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 thr ee-dimensional flow domain, but few have been rigorously tested, mainl y because of the lack of experimental data. The objectives of this stu dy were to obtain water how and solute transport measurements during t hree-dimensional, axially symmetric water how, using time domain refle ctometry (TDR), and to test some of the existing theories of three-dim ensional 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 applie d at the corner of the box, and a pulse of KCl added as a tracer. Meas urements of volumetric water content, theta, and resident solute conce ntration, C-R, as a function of time and radial distance were made alo ng 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 mea sured solute travel times (t) produced estimates of the slope (alpha) of the exponential hydraulic conductivity function that were comparab le to independently determined values. Estimation of alpha from t alo ng a single flowline, using a quasilinear solution, offers potential f or 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.