Land reshaping of lowland clay soils: I. Modelling report

The land planing studies, which were carried out by Can-Ag Enterprises Limited, were mathematically modelled using a modified version of the Chemicals, Runoff and Erosion from Agricultural Management Systems (CREAMS, Ver. 1.7) model. This modelling assignment focused on the first phase of model application, the prediction of overland flow episodes, and was based on a procedure which encompassed five areas of model development and application. These areas included problem identification, stated objective, development of method, results and evaluation of results. Based on this procedure, 116 out of 130 observed episodes of overland flow were predicted for the twelve fields in the land planing studies for the time period from April '89 to September '90. In addition, 38 predictions were made which could not be explained, i.e. the failure of monitoring equipment. These results were dependent on a number of factors including the proximity of an agricultural field to precipitation measurement as well as the seasonal variation in infiltration characteristics of heavy clay soils. The predictions of overland flow episodes resulted from a novel approach of applying the CREAMS Ver. 1.7 model to agricultural fields across seasons. This approach provided a solid basis for the next phase of modelling application: an emphasis on the prediction of flow quantities and sediment and phosphorus concentrations and loadings. The framework for such an emphasis could easily be patterned on the framework developed in this assignment, the first phase of model application.