Geostatistical analysis of field hydraulic conductivity in compacted clay
Hydraulic conductivity (K) of fractured or porous materials is associated intimately with water flow and chemical transport. Basic concepts imply uniform flux through a homogeneous cross-sectional area. If flow were to occur only through part of the area, actual rates could be considerably different. Because laboratory values of K in compacted clays seldom agree with field estimates, questions arise as to what the true values of K are and how they should be estimated. Hydraulic conductivity values were measured on a 10 x 25 m elevated bridge-like platform. A constant water level was maintained for 1 yr over a 0.3-m thick layer of compacted clay, and inflow and outflow rates were monitored using 10 x 25 grids of 0.3-m diameter infiltration rings and outflow drains subtending approximately 1 x 1 m blocks of compacted clay. Variography of inflow and outflow data established relationships between cores and blocks of clay, respectively. Because distributions of outflow rates were much less and bore little resemblance to the distributions of break-through rates based on tracer studies, presence of macropores and preferential flow through the macropores was suspected. Subsequently, probability kriging was applied to reevaluate distribution of flux rates and possible location of macropores. Sites exceeding a threshold outflow of 100 x 10/sup -9/ m/s were classified as outliers and were assumed to probably contain a significant population of macropores. Different sampling schemes were examined. Variogram analysis of outflows with and without outliers suggested adequacy of sampling the site at 50 randomly chosen locations. Because of the potential contribution of macropores to pollutant transport and the practical necessity of extrapolating small plot values to larger areas, conditional simulations with and without outliers were carried out.
- Research Organization:
- Dept. of Agriculture, University Park, PA (USA)
- OSTI ID:
- 6413799
- Report Number(s):
- CONF-8704137-
- Journal Information:
- J. Int. Assoc. Math. Geol.; (United States), Vol. 20:4; Conference: MGUS '87, Redwood City, CA, USA, 13 Apr 1987
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
CLAYS
HYDRAULIC CONDUCTIVITY
GEOLOGIC DEPOSITS
STATISTICAL MODELS
POLLUTANTS
ENVIRONMENTAL TRANSPORT
TOXIC MATERIALS
COMPACTING
COMPUTERIZED SIMULATION
FILTRATION
FRACTURED RESERVOIRS
GROUND WATER
HYDROLOGY
KRIGING
LAND POLLUTION CONTROL
MAPPING
PERMEABILITY
POROSITY
PROBABILITY
SAMPLING
TRACER TECHNIQUES
WATER INFLUX
WATER POLLUTION CONTROL
CONTROL
HYDROGEN COMPOUNDS
ISOTOPE APPLICATIONS
MASS TRANSFER
MATERIALS
MATHEMATICAL MODELS
MATHEMATICS
OXYGEN COMPOUNDS
POLLUTION CONTROL
SEPARATION PROCESSES
SIMULATION
STATISTICS
WATER
510200* - Environment
Terrestrial- Chemicals Monitoring & Transport- (-1989)
520200 - Environment
Aquatic- Chemicals Monitoring & Transport- (-1989)