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Incorporation and Evaluation of a River Water Quality Model to NAPRA WWW Decision Support System

Published by the American Society of Agricultural and Biological Engineers, St. Joseph, Michigan www.asabe.org

Citation:  Paper number  012127,  2001 ASAE Annual Meeting. (doi: 10.13031/2013.7389) @2001
Authors:   Kyoung Jae Lim, Bernard A. Engel, Amots Hetzroni
Keywords:   GLEAMS 3.0, NAPRA, Pesticides, Nutrients, Water Quality, Decision Support Models

The spatial variability of the saturated hydraulic conductivity (Ks ) of a greenhouse banana plantation volcanic soil was investigated with three different permeameters: a) the Philip-Dunne field permeameter, an easy to implement and low cost device; b) the Guelph field permeameter; and c) the constant-head lab permeameter. Ks was measured on a 14x5 array of 2.5mx5m rectangles at 15 cm depth using the above three methods. In the case of the lab permeameter a sinusoidal spatial variation of Ks was coincident with the underlying alignment of banana plants on the field. To discard the possibility of an artifact the original 70 point mesh was doubled by intercalation of a second 14x5 grid, such that the lab Ks was finally determined on a 140 points 2.5x2.5 square grid. Far from diluting such anisotropy this was further strengthen after inclusion of the new 70 points. The porosity determined on the same lab cores shows a similar sigmoidal trend, thus pointing towards a plausible explanation for such variability. In fact both parameters follow a power-law relation of the form Ks=a*porosity^b (R=0.62) as stated by Archie's law. Although the two-field methods: Guelph and Philip-Dunne, also follow a similar alignment trend this is not so evident, suggesting that additional factors affect Ks measured in the field. Finally geostatistical techniques are used to further investigate this spatial dependence. A log-transformation was found to be both a symmetrizing and variance stabilizing transformation of the Ks data.

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