A framework for understanding the linkages between land and water quality impacts

Abstract

Different soils, landscapes and water pathways vary at a range of spatial and temporal scales in their propensity to yield, transport and attenuate contaminants. This affects a land's suitability t various types and intensities of use. For instance, one national-scale study has found that , on average, 55% of nitrogen (N) and phosphorus (P) lost from productive land uses in New Zealand are attenuated as they make their way through catchments to the sea, but proportions attenuated vary widely across and between landscapes. Thus, the limit setting processes and the actual limits applied to land uses by regulators under the NPS-FM (National Policy Statement for Freshwater Management) to safeguard the life-supporting capacity of freshwaters and the associated health of people and communities need to take into account these differences in transport and attenuation between contaminant sources and sites where water quality attributes are defined. The Sources & Flows programme in the Our Land & Water National Science Challenge aims to develop a framework that will synthesise our existing knowledge of contaminant sources and pathways to predict the spatial and temporal effect of these attenuating factors on contaminant transport. The proposed framework will build on existing frameworks that operate at smaller scales e.g. the farm dairy effluent risk framework. This framework will be supported by a national scale "source-delivery-attenuation" analysis that will identify the gaps in the state of our current knowledge (with existing models) and measured stream loads. We will also investigate the use of "indirect" methods, such as hydrograph and pollutograph analysis, and tracers, to verify contaminant pathways. Such analyses will support development of the framework and allow us to extrapolate to areas where little base-line data are available. With appropriate knowledge, productive enterprises will have the opportunity to adapt and tailor their land use and management practices to work within the natural and built attenuation capacities of their landscape.