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Hyporheic zones are commonly regarded as resilient and enduring interfaces between groundwater and surface water in river corridors. In particular, bedform-induced advective pumping hyporheic exchange (bedform-induced exchange) is often perceived as a relatively persistent mechanism in natural river systems driving water, solutes, and energy exchanges between the channel and its surrounding streambed sediments. Numerous studies have been based on this presumption. To evaluate the persistence of hyporheic zones under varying hydrologic conditions, we use a multi-physics framework to model advective pumping bedform-induced hyporheic exchange in response to a series of seasonal- and event-scale groundwater table fluctuation scenarios, which lead to episodic river-aquifer disconnections and reconnections. Our results suggest that hyporheic exchange is not as ubiquitous as generally assumed. Instead, the bedform-induced hyporheic exchange is restricted to a narrow range of conditions characterized by minor river-groundwater head differences, is intermittent, and can be easily obliterated by minor losing groundwater conditions. These findings shed light on the fragility of bedform-induced hyporheic exchange and have important implications for biogeochemical transformations along river corridors.
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How daily groundwater table drawdown affects the diel rhythm of hyporheic exchange
Abstract. Groundwater table dynamics extensively modify the volume of the hyporheic zoneand the rate of hyporheic exchange processes. Understanding the effects ofdaily groundwater table fluctuations on the tightly coupled flow and heattransport within hyporheic zones is crucial for water resourcesmanagement. With this aim in mind, a physically based model is used to explorehyporheic responses to varying groundwater table fluctuationscenarios. The effects of different timing and amplitude of groundwater tabledaily drawdowns under gaining and losing conditions are explored in hyporheiczones influenced by natural flood events and diel river temperaturefluctuations. We find that both diel river temperature fluctuations and dailygroundwater table drawdowns play important roles in determining thespatiotemporal variability of hyporheic exchange rates, temperature ofexfiltrating hyporheic fluxes, mean residence times, and hyporheicdenitrification potentials. Groundwater table dynamics present substantiallydistinct impacts on hyporheic exchange under gaining or losing conditions. Thetiming of groundwater table drawdown has a direct influence on hyporheicexchange rates and hyporheic buffering capacity on thermaldisturbances. Consequently, the selection of aquifer pumping regimes hassignificant impacts on the dispersal of pollutants in the aquifer and thermalheterogeneity in the sediment.
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- PAR ID:
- 10278132
- Date Published:
- Journal Name:
- Hydrology and Earth System Sciences
- Volume:
- 25
- Issue:
- 4
- ISSN:
- 1607-7938
- Page Range / eLocation ID:
- 1905 to 1921
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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- Free Publicly Accessible Full Text
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Accepted Manuscript
- Journal Article:
- https://doi.org/10.5194/hess-25-1905-2021
