Field Evaluation of a Water Management Simulation Model

Abstract

ABSTRACT THE water management simulation model, DRAINMOD, was tested using field data for over 5 yr of record from three locations in the NC Coastal Plains. Each site had field scale drainage systems with provisions for subirrigation and controlled drainage. Three soil types and five different drainage system designs were included in the experiment from which 21 site-yr of data were obtained. Rainfall intensity and water table elevations were measured continuously at each site and the observed day end water table elevations were compared to predicted values. Effective lateral hydraulic conductivity values were measured in the field using both auger hole and water table drawdown methods. Numerous other field and laboratory mea-surements were made for each soil to determine input soil property and site parameter data. Comparison of predicted and measured water table elevations were in excellent agreement with the daily water table depths having standard errors of estimate ranging from 7.5 to 19.6 cm. The average absolute devia-tion between predicted and observed water table depths for 21 site-years of data (approximately 7400 pairs of daily predicted and measured values) was only 8.1 cm. Based on the results of the study, DRAINMOD can be reliably used to predict the effect of drainage system design on water table elevations.