Tracing Recharge from Sinking Streams over Spatial Dimensions of Kilometers in a Karst Aquifer

This manuscript was handled by P. Baveye, Editor-in-ChiefKeywords: Groundwater Karst Parameter estimation Inverse modeling Groundwater age s u m m a r y Convolution modeling is useful for investigating the temporal distribution of groundwater age based on environmental tracers. The framework of a quasi-transient convolution model that is applicable to twodomain flow in karst aquifers is presented. The model was designed to provide an acceptable level of statistical confidence in parameter estimates when only chlorofluorocarbon (CFC) and tritium ( 3 H) data are available. We show how inverse modeling and uncertainty assessment can be used to constrain model parameterization to a level warranted by available data while allowing major aspects of the flow system to be examined. As an example, the model was applied to water from a pumped well open to the Madison aquifer in central USA with input functions of CFC-11, CFC-12, CFC-113, and 3 H, and was calibrated to several samples collected during a 16-year period. A bimodal age distribution was modeled to represent quick and slow flow less than 50 years old. The effects of pumping and hydraulic head on the relative volumetric fractions of these domains were found to be influential factors for transient flow. Quick flow and slow flow were estimated to be distributed mainly within the age ranges of 0-2 and 26-41 years, respectively. The fraction of long-term flow (>50 years) was estimated but was not dateable. The different tracers had different degrees of influence on parameter estimation and uncertainty assessments, where 3

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“…These isotopes also indicate that 89-100% of water sampled from well RC11 was recharged by Spring Creek (Greene, 1997;Fig. 2).…”

Section: Model Applicationmentioning

confidence: 84%

Age-distribution estimation for karst groundwater: Issues of parameterization and complexity in inverse modeling by convolution

Long

Putnam

2009

Journal of Hydrology

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“…Typically, waters more depleted in d 18 O come from precipitation in cooler regions or climactic periods, while evaporation tends to produce more enriched values. As such they can be used to delineate different water sources to aquifers and between local and regional discharge (Greene 1997;Williams and Rodoni 1997;Carreon-Diazconti et al 2003;Bonotto 2006).…”

Section: Resultsmentioning

confidence: 99%

The use of oxygen isotopic ratios to identify natural and anthropogenic mercury concentrations in the Lower Brazilian Pantanal

et al. 2011

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Previous studies in the Amazon Basin and the Upper Pantanal show widespread mercury contamination of fish and water as a result of gold mining, and subsequent volatilization of mercury during the recovery process. A study was initiated to assess whether atmospheric transport of mercury to the south has resulted in elevated levels in water and fish in the Lower Pantanal. Water samples were collected from streams and rivers from the Pantanal (Mato Grosso do Sul) down into the southernmost state of Brazil (Rio Grande do Sul) for total Hg concentration and oxygen isotopic analyses. Based on oxygen isotopes and conductivity, surface water samples can be considered as mixtures of three endmembers: groundwater, rain and ''aged'' surface water. Lowest concentrations (\2 ng/L) of total Hg were observed in the northernmost samples, especially those associated with the groundwater sources. Further south, Hg concentrations tended to increase, but higher concentrations ([2 ng/L) likely reflect direct input from more localized watershed sources. Fish collected from streams in the Pantanal had extremely low concentrations of total Hg regardless of their size or feeding habit, although one large carnivorous fish ([2 kg) had concentrations approaching 400 ng/g wet wt. All concentrations, however, were considerably lower than those observed in similar species from the region of the Amazon Basin affected by gold mining.

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“…The slope of hydraulic head for the 5 days before and 5 days after this event was 0.05 and 0.39 m/d, respectively. Previous studies indicate a predominant groundwater flow path that originates at the Spring Creek sink and flows north toward Jackson-Cleghorn Springs about 3 km north of the study area (Greene, 1997;Anderson et al, 1999;Naus et al, 2001;Long and Putnam, 2004), and that this likely is the result of a major karst conduit (Long et al, 2008). A fluorescent dye injection into the Spring Creek sink is consistent with these studies, where tracer velocities to five wells in the study area ranged from about 230 to 1360 m/d (Putnam and Long, 2007).…”

Section: Study Area and Data Collectionmentioning

confidence: 98%

A one-dimensional heat-transport model for conduit flow in karst aquifers

Long¹,

Gilcrease²

2009

Journal of Hydrology

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s u m m a r y A one-dimensional heat-transport model for conduit flow in karst aquifers is presented as an alternative to two or three-dimensional distributed-parameter models, which are data intensive and require knowledge of conduit locations. This model can be applied for cases where water temperature in a well or spring receives all or part of its water from a phreatic conduit. Heat transport in the conduit is simulated by using a physically-based heat-transport equation that accounts for inflow of diffuse flow from smaller openings and fissures in the surrounding aquifer during periods of low recharge. Additional diffuse flow that is within the zone of influence of the well or spring but has not interacted with the conduit is accounted for with a binary mixing equation to proportion these different water sources. The estimation of this proportion through inverse modeling is useful for the assessment of contaminant vulnerability and well-head or spring protection. The model was applied to 7 months of continuous temperature data for a sinking stream that recharges a conduit and a pumped well open to the Madison aquifer in western South Dakota. The simulated conduit-flow fraction to the well ranged from 2% to 31% of total flow, and simulated conduit velocity ranged from 44 to 353 m/d.Published by Elsevier B.V. IntroductionThe use of heat as a groundwater tracer, in contrast to the use of chemical tracers, is attractive because of the ease of measuring temperature with high precision (errors as low as ±0.03°C). Groundwater temperatures are influenced by the temperature of recharge, mixing of different waters resulting from groundwater flow, and the earth's geothermal gradient. A long history of the use of heat as a groundwater tracer beginning in the 1960s is described by Anderson (2005). A few examples of the numerous heat-transfer applications in hydrology include those by Bredehoeft and Papadopulos (1965), Edinger et al. (1968), Lu and Ge (1996), Bogan et al. (2003), andShoemaker et al. (2005). Groundwater flow and heat-transport computer codes include Voss and Provost (2002) and Healy and Ronan (1996).Temperature fluctuations at the outlets of karst aquifers commonly are observed to range from 0.01 to several degrees Celsius (Benderitter et al., 1993). There are several examples of heat-transfer method development and applications for karst hydrology. Applications to assess cave temperatures and gaining and sinking streams include Genthon et al. Two-or three-dimensional distributed-parameter models are data intensive and are useful when the locations of conduits are known; however, information on conduit locations usually is unavailable. For cases where wells or springs have a temperature response that is influenced by conduit flow, but the conduit network is not well defined, an alternative approach may be useful. This paper presents a one-dimensional numerical heat-transport model that is explored as an alternative that might be useful when a primary objective is to estimate the relative fractions of cond...

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Tracing Recharge from Sinking Streams over Spatial Dimensions of Kilometers in a Karst Aquifer

Cited by 32 publications

References 18 publications

Age-distribution estimation for karst groundwater: Issues of parameterization and complexity in inverse modeling by convolution

Age-distribution estimation for karst groundwater: Issues of parameterization and complexity in inverse modeling by convolution

The use of oxygen isotopic ratios to identify natural and anthropogenic mercury concentrations in the Lower Brazilian Pantanal

A one-dimensional heat-transport model for conduit flow in karst aquifers

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