Journal ArticleHow daily groundwater table drawdown affects the diel rhythm of hyporheic exchangeWu, Liwen; Gomez-Velez, Jesus D.; Krause, Stefan; Wörman, Anders; Singh, Tanu; Nützmann, Gunnar; Lewandowski, JörgnullAbstract. 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.2021-01-0110278132Hydrology and Earth System Sciences2541905 to 19211607-7938https://doi.org/10.5194/hess-25-1905-20212021015; 1830172; 2020814National Science Foundation