Making sense of complex data
The data used in the models covers a range of areas including land use, characteristics of the catchments like rainfall and topography, and observations made in the river from sampling, like nutrient concentrations and periphyton levels. “What our models are really doing is trying to describe the way in which contaminants (nitrogen, phosphorus, sediment and E.coli) are generated in those catchments, and how they’re then transported down the catchment, and what happens to them in the receiving environments – the estuaries.”
“We build the models that describe the chain of events, and then once the models are built, they provide a simple representation of the whole system,” Ton says. “We then interrogate that. We make sense of the data in the model, and then use it to say ‘ah ha’ – there’s a level of response in the estuary that is unacceptable. What level would be acceptable, and what level of reduction in contaminants is needed to achieve that?” This type of work has been done in New Zealand for over a decade in response to the need to set environmental limits.“ We recognise there are places around New Zealand, and Southland is an example, where we are generating more nutrients than what is acceptable and we need to reduce those. “I’ve done work at the national scale on the current levels of nutrients, and how they compare with the regulatory criteria. From that work we knew that some regions in New Zealand, including Southland have quite large gaps between where they currently are and what’s acceptable.”
The models deployed in Southland and elsewhere around the country are the culmination of over three decades of research. This science is another piece of the puzzle in Environment Southland’s work programme focused on meeting the community’s expectations and Government requirements for freshwater. The science programme has been running for over four years, and will combine with economic analysis to support a plan change to the proposed Southland Water and Land Plan in the next two years. “One of the things that makes Southland quite unique is that it has these large, and very agriculturally-dominated catchments. Then those catchments finish in sensitive estuaries – sensitive to nutrient loads. “You don’t see that in many other places around New Zealand, and that does make Southland a challenging environment with respect to that combination of a productive agricultural landscape while achieving good environmental outcomes. That combination of things comes together in a challenging way.”
