Mixing Enhancement Mechanisms in Aquifers Affected by Hydropeaking: Insights From Flow‐Through Laboratory Experiments

Self Cite

Section: Discussionmentioning

confidence: 99%

Drought Conditions Enhance Groundwater Table Fluctuations Caused by Hydropower Plant Management

Hazas

Marcolini

Castagna

et al. 2022

Self Cite

“…Finally, the surface and groundwater flow were assumed to be steady state in both laboratory setup and numerical models. However, the HE is strongly enhanced by hydropeaking as revealed by Ziliotto et al (2021) who investigated the mixing enhancements in HZ by flow alteration using laboratory experiments. The hyporheic flow field may become more complex and the HE characteristics such as scale and RT of HE may change over time due to the dynamics in Q.…”

Section: Study Limitationsmentioning

confidence: 99%

Hyporheic Exchange in a Straight Stream With Alternate Bars

Huang

Chui

2022

Hyporheic exchange (HE) refers to the exchange of water and substances between surface water and saturated sediments, and the region involved in this exchange is termed as hyporheic zone (HZ) (Elliott & Brooks, 1997a;Harvey & Bencala, 1993;Vaux, 1968). The downwelling surface water actively carries various dissolved and suspended matters into the HZ, supporting stratified faunas such as microorganism and invertebrate, etc. The upwelling groundwater generally contains rich nutrients, forming hot-spots of primary production in the stream. Thus, the HE is vital to fundamental reactions in HZ (Tonina & Buffington, 2011) and is very important for the upkeeping of stream ecosystem functions and water quality in a stream. Therefore, the HE in streams has received increasing attention of studies in past decades (e.g.,

“…Mixing‐induced reactions in porous media affect the transport, transformation and degradation of chemical and biological substances in subsurface environments (Dentz et al., 2011, 2023; Rolle & Le Borgne, 2019; Valocchi et al., 2019). Hence, they play a central role in a large range of applications such as hyporheic zone processes (Bandopadhyay et al., 2018; Hester et al., 2017; Ziliotto et al., 2021), freshwater‐saltwater mixing (De Vriendt et al., 2022), soil and groundwater remediation (Fu et al., 2014; Kitanidis & McCarty, 2012; Wang et al., 2022), geological carbon sequestration (Szulczewski et al., 2012; Zoback & Gorelick, 2012), hydrogen storage (Lysyy et al., 2022; Tarkowski, 2019) and geothermal systems (Burté et al., 2019). Reactions in porous media often occur in incompletely mixed conditions, where reactants are partly segregated and reaction rates are limited by mixing (de Anna, Dentz, et al., 2014; Gramling et al., 2002; Sole‐Mari et al., 2020).…”

Section: Introductionmentioning

confidence: 99%

Enhanced Mixing and Reaction in Converging Flows: Theory and Pore‐Scale Imaging

Izumoto

Heyman

Huisman

et al. 2023

Mixing fronts at the interface of opposing flows are compressed at a constant rate. The resulting exponential stretching of fluid elements leads to enhanced chemical gradients and biogeochemical processes. This process is similar as what occurs in the pore space of 3D chaotic flows. However, it is so far not known how such fluid compression controls the amplitude of mixing and reaction rates in porous media. Here we derive analytical predictions for the mixing width, the maximum reaction rate and the reaction intensity in compressed mixing fronts as a function of the Péclet and Damköhler numbers. We developed an experimental setup providing pore scale measurements of mixing and reaction rates in mixing fronts at the interface of converging flows. The theory accurately predicts the scaling of mixing and reaction with the Péclet number both in porous micromodels and simple Hele‐Shaw cells. Additionally, we found that the presence of pore scale heterogeneities in the porous micromodels enhances reaction rates by a factor of 4 compared to the Hele‐Shaw cells. Using numerical simulations of pore scale velocity fields, we attributed this phenomenon to the enhancement of pore‐scale compression due to the presence of grains in accelerating flows. These findings provide new insights into the dynamics of mixing‐induced reactions in porous media.