bomar ◽

Meredith Mackey

Keyword(s):

Riparian Zone ◽

Regulated River ◽

Hyporheic Exchange

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Influence of Streambed Heterogeneity on Hyporheic Flow and Sorptive Solute Transport

Water ◽

10.3390/w12061547 ◽

2020 ◽

Vol 12 (6) ◽

pp. 1547 ◽

Cited By ~ 1

Author(s):

Yuanhong Liu ◽

Corey D. Wallace ◽

Yaoquan Zhou ◽

Reza Ershadnia ◽

Faranak Behzadi ◽

...

Keyword(s):

Solute Transport ◽

Hyporheic Zone ◽

Preferential Flow ◽

Hyporheic Exchange ◽

Sorptive Capacity ◽

Hyporheic Flow ◽

Sedimentary Architecture ◽

Mixing Dynamics ◽

Facies Types ◽

Sediment Heterogeneity

The subsurface region where river water and groundwater actively mix (the hyporheic zone) plays an important role in conservative and reactive solute transport along rivers. Deposits of high-conductivity (K) sediments along rivers can strongly control hyporheic processes by channeling flow along preferential flow paths wherever they intersect the channel boundary. Our goal is to understand how sediment heterogeneity influences conservative and sorptive solute transport within hyporheic zones containing high- and low-K sediment facies types. The sedimentary architecture of high-K facies is modeled using commonly observed characteristics (e.g., volume proportion and mean length), and their spatial connectivity is quantified to evaluate its effect on hyporheic mixing dynamics. Numerical simulations incorporate physical and chemical heterogeneity by representing spatial variability in both K and in the sediment sorption distribution coefficient ( K d ). Sediment heterogeneity significantly enhances hyporheic exchange and skews solute breakthrough behavior, while in homogeneous sediments, interfacial flux and solute transport are instead controlled by geomorphology and local-scale riverbed topographies. The hyporheic zone is compressed in sediments with high sorptive capacity, which limits solute interactions to only a small portion of the sedimentary architecture and thus increases retention. Our results have practical implications for groundwater quality, including remediation strategies for contaminants of emerging concern.

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