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Development of guidance on parameter estimation for MACRO - PL0538

The MACRO model is increasingly used to simulate movement of pesticides to surface waters via drainflow and leaching to depth through soils prone to preferential flow. Recent work by SSLRC for PSD concluded that MACRO is and should continue to be the preferred preferential flow model for regulatory use. However, the predictive use of MACRO is greatly restricted by difficulties in robust parameter selection, particularly as the model is sensitive to changes in many of the problematic parameters. This proposal is for a 12-month project to develop guidance on parameter selection for MACRO.
The work will concentrate on two main areas. First, guidance for selecting robust input parameters from readily available information will be developed. The model will be applied to a number of existing datasets and selected parameters will be calibrated and validated. Parameter ranges, representative values for a number of soils and estimation routines to generate parameters from readily available information will be identified. The second area of work aims at providing protocols for additional measurements which could support parameter estimation. These include additional laboratory and field measurements or controlled leaching studies with small intact soil columns to independently derive the more uncertain parameters. The development of protocols for any experimental work suggested will initially be based on the re-analysis of existing datasets. Additional experiments are proposed to be carried out to complement the available information. The research will significantly strengthen the modelling process and improve the confidence of regulators in results. It will run alongside current work to update the user interface for MACRO which is being undertaken by Prof. Nick Jarvis, Swedish University of Agricultural Sciences, Uppsala, Sweden and this will ensure rapid and effective dissemination of results.
The aim of this study is to develop guidance on parameter estimation for the pesticide leaching model MACRO. The objectives are:
1. To provide detailed guidance to modellers on how to select ‘difficult’ parameters for the MACRO model (particularly those relating to preferential flow) from readily available information.
2. To provide outline protocols for additional measurements which could be made on experimental soils to facilitate parameter selection for the MACRO model.
Project Documents
• Final Report : Development of guidance on parameter estimation for MACRO   (1399k)
Time-Scale and Cost
From: 2000

To: 2001

Cost: £35,875
Contractor / Funded Organisations
Soil Survey and Land Research Centre
Environmental Effects              
Pest and Weed Control              
Pesticide use              
Plants and Animals              
Fields of Study
Pesticide Safety