A new analytical expression for ultimate specific yield and shallow groundwater drainage

Cheng, Donghui; Wang, Yuhong; Duan, Junyi; Chen, Xunhong; Yang, Sheng

doi:10.1002/hyp.10306

Cited by 16 publications

(27 citation statements)

References 15 publications

(20 reference statements)

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“…by means of Taylor series in Cheng et al . (), with increasing errors for larger water level changes.…”

Section: Introductionmentioning

confidence: 91%

“…Following Figure and the paragraph in the preceding text, the specific yield of the soil ( S y ,soil ) for a certain depth increment between zu and zl can be calculated as the difference of the integrals of two soil moisture profiles (∆ A soil = A zu ,soil − A zl ,soil ) of two water levels divided by ∆ z with the following equation (e.g. Crosbie et al ., and Cheng et al ., ):

S_{y, soil} = \frac{1}{normalΔ z} \cdot ((), A_{z u, soil} - A_{z l, soil}) = \frac{1}{normalΔ z} \cdot ((), \underset{A_{z u, soil}}{\underset{true⏟}{Δ z \cdot θ_{s} + \int_{z u}^{0} θ (z) d z}} - \underset{A_{z l, soil}}{\underset{true⏟}{true {true\int}_{z l}^{0} θ ((), z) d z}}) = θ_{s} - \frac{1}{normalΔ z} true {true\int}_{z u}^{z l} θ ((), z) d z

where zl is the lower and zu is the upper water level (∆ z = zu − zl ) with z being 0 at the soil surface (later in case of a microrelief, z = 0 corresponds to the mean elevation of the soil surface) and negative below the ground. θ ( z ) is the volumetric water content at pressure head h = z .…”

Section: Introductionmentioning

confidence: 99%

“…It equals the saturated water content θ s for pressure heads h > 0. Several authors gave analytical expressions for calculating S y based on the parameterization of the water retention function by Brooks and Corey () (Duke, ; Nachabe, ) and by van Genuchten () (Crosbie et al ., ; Cheng et al ., ) in the following referred as VG . It should be noted that analytical expressions calculating S y with VG as parameterization for θ are an approximation, e.g.…”

Section: Introductionmentioning

confidence: 99%

“…Following Figure 1 and the paragraph in the preceding text, the specific yield of the soil (S y,soil ) for a certain depth increment between zu and zl can be calculated as the difference of the integrals of two soil moisture profiles (ΔA soil = A zu,soil À A zl,soil ) of two water levels divided by Δz with the following equation (e.g. Crosbie et al, 2005 andCheng et al, 2015):…”

Section: Introductionmentioning

confidence: 99%

“…It should be noted that analytical expressions calculating S y with VG as parameterization for θ are an approximation, e.g. by means of Taylor series in Cheng et al (2015), with increasing errors for larger water level changes. For periods of inundation, S y is defined by the specific yield above the soil surface (S y,surface ), which is here assumed to be 1, which corresponds to an open water surface.…”

Section: Introductionmentioning

confidence: 99%

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One‐dimensional expression to calculate specific yield for shallow groundwater systems with microrelief

Dettmann¹,

Bechtold²

2015

Hydrol. Process.

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Although the importance to account for microrelief in the calculation of specific yields for shallow groundwater systems is well recognized, the microrelief influence is often treated very simplified, which can cause considerable errors. We provide a general onedimensional expression that correctly represents the effect of a microrelief on the total specific yield that is composed of the soil and surface specific yield. The one-dimensional expression can be applied for different soil hydraulic parameterizations and soil surface elevation frequency distributions. Applying different van Genuchten parameters and a simple linear microrelief model, we demonstrate that the specific yield is influenced by the microrelief not only when surface storage directly contributes to specific yield by (partial) inundation but also when water levels are lower than the minimum surface elevation. Compared with a simplified representation of the soil specific yield, in which a mean soil surface is assumed for the calculation of soil specific yield, the correct representation can lead to lower as well as higher soil specific yields depending on the specific interaction of the soil water retention characteristics and the microrelief. The new equation can be used to obtain more accurate evapotranspiration estimates from water level fluctuations and to account for the effect of microtopographic subgrid variability on simulated water levels of spatially distributed hydrological models.

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“…by means of Taylor series in Cheng et al . (), with increasing errors for larger water level changes.…”

Section: Introductionmentioning

confidence: 91%

S_{y, soil} = \frac{1}{normalΔ z} \cdot ((), A_{z u, soil} - A_{z l, soil}) = \frac{1}{normalΔ z} \cdot ((), \underset{A_{z u, soil}}{\underset{true⏟}{Δ z \cdot θ_{s} + \int_{z u}^{0} θ (z) d z}} - \underset{A_{z l, soil}}{\underset{true⏟}{true {true\int}_{z l}^{0} θ ((), z) d z}}) = θ_{s} - \frac{1}{normalΔ z} true {true\int}_{z u}^{z l} θ ((), z) d z

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 3 more Smart Citations

One‐dimensional expression to calculate specific yield for shallow groundwater systems with microrelief

Dettmann¹,

Bechtold²

2015

Hydrol. Process.

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A hydrographic method to identify the groundwater net recharge, barometric effect and evapotranspiration from a complicated semidiurnal water table fluctuation

Cheng

Yuan

2021

Hydrological Processes

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A hydrographic method was proposed to separate out the hourly scaled groundwater level changes caused by net recharge, barometric effects and evapotranspiration from a semidiurnal water table fluctuation. A characteristic midnight time, with a turning point of the barometric pressure change and high relative air humidity, which meant that neither the barometric effect nor groundwater evapotranspiration occurred, was proposed for determining the net recharge rate r net . Then, the barometric efficiency f bar was estimated using the other time period without evapotranspiration, and the evapotranspiration rate r ETG was finally obtained using the remainder of the water level changes. A case example illustrated that estimation of f bar using the proposed method was more accurate than that using the traditional error analysis method, which may result in a significant underestimation under the condition of the present water level changes. Additionally, the abnormal semidiurnal fluctuations, more specifically, two step-down fluctuations, which may be a common pattern when the groundwater level is controlled by net recharge, barometric effects and evapotranspiration, can be well understood using the three components separated out. The results also showed that nighttime groundwater evapotranspiration, accounting for an average of 23% of that during the daytime, cannot be ignored.

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A little relief: Ecological functions and autogenesis of wetland microtopography

et al. 2020

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Microtopography, or the small‐scale variation in ground surface height (10−1–100 m) over short (100–102 m) spatial scales, is a ubiquitous feature of wetlands globally. This variation in elevation, characterized by local high (“hummocks”) and low (“hollows”) patches, is more structured than what is observed in uplands, and is intertwined with concordantly structured spatiotemporal variability in hydrologic regimes and associated ecological processes. The importance of microtopography in wetlands is manifold, with critical influence on local hydrological, biogeochemical, and biological processes. Further, the creation and maintenance of wetland microtopography is a balance between activation processes (i.e., those that induce random elevation variation) and autogenic reinforcement processes (i.e., those that provide the feedbacks necessary for the persistence of microtopography). While there are many mechanisms that create vertical structure (e.g., tree falls, accumulation of roots and soil organic matter, and sediment deposition), they all yield a similar core feedback to enhance and sustain microtopographic structure. Finally, microtopography contributes to spatial patterning that confers emergent ecosystem‐scale functions such as hydrologic storage and flows, carbon cycling, organism dispersal, and biodiversity. There is an ongoing need to study the origins and implications of this fine‐scale variation in elevation, as well as the utility of including microtopography in model predictions and ecological restoration efforts. This article is categorized under: Water and Life > Conservation, Management, and Awareness

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A new analytical expression for ultimate specific yield and shallow groundwater drainage

Cited by 16 publications

References 15 publications

One‐dimensional expression to calculate specific yield for shallow groundwater systems with microrelief

One‐dimensional expression to calculate specific yield for shallow groundwater systems with microrelief

A hydrographic method to identify the groundwater net recharge, barometric effect and evapotranspiration from a complicated semidiurnal water table fluctuation

A little relief: Ecological functions and autogenesis of wetland microtopography

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