Preferential flow, diffuse flow, and perching in an interbedded fractured-rock unsaturated zone

Nimmo, John R.; Creasey, K. M.; Perkins, K. S.; Mirus, Benjamin B.

doi:10.1007/s10040-016-1496-6

Cited by 10 publications

(11 citation statements)

References 39 publications

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“…To achieve broader applications, Nimmo et al. (2017) recommended the extension to the transient case as a further development of their model for quantification of flow through sedimentary layers. This would allow their model to predict "early‐stage travel times and lateral travel times in perched layers, important for events of relatively short duration, and also estimate the time and conditions required to establish steadiness."…”

Section: Resultsmentioning

confidence: 99%

A methodology for simulating perched conditions in multilayer aquifer systems with 2D variably saturated flow

Aguilera

Heredia

Román

2021

Vadose Zone Journal

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Simulatingflow through multilayer aquifer systems is essential for groundwater management applications such evaluating natural recharge, assessing managed aquifer recharge (MAR), the characterization of surface water–groundwater interactions, and groundwater pollution risk analysis. However, dealing with flow through variably saturated porous media with perched water tables is a difficult task. Usual codes for groundwater flow modeling such as MODFLOW, TOUGH2, and FEFLOW require tedious procedures based on simplified assumptions and approximations. This paper presents a simple approach to simulate two‐dimensional flow through perched aquifers and aquitards in deep vadose zones by combining the Dirichlet and Neumann boundary conditions that may apply to any code simulating unsaturated flow. The proposed approach is illustrated with the unsaturated flow code VS2DTI. The main strengths of the proposed methodology are (a) variably saturated flow in the multilayer system is solved using Richards’ equation, taking into account the lateral flow that sustains observed water levels in perched aquifers and variations in recharge; (b) a Dirichlet‐type boundary condition at the top perched water table is substituted by a Neumann‐type boundary condition, allowing for the representation of any disturbance (e.g., infiltration from ponds, pumping from wells, etc.), regardless of duration and intensity; and (c) the impact of the disturbance is evaluated by comparing the responses of the undisturbed and the disturbed systems. The versatility of this methodology is applied to a MAR case study of a deep aquifer in a sedimentary basin where aquitards limit its feasibility.

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Section: Resultsmentioning

confidence: 99%

A methodology for simulating perched conditions in multilayer aquifer systems with 2D variably saturated flow

Aguilera

Heredia

Román

2021

Vadose Zone Journal

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“…Even though substantial efforts have been made to uncover the hydraulic behaviours of unsaturated flow through the single fracture-matrix system [7,[27][28][29][30], there is still a lack of laboratory experiments for the determination of unsaturated hydraulic properties, including suction and saturation, under fracture/matrix interactions. Here, we followed the methods of Zhong et al [31] to present an experimental apparatus for assessing unsaturated fluid flow through an analog fracture-matrix system.…”

Section: Introductionmentioning

confidence: 99%

Experimental Study of Rainfall Infiltration in an Analog Fracture‐matrix System

Zhong

Gao

2021

Advances in Materials Science and Engineering

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In this study, an experimental apparatus was developed to investigate unsaturated infiltration in an analog fracture-matrix system. Fracture and adjacent matrix is simulated by sands with various particle sizes. Four rainfall infiltration experiments were performed on the analog fracture-matrix system at a constant rainfall rate of 100 mm/h. The process of rainfall infiltration is measured by a combination method of tensiometers and quick moisture apparatus. The measured results reveal that fracture-matrix interactions certainly exert influences on the hydraulic behaviour of unsaturated fractured matrix, and the fluid flow mainly infiltrates along the nonuniform paths within the matrix. Moreover, it is observed that the influences are greater when using a coarser sand to mimic the fracture. Specifically, the wetting phase in the matrix moves faster than that in the fracture; the fracture, therefore, acts as a vertical capillary barrier, but there exists lateral water exchange from the matrix to the fracture. Overall, this study has demonstrated the importance of fracture/matrix interactions, which should be considered when dealing with unsaturated flow through permeable matrices.

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“…into bedrock, where hydraulic (Nimmo et al, 2017) and biological (Leshem, 1970) processes can differ significantly from soils. This bedrock retains relict primary rock structures such as bedding or joint planes, and in some cases, can be so weathered as to be called a C-horizon or saprolite.…”

mentioning

confidence: 99%

Evidence for widespread woody plant use of water stored in bedrock

McCormick

Dralle

Hahm

et al. 2021

Preprint

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Woody plant transpiration is a major control on Earth’s climate system, streamﬂow, and human water supply. Soils are widely considered to be the primary reservoir of water for woody plants, however, plants also access water stored in the fractures and pores of bedrock, either as rock moisture (water stored in the unsaturated zone) (Schwinning, 2010) or bedrock groundwater (below the water table) (Miller et al., 2010). Bedrock as a water source for plants has not been evaluated over large scales, and consequently, its importance to terrestrial water and carbon cycling is poorly known (Fan et al., 2019). Here, we show that woody plants routinely access signiﬁcant quantities of water stored in bedrock —commonly as rock moisture —for transpiration across diverse climates and biomes. For example, in California, the volume of bedrock water transpired by woody vegetation annually exceeds that stored in man-made reservoirs, and woody vegetation that withdraws bedrock water accounts for over 50% of the aboveground carbon stocks in the state. Our ﬁndings show that bedrock water storage dynamics are a critical element of terrestrial water cycling and therefore necessary to capture the effect of shifting climate on woody ecosystems, above- and belowground carbon storage, and water resources.

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Preferential flow, diffuse flow, and perching in an interbedded fractured-rock unsaturated zone

Cited by 10 publications

References 39 publications

A methodology for simulating perched conditions in multilayer aquifer systems with 2D variably saturated flow

A methodology for simulating perched conditions in multilayer aquifer systems with 2D variably saturated flow

Experimental Study of Rainfall Infiltration in an Analog Fracture‐matrix System

Evidence for widespread woody plant use of water stored in bedrock

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