DEVELOPMENT AND EVALUATION OF A MACROPOREFLOW COMPONENT FOR LEACHM

Abstract

(Leaching Estimation And Chemistry Model) and a modified LEACHM were used to predict NO3-Nand atrazine transport in two Kansas soils. NO3-N and atrazine concentration data obtained from two monolith weighinglysimeters containing two different Kansas soils were used to calibrate and validate the nitrogen and pesticide versions ofLEACHM. Since LEACHM (ver. 3.0) does not include any means to deal with macropore flow, the macropore flowsubroutine from RZWQM (Root Zone Water Quality Model) was incorporated into LEACHM. Measured concentrations ofNO3-N and atrazine were compared with those predicted by LEACHM with and without the macropore flow subroutine. Ingeneral, concentrations predicted by both models tend to follow the trend of measured concentrations. Addition of themacropore flow subroutine improved the predictions a little, especially for atrazine transport in silty clay loam soil.However, no such improvement was observed in sandy loam soil. Overall, the results of this study showed that addition ofthe macropore flow component had potential for improving prediction capability of LEACHM in silty clay loam soils. Theuse of more site specific macroporosity data is likely to improve the model predictions.