Title of article :
Linear model describing three components of flow in karst aquifers using 18O data
Author/Authors :
Andrew J. Long، نويسنده , , Larry D. Putnam، نويسنده ,
Issue Information :
روزنامه با شماره پیاپی سال 2004
Pages :
17
From page :
254
To page :
270
Abstract :
The stable isotope of oxygen, 18O, is used as a naturally occurring ground-water tracer. Time-series data for δ18O are analyzed to model the distinct responses and relative proportions of the conduit, intermediate, and diffuse flow components in karst aquifers. This analysis also describes mathematically the dynamics of the transient fluid interchange between conduits and diffusive networks. Conduit and intermediate flow are described by linear-systems methods, whereas diffuse flow is described by mass-balance methods. An automated optimization process estimates parameters of lognormal, Pearson type III, and gamma distributions, which are used as transfer functions in linear-systems analysis. Diffuse flow and mixing parameters also are estimated by these optimization methods. Results indicate the relative proximity of a well to a main conduit flowpath and can help to predict the movement and residence times of potential contaminants. The three-component linear model is applied to five wells, which respond to changes in the isotopic composition of point recharge water from a sinking stream in the Madison aquifer in the Black Hills of South Dakota. Flow velocities as much as 540 m/d and system memories of as much as 71 years are estimated by this method. Also, the mean, median, and standard deviation of traveltimes; time to peak response; and the relative fraction of flow for each of the three components are determined for these wells. This analysis infers that flow may branch apart and rejoin as a result of an anastomotic (or channeled) karst network.
Keywords :
Signal processing , Mathematical models , Stable isotopes , Karst aquifers , Linear systems , Aquifer response
Journal title :
Journal of Hydrology
Serial Year :
2004
Journal title :
Journal of Hydrology
Record number :
1098315
Link To Document :
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