ANALYSIS OF WATER AND SOLUTE TRANSPORT AWAY FROM A SURFACE POINT-SOURCE

Mathematical theories describing the movement of water and solute away from sources of Limited spatial extent mostly assume some form of three-dimensional flow domain, but few have been rigorously tested, mainly because of the lack of experimental data. The objectives of this study were to obtain water how and solute transport measurements during three-dimensional, axially symmetric water how, using time domain reflectometry (TDR), and to test some of the existing theories of three-dimensional flow and transport using the measured data. A sandy soil was packed into a Plexiglas box fitted with curved TDR probes at different radial distances from one corner. A constant flux of water was applied at the corner of the box, and a pulse of KCl added as a tracer. Measurements of volumetric water content, theta, and resident solute concentration, C-R, as a function of time and radial distance were made along four Bowlines. The utility of a quasilinear solution was evaluated by comparing measured and predicted profiles of theta at steady state, and the distribution of solute travel times along various transects. Along the various streamlines, nonlinear least-squares analysis of measured solute travel times (t*) produced estimates of the slope (alpha) of the exponential hydraulic conductivity function that were comparable to independently determined values. Estimation of alpha from t* along a single flowline, using a quasilinear solution, offers potential for field application. This technique could be used as a first step in the investigation of contaminant migration from point sources, or used in trickle-irrigation design.