Mechanisms of recharge in a fractured porous rock aquifer in a semi-arid region

Manna, F.; Walton, Kenneth M.; Cherry, John A.; Parker, Beth L.

doi:10.1016/j.jhydrol.2017.10.060

Cited by 31 publications

(39 citation statements)

References 45 publications

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“…For this reason, many semiarid regions have experienced a considerable reduction of groundwater storage as pumping has greatly exceeded natural recharge. Subsequently, researchers in these critical regions are focusing on studies aimed at understanding recharge processes and determining effective ways in which recharge can be enhanced naturally (Carrillo-Rivera, 2000, Carrera-Hernández et al, 2016, Manna et al, 2017, Müller et al, 2016Scanlon, et al, 2010;Sharda, et al, 2006). Groundwater recharge (GWR) refers to the entry of meteoric water across the water table after first entering the soil zone.…”

Section: Introductionmentioning

confidence: 99%

Estimation of natural groundwater recharge in the Aguascalientes semiarid valley, Mexico

Guerrero-Martínez¹,

Hernández-Marı́n²,

Burbey³

2018

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Groundwater recharge (GWR) is analyzed and evaluated within the Aguascalientes Valley by means of a modified linearized Boussinesq equation and the Water Table Fluctuations (WTF) technique. These techniques use the specific yield, water table variations and the subsurface drainage of groundwater. The methodology is applied to the semiarid Aguascalientes valley, which contains a thick vadose zone. The combination of the analytical solution based on the Boussinesq equation and the WTF technique, allows the method to be applied in areas with deep groundwater levels, such as the Aguascalientes valley, without the need for high temporal resolution data. The data for the application of the method were provided by various government agencies and includes information on 145 wells positioned within the valley during the period 1985-2015. The specific yield and the transmissivity were integrated from the results of two previous investigations. Results indicate that the variation of recharge ranges from 0.86 to 525.69 mm/year in the analyzed period, with the highest recharge rates occurring in the north and center parts of the valley and is likely attributed to high specific yield and vertical hydraulic conductivity due to the presence of coarse permeable soils present in the area. Conversely, the lowest recharge rates were found to occur near the north and south borders of the valley. RESUMENEn la presente investigación, la recarga de agua subterránea (GWR) se analiza y evalúa dentro del Valle de Aguascalientes mediante el ajuste a la ecuación linealizada de Boussinesq y la técnica Water Table Fluctuation (WTF), que involucra el rendimiento específico, la variación del nivel freático y el drenaje subsuperficial de aguas subterráneas. La metodología se aplica al semiárido valle de Aguascalientes que contiene una zona vadosa espesa. La combinación de la solución analítica basada en la ecuación de Boussinesq y la técnica WTF permite que el método se aplique en áreas con niveles profundos de aguas subterráneas, como el valle de Aguascalientes, sin la necesidad de datos de alta resolución temporal. Los datos para la aplicación del método fueron provistos por varias agencias gubernamentales a través de la información de 145 pozos ubicados a lo largo del valle durante el período 1985-2015. El rendimiento específico se integró a partir de los resultados de dos trabajos anteriores, así como la transmisividad. Como resultado, la variación de la altura de recarga se obtuvo de 0.86 a 525.69 mm/año en el período analizado, las tasas de recarga más altas se presentan al norte y al centro del valle, probablemente atribuidas a un alto rendimiento específico y conductividad hidráulica debido a la presencia de suelos permeables gruesos presentes en el área, por otro lado, las fronteras norte y sur del valle tienen las tasas de recarga más bajas.Palabras clave: recarga de agua subterránea; valle de Aguascalientes;

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Section: Introductionmentioning

confidence: 99%

Estimation of natural groundwater recharge in the Aguascalientes semiarid valley, Mexico

Guerrero-Martínez¹,

Hernández-Marı́n²,

Burbey³

2018

revmexcg

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“…The model was calibrated using measurements of runoff from instrumented outfall flows and quarterly observations of groundwater levels in 17 wells distributed across the catchment for the simulated period. The simulation results were also validated through comparison with previous independent recharge estimates based on application of the Chloride Mass Balance (Manna et al, 2016;Manna et al, 2017) and through the analysis of water isotopes from rainfall and groundwater that indicated the timing…”

Section: Pagementioning

confidence: 90%

“…mass balance (CMB), based on measurement of chloride in atmospheric deposition, surface water and groundwater, Manna et al (2016) estimated a long-term average recharge of 19 mm y -1 , corresponding to the 4.2 % of the average precipitation (455 mm for the period 1878-2014). More recently, Manna et al (2017) analyzed porewater Cl concentration profiles from the vadose and groundwater zones at 11 locations across the site. This provided spatially variable, long-term recharge values ranging from 4 to 23 mm y -1 and indicated that, on average, 80% of the flow in the vadose zone occurs as intergranular flow in the rock matrix and 20% as fracture flow.…”

Section: Pagementioning

confidence: 99%

“…of recharge. Finally, we proposed a conceptual model for various recharge conditions in the fractured sandstone aquifer based on the results of the MIKE SHE simulation along with findings of previous recharge studies for the site (Manna et al, 2016;Manna et al, 2017). In particular, the MIKE SHE simulations contributed to the conceptual model concerning the role of surface variability on the hydrological processes whereas the Cl-based studies informed the flow mechanisms in the underlying portion of the system.…”

Section: Pagementioning

confidence: 99%

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Spatial and temporal variability of groundwater recharge in a sandstone aquifer in a semi-arid region

Manna¹,

Murray²,

Abbey³

et al. 2018

Preprint

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Abstract. With the aim to understand the spatial and temporal variability of groundwater recharge, a high-resolution, spatially-distributed numerical model (MIKE SHE) representing surface water and groundwater was used to simulate responses to precipitation in a 2.16 km2 upland catchment on fractured sandstone near Los Angeles, California. Exceptionally high temporal and spatial resolution was used for this catchment modeling: an hourly time-step, a 20 × 20 meter grid in the horizontal plane and 240 numerical layers distributed vertically within the thick vadose zone and in the upper part of the groundwater zone. The finest-practical spatial and temporal resolution were selected to accommodate the large degree of surface and subsurface variability of catchment features. Physical property values for the different lithologies were assigned based on previous on-site investigations whereas the parameters controlling streamflow and evapotranspiration were derived from literature information. The calibration of streamflow at the outfall and of transient and average hydraulic head provided confidence in the reasonableness of these input values and in the ability of the model to reproduce observed processes. Confidence in the calibrated model was enhanced by validation through, (i) comparison of simulated average recharge to estimates based on the applications of the chloride mass-balance method from data from the groundwater and vadose zones within and beyond the catchment (Manna et al., 2016; Manna et al., 2017) and, (ii) comparison of the water isotope signature (18O and 2H) in shallow groundwater to the variability of isotope signatures for precipitation events over an annual cycle. The average simulated recharge across the catchment for the period 1995–2014 is 16 mm y−1 (4 % of the average annual precipitation), which is consistent with previous estimates obtained by using the chloride mass balance method (4.2 % of the average precipitation). However, one of the most unexpected results was that local recharge was simulated to vary from 0 to > 1000 mm y−1 due to episodic precipitation and overland runoff effects. This recharge occurs episodically with the major flux events at the bottom of the evapotranspiration zone, as simulated by MIKE SHE and confirmed by the isotope signatures, occurring only at the end of the rainy season. This is the first study that combines MIKE SHE simulations with the analysis of water isotopes in groundwater and rainfall to determine the timing of recharge processes in semi-arid regions. The study advances the understanding of recharge and unsaturated flow processes in semi-arid regions and enhances our ability to predict the effects of surface and subsurface features on recharge rates. This is crucial in highly heterogeneous contaminated sites because different contaminant source areas have widely varying recharge and, hence, groundwater fluxes impacting their mobility.

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“…Fractured rocks play a critically important role in a wide variety of geoscience problems including groundwater flow and contaminant transport, aquifer remediation, hydrocarbon extraction, geothermal resource exploitation and the long-term underground storage of CO 2 and nuclear waste (Geiger & Kolditz & Clauser 1998;Neuman 2005;Rotter et al 2008;Carneiro 2009;Emmanuel 2010;Follin et al 2014;Manna et al 2017;Zhao et al 2017). Numerous studies have been devoted to the development of methods for the identification and characterization of subsurface fractures and fracture networks, with the overall aim of improving conceptual and numerical models of flow and transport in fractured-rock environments (Bonnet et al 2001;Berkowitz 2002;Davy et al 2010;NAP 2015).…”

Section: Introductionmentioning

confidence: 99%

Comparison of REV size and tensor characteristics for the electrical and hydraulic conductivities in fractured rock

Demirel

Irving

Roubinet

2018

Geophysical Journal International

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The representative elementary volume (REV) is a critically important concept in fractured rock investigations as it tells us at what scale the fractured domain can be represented by an anisotropic tensor as opposed to requiring the details of each individual fracture for modelling purposes. Whereas the REV size and corresponding tensor characteristics for the hydraulic conductivity (K) in fractured rock have been the subject of numerous previous investigations, no studies to date have focused on the electrical conductivity (σ). This is despite the fact that geoelectrical measurements are arguably the most popular means of geophysically investigating fractured rock, typically via azimuthal resistivity surveying where the observed electrical anisotropy is commonly used to infer hydraulic characteristics. In this paper, we attempt to fill this void and present a systematic numerical study of the impacts of changes in fracturenetwork properties on the REV size and equivalent tensor characteristics for both the electrical and hydraulic conductivities. We employ a combined statistical and numerical approach where the size of the REV is estimated from the conductivity variability observed across multiple stochastic fracture-network realizations for various domain sizes. Two important differences between fluid and electric current flow in fractured media are found to lead to significant differences in the REV size and tensor characteristics for σ and K; these are the greater importance of the matrix in the electrical case and the single power instead of cubic dependence of electric current flow upon aperture. Specifically, the REV for the electrical conductivity will always be smaller than that for the hydraulic conductivity, and the corresponding equivalent tensor will exhibit less anisotropy, often with notably different principal orientations. These findings are of key importance for the eventual interpretation of geoelectrical measurements in fractured rock, where we conclude that extreme caution must be taken when attempting to make the link to hydraulic properties.

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Mechanisms of recharge in a fractured porous rock aquifer in a semi-arid region

Cited by 31 publications

References 45 publications

Estimation of natural groundwater recharge in the Aguascalientes semiarid valley, Mexico

Estimation of natural groundwater recharge in the Aguascalientes semiarid valley, Mexico

Spatial and temporal variability of groundwater recharge in a sandstone aquifer in a semi-arid region

Comparison of REV size and tensor characteristics for the electrical and hydraulic conductivities in fractured rock

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