Premium
A Field Study of Solute Dispersion in a Shallow, Unconfined Aquifer
Author(s) -
Leland D. F.,
Hillel D.
Publication year - 1982
Publication title -
soil science society of america journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.836
H-Index - 168
eISSN - 1435-0661
pISSN - 0361-5995
DOI - 10.2136/sssaj1982.03615995004600050004x
Subject(s) - tracer , geology , aquifer , infiltrometer , soil science , hydraulic conductivity , dispersion (optics) , mineralogy , geotechnical engineering , geomorphology , hydrology (agriculture) , soil water , groundwater , optics , physics , nuclear physics
A natural gradient tracer test was performed to (i) characterize the patterns of variation of saturated hydraulic conductivity ( K s ) and longitudinal dispersivity (α L ) in a shallow, unconfined aquifer in a sandy soil on a sloping site and to (ii) examine scale effects on quantification of α L . Chloride tracer was injected into the saturated zone, and its downslope movement was monitored by means of multilevel samplers. Results show that the mean value of K s derived from the tracer test was in close agreement with values obtained independently on undisturbed core samples and from double‐ring infiltrometer tests performed in situ. Results also indicate a nonuniform distribution of velocity on both vertical and horizontal transects at right angles to the mean direction of flow. Values of α L , calculated using a simplified solution of the two‐dimensional advective‐dispersive equation, show a nonuniform distribution of α L in the profile and reveal that increasing the scale of measurement vertically at right angle to the flow leads to larger measured values of dispersivity. The effect was observed with a change in scale from point measurements to averages taken over the 60‐ to 75‐cm thickness of the profile's saturated zone. The frequency of sampling is also shown to have a significant effect on quantification of α L .