Pitfalls in application of the conventional chloride mass balance (CMB) in karst aquifers and use of the generalised CMB method

Somaratne, Nara

doi:10.1007/s12665-015-4038-y

Cited by 10 publications

(20 citation statements)

References 21 publications

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“…Because the CMB method may present limitations in some disadvantageous hydrogeological contexts [53,54], some additional processes must be considered for recharge evaluations in Las Cañadas aquifer system, such as (1) the possibility of mixing chloride flow mass rates produced by recharge infiltrated at different elevations [20]; (2) the variable rainfall-runoff partitioning and recharge mechanisms, land use, and soil-vegetation conditions with elevation [14]; (3) the potential contribution of non-atmospheric chloride to groundwater from endogenous halides and human activities [21]; and (4) the potential storage of chloride in the soil and vadose zones [8,17].…”

Section: The Chloride Mass Balance (Cmb) Methods Application In the Stmentioning

confidence: 99%

Aquifer Recharge Estimation through Atmospheric Chloride Mass Balance at Las Cañadas Caldera, Tenerife, Canary Islands, Spain

Marrero-Diaz

Alcalá

Pérez

et al. 2015

Water

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Abstract:The atmospheric chloride mass balance (CMB) method was used to estimate net aquifer recharge in Las Cañadas Caldera, an endorheic summit aquifer area about 2000 m a.s.l. with negligible surface runoff, which hosts the largest freshwater reserve in Tenerife Island, Canary Islands, Spain. The wet hydrological year 2005-2006 was selected to compare yearly atmospheric chloride bulk deposition and average chloride content in recharge water just above the water table, both deduced from periodical sampling. The potential contribution of chloride to groundwater from endogenous HCl gas may invalidate OPEN ACCESSWater 2015, 7 2452 the CMB method. The chloride-to-bromide molar ratio was an efficient tracer used to select recharge water samples having atmospheric origin of chloride. Yearly net aquifer recharge was 631 mm year −1 , i.e., 69% of yearly precipitation. This result is in agreement with potential aquifer recharge estimated through an independent lumped-parameter rainfall-runoff model operated by the Insular Water Council of Tenerife. This paper illustrates basic procedures and routines to use the CMB method for aquifer recharge in active volcanic oceanic islands having sparse-data coverage and groundwater receiving contribution of endogenous halides.

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Section: The Chloride Mass Balance (Cmb) Methods Application In the Stmentioning

confidence: 99%

Aquifer Recharge Estimation through Atmospheric Chloride Mass Balance at Las Cañadas Caldera, Tenerife, Canary Islands, Spain

Marrero-Diaz

Alcalá

Pérez

et al. 2015

Water

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“…With the onset of receiving surface runoff, these sinkholes become active and would act as the sources of point recharge (Figure 9). Somaratne (2015b) reports that during the 1986 flood event, discharge to the Scowns sinkhole was measured at the rate of 500-2000 m O data were used to infer the degree of mixing along flow paths from the primary recharge source (Poocher Swamp) to the sampling point. In a karsitic aquifer composition of groundwater chemistry at a sampling point represents a contribution from matrix and conduit flow components.…”

Section: Evidence From Em Surveymentioning

confidence: 99%

Integrated Use of Geological, Geophysical, Radiocarbon and Stable Isotopes Data for Tracing the Conduit Flow Paths in a Small Karstic Aquifer: Poocher Swamp Freshwater Lens, South Australia

Somaratne¹,

Mann²

2016

ENRR

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An integrated approach combining lithological logs, downhole geophysics, electromagnetic survey and the distribution of radiocarbon ( 14 C) and the stable isotopes of water molecules ( 18 O) were used to identify the conduit flow paths of a small freshwater lens. Lost circulation zones, where drilling fluid flows into geological formation instead returning up the annulus recorded during water well drilling, were considered as the major fracture zones. The presence of high porosity zones within boreholes were identified using caliper, gamma and neutron logs. These methods were used to identify the depth intervals at which cavities and the existence of conduit porosity within the boreholes. Transient electromagnetic (TEM) method was used to investigate resistivity anomalies in the profiles along nine pre-determined lines across the freshwater lens. Resistivity anomalies were related to borehole information and other surface features such as sinkholes. Low resistivity zones of the TEM tomography sections had excellent correlation to fracture zones identified during well drilling, and downhole geophysical logs. Similarly, high resistivity zones in the profiles correlate well with the zones of O signatures of the groundwater confirm the presence of conduits and potential pathways of preferential flows. This investigation illustrates the effectiveness using an integrated approach to trace the conduit flow paths in karst aquifers. The information gained from the study is currently being used for the management of the freshwater lens.

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“…For Equation (1) to hold after replacing cR with groundwater chloride (cg), cR must be in equilibrium with cg (saturated version of CMB) [3]. This is not the case with point recharge through sinkholes as Werner [2] anticipates, as point recharge occupies mostly conduit porosity areas.…”

Section: −3mentioning

confidence: 99%

“…Zhu et al [18] highlights that for the saturated version of CMB to be applicable; groundwater movement in both unsaturated and saturated zones should be approximated as one-dimensional piston flow. This essentially means that chloride concentration of the mass flux crossing the piezometric surface (cR) is at equilibrium with groundwater chloride (cg) [3]. When chloride concentrations of groundwater samples (cg) are used as cR values in Equation (1) for saturated zone application, the recharge rates determined from the conventional CMB apply to locations in the catchment where the samples are recharged, not where the samples are collected [3].…”

Section: −3mentioning

confidence: 99%

“…This limits application of recharge estimation methods, such as the conventional chloride mass balance (CMB) as the basic premise of the CMB is violated. The conventional CMB is not suitable for accounting chloride mass balance in groundwater systems displaying extreme range of chloride concentrations and complex mixing [3]. Over simplification of karst aquifer systems to suit application of the conventional CMB or 1-D unsaturated modelling as described in Werner [2], is not suitable use of these recharge estimation methods.…”

Section: Introductionmentioning

confidence: 99%

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Karst Aquifer Recharge: A Case History of over Simplification from the Uley South Basin, South Australia

Somaratne

2015

Water

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Abstract:The article "Karst aquifer recharge: Comments on 'Characteristics of Point Recharge in Karst Aquifers', by Adrian D. Werner, 2014, Water 6, doi:10.3390/w6123727" provides misrepresentation in some parts of Somaratne [1]. The description of Uley South Quaternary Limestone (QL) as unconsolidated or poorly consolidated aeolianite sediments with the presence of well-mixed groundwater in Uley South [2] appears unsubstantiated. Examination of 98 lithological descriptions with corresponding drillers' logs show only two wells containing bands of unconsolidated sediments. In Uley South basin, about 70% of salinity profiles obtained by electrical conductivity (EC) logging from monitoring wells show stratification. The central and north central areas of the basin receive leakage from the Tertiary Sand (TS) aquifer thereby influencing QL groundwater characteristics, such as chemistry, age and isotope composition. The presence of conduit pathways is evident in salinity profiles taken away from TS water affected areas. Pumping tests derived aquifer parameters show strong heterogeneity, a typical characteristic of karst aquifers. Uley South QL aquifer recharge is derived from three sources; diffuse recharge, point recharge from sinkholes and continuous leakage of TS water. This limits application of recharge estimation methods, such as the conventional chloride mass balance (CMB) as the basic premise of the CMB is violated. The conventional CMB is not suitable for accounting chloride mass balance in groundwater systems displaying extreme range of chloride concentrations and complex mixing [3]. Over simplification of karst aquifer systems to suit application of the conventional CMB or 1-D unsaturated modelling as described in Werner [2], is not suitable use of these recharge estimation methods.

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Pitfalls in application of the conventional chloride mass balance (CMB) in karst aquifers and use of the generalised CMB method

Cited by 10 publications

References 21 publications

Aquifer Recharge Estimation through Atmospheric Chloride Mass Balance at Las Cañadas Caldera, Tenerife, Canary Islands, Spain

Aquifer Recharge Estimation through Atmospheric Chloride Mass Balance at Las Cañadas Caldera, Tenerife, Canary Islands, Spain

Integrated Use of Geological, Geophysical, Radiocarbon and Stable Isotopes Data for Tracing the Conduit Flow Paths in a Small Karstic Aquifer: Poocher Swamp Freshwater Lens, South Australia

Karst Aquifer Recharge: A Case History of over Simplification from the Uley South Basin, South Australia

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