Evolution of isolated caves in porous limestone by mixing of phreatic water and surface water at the water table of unconfined aquifers: A model approach

Citation

Material Information

Title:
Evolution of isolated caves in porous limestone by mixing of phreatic water and surface water at the water table of unconfined aquifers: A model approach
Series Title:
Journal of Hydrology
Creator:
Dreybrodt, Wolfgang
Romanov, Douchko
Kaufmann, Georg
Publication Date:
Language:
English

Subjects

Subjects / Keywords:
Porous Limestone ( local )
Floridal Cavesl Dissolutionl Mixing Corrosion ( local )
Genre:
serial ( sobekcm )

Notes

Abstract:
When water from the surface, e.g. from a lake flows through porous carbonate rocks down along some region with high hydraulic conductivity and encounters the water table of a phreatic aquifer both waters mix by diffusion along their boundary. In a carbonate aquifer, where both surface and phreatic waters are saturated with respect to calcite, mixing corrosion causes renewed dissolution of the carbonate rock in the diffusional mixing zone extending from the boundary separating the phreatic water from the surface water encountering it. A numerical model is presented from which the initial change of porosity in such a diffusional mixing zone is obtained. The initial change of porosity dΦ/dt/0 is proportional to and d2Δceq(m)/dm2. m(x, y) is the spatial distribution of the mixing ratio, m = Vsur/(Vsur + Vphr), and the Vs assign the corresponding volumes of surface and phreatic water. d2Δceq/dm2 is the second derivative of Δceq, the renewed dissolution capacity of the mixed solution. It has been calculated for three geochemical scenarios with differing CO2 concentrations of surface and phreatic water by use of PHREEQC-2. The spatial distribution m(x, y) is obtained by using MODFLOW and MT3DMS in a modeling domain with constant hydraulic conductivity for various flow velocities of the phreatic aquifer. From the results the time scale of cave evolution is estimated. Passages of dimensions of about one meter in width and several 10 cm in height, extending in length along the border line, where surface and phreatic water meet, can be created in time scales of 10 000 years. These caves are horizontal with blind ending passages and resemble closely to the isolated caves observed in Central West Florida. For more realistic modeling we have used a geostatistical local distribution of hydraulic conductivities in the modeling domain. For a correlation length of 1% of the length of modeling domain the spatial distribution extends deeper into the flow direction. When the correlation length is increased by a factor of 10 flow foc
Original Version:
Journal of Hydrology, Vol. 376, no. 1-2 (2009-09-30).

Record Information

Source Institution:
University of South Florida Library
Holding Location:
University of South Florida
Rights Management:
This object is protected by copyright, and is made available here for research and educational purposes. Permission to reuse, publish, or reproduce the object beyond the bounds of Fair Use or other exemptions to copyright law must be obtained from the copyright holder.

USFLDC Membership

Aggregations:
University of South Florida
Karst Information Portal

Postcard Information

Format:
serial

printinsert_linkshareget_appmore_horiz

Download Options

close

No images or PDF downloads are available for this resource.


Cite this item close

APA

Cras ut cursus ante, a fringilla nunc. Mauris lorem nunc, cursus sit amet enim ac, vehicula vestibulum mi. Mauris viverra nisl vel enim faucibus porta. Praesent sit amet ornare diam, non finibus nulla.

MLA

Cras efficitur magna et sapien varius, luctus ullamcorper dolor convallis. Orci varius natoque penatibus et magnis dis parturient montes, nascetur ridiculus mus. Fusce sit amet justo ut erat laoreet congue sed a ante.

CHICAGO

Phasellus ornare in augue eu imperdiet. Donec malesuada sapien ante, at vehicula orci tempor molestie. Proin vitae urna elit. Pellentesque vitae nisi et diam euismod malesuada aliquet non erat.

WIKIPEDIA

Nunc fringilla dolor ut dictum placerat. Proin ac neque rutrum, consectetur ligula id, laoreet ligula. Nulla lorem massa, consectetur vitae consequat in, lobortis at dolor. Nunc sed leo odio.