Predicting the effects of landuse on water quality – Stage I
Reports on Stage I tasks
The overall approach for Stage I of the research was to generate a common framework for all models in this first year, link at least one model (SPARROW) to the framework, and begin to develop linkages between the modelling framework and individual models (e.g., the OVERSEER, SPASMO, and EnSus models). These other models will be linked to the framework in Stages II or III of the project. Section 4 reports on the first project workshop, Sections 5 to 10 summarise progress on individual tasks, and Section 11 offers some suggestions for the work needed in the second and third stages of the project. Sections 14 to 16 contain technical background material for the SPASMO, OVERSEER, and triple bottom line accounting models, while Sections 17 and 18 contain administrative information such as the Stage I contract, and contact details of current project participants.
Connections Among Tasks in Sections 5 to 10
This project comprises a number of tasks that are proceeding in parallel, in order to produce a linked modelling system that operates at several levels of spatial detail. The catchment-modelling framework outlined in Section 5.1 is being used to connect models such as SPARROW (Section 5.2 and Section 6), OVERSEER (Section 7), SPASMO (Section 8), EnSus (Section 9), and triple bottom line accounts (Section 10). In every case except the last, an existing modelling technique is being linked to the modelling framework. By using existing models, there are very substantial savings on the cost of model development, and more of the project resource can be put into integration of models, and into case studies.
Because the models have a wide range of approaches, there are significant differences in the style of reporting between the following sections of this report. Some of the modelling techniques being used are more compatible with the framework than others. The following paragraphs outline the current status of the framework, and each model in relation to the framework. These comments should assist in explaining why each of the tasks is being done, and how they contribute to the goals of the project.
The modelling framework (Section 5.1) is in place, and has been designed to be able to link to a wide range of model types. More work is needed to link to models other than SPARROW. The connection between the framework and the SPARROW model is in place and operating very efficiently.
The SPARROW model (Section 5.2) is operating as a component of the modelling framework, and the model for N is complete. The extension of the SPARROW model to include groundwater (Section 6) is also complete, but has not yet been finally linked to the framework. However, it is so similar to the already-linked standard SPARROW model that very little additional work is needed on the system linkages. Most of the remaining work with the groundwater model is in estimating the model parameters.
The links between the OVERSEER® model (Section 7) and the framework are clearly specified, and no particular difficulties are expected in linking it so that it will provide N leaching results for farms. A detailed design has been completed to specify the information to be exchanged between OVERSEER® and the modelling framework. More work is needed on the identification of representative ranges of rainfall, soils and topography for each of the farm types (scenarios) described in Section 7.2. OVERSEER® is intended to be run automatically from the framework, for representative case studies that cover all pastoral agriculture in the catchment of interest.
Links between the SPASMO model (Section 8) and the framework are not yet clearly defined. The SPASMO model is the most numerically detailed of all the models in this project, and requires a long sequence of site-specific daily climate information as input data. In this first year of the project, it is being used to generate information on N leaching for case studies, and these have been essential for the triple bottom line work (Section 10). Ideally, the SPASMO model would be linked into the modelling framework in the same way as OVERSEER, that is, as a model which can be run automatically from the framework, for representative case studies that cover all horticultural crops in the catchment of interest.
The EnSus results (Section 9) provide a national view of N leaching risk, which complements the national SPARROW modelling work (Section 5.2) for N and P. The EnSus approach is at a finer spatial scale than SPARROW. However, it does not estimate spatially integrated responses over catchments, and does not take account of in-stream attenuation processes. The EnSus model can be summarised as a set of rules that combine maps of soil attributes, rainfall, and land use/management into maps of leaching risk. These rules are documented in Section 9, and can easily be implemented as part of the catchment modelling framework, although no work has begun on that link. Land use/management change scenarios can be investigated by changing the map of land use/management to which the rules are applied.
The triple-bottom line accounting work (Section 10) has produced simple approximate methods to estimate the N leaching, income and employment outcomes of various land uses. The approach used for this work is simpler than the other modelling approaches, and has the advantage that it covers a wider range of land uses than any other model. The model equations (Section 16) are available in a form that is easily linked to the modelling framework, but no work has begun on that linkage.
A summary of the progress of each system component is provided in Table 3-1. Although some of the model components have made little progress on model integration in this first year of the project, this is not in itself a cause for concern. For some of the models, development or application of the model itself was seen as a higher priority in the early stages of the project. For at least two of the models (EnSus and Triple Bottom Line accounting), little work is needed to integrate them into the catchment modelling framework.
Table 3-1: Summary of progress in model development and model integration. These (admittedly subjective) assessments are not concerned with the quality of work being done, but reflect the complexity of the task, the resources allocated to it so far, and the priorities set by the funding agency.
| System component | Progress on development | Progress on Integration |
|---|---|---|
| Modelling Framework | Medium | Medium |
| SPARROW (N) | Medium | High |
| SPARROW-G/W (N) | Low | High |
| OVERSEER | High | Medium |
| SPASMO | High | Low |
| EnSus (N) | Medium | Low* |
| Triple Bottom Line (N, $, jobs) | Medium | Low* |
* Relatively little effort will be needed to achieve a high level of model integration
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