Dépendance à la profondeur et modèles exponentiels de perméabilité dans des cônes de déjection graveleux

Sakata, Yoshitaka; Ikeda, Ryuji

doi:10.1007/s10040-013-0961-8

Cited by 19 publications

(13 citation statements)

References 43 publications

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“…In general, porosity and permeability of continental crusts decrease with depth, and over depths of kilometers, the decrease appears linear in competent rocks such as sandstone and exponential in less competent rocks such as shale and mudstone (e.g., Kuang & Jiao, ; Manning & Ingebritsen, ; Saar & Manga, ; Shmonov et al, ; Stober, ). At depths of meters to tens of meters that are more relevant to ESM time scales, it is widely observed and modeled that porosity and permeability decrease exponentially with depth (Beven & Kirkby, ; Cardenas & Jiang, ; Decharme et al, ; Fan et al, ; Heimsath et al, ; Jiang et al, , ; Milly et al, ; Sakata & Ikeda, ; Wang et al, ). An exponential function with monotonic decrease with depth does not represent the sharp transitions or local reversals in porosity and permeability that are frequently found in sedimentary rocks, but it preserves the overall trend while integrating fluid flow over depth, circumventing the difficult problem of parameterizing fine‐scaled vertical heterogeneity.…”

Section: Representing Hillslope Hydrology In Esmsmentioning

confidence: 99%

Hillslope Hydrology in Global Change Research and Earth System Modeling

Fan

Clark

Lawrence

et al. 2019

Water Resources Research

344

319

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Earth System Models (ESMs) are essential tools for understanding and predicting global change, but they cannot explicitly resolve hillslope-scale terrain structures that fundamentally organize water, energy, and biogeochemical stores and fluxes at subgrid scales. Here we bring together hydrologists, Critical Zone scientists, and ESM developers, to explore how hillslope structures may modulate ESM grid-level water, energy, and biogeochemical fluxes. In contrast to the one-dimensional (1-D), 2-to 3-m deep, and free-draining soil hydrology in most ESM land models, we hypothesize that 3-D, lateral ridge-to-valley flow through shallow and deep paths and insolation contrasts between sunny and shady slopes are the top two globally quantifiable organizers of water and energy (and vegetation) within an ESM grid cell. We hypothesize that these two processes are likely to impact ESM predictions where (and when) water and/or energy are limiting. We further hypothesize that, if implemented in ESM land models, these processes will increase simulated continental water storage and residence time, buffering terrestrial ecosystems against seasonal and interannual droughts. We explore efficient ways to capture these mechanisms in ESMs and identify critical knowledge gaps preventing us from scaling up hillslope to global processes. One such gap is our extremely limited knowledge of the subsurface, where water is stored (supporting vegetation) and released to stream baseflow (supporting aquatic ecosystems). We conclude with a set of organizing

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Section: Representing Hillslope Hydrology In Esmsmentioning

confidence: 99%

Hillslope Hydrology in Global Change Research and Earth System Modeling

Fan

Clark

Lawrence

et al. 2019

Water Resources Research

344

319

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“…Direct measurements of K by slug tests (solid squares at DW‐1) might show unobvious decrease of K with depth because of the large variation of K in the Holocene gravel aquifer. Sakata and Ikeda () estimated the effective hydraulic conductivity

\overset{true‾}{K}

(open squares) from the core properties. A moving average analysis (solid line) revealed a vertical trend from the surface down to 30‐m depth, and was established as an exponential function of depth z (m):

\begin{matrix} \overline{K} = {\overset{true‾}{K}}_{0} \exp ((), - A z) \\ = 1 0^{- 2.3} \exp ((), - 0.11 z) at z < z_{0} \end{matrix}

…”

Section: Methodsmentioning

confidence: 99%

“…Aquifers II, III, and IV are described in the text. The vertical profile of Y was taken from Sakata and Ikeda (); solid squares, open squares, and solid line denote Y values measured by slug tests, Y values estimated from undisturbed cores, and moving averages of estimated Y , respectively.…”

Section: Methodsmentioning

confidence: 99%

Heat as a Tracer for Examining Depth‐Decaying Permeability in Gravel Deposits

Sakata

2014

Groundwater

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12Depth dependence of permeability can appear in any geologic setting; however, vertical trends 13 in alluvial gravel deposits are poorly understood because of the high variability of hydraulic 14 conductivity K in monotonic sequences. This paper examines the sensitivity of depth-decaying 15 permeability through heat transport simulation around a river's losing reach in the Toyohira River hydraulic gradient also appears in the observation wells for this analysis, as described below.

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“…There are unconfined gravel sequences, which constitute a groundwater reservoir with a total pumping rate of over 80,000 m 3 /d. River seepage is the main source for recharging groundwater (Hu et al 2010;Sakata and Ikeda, 2012), and the filtration process from the river to the deeper levels is controlled by the depth-decaying permeability of gravel deposits on a scale of tens of meters (Sakata and Ikeda, 2013). However, Monte Carlo simulation revealed the importance of heterogeneity on a smaller scale (1 m) for interpreting heat transport between surface water and groundwater (Sakata 2015).…”

Section: Case Studymentioning

confidence: 99%

Analysis of partially penetrating slug tests in a stratified formation by alternating piezometer and tube methods

Sakata

Imai²,

Ikeda

et al. 2015

Journal of Hydrology

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In partially penetrating slug tests, hydraulic conductivity (K) estimates might not necessarily be valid because of vertical flows in heterogeneous formations. We assess the error in hypothetical stratified formations by numerical sensitivity analysis, and propose an effective method for compensation by incorporating two types of casing configuration (piezometer and tube). The hypothetical stratified formation consists of completely horizontal layers, each 1 m thick; the permeability is different between, but not within, layers. In this study, conductivity estimates in the piezometer and tube methods are calculated by assigning various patterns of conductivity to the test, upper, and lower layers: K T , K U , and K L . The effect of vertical flow becomes significant when K T is small relative to K U or K L , and K L is more important than K U because the base of the borehole is open to the lower formation. The conductivity ratios (estimate over actual value) are treated as approximately linearly dependent on logarithms of K T /K U and K T /K L , so that conductivity estimates can be straightforwardly derived from one piezometer measurement and two tube measurements at the top and bottom of the screen. The linear relations are evaluated and constant parameters are determined under specific conditions. This study also recommends alternating piezometer and tube methods in the drilling procedure because the actual variation of K with depth is larger than that found using isolated measurements, as shown in a field study of alluvial fan gravel deposits in Sapporo, Japan. KeywordsSlug tests, Partially penetrating well, Hydraulic conductivity, Sensitivity analysis, Numerical simulation, Heterogeneity 1．IntroductionSlug tests are employed in both practical engineering and scientific studies to determine in situ hydraulic conductivity, K, by measuring the recovery of head in a single borehole after artificially raising or lowering the water level in the well. Although slug tests are sensitive to artificial and natural conditions in the well (e.g., Black, 2010), they are useful because they are simpler, cost less, and require less equipment than multiple pumping tests. It is also common for slug tests to have a logistical advantage, especially in groundwater contamination investigations. One reason is that slug tests can be conducted without removing or adding water, by lowering a solid piece of metal, called a slug, into a well, which does not disturb the site of suspected contamination. Another reason is that slug test results are related mainly to permeability on a small scale, and thus local information is directly relevant to preferential flow paths for contamination plumes. In addition, a series of slug tests at multiple depths aids in interpreting vertical variations of K.When such vertical profiles are interpolated among different locations, three dimensional distributions of K can be obtained for an individual site. Various previous studies have shown the spatial variability in K obtained from slug test an...

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Dépendance à la profondeur et modèles exponentiels de perméabilité dans des cônes de déjection graveleux

Cited by 19 publications

References 43 publications

Hillslope Hydrology in Global Change Research and Earth System Modeling

Hillslope Hydrology in Global Change Research and Earth System Modeling

Heat as a Tracer for Examining Depth‐Decaying Permeability in Gravel Deposits

Analysis of partially penetrating slug tests in a stratified formation by alternating piezometer and tube methods

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