APPLICATION OF THE OPTIMIZATION METHOD FOR ESTIMATING INFILTRATION CHARACTERISTICS IN FURROW IRRIGATION AND ITS COMPARISON WITH OTHER METHODS

The infiltration characteristics of a soil vary spatially and temporal ly, and due to this the available methods for estimating the character istics in furrow irrigation are either not suitable or have restrictio ns for their field use. An optimization method based on the volume bal ance approach, originally developed for estimating infiltration parame ters in border irrigation, and using multiple observations of arrival time of the wetting front was modified for furrow irrigation. The meth od was applied to 13 irrigation events on furrows monitored on a farm in northern New South Wales, Australia. The soil type at the experimen tal site has a high clay content (up to 67%) and develops cracks when dry. in addition to the optimization method, one-point and two-point m ethods using observations of arrival time reported in the literature w ere also used. The accuracy of different methods was evaluated by comp aring the calculated total volume of water infiltrated into the furrow with that observed in the field. The optimization method was the most accurate and the one-point and the two-point were the least accurate among three methods considered in the present study. A possible explan ation for a poor performance of the one-point and two-point methods mi ght be related to the assumptions made in the derivation of the method s and the unsuitability of the Philip and the Kostiakov infiltration e quations used for the field condition in the present study. (C) 1997 E lsevier Science B.V.